Design and Qntrol of Network : ‘I 

Architecture in Radiation-Curable 

Toughened Semi-Interpenetrating 

Network Resin Systems 

by Kevin M. Kit, James M. Sands, 

and Steven H. M&night 

ARGTR-2693 March 2002 

Approved for public release; distribution is unlimited. 

20020604 382 
The findings in this report are not to be construed as an 

official Department of the Army position unless so 

designated by other authorized documents. 

Citation of manufacturer’s or trade names does not 

constitute an official endorsement or approval of the use 

thereof. 

Destroy this report when it is no longer needed. Do not 

return it to the originator. 
Army Research Laboratory 

Aberdeen Proving Ground, MD 210055069 

ARL-TR-2693 March 2002 

Design and Control of Network 

Architecture in Radiation-Curable 

Toughened Semi-Interpenetrating 

Network Resin Systems 

Kevin M. Kit 

University of Tennessee 

James M. Sands and Steven H. M&night 

Weapons and Materials Research Directorate, ARL 

Approved for public release; distibution is unlimited. 
Abstract 

Several issues related to the development of a radiation-curable rubbertoughened epoxy resin are investigated by performing a statistical analysis of 

semi-interpenetrating polymer blend formulations. The statistical analysis 

provided predictions for branching coefficient, copolymer molecular weight, and 

rubber-to-network connectivity for the B-staged interpenetrating networks. 

These statistical metrics relate to the properties of thermally generated B-stage 

networks, prior to secondary network formation using radiation cure methods 

such as electron beam or ultraviolet excitation. The components of these resins 

were described, and a procedure was developed to determine the exact weight 

fractions of each component that must be mixed together to achieve a desired 

branching coefficient and resin composition. Compositional variables include 

weight ratio of the two dimethacrylates, weight ratio of the two monoepoxides, 

and weight ratio of epoxides to dimethacrylates. Using the raw materials 

selected for this study, we determined that many network structures are not 

attainable. Specifically, it is not possible to prepare B-stage resins without the 

use of mono- or difunctional units, such as phenyl glycidyl ether (PGE) or 

methacrylated digicydyl ether of bisphenol A @isGMA). The possible 

formulations are determined, and a map is proposed showing the combinations 

of PGE and bisGMA content that are allowed for B-stage formation. 
Acknowledgments 

We gratefully acknowledge the Shell Chemical Company and Air Products for 

providing material samples during the testing and formulation phases of this 

project. Support for this work was provided by the United States Department of 

Defense through the Strategic Environmental Research and Development 

Program (SERDP) under pollution prevention program IT-1109, “Non-Polluting 

Composite Repair and Remanufacturing for Military Applications.” 

. . . 

ill 

Contents 

Acknowledgments 

. . . 

111 

List of Figures 

List of Tables 

1. Introduction 1 

2. Design of Network Structure 4 

2.1 Materials .......................................................................................................... 5 

2.1.1 Diepoxides .......................................................................................... 5 

2.1.2 Amine Curing Agent ........................................................................ 5 

2.1.3 Monoepoxides .................................................................................... 5 

2.1.4 Liquid Elastomers ............................................................................. 5 

2.1.5 Dixnethacrylates ................................................................................. 6 

2.1.6 Dual Functional Monomer (DFM) .................................................. 6 

2.2 Resin Specifications for Producing B-Staged IPN Resins.. ....................... . 

2.2.1 Composition of ARL1015 ................................................................. 6 

2.2.2 Branching Coefficient of B-Stage Resin, aB ................................. .7 

2.2.3 Rubber Fraction, w m bb ~ ...................................................................... 7 

2.2.4 Matrix Composition, p ...................................................................... 7 

2.2.5 Monoepoxide Composition, y .......................................................... 7 

2.2.6 Dimethacrylate Composition, 6 ....................................................... 7 

2.3 Resin Formulation .......................................................................................... 8 

2.3.1 Stoichiometric Balance ...................................................................... 8 

2.3.2 Branching Coefficient ...................................................................... 

.8 

2.3.4 Rubber Fraction ................................................................................. 9 

2.3.5 Matrix Composition .......................................................................... 9 

2.3.6 Monoepoxide Composition ............................................................. 9 

2.3.7 Dimethacrylate Composition ........................................................... 9 

2.3.8 Mass Balance ...................................................................................... 9 

2.4 Discussion ...................................................................................................... 10 

V 
3. Statistical Analysis of Network Development 11 

3.1 Branching Coefficient ................................................................................. .12 

3.2 Molecules Containing PACM Units ......................................................... .13 

3.3 Molecules Containing ATBN Units .......................................................... .14 

3.4 Linear Structural Units ............................................................................... .14 

3.5 Branched Molecules.. .................................................................................. .17 

3.6 Implications.. ................................................................................................ .18 

4. Phase Equilibria 18 

4.1 Calculation of Solubility Parameters ........................................................ .18 

4.2 Free Energy of Mixing.. .............................................................................. .20 

4.3 Experimental Results .................................................................................. .22 

5. Effect of Radiation Exposure on Rubber Properties 23 

6. Summary of Results, Conclusions, and Recommendations 25 

7. References 29 

Distribution List 31 

Report Documentation Page 45 
List of Figures 

Figure 1. Methods of achieving interpenetrating polymer networks in 

one- and two-step cure cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Figure 2. Map of possible formulations for wi = 0.3 and p = 0.5 for 

different values of R (legend). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Figure 3. Tan 6 as a function of temperature for cured epoxy resins 

containing differing amounts of nitrile rubber before exposure to 

e-beam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 

Figure 4. Tan 6 as a function of temperature for cured epoxy resins 

containing 10% &rile rubber before and after exposure to e-beam. . . . . . . . . . . . . . . . 24 

Figure 5. Tan 6 as a function of temperature for cured epoxy resins 

containing 15 % nitrile rubber before and after exposure to e-beam. . . . . . . . . . . . . . . . 25 

vii 
. . . 

Vlll 
List of Tables 

Table 1. Calculated solubility parameters of components before and after 

epoxy/amine reactions occur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

Table 2. Binary interaction parameters, d(cm-3), between components 

before and after epoxy/ amine reaction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

Table 3. Binary interaction parameters, i (cm-s), between components 

after epoxy/amine reaction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..-..-..-.....-....... 20 

Table 4. Binary interaction parameters, B (cm-s), between components 

after epoxy/amine reaction for a typical formulation (R = 1, a = 0.3) at 

20 “C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

ix 

1. Introduction 

The desire to move polymer composite manufacturing from traditional autoclave 

processing towards non-autoclave techniques has spawned interest in several 

non-thermal curing methods for thermosetting polymer systems. Recently, 

several curing methods have received wide attention and have shown promise as 

alternatives to thermal curing systems used presently. Specifically, rapid cure of 

cationic or free radical structural resins by electron-beam (e-beam) radiation has 

been identified as a breakthrough technology that may significantly reduce the 

costs associated with advanced composite materials. In theory, the cost 

reductions are derived from decreased capital investments on autoclave 

equipment and increased yields from reduced cure cycles. However, these 

arguments necessarily assume that the performance of the composites cured 

using e-beam irradiation will be equivalent to or better than their thermally 

cured counterparts. To date, the resin dominated composite properties and the 

properties of e-beamed adhesive joints do not meet the specified target values of 

the thermally cured baseline materials. 

The poor performance of the e-beamed materials has been attributed to a number 

of effects. Poor resin properties and questionable resin-reinforcement adhesion 

have been identified as probable causes for substandard mechanical properties. 

Most notably, the resins that have been developed to date have been very brittle. 

Consequently, major efforts have been directed at improving the toughness of 

cationic epoxy-based electron beam resins. The goals of these programs have 

been to meet the performance standards obtained using thermally cured 

aerospace-grade-toughened epoxy prepreg materials. While some progress has 

been made through these efforts, it is clear that a good balance between 

toughness, modulus, and service temperature has not been achieved. 

To date, this research has focused on the use of cationic resins. Various 

approaches have been used to toughen cationic resins with moderate success. 

Unfortunately, many of the methods that are available to toughen thermally 

cured epoxies are not possible with cationic e-beam systems. The types of twophase morphologies associated with toughened epoxies are difficult to achieve 

with these e-beam systems. Furthermore, the possibility and methods of chain 

extension of cationic epoxies are not well understood. Therefore, the synergistic 

effects of second phase toughening and chain extension in the host matrix cannot 

be capitalized in the e-beam systems. Flexibilizers have been used effectively to 

toughen these systems. Not surprisingly, this approach results in unacceptable 

decreases in glass transition temperatures and ultimate service temperatures. 

Efforts to toughen these resins continue and hopefully suitable resins will be 

developed. 

1 
The specific work described previously has summarily dismissed the use of free 

radical curing systems for composite applications due to bad experiences with 

excessive shrinkage, poor modulus retention, and brittleness. Yet, concurrent 

with the cationic toughening research, new innovative approaches have solved 

many of the problems previously associated with free radical curing e-beam 

resins. The use of sequential interpenetrating networks (S-IPNs) has 

substantially improved the properties of free radical systems. Previous 

researchers have used the S-IPN method to produce resins with low shrinkage, 

high toughness, and good translation to composite properties [1, 21. This 

approach is not a wholly e-beam curing method, but rather a thermal-radiation 

dual cure hybrid solution that may prove useful in many applications. 

The S-IPN approach has been reported elsewhere and will only be reviewed 

here. Figure 1 shows the S-IPN cure mechanisms schematically. Essentially, the 

resin consists of several components that are selected to provide a balance of 

processing ease with good end-use properties. After initial mixing of the 

components, the resins are first cured at slightly elevated temperatures (around 

60 “C). During this stage, the thermally curing monomers will react to form a 

highly branched (or gelled) copolymer that is swelled by the unreacted 

dimethacrylates. Typical chemistries used in the condensation step include 

epoxy-amine and isocyanate-polyol (polyurethane) systems. The condensation 

reaction proceeds to completion and remains relatively stable until further 

reacted by exposure to radiation. 

Monomers 

, Simultaneous Interpenetrating 

Polymer Network (SIN) 

Network A 

+ 

Network B + initia 

E-BEAM 

Room Temp. 

\ 

Network 

or Thermal + jn:Gn+r 

P....^ 

Network B 

Sequential 

Interpenetrating 

Polymer Network 

(S-IPN) 

B-stage or C-Stage 

Figure 1. Methods of achieving interpenetrating polymer networks in one- and two-step 

cure cycles. 

2 
If the thermal curing reaction completes prior to the critical conversion for 

gelation, the material is commonly referred to as a “B-staged” resin. At this 

point, the resin will be a highly viscous liquid. Physically, this material is ‘a 

mixture of a highly branched polydisperse polymer and unreacted free radical 

monomers. It can be produced by either controlling the degree of branching by 

appropriate selection of starting monomers or by freezing the reaction prior to 

gelation. Beyond the gel point, the material is referred to as the “c-stage,” which 

is a gelled network that is swollen by the unreacted free radical monomers. The 

nature of this network will greatly control the structure and properties of the 

final e-beamed material and permits great flexibility to influence processibility 

and final performance. 

After the thermal reaction has completed, the resin is irradiated by an electron 

beam source. (Alternatively, ultraviolet radiation could be used for this 

purpose.) This radiation “post-bake” fully cures the free radical portion of the 

S-IPN to form the final structure. The properties of the fully cured SIPN are 

determined by controlling the structure of the monomer building blocks. 

Materials ranging from compliant elastomeric networks to high glass transition 

temperature (Ts - 180 “C) resins can be produced. Also, importantly, the ability 

to control the molecular weight distribution during the condensation stage of the 

polymerization permits the use of traditional secondary phase toughening, 

which results in superior composite and adhesive properties. 

The purpose of this report is to document the materials’ design strategies that 

permit careful control of the network structure. Due to the complicated nature of 

these resins, a linear system of equations has been derived to describe the 

composition and stoichiometry of the S-IPN resins. Furthermore, this approach 

will be used to determine optimum compositions for phase separation of 

elastomeric or thermoplastic tougheners: This materials-by-design approach was 

absolutely necessary to achieve the chemistry and microstructure that provided 

the required performance levels for adhesive and composite applications. 

In this work we will focus on S-IPNs comprised of a thermally cured epoxyamine network and a combination of two different free radical monomers. In 

some cases, a reactive elastomer will be incorporated into the system to provide 

enhanced toughness. In general, the S-IPN resins will have five or more 

components including mono- and diepoxide monomers, diamine curing agents, 

reactive polymeric rubber, and dimethacrylate monomers. If reactive rubber 

tougheners are used, it is desired that the rubber phase separates from the other 

components during the initial epoxy-amine cure. These rubber particles are 

known to significantly improve the fracture toughness of epoxy resins without 

severely reducing the service temperature of the base resin [3]. Upon electron 

beam irradiation, an interconnected, interpenetrating network of epoxy and 

dimethacrylate units is created. After the resins are fully cured, they are hard 

solids, and no further change in the morphology of the rubber particles is 

3 
possible. This is an essential feature of second phase-toughened thermosets. 

Rubber that remains dissolved in the host matrix will not effectively toughen the 

resin and will also have a deleterious effect on Ts. 

The objectives of this work are to (1) develop a procedure for determining the 

proper amounts of each component to be added to the resin, (2) predict the 

conditions which will result in phase separation of the rubber, and (3) investigate 

the coalescence of rubber particles in the B-stage resin over time. 

A procedure was developed to determine appropriate resin formulations as a 

function of several input parameters such as desired rubber weight fraction and 

dimethacrylate composition. The time-dependent coalescence of rubber particles 

will depend on the mobility of the rubber molecules. Their mobility will be 

severely affected by the degree to which they are connected to the copolymer 

and the average molecular weight of the copolymer. Predictions of connectivity 

and molecular weight are derived by use of a statistical analysis of the copolymer 

during cure but prior to gelation. A thermodynamic analysis was carried out to 

investigate the conditions that will lead to phase separation of the B-stage resin. 

Also briefly presented are results of the effect of electron beam exposure on the 

properties of the rubber and results of an oxidation study of nickel particles. 

2. Design of Network Structure 

The desired attributes of the resin will determine the appropriate formulation 

(i.e., the weight fractions of the components). A major advantage of these SIPN 

structures is the ability to tailor the properties of the network structure to achieve 

desirable properties in the final product. These include rubber fraction, 

epoxy/amine stoichiometric balance, branching coefficient the resin after thermal 

cure, branching coefficient after complete cure, the fraction of epoxy-amine 

versus free radical species, and relative fractions of the different dimethacrylates. 

The use of at least two dimethacrylates (one aromatic and one aliphatic) allows 

for better control of the viscosity of the resin. An added advantage of the S-IPN 

approach is that the two networks can be linked to one another by using a 

multifunctional monomer that acts as a coupling agent between the thermal 

curing and radiation curing networks. It is believed that this coupling is partially 

responsible for the reduction in cure shrinkage and improved mechanical 

properties of the SIPN compared to traditional free radical systems. 

The S-IPN systems that are described here are very complicated and comprised 

of many different components. Traditional formulation of thermoset resins is 

usually limited to a few components and optimized empirically or using very 

simplistic design rules. For example, in amine cured epoxies, the stoichiometry 

is usually balanced between the epoxies and amines that are used in a given 
formulation. In the materials described here, this simple constraint must be 

balanced to accommodate coupling monomers, non-reactive diluents, rubber 

modifiers, and controlled branching coefficients. The control and balance of 

these features will ultimately control the toughness, modulus, and service 

temperature of these resins. Therefore a more elegant network design approach 

must be used to assist in the formulation of these resins. 

The design of the network structure is a formulation procedure based on the fact 

that n conditions must be specified in order to determine the weight fractions of 

n components. These conditions will ensure that the desired attributes are 

attained. The resins of interest and the procedure for determining their 

formulations will now be explained. This procedure specifically applies to a 

resin containing the types of components listed in the next section for both 

B-staged one-part resins and gelled (C-staged) resin types. It is hoped that this 

methodology will be presented in such a way that it could easily be modified to 

apply to similar resins containing any components of interest. Limitations and 

assumptions of this model will be presented next. 

2.1 Materials 

2.1.1 Diepoxides 

The primary diepoxide that has been employed is a diglycidyl ether of bisphenol 

A (DGEBA) supplied by Shell as Epon 828. This will be referred to as 828. 

M = 390 g/mol. Additionally, higher molecular weight DGEBA resins are used 

in instances to impart greater flexibility and to chain extend the epoxy network 

when necessary. These will be identified as they are used. 

2.1.2 Amine Curing Agent 

The curing agent is bis(p-aminocyclohexyl)methane supplied by Air Products as 

PACM-20. This will be referred to as PACM. M = 210 g/mol. 

2.1.3 Monoepoxides 

These monomers have only one functional group and are used to control branch 

structure in the B-stage resin. Specifically, phenyl glycidyl ether @GE), supplied 

by Shell as HELOXY 63 Modifier, was used to prevent gelation of the one-part 

extended shelf-life resin formulations. M = 150 g/mol. 

2.1.4 Liquid Elastomers 

Several different rubbers were used in this study. Primarily end-functionalized 

butyl nitrile rubbers were used. These materials are random copolymers of 

butadiene and acrylonitrile containing typically 18% acrylonitrile by mole with 

reactive chain terminators. The types of end-group functionality that were 

examined here included epoxy and amine groups. The epoxy-terminated 
materials (ETBN) were generally provided as a mixture of the rubber and 

DGEBA and were obtained from Shell Chemicals. Amine-terminated butyl 

nitrile (ATBN) rubber was supplied by B. F. Goodrich as Hycar 1300. It has a 

number average molecular weight of 3900 and is difunctional. 

2.1.5 Dimethacrylates 

Two dimethacrylates are used. One is fully methacrylated diglycidyl ether of 

bisphenol A supplied by Sartomer (CN 151) and referred to as bisGMA. The 

other is 1,6 hexanediol dimethacrylate supplied by Sartomer (SR 239) and 

referred to as HDDMA. Differing amounts of these can be used to control the 

viscosity of the B-stage resin. MHDDMA = 254 g/mol; Mbiscm= 552 g/mol. 

2.1.6 Dual Functional Monomer (DFM) 

This is a DGEBA molecule in which one epoxide group has reacted with 

methacrylic acid and therefore is a monoepoxide. The unreacted epoxide group 

on the DFM is free to react with an amine during the formation of the S-IPN, 

while the methacrylated end is capable of reacting with other methacrylates 

during irradiation. During synthesis, if the mole ratio of methacrylic acid to 

DGEBA, R, is less than two, there will be three different products of this reaction. 

Some DGEBA will partially react producing one the DFM unreacted epoxide 

group and one methacrylate group. A statistical-portion DGEBA will not 

participate in the reaction and keep two unreacted epoxy groups. Consequently, 

some DGEBA will become fully methacrylated. (If Epon 828 is used as the 

DGEBA, this product is identical to the bisGMA dimethacrylate supplied by 

Sartomer.) The mixture of these products is designated ARL1015. The mole 

fractions of Epon 828, DFM, and bisGMA in the ARL1015 are given, respectively, 

by (l-R/2)2, R(l-R/2), and (R/2)2. If Epon 828 is used, the MDFM = 466 g/mol. 

2.2 Resin Specifications for Producing B-Staged IPN Resins 

In order to determine the appropriate mixing proportions of the starting 

materials, the following parameters must be specified: 

2.2.1 Composition of ARL1015 

As stated above, the molar fractions are determined by R, the initial mole ratio of 

methacrylic acid to diepoxide used in the production of ARL1015 14, 51. The 

weight fractions for the diepoxide, dimethacrylate, and difunctional monomer 

(X DE, xDE, xDE), respectively, are calculated as follows. 

6 
x,,=o-R/2)‘~ 

DFM 

xDM =(Rl2yz 

DFM 

xDFM= R(l-R/2) z=R(l-R/2). 

DFM 

2.2.2 Branching Coefficient of B-Stage Resin, a, 

In order to prevent the B-stage resin from gelling, a, must be lower than 

1 /(l - f ), where f is the functionality of the curing agent. PACM is 

tetrafunctional, so a, must be specified to be below l/3. This can be done in 

two ways. First, it can be done by stopping the reaction prior to the critical 

conversion for gelation. Alternatively, active hydrogens on the amine curing 

agent can be end-capped with monofunctional epoxies so that only l/3 of the 

active groups react with an difunctional epoxy. Upon conversion completion, all 

amine hydrogens will have reacted without gelation, creating a viscous highly 

branched copolymer mixed with the methacrylates. In this work we will use the 

second method since it will produce a more highly stable B-staged product. 

2.2.3 Rubber Fraction, zurubber 

This is the desired overall weight fraction of rubber in the resin. 

2.2.4 Matrix Composition, j? 

This is defined as the epoxide network weight (excluding DFM) divided by total 

weight (excluding DFM and rubber). 

B= 

WPACM + ws2* + XDEWlols +WPCE 

wPACM + w828 + wPGE + wbisGMA + wHDDMA + c1 - xDFM )wlOIS ’ 

2.2.5 Monoepoxide Composition, y 

This is defined as the weight of PGE divided by weight of both monoepoxides 

(PGE and DFM). 

Y = 

WPGE 

. 

wPGE + xDFMwlOIS 

2.2.6 Dimethacrylate Composition, S 

This is defined as the weight of bisGMA divided by weight of both 

dimethacrylates (bisGMA and HDDMA). 
6= wbisGUA +xDMw1015 

wbisGMA + xDMwlOIS + wHDDMA . 

2.3 Resin Formulation 

For the one-part B-staged resins studied here, seven ingredients 

will comprise the mixture. These seven required weight fractions 

(W828~WPACM~WAlBN~W,015~WPGE~WbisGMA~WHDDMA) are determined bY the 

simultaneous solution of seven equations which are based on stoichiometric and 

mass balances and the previous specifications. 

The actual weight fractions of Epon 828 and bisGMA present in the resin will be 

larger than the computed values of wgz8 and wbticMA because these species are 

also present in ARL1015. 

2.3.1 Stoichiometric Balance 

For these resins, an exact stoichiometric balance of amines and epoxides is 

desired. Each PACM is capable of reacting with four epoxides and each ATBN 

with two. Therefore the following equation must be satisfied: 

wPACM WATBN w828 

--- 

XDEWlOl5 xDFMw1015 _ wpGE =o, 

E&‘ACM + E&TBN E&28 EWDE - E%FM EW,,, 

(1) 

where EW;. is the equivalent weight of i and is equal to the molecular weight of 

i divided by the functionality of i . 

2.3.2 Branching Coefficient 

The branching coefficient a, of the epoxy copolymer in the B-stage resin is a 

nonlinear function of the weight fractions. From section 3.1, it is known that 

UZ~ = p828pPAcM /(l - p828pAmN). This equation is nonlinear in the weight fractions 

and can be written as 

aB 

wPACM WATBN 

EWPACM + E wATBN 1 

wS28 + XDEW1015 wPACM 

- =o. 

EW,28 EW,CM 

If PATBN is small (it is typically around 0.05 for these resins), then ppAcM is close 

to 1 and a, is approximately equal to a; = p828. This leads to the following 

linear equation: 

wPACM WATBN 1 W828 + XDEWlOl5 

EW,, + EWA,, -2 EF2* 

) 0. 

= 

(2) 
2.3.4 Rubber Fraction 

Specification of the overall rubber weight fraction requires that 

WATBN = Wrubberm (3) 

2.3.5 Matrix Composition 

This specification is rewritten as 

t1 - PjwPACM + c1 - fl>(w828 + xDEw,O,,)+ c1 - PlwPGE 

-P(wbisGMA + xDMwlOIS)- pwHDDMA = ’ * 

2.3.6 Monoepoxide Composition 

This specification is rewritten as 

(1 - YhPGE - Y xDFMw1015 - 

-0. 

2.3.7 Dimethacrylate Composition 

This specification is rewritten as 

c1 -6)(wb,GM4 +xDMw101S)-~wHDDM4 =‘- 

2.3.8 Mass Balance 

All the weight fraction must sum to one. 

(4) 

(5) 

(6) 

wPACM + wAlTiN + w828 + wlOl5 + wPGE + wbirGM4 + wHDDMA = ’ * (7) 

Equations 1-7 can be written in matrix form. 

I \ 

w828 

wPACM 

wAIBN 

A< wlols ‘= 

0 

0 

W rubber 

0 

0 

0 

1 

(8) 

where 

9 
A= 

-1 1 1 XDE xDFM -1 

-- -- - 

E&28 EW,,CM E6TBN EW,, EW,,, E&, 

0 0 

-1 1 1 -XDE 

"EK28 

0 00 

EK%CM -emv apEW,, 

0 0 1 0 0 00 

1-p 1-p 0 0-Pb~i5-b~~ l-P -P -P 

0 0 0 -PDFM l-y 0 0 

0 0 0 t1 - exD.b4 0 1-s -6 

1 1 1 1 1 1 1 

*a) 

The weight fractions of the starting materials that satisfy the specifications lis :ed 

previously are found by solving equation 8. 

Using this procedure, it is not possible to specify a, exactly because of the use of 

equation 2. After computation of the weight fractions, the real value of aB 

should be computed (see section 3.1) to ensure that it is less than l/3 and close to 

the desired value. If this value is unacceptable, a new value of a; should be 

specified and aB checked again. 

2.4 Discussion 

Because both Epon 828 and bisGMA are always present in ARL1015, some 

formulations are not possible. As stated previously, the mole fractions of Epon 

828, DFM, and bisGMA in the ARL1015 are given, respectively, by (l-R/2)2, 

R(l-R/2), and (R/2)2, where R is the molar ratio at which methacrylic acid and 

Epon 828 are mixed in the production of ARL1015. The presence of the 

difunctional Epon 828 in ARL1015 is undesirable because the ratio of diepoxides 

to monoepoxides must be kept low to avoid gelation of the B-stage resin. If the 

molar ratio of Epon 828 to DFM in ARL1015 is too large, PGE must be added to 

the resin to prevent gelation. This is undesirable because PGE will not react with 

the methacrylate network during final curing and the properties of the resin will 

suffer. If R = 1, the molar ratio of Epon 828 to DFM in ARL1015 is l/2. 

For larger values of R, this ratio decreases, but the fraction of bisGMA increases. 

The possible formulations which can be made with aB = 0.3 and p = 0.5 are 

shown in Figure 2. This figure shows combinations of the weight fraction of PGE 

in the resin and 6 which are possible when using ARL1015 made with different 

values of R. Recall that 6 is the fraction of the dimethacrylates that are bisGMA. 

10 
0.8 

6 0.6 

0.4 

0.2 

0.0 

. 

0.00 0.05 0.10 0.15 0.20 

weight fraction PGE 

0.25 

- 1.0 

. . . . 1.1 

-- 1.2 

- .- 1.3 

- 1.4 

- - 1.5 

-- 1.6 

- 1.7 

. . . . 1.8 

-- 1.9 

Figure 2. Map of possible formulations for aB = 0.3 and p = 0.5 for different values of R 

Oe$Fd)- 

For low values of R (<1.5), some amount of PGE must always be added to the 

resin to ensure that ar, = 0.3. For larger values of R (e.g., R 2 1.5), PGE does not 

need to be added, but the minimum value of 6 will be greater than 0.5. This will 

limit the extent to which the viscosity of the B-stage resin can be controlled. 

Therefore, a compromise between minimum PGE and bisGMA contents in these 

resins must be made. 

3. Statistical Analysis of Network Development 

The mobility or diffusivity of the rubber in the B-stage resin will determine the 

extent to which rubber particles can form via phase separation and the rate at 

which these particles can coalesce with time. The diffusivity of the rubber is very 

dependent on the size and structure of the molecules of which it is a part. The 

extent to which the rubber is connected to the epoxy copolymer will also affect 

the extent to which epoxy units are incorporated into the rubber particles and the 

adhesion between the rubber particles and the matrix. 

Consider the copolymer obtained by complete reaction of PACM, Epon 828, 

DFM, PGE, and ATBN. Recall that PACM is a tetrafunctional amine, ATBN is a 

difunctional amine, Epon 828 is a difunctional epoxide, and PGE and DFM are 

monofunctional epoxides. 

11 
Define Ps28~ PDFMJ and PPGE as the fraction of epoxides which belong to Epon 

828, PGE, and DFM, respectively. These are 

2x2, wDFM 

428 M 

pm = 2w,,, 

DFM 

wDFM 

PDFM = zw 

I 828 ! wDFM I wPGE 

j%28 ’ MDFM ’ MPGE 

wPGE 

M PGE 

ppGE = 2w828 ! wDFM ! wPGE ’ 

428 ’ MDFM ’ MPGE 

where wi and Mi are the weight fraction and molecular weight of component i . 

After all epoxides and amines have reacted, these fractions will equal the 

probability that an amine hydrogen chosen at random has reacted with these 

species. 

Similarly, define ppAcM and pAmN as the fraction of amine hydrogen atoms, 

which belong to PACM and ATBN, respectively. These are 

4WPACM 2WA,N 

M PACM 

PPACM = 4WPA, + 2WATBN and PAEIN= 4wp 

MA 

AC M +fTWA, * 

M PACM M A7BN M PACM M ATBN 

3.1 Branching Coefficient 

The branching coefficient aB of the copolymer is defined as the probability that 

any functional unit on a multifunctional monomer (f > 2 ) is connected via a 

chain of difunciional units to another multifunctional monomer [6]. The only 

multifunctional monomer is this case is PACM (f = 4 ). 

Each amine functional unit can be connected to one of the following three 

structural units. 

(1) A pendant chain containing i 828 units, i ATBN units, and 1 PGE unit 

-[828 - ATBNli - PGE . 

(2) A pendant chain containing i 828 units, i ATBN units, and 1 DFM unit 

-[828 - ATBN], - DFM. 

(3) A linkage chain containing i+ 1 828 units and i ATBN units that are 

connected to a PACM unit 

-[828 - ATBNli - 828 - PACM. 

12 
The probability p1 that an amine functional unit is connected to (1) is 

P*(Q= 6s26PMBN)IPPGE~ 

Similarly, 

Pm= 6828PAnJPLmi 

Pm = b3*8PmGvYP*28PE4C. 

The probability that an amine functional unit is connected to 1 with any value of 

i equals 

i=O 

Similarly, 

As a check, it can easily be shown that 4 + p2 + p3 = 1. Since p3 is the probability 

that an amine functional group is connected to a multifunctional PACM unit, it is 

also equal to the branching coefficient, a,. 

3.2 Molecules Containing PACM Units 

Any molecule containing a PACM unit must be considered a branched 

copolymer molecule. The properties of the copolymer will depend on the 

fraction of pendant and linkage chains that contain the flexible ATBN units. The 

fraction of these pendant and linkage chains that contain at least n ATBN units 

is given by 

gP,+gP&Ps 

i=n i=n i=n 

f p, f Tp, +f+p3 = (P8PaK 

i=O i=O i=O 

where 

m 

c Pi =p". 

i=n 1-P 

13 
For a typical resin formulation, ps18 = 0.3 and pAmN = 0.05. Therefore, the 

fraction of pendant and linkage chains that contain at least one ATBN unit is 

0.015, and the fraction of chains that contain at least two ATBN units is 

2.25 x lOa. 

3.3 Molecules Containing ATBN Units 

There are two types of molecules that may contain ATBN units: branched and 

linear. The linear molecules must not contain any PACM units. Since ATBN also 

has an amine functionality, the probability that an ATBN functional group is 

connected via a linkage chain to a PACM unit is equal to a,. The probability 

that both ends of an ATBN unit are not connected to a PACM (i.e., it is part of a 

linear molecule) is equal to (1 - aB)2, and the probability that an ATBN unit is 

connected to a PACM (i.e., it is part of a branched molecule) is 1 - (1 - aB)2 . 

For a typical value of cx (0.3), 51% of the ATBN units are connected to a PACM 

(i.e., a branched copolymer) and 49% of the ATBN units are part of a linear chain. 

3.4 Linear Structural Units 

After full epoxy reaction, there will be three types of linear structures: 

l links between two PACM units, 

l pendant chains connected to one PACM unit, and 

l linear chains not connected to PACM (must contain at least one ATBN 

unit). 

Because each of these must contain an epoxy, the distribution of these three types 

of chains can be determined as follows: pick an epoxy group at random and 

determine the probability that it belongs one of the three types listed previously. 

If a diepoxide (828) is found, all three types are possible. They are 

(1) A linkage chain containing an 828 reacted with i ATBN, i 828, and one 

PACM on one side and j ATBN, j 828, and 1 PACM on the other side; 

PACM - [828 - ATBNli - 828 - [ATBN - 828& - PACM . 

(2) A pendant chain containing an 828 reacted with i ATBN, i 828, and one 

PACM on one side and j-t 1 ATBN, j 828 units, and one end cap unit 

(PGE or DFM) on the other side; 

PACM - [828 - ATBN], - 828 - [ATBN -82$ - ATBN - cfv . 

(3) A linear chain containing an 828 reacted with i + 1 ATBN, i 828, and one 

end cap unit on one side and j + 1 ATBN, j 828, and one end cap unit on 

the other side; 

14 
cfv - ATBN - [828 - ATBN], - 828 - [ATBN - 82s1, - ATBN - CAP. 

If an end cap is found, only two types are possible. They are 

(4) A pendant chain containing an end cap reacted with i ATBN, i 828, and 

one PACM; 

CAP - [ATBN - 8281, - PACM . 

(5) A linear chain containing an end cap reacted with i + 1 ATBN, i 828, and 

another end cap; 

CAP - [AT’IV- 8281, - ATBN - CAP. 

The probability of finding an 828 when selecting an epoxy unit at random is 

n 

’ = n 828 *** ’ 

828 + %AP 

where ns2* is the number of difunctional828 molecules and nw is the number 

of end caps (i.e., monofunctional epoxides). In terms of ps2* and ys2* = 

P828 

2 - p828 ’ 

the probability of finding a monofunctional epoxide when selecting an epoxy 

unit at random is ycAp = 1 -ys2*. 

The probability of finding an 828 unit as part of structure (4) (connected to i 

ATBN/828 units and a PACM on one side and j ATBN/828 tits and a PACM 

on the other side) in Y828bAmNP828)i (1 - PAmN)(pRmNP828 r’<l -PA,) or 

p&k!) =y828(‘- h!?N)2(PATBNP828)i+j’ 

Similarly, the probabilities of finding sizuctures 5-8 when selecting an epoxy unit 

at random are 

PS &j) = 2Y828(1 - h&d1 - P828 kATBN @ATBNP828 y+’ 

. p6 kj) = Y828c1 - P828 )*PiTBN @A?d828 )‘+’ 

P, ci) = &A,(’ - h23,&4~~P828)i 

P8@ = YCAJ’PATBN (l- P828 ) (PM’BiV~828 Ii. 

The factor of 2 in the p2 expression is needed because the (2) structure can have 

the end cap on either end and both possibilities must be considered. The 

probability of finding an 828 unit as part of structure (4) with any value of i or j 

is 

15 
;=o;=o i=O j=O 

_ Y828 (1 - PATBN)2 . 

- (I- PAmvP828 )' 

Similarly, the probabilities of finding structures 5-8 with value of i or j when 

selecting an epoxy unit at random are 

p2 = JP F,p,(i,j) =2Ydl - P, )(l - Ps)P, 

i=O j=O (1 - P,Pd2 

p3 = 2 Tp,(i, j) = y~~~pp$;” 

i=O j=O 

p4 = gp,(i) = t1 ;RFiiOY 

i=o 

P, = pps(j)= (l-Y*)(lsP0Ip, . 

i=o l-POPS 

It can be shown that these sum to one. Typical numbers for these fractions 

(assuming ps2* = 0.3 and pAmN = 0.05 ) are 

p4 =0.164, p5 = 0.012, p6 =2.22E-4, 

p7 = 0.794, and p, = 0.029. 

The fraction of linear structures that are links between PACM is given by 

Gnk = 4. The fraction of linear structures that are PACM pendants are 

P penailnt = P5 + P,. The fraction of linear structures that are not connected to 

PACM (linear molecules) are $,,,, = P6 + Pg. Typical values for these are 

eink = 0.164, Ppendnnr = 0.806, and ciinear = 0.029. 

It is also possible to calculate the average values of i + j and i for each of the 

three structural types. For the linkages, the average number of ATBN/828 pairs 

is 

16 
For the typical values stated previously, the average value of i + j for this 

linkage chains is 4.03. Structure 7 describes all possible pendant chains. 

Therefore, for the pendants, the average number of ATbN/828 pairs is 

For the typical values stated previously, the average value of i in the pendant 

chains is 4.015. 

Structure 8 describes all possible linear molecules. Therefore, for the linear 

molecules, the average number of ATbN/828 pairs is 

i=O i=O 

For the typical values stated above, the average value of i is 4.015, and the 

average number of ATBN units in the linear molecules is ~1.015. Therefore, most 

of the linear molecules contain just one ATJ3N unit and two monofunctional 

units (PGE or DFM). 

3.5 Branched Molecules 

Now that the length and rubber content of linkage and pendant chains are 

known, the molecular weight distribution of the branched copolymer can be 

predicted. The size distribution below the gel point for self condensing f 

functional units has been derived by Flory [6]. The fact that the PACM molecules 

in the resins of interest here are connected by linear structures will not affect the 

distribution of the number of PACM units linked together. 

The number fraction of all copolymers molecules that contain x PACM units is 

&p-y1 -a)**+* (3x)! 

n, = 

l-2a, (2X + 2)! x! - 

Using this expression, it can be found [3] that the number and weight average 

number of PACM units per molecule is 

1 z=-- 

l-2ar 

and 

l+a x,?--- 

l-3a * 

17 
l+ar x,=- 

l-3cr:. 

It should be noted that these results are limited to aB c 1 / 3 (pre-gelation). These 

results indicate that the weight average molecular weight (and the viscosity) will 

approach infinity when a, approaches l/3. It can easily be determined that 

each xmer must contain 2x + 2 pendant chains and x - 1 linkage chains. When 

a, = 0.3, the weight average number of PACM units per molecule is 13. A 

molecule this size will contain 28 pendant chains and 12 linkage chains and have 

a molecular weight of about 19,000 g/mol. 

3.6 Implications 

It is predicted that for typical resin formulations, approximately 1.5% of pendant 

and linkage chains in the copolymer will contain ATBN rubber units. 

Approximately half of the ATBN units will be incorporated into the copolymer, 

while the other half will exist as a part of linear chains, most of which (>98%) will 

contain just one ATBN unit and two end caps (DFM or PGE). These rubber units 

will have a much higher mobility than the ATBN units that are incorporated into 

the copolymer chains, which on average contain 18 PACM units, 28 pendants, 

and 17 links. 

4. Phase Equilibria 

Butyl nitrile rubber is added to these resins to increase their toughness. It is well 

known that the presence of small, dispersed, rubber domains can greatly 

improve the toughness of brittle polymers. However, when all of the 

components are initially mixed, they are completely miscible with each other. 

The rubber will begin to phase separate into dispersed particles only after the 

epoxy/amine reaction has occurred to some extent. As this reaction progresses, 

the molecular weight of the epoxy copolymer increases [7, 81. This increase in 

molecular weight decreases the entropy of mixing and favors phase separation of 

the rubber. 

Phase separation in epoxy/rubber systems has been studied previously and 

predictions of the time evolution of particle formation have been made [7, 91. 

However, the present resins will behave differently due to the presence of the 

difunctional monomer and the dimethacrylates. This section documents efforts 

to predict conditions under which the resins will phase separate. 

4.1 Calculation of Solubility Parameters 

In order to predict whether phase separation will occur, it is necessary to know 

the solubility parameters for the components. These were calculated for each 

18 
component before and after epoxy/amine reaction using a group contribution 

method using the procedures and data of van Krevelen [lo]. 

The solubility parameter, 6, has units of J”2 /cm3’2. Table 1 provides the 

solubility parameters of the components before and after epoxy/amine reactions 

occur. Note that the solubility parameters of neither dimethacrylate (bisGMA 

and HDDMA) change because they do not react at this stage. 

Table 1. Calculated solubility parameters of components before and after epoxy/amine 

reactions occur. 

Component 

EDon 828 

6 (Jl/2/cm3/2) 

Before Reacting After Reacting 

18.15 20.62 

PACM 18.69 18.01 

ATBN 16.75 16.75 

DFM 19.46 20.46 

PGE 19.74 23.00 

BisGMA 20.33 20.33 

HDDMA 18.85 18.85 

Binary interaction parameters, dj, between components i and j were 

calculated using 

xl, = (dj: -+I2 

‘I RT ’ 

where Ji is the solubility parameter of component i , R is the gas constant, and 

T is the absolute temperature. 

Since the phase behavior of these resins is most important at room temperature, 

2’ values before and after reaction are shown in Tables 2 and 3 at 20 “C. In 

general, larger positive values of x’ will favor phase separation. 

Table 2. Binary interaction parameters, d(cm-31, between components before and after 

epoxy/amine reaction. 

Component Epon 828 PACM ATBN DFM PGE BisGMA HDDMA 

Epon 828 1.75 e-3 1.18 e-2 1.03 e-2 1.52 e-2 2.86 e-2 2.95 e-3 

PACM 1.75 e-3 2.26 e-2 3.57 e-3 6.63 e-3 1.62 e-2 1.54 e4 

ATBN 1.18 e-2 2.26 e-2 4.42 e-2 5.38 e-2 7.71 e-2 2.65 e-2 

DFM 1.03 e-2 3.57 e-3 4.42 e-2 4.71 e-4 4.55 e-3 2.24 e-3 

PGE 1.52 e-2 6.63 e-3 5.38 e-2 4.71 e-4 2.09 e-3 4.76 e-3 

1 BisGMA 1 2.86 e-2 1 1.62 e-2 1 7.71 e-2 1 4.55 e-3 1 2.09 e-3 I I 1.32 e-2 I 

HDDMA 1 2.95 e-3 1 1.54 e-4 1 2.65 e-2 1 2.24 e-3 1 4.76 e-3 1 1.32 e-2 I I 

19 
Table 3. Binary interaction parameters, ;1/ (cm-3), between components after 

epoxy/amine reaction. 

Component Epon828 PACM ATBN DFM PGE BisGMA HDDMA 

Epon 828 4.12 e-2 9.02 e-2 1.60 e4 3.40 e-2 5.16 e-4 1.89 em2 

PACM 1 4.12 e-2 1 9.47e-3 3.62 e-2 1.50 e-1 3.25 e-2 4.29 e3 

ATBN 1 9.02 e-2 ) 9.47 e-3 8.28 e-2 2.35 e-1 7.71 e-2 2.65 e-2 

DFM ( 1.60e-4 1 3.62e-2 1 8.28e-2 1 ) 3.88e-i , ., 1.02e-4 -.--- , 1.56 -.-- e-2 _ , 

PGE 3.40 e-2 1.50 e-l 2.35 e-1 3.88 e-2 4.29 e-2 1.04 e-l 

BisGMA 5.16 e-4 3.25 e-2 7.71 e-2 1.02 e4 4.29 e-2 1.32 e-2 

HDDMA 1.89 e-2 4.29 e-3 2.65 e-2 1.56 e-2 1.04 e-1 1.32 e-2 

4.2 Free Energy of Mixing 

The Flory-Huggins theory [ll] will be used to predict the phase equilibria of 

these resins. The free energy change per unit volume of the solution, AG:, 

associated with mixing N components to form a single phase is given by 

AG; = AH”, - TAS; I 

where AH: is the enthalpy of mixing per unit volume of the solution and AS: is 

the entropy of mixing per unit volume of the solution. According to the FloryHuggins theory, these are given by 

AH; = RTk 2 &I++~ 

i=l j=i+l 

and 

where R is the gas constant, T is absolute temperature, 4,. is the volume fraction 

of component i, v,is the molar volume of component i, and x,i is the binary 

interaction parameter defined previously. ASi is always negative, and this 

favors mixing (hinders phase separation). AIYL is usually positive, and this 

favors phase separation. The free energy of mixing per unit volume of the 

solution is then 

This equation will give the free energy change upon mixing of N components 

into a single phase. For the current resins of interest, this will apply only for the 

20 
initial mixture of components before the amine and epoxy groups beg-in to react. 

After the epoxy and amine reactions have occurred, a different approach is 

needed. After the epoxy/amine reaction, the resin will consist of only three 

components. These are bisGMA, HDDMA, and a random copolymer consisting 

of Epon 828, PACM, PGE, DFM, and ATBN units. The ATBN units ,are much 

longer than the others and are long enough to allow them to phase separate from 

the others. Therefore, the resins should be treated as though they are composed 

of four components-bisGMA, HDDMA, ATBN, and a random copolymer 

consisting of Epon 828, PACM, PGE, and DFM units. 

Binary interaction parameters must now be determined between these four 

components to predict the phase separation behavior of the B-stage resins. When 

one or more of the components in a mixture are copolymers, the interaction 

parameter is usually designated B . The binary interaction parameters between 

the three pure components (bisGMA, HDDMA, ATBN) are just equal to the x’ 

values after reaction for those pairs. 

In general, the binary interaction parameter between two copolymers I and J is 

calculated as follows. Assume that I is comprised of n, different units and J is 

made up of n, different units. Number the different units in I from 1 to n,, 

and number the different units in J from n, +l through n, + nj . The 

interaction parameter BY between I and J is 

k=l I=k+l k=n,+l I=k+l 

where & are the pure component binary interaction parameters and 4; is the 

volume fraction of unit k in component I. If n, = n, = 1 (i.e., both components are 

pure), then BY just equals & as stated above. 

There is only one copolymer in the B-stage resin, so the case where n, > 1 and 

n, = 1 is of interest. For this case, the QIkJ terms are zero because J is a pure 

component and 

k=l k=l I=k+l 

where i is the copolymer and j is one of the other components. This equation 

can now be used to calculate the interaction parameters between the copolymer 

and each of the other three components (bisGMA, HDDMA, and ATBN). These 

parameters are functions of the composition of the copolymer and will depend 

on the exact formulation of the resin. Values of the B parameters at 20 “C for a 

typical formulation (R = 1, a = 0.3) are shown in Table 4. 

21 
Table 4. Binary interaction parameters, B (cm-s), between components after epoxy/amine 

reaction for a typical formulation (R = 1, a = 0.3) at 20 “C. 

Component 

Copolymer 

ATBN 

BisGMA 

HDDMA 

Copolymer 

5.82 e-3 

1.42 e-5 

1.10 e-3 

ATBN 

5.82 e-3 

7.71 e-2 

2.65 e-2 

BisGMA 

1.42 e-5 

7.71 e-2 

1.32 e-2 

HDDMA 

1.10 e-3 

2.65 e-2 

1.32 e-2 

The free energy of mixing of the B-stage resin can now be written as 

with N (the total number of components) equal to 4. This expression can be 

used to generate a phase diagram that can be used to predict the conditions 

(compositions and temperatures), which will lead to phase separation. 

The molecular weight of the copolymer affects AG: through its molar volume 

that is proportional to molecular weight. As the molecular weight (and molar 

volume) of the copolymer increases as the epoxy/amine reactions occur, the 

$ll$!5 t erm for the copolymer decreases and may cause phase separation to 

i 

occur. However, the presence of the dimethacrylates (which do not react at this 

stage) will not allow the entropy of mixing to approach zero because their molar 

volumes remain constant and relatively small. HDDMA has a smaller molar 

vohnne (259 cm3/mol) than bisGMA (480 cma/mol). Therefore, resins with 

larger amounts of dimethacrylates and larger HDDMA/bisGMA ratios will be 

less likely to phase separate. This effect has been observed experimentally. 

4.3 Experimental Results 

Resins with two different values of 6 (0.4 and 0.63) but identical values of CL 

(0.33), p (0.37), and y (0.2) were each prepared with 10% and 15% ATBN rubber. 

These were mixed at room temperature for 10 n-tin, cured at 60 “C for 12 hr, and 

degassed at 60 “C in a vacuum oven. Recall that 6 is the ratio of the weight of 

bisGMA to the combined weight of bisGMA and HDDMA. In each case, the 

resins with 6 = 0.63 were cloudy (almost opaque) in appearance after the 

epoxy/amine reaction was complete. The cloudy appearance is most likely due 

to light scattering by phase separated rubber particles and is a strong indication 

that phase separation has occurred. Both resins with 6 = 0.4, however, were not 

cloudy and appeared transparent. Although transparency is not a definitive 

indication that phase separation did not occur, it indicates the possibility that it 

did not occur. Several resins were prepared without ARL1015 or PGE. These 

contained PACM, Epon 828, bisGMA, HDDMA, and between 5% and 15 % ATBN 

22 
rubber. Of these resins, all of those with p < 0.45 appeared cloudy, while those 

with p > 0.45 were transparent. Recall that B is the ratio of epoxide units to 

dimethacrylate units. These observations support the prediction that increases in 

dimethacrylate content and in the HDDMA/bisGMA ratio decrease the tendency 

of these resins to phase separate. 

Another interesting observation was noticed for the resins mentioned previously 

with 6 = 0.4. After curing and cooling to room temperature, these resins were 

transparent. However, when heated to 70 “C they became cloudy. When 

subsequently cooled, the cloudiness disappeared (i.e., the change was reversible). 

This observation is an indication that these resins may have a lower critical 

solution temperature, and phase separation may occur as the resins are heated. 

This phase behavior cannot be predicted by the Flory-Huggins theory. It should 

be studied further because it could be used to induce formation of rubber 

particles before the resin is finally cured by exposure to an electron beam. 

5. Bffect of Radiation Exposure on Rubber Properties 

The impact of electron beam exposure on the properties of nitriIe rubber was 

investigated using dynamic mechanical analysis (DMA). .Experiments were 

carried out using a TA Instruments DMA 2980. Samples approximately 20 mm 

long were loaded in the single cantilever configuration with an amplitude of 

20 pm at a frequency of 0.1 Hz. Storage and loss moduli were recorded from 

-120” to 20 “C with a heating rate of 1 OC/min. 

Simple formulations consisting only of Epon 828, PACM, and ATBN were used. 

These were mixed in stoichiometric ratios (two epoxides for each amine) and 

rubber fraction varied from 0% to 15%. These resins were cured at 60 “C for 

12 hr. DMA was performed on these resins before and after exposure to an 

electron beam. The exposure was identical to the exposure used in the final 

curing of the one-part resins. The loss factor (tan 6) data for these resins are 

shown in Figures 2-5. The data for the unexposed resins is shown in Figure 3. 

The 0% rubber sample exhibits a maximum in tan 6 at -57.3. 

This peak can be attributed to the epoxy j3 relaxation [7j. The data for 10% and 

15% rubber show shoulders near this temperature, and these can also be 

attributed to the epoxy p relaxation. These also show maxima at higher 

temperatures (-37.2 “C for 10% and -36.1 “C for 15%), which indicate the 

position of the glass transition temperature (Ts) of the nitrile rubber. Figures 3 

and 4 show tan F vs. temperature for the 10% and 15% rubber resins before and 

after exposure to the electron beam. After exposure, Ts of the rubber drops by 

23 
0.08 

0.06 to 

5 0.04 

0.02 

0.00 

-120 -80 

Temperature (W) 

Figure 3. Tan 6 as a function of temperature for cured epoxy resins containing differing 

amounts of nitrile rubber before exposure to e-beam. 

0.06 1 

a 

5 0.04 - 

0.02 - 

- before 

-120 -80 -40' 0 40 

Temperature (OC) 

Figure 4. Tan 6 as a function of temperature for cured epoxy resins containing 10% nitrile 

rubber before and after exposure to e-beam. 

24 
0.08 1 I 

0.06 - /-A 

I : ; ._ - before 

:’ . . . after 

,........ _ ..: 

I 

0.00 ’ 4 

-120 -80 -40 0 40 

Temperature (OC) 

Figure 5. Tan 6 as a function of temperature for cured epoxy resins containing 15% nitrile 

rubber before and after exposure to e-beam. 

1 “C in the 10% resin and 2.4 “C in the 15% resin. It was feared that exposure to 

the electron beam might cause the rubber to crosslink to a greater extent. This 

would adversely affect the ability of the rubber to toughen these resins. 

However, the small increases in Ts of the rubber after exposure indicates that 

little crosslinking is occurring, and the ability of the rubber to toughen these 

resins should not be affected. 

6. Summary of Results, Conclusions, and Recommendations 

Several issues related to the development of a radiation-curable rubbertoughened epoxy resin have been addressed. These issues are related to the 

properties of the B-stage resin (i.e., after epoxy/amine reaction but before final 

curing by exposure to an electron beam.) The components of these resins were 

described, and a procedure was developed to determine the exact weight 

fractions of each component that must be mixed together to achieve desired 

branching coefficient and composition. Compositional variables include weight 

ratio of the two dimethacrylates, weight ratio of the two monoepoxides, and 

weight ratio of epoxides to dimethacrylates. Due to the nature of the production 

of one of the monoepoxides (the dual functional monomer), some formulations 

are not possible. More specifically, it is not possible to prepare these resins 

without either PGE or bisGMA. Using the developed procedure, a map of 

possible formulations was generated. This map shows the combinations of PGE 

and bisGMA content that are allowed and those that are not. A resin with a 

25 
larger amount of PGE may have less bisGMA, while a resin with a lower amount 

of PGE must have more bisGMA. The addition of PGE will degrade the 

properties of the fully cured resin, while a minimum amount of bisGMA will 

limit the extent to which the viscosity of the B-stage resin can be controlled. 

Therefore, a compromise between reduced control of B-stage viscosity and final 

properties must be made. Procedures can be developed for similar resins with 

only slight modifications to the existing procedure. 

A statistical analysis of the branched copolymer was performed to provide 

predictions for branching coefficient, copolymer molecular weight, and rubber 

connectivity for the B-stage resin. The copolymer consists of PACM units, which 

are each connected to four linear structures. These linear structures can be links 

between two PACM units or pendant chains, which are only connected to one 

PACM unit. It was predicted that for typical resin formulations, approximately 

1.5% of pendant and linkage chains in the copolymer would contain ATBN 

rubber units. It was also predicted that approximately half of the ATBN units 

would be incorporated into the copolymer, while the other half would exist as 

parts of linear chains, most of which (>98%) contain just one ATBN unit and two 

end caps (DFM or PGE). These rubber units will have a much higher mobility 

than the ATBN units that are incorporated into the copolymer chains, which on 

average contain 18 PACM units, 28 pendants, and 17 links. The presence of these 

linear ATBN-containing molecules may cause the rate at which rubber particles 

coalesce to be unacceptably large. If the latter proves true, the use of an epoxide 

functional rubber would force all of the rubber to be connected to PACM units 

and hence to the branched copolymer. The coalescence rate of the rubber 

particles should be studied for these resins as functions of the branching 

coefficient and the HDDMA/bisGMA ratio. A decrease in the 

HDDMA/bisGMA ratio would result in an increase in the viscosity of the 

B-stage resin since bisGMA is more viscous that HDDMA. This would also 

reduce the coalescence rate. Coalesce rates for these resins can be measured 

using time-resolved laser light scattering or microscopy [12,13]. 

The thermodynamics of phase separation of these resins was addressed. A 

procedure for determining the free energy of mixing, AGL , of the initial mixture 

of components and the B-stage resin was described. This information can be 

used to generate a phase diagram for these resins that will predict the conditions 

(branching coefficient, temperature, resin composition) under which phase 

separation will occur. This is important because the mechanical properties of the 

fully cured resin will depend on the extent to which the ATBN rubber phase 

separates from the other components. Experimental results and preliminary 

predictions indicate that decreases in either the total dimethacrylate content or 

the HDDMA/bisGMA ratio lead to an increased tendency towards phase 

separation of the rubber. It is recommended that modeling and experimental 

determination of the phase behavior of these resin be studied further. 

26 
Generation of the phase diagram will allow the compositions of the matrix and 

particulate phases to be predicted as Afunctions of dimethacrylate content, 

branching coefficient, and temperature. Some of these resins appeared to exhibit 

a lower critical solution temperature. That is, phase separation appeared to 

occur when the temperature was raised approximately 50 “C above ambient and 

disappear when cooled back to ambient temperature. B-stage resins that exhibit 

this type of behavior may have practical applications. Since they exist as a single 

phase at ambient temperature, the problem of coalescence is avoided while being 

stored at ambient temperature. The resins could then be heated immediately 

before the final curing step to achieve the desired phase separation. 

27 
28 
7. References 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

Baidak, A. A., J. M. Liegeois, and L. H. Sperling. “Simultaneous 

Interpenetrating Polymer Networks Based on Epoxy-Acrylate 

Combinations.” Journal of Polymer Science Polymer Physics, vol. 35, p. 1973, 

1997. 

Goodman, D. L., and G. R. Palmese. “Method for Making Fiber Reinforced 

Composites and Coatings.” U.S. Patent No. 5,891,292,1999. 

Riew, C. K., and A. J. Kinloch (editors). ToughenecI PZasfics I: Science and 

Engineering. Washington, DC: American Chemical Society, 1993. 

Doyle, T. E., F. Fekete, P. J. Kennan, and W. J. Plant. “Combination Catalyst 

Inhibitor for B-Hydroxy Carboxylic Esters.” U.S. Patent No. 3,317,465,1967. 

Dalal, U. P. “The Formation of In Situ Sequential Interpenetrating Polymer 

Networks Via Thermal and Radiative Curing.” Master’s thesis, University of 

Delaware, 1999. 

Flory, P. J. Principles of PoZymer Chemistry. Ithaca, NY: Cornell University 

Press, 1953. 

Verchere, D., J.-P. Pascault, H. Sautereau, S. M. Moschiar, C. C. Riccardi, and 

R. J. J. Williams. “Rubber-Modified Epoxies. II. Influence of the Cure 

Schedule and Rubber Concentration on the Generated Morphology.” JoumaZ 

of Applied Polymer Science, vol. 42, p. 701,199l. 

Huang, Y., D. L. Hun&on, A. J. Kinloch, and C. K. Riew. “Mechanisms of 

Toughening Therrnoset Resins.” Toughened Pikstics I: Science and Engineering, 

edited by C. K. Riew and A. J. Kinloch, American Chemical Society, 

Washington, DC, 1993. 

Verchere, D., H. Sautereau, J.-P. Pascault, S. M. Moschiar, C. C. Riccardi, and 

R. J. J. Williams. “Rubber-Modified Epoxies. I. Influence of CarboxylTerminated Butadiene-Acrylonitrile Random Copolymers (CTBN) on the 

Polymerization and Phase Separation Processes.” JoumaI of Applied Polymer 

Science, vol. 41, no. 3, p. 467,199O. 

van Krevelen, D. W. Properfies of Polymers. 3rd Ed., Amsterdam: Elsevier 

Science Publishers, 1990. 

11. Strobl, G. The Physics of PoZynzers. Berlin Springer-Verlag, 1996. 

12. Rusu, D., and E. Peuvrel-Disdier. “In Situ Characterization by Small Angle 

Light Scattering of the Shear-Induced Coalescence Mechanisms in Immiscible 

Polymer Blends.” JoumaZ of Rheology, vol. 43, no. 6, p. 1391,1999. 

29 
13. Fortelny, I., A. Zivny, and J. Juza. “Coarsening of the Phase Structure in 

Immiscible Polymer Blends. Coalescence or Ostwald Ripening?” @maZ of 

Polymer Science. Part B, Polymer Physics, vol. 37, no. 3, p. 181,1999. 

30 
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AT URBANA CHAMPAIGN 

J ECONOMY 

1304 WEST GREEN ST 115B 

URBANA IL 61801 

2 DREXEL UNIV 

ASDWANG 

G PALMESE 

32ND & CHESTNUT ST 

PHILADELPHIA PA 19104 

5 UNIV OF TENN 

AT KNOXVILLE 

KKlT 

434 DOUGHERTY ENGRG BLDG 

KNOXVILLE TN 379962200 

2 BOEING 

M WILENSKI 

J BURGESS 

PO BOX 3999 MC73 09 

SEATTLE WA 981242499 

NO. OF 

COPIES ORGANIZATION 

1 E BEAM SERVICES INC 

M STERN 

32 MELRICH RD 

CRANBURY NJ 08512 

2 UCB CHEMICALS CORF 

M JOHNSON 

S WILLIAMSON 

2000 LAKE PARK DR 

SMYRNA GA 30080 

1 APPLIED POLERAMIC INC 

R MOULTON 

850 TEAL DR 

BENICIA CA 94510-1249 

2 SCIENCE RESEARCH LAB 

C BYRNE 

15 WARD ST 

SOMERVILLE MA 02143 

3 HYDROGEOLOGIC INC 

SERDP/ESTCP SUPPORT OFC 

S WALSH 

1155 HERNDON PKWY 

SUITE 900 

HERNDON VA 20170 

1 LOCKHEED MARTIN 

TACTICAL AIRCRAFT SYS 

I’ KIRN 

1 LOCKHEED BLVD 

PO BOX 748 MS 2852 

FORT WORTH TX 76101-0748 

2 MICHIGAN STATE UNIVERSITY 

COMPOSITES CTR 

L DRZAL 

B DEFOORT 

2100 ENGINEERING BLDG 

EAST LANSING MI 488241226 

1 ADHERENT TECHNOLOGIES INC 

A HOYT 

11208 COCI-BTI ST 

ALBUQUERQUE NM 87123 

2 ORNL 

R DABESTANI MS 6100 

I IVANOV MS 6100 

PO BOX 2008 BLDG 4500S 

OAK RIDGE TN 37831 

40 
NO. OF 

COPIES ORGANIZATION 

1 ORNL 

CJANKEMS8048 

PO BOX 2008 BLDG 4500s 

OAK RIDGE TN 37831 

ABERDEEN PROVING GROUND 

1 DIRECTOR 

USAMSAA 

P DIETZ 

392 HOPKINS RD 

AMXSYTD 

APG MD 21005-5071 

1 DIRECTOR 

US ARMY RESEARCH LAB 

AMSRL OP AP L 

APG MD 21005-5066 

87 DIRUSARL 

AMSRL CI 

AMSRL CI S 

AMARK 

AMSRL CS IO FI 

M ADAMSON 

AMSRL SL BA 

AMSRL SL BL 

D BELY 

R HENRY 

AMSRL SL BG 

AMSRL SL I 

AMSRL WM 

J SMITH 

AMSRL WM B 

A HORST 

AMSRLWMBA 

D LYON 

AMSRL WM BC 

J NEWILL 

P PLosTINs 

SWILKERSON 

A ZIELINSKI 

AMSRL WM BD 

R FIFER 

B FORCH 

R PESCE RODRIGUEZ 

BRICE 

AMSRL WM BE 

C LEVERITT 

AMSRL WM BF 

J LACETERA 

NO. OF 

COPIES ORGANIZATION 

ABERDEEN PROVING GROUND (CONT) 

AMSRL WM BR 

J BORNSTEIN 

C SHOEMAKER 

AMSRL WM M 

G HAGNAUER 

J MCCAULEY 

DVIECHNICKI 

AMSRL WM MA 

L GHIORSE 

S MCKNIGHT 

AMSRL WM MB 

J BENDER 

T BOGETTI 

R BOSSOLI 

L BURTON 

P DEHMER 

R DOOLEY 

W DRYSDALE 

BFINK 

G GAZONAS 

S GHIORSE 

D GRANVILLE 

D HENRY 

DHOPKINS 

C HOPPEL 

R KASTE 

M KLUSEWITZ 

M LEADORE 

R LIEB 

E RIGAS 

JSm 

D SPAGNUOLO 

W SPURGEON 

J TZENG 

E WETZEL 

AMSRL WM MB ALC 

A FRYDMAN 

AMRSLWMMC 

J BEATI’Y 

ECHIN 

J LASALVIA 

J MONTGOMERY 

J WELLS 

A WERECZCAK 

AMSRL WM MD 

W ROY 

S WALSH 

AMSRL WM T 

B BURNS 

M ZOLTOSKI 

41 
NO. OF 

COPIES ORGANIZATION 

ABERDEEN PROVING GROUND (CONT) 

AMSRL WM TA 

W BRUCHEY 

M BURKINS 

W GILLICH 

B GOOCH 

E HORWATH 

T HAVEL 

M NORMANDIA 

J RUNYEON 

AMRSLWMTB 

P BAKER 

D KOOKER 

AMSRL WM TC 

R COATES 

AMSRL WM TD 

M BOTELER 

DDANDEKAR 

A DAS GUI’TA 

F GREGORY 

T HADUCH 

T MOYNIHAN 

M RAFTENBERG 

T WEERASOORIYA 

AMSRL WM TE 

A NIILER 

J POWELL 

AMSRL SS SD 

H WALLACE 

AMSRL SS SE DS 

R ATKINSON 

R REYZER 

42 
NO. OF 

COPIES ORGANIZATION 

1 ACSION INDUSTRIES 

V LOPATA 

PO BOX 429 

PINAWA MB ROE 1LO 

CANADA 

1 NATL RSRCH CNCL CANADA 

A JOHNSTON 

1500 MONTREAL ROAD BLDG M 3 

OTTAWA ON KlA OR6 

CANADA 

1 NATL RSRCH CNCL CANADA 

K COLE 

75 DE MORTAGNE BLVD 

BOUCHERVILLE QUEBEC J4B 6Y4 

CANADA 

43 
44 
REPORT DOCUMENTATION PAGE Form Approved 

OhlB No. 0704-0188 

Kevin M. Kit,* James M. Sands, and Steven H. M&night 

ATINI AMSRL-WM-MB 

Aberdeen Proving Ground, MD 210055069 

------.-I ..--- -.--..---.--a 

Strategic Environmental Research and Development Program Office 

901 North Stuart St. 

Arlington, VA 22203 

._.-. - .___.... _- . - . . .._..... - 

AGENCY REPORT NUMBER 

*University of Tennessee, Department of Materials Science and Engineering, Knoxville, TN 37912-2200 

12a. DlSTRlBUTlON/AVAlLABILlTY STATEMENT 

Approved for public release, distribution is unlimited. 

12b. DISTRIBUTION CODE 

13. ABSTRACTfMaximum 200 words) 

Several issues related to the development of a radiation-curable rubber-toughened epoxy resin are investigated bJ 

performing a statistical analysis of semi-interpenetrating polymer blend formulations. The statistical analysis providec 

predictions for branching coefficient, copolymer molecular weight, and rubber-to-network connectivity for the B-stagec 

interpenetrating networks. These statistical metrics relate to the properties of thermally generated B-stage networks 

prior to secondary network formation using radiation cure methods, such as electron beam or ultraviolet excitation. The 

components of these resins were described, and a procedure was developed to determine the exact weight fractions oj 

each component that must be mixed together to achieve a desired branching coefficient and resin composition. 

Compositional variables include weight ratio of the two dimethacrylates, weight ratio of the two monoepoxides, ant 

weight ratio of epoxides to dimethacrylates. Using the raw materials selected for this study, we determined that manJ 

network structures are not attainable. Specifically, it is not possible to prepare B-stage resins without the use of mono. 

or difunctional units, such as phenyl glycidyl ether (PGE) or methacrylated digicydyl ether of bisphenol A (bisGMA). 

The possible formulations are determined, and a map is proposed showing the combinations of PGE and bisGMA 

content that are allowed for B-stage formation. 

14. SUBJECT TERMS 

radiation cure, JPN, network design, controllable formulation 

15. NUMBER OF PAGES 

50 

16. PRICE CODE 

17. SECURITY CLASSIFICATION 16. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT 

OF REPORT OF THIS PAGE OF ABSTRACT 

UNCLASSIFIBD UNCLASSJFJED UNCLASSIFIED UL 

WeSCribed by ANSI Std. 239-W 298-l 02