bluuebunny/crossref_metadata_2025 huggingface dataset:
Ionomer/ionomer thermoplastic IPNs based on poly(n‐butyl acrylate) and polystyrene
Authors: Nishiyama Y. , Sperling L. H.
Published: April 2003

Thermoplastic interpenetrating polymer networks (IPNs) were prepared by combining poly(n‐butyl acrylate) with polystyrene, both polymers crosslinked independently with acrylic acid anhydride (AAA). Decrosslinking of both polymers was carried out by hydrolysis of the anhydride bonds. Neutralization of the carboxylic acid groups to form the ionomer was carried out in a Brabender Plasticorder. Two subclasses of thermoplastic IPNs were studied: (1) Chemically blended thermoplastic IPNs (CBT IPNs) were prepared by synthesizing polymer II in polymer I in a sequential synthesis; (2) mechanically blended thermoplastic IPNs (MBT IPNs) were prepared by melt blending separately synthesized polymers. Rheovibron characterization revealed that of the two combinations, the CBT IPNs were better mixed than the MBT IPNs. Investigations of phase continuity via melt viscosity and modulus suggest that the CBT IPNs have some degree of dual phase continuity. Transmission electron microscopy suggests dual phase continuity and relatively small phase domains, 2000–5000 Å for the CBT IPNs. The mechanical properties from tensile and Izod impact tests showed that the CBT IPNs were stronger than the MBT IPNs.
Addition polyimides. I. Kinetics of cure reaction and thermal decomposition of bismaleimides
Authors: Ninan K. N. , Krishnan K. , Mathew Jainamma
Published: April 2003

The thermal polymerization of four structurally different bismaleimide resins, prepared by reacting maleic anhydride with four aromatic diamines, viz., 4,4′‐diaminodiphenyl methane, 4,4′‐diamino diphenyl ether, 4,4′‐diamino diphenyl sulfone, and 3,3′‐diamino diphenyl sulfone, was followed by differential scanning calorimetry (DSC). The enthalpy change and the kinetic constants for the polymerization reactions were evaluated from the DSC curves. Thermal stability of the cured polymers was studied by thermogravimetry (TG). The kinetic parameters, viz., activation energy E and preexponential factor A, for the thermal decomposition of the cured bismaleimides were calculated from the TG curves using three nonmechanistic integral equations. The kinetic constants (E and A) follow a trend similar to the thermal stability of the polymers.
Characteristics of polymerization‐filled polyethylenes (“Norplastics”) and compositions on the basis of norplastics
Authors: Enikolopian N. S. , Fridman A. A. , Popov W. L. , Stalnova I. O. , Brikenstein A. A. , Rudakov W. M. , Gherasina N. P. , Tchalykh A. E.
Published: April 2003

The peculiarities of a new type of materials—polymerization‐filled polymers (“Norplastics”)—have been studied. Norplastics were tested as polymer fillers. The structure morphological properties of high‐filled polymer composites (HFPC), prepared both with norplastics as fillers and traditional mineral dispersed fillers, have been examined.
Liquid‐rubber‐modified epoxy adhesives cured with dicyandiamide. II.–Morphology and adhesion strengths
Authors: Lee Yu‐Der , Wang Shi‐Kwun , Chin Wei‐Kuo
Published: April 2003

The lap shear and T‐peel strengths of n‐butylacrylate/acrylic acid (nBA/AA)‐copolymer‐modified DGEBA adhesive were evaluated. Adherends used in this study included carbon‐fiber‐reinforced plastics (CFRP), glass‐fiber‐reinforced plastics (GFRP), and aluminum. It was found that the adhesive strengths could be improved by incorporating nBA/AA copolymer in the DGEBA matrix. An optimum functionality of the copolymer existed for maximum lap shear strength. Morphological studies revealed that the adhesive strength was also influenced by the compastibility between the copolymer and the matrix, the property of the adherend as well as the addition of the bisphenol A.
Annealing effects on the crystallinity of polyetheretherketone (PEEK) and its carbon fiber composite
Authors: Ostberg Gunilla M. K. , Seferis James C.
Published: April 2003

The degree of crystallinity of polyetheretherketone (PEEK) has been measured using both the density gradient technique (DGT) and differential scanning calorimetry (DSC). The difference in results between the methods was shown to depend on crystallization taking place during the heating scan in the DSC. By freezing the sample at different stages of the DSC thermogram and measuring its crystallinity in the density gradient column, the existence of induced crystallization for PEEK was established. Though this induced crystallization is not visible in the DSC thermogram, it must be taken into account when comparing the degree of crystallinity measured by the two methods. The induced crystallization was in turn interpreted as a result of an increase in crystal perfection that is also commonly observed during the initial stages of the annealing process. Accordingly, the effect of annealing on the crystallinity was also investigated. DSC scans on annealed samples exhibited a small endothermic peak at approximately 10°C above the annealing temperature. This peak was observed in both neat PEEK and its carbon fiber‐reinforced composite. Annealed PEEK shows, therefore, two melting transitions, a low one which depends on the annealing temperature and a high one which is independent of annealing temperature conditions. Collectively, the results of this study demonstrate that processing conditions and morphological features must be considered in characterizing semicrystalline‐based matrix polymers for high performance composites.
Phase rearrangement in two‐stage emulsion polymers of butyl acrylate and styrene: Mechanical properties
Authors: O'Connor Kevin M. , Tsaur Sheng‐Liang
Published: April 2003

The mechanical and thermal properties of films from a series of two‐stage emulsion polymers were investigated. The emulsion polymers were made by polymerizng styrene in the presence of a preformed poly(butyl acrylate‐co‐divinyl benzene) seed latex. The effects of seed particle size, seed particle crosslinking via the amount of divinyl benzene, styrene/butyl acrylate ratio, and thermal history on the film properties were studied. Latex particles were characterized by light scattering and film formation behavior. Dried films were characterized by differential scanning calorimetry, dynamic mechanical analysis, and stress‐strain behavior. Although evidence was obtained for nearly complete phase separation between the polystyrene (PS) and poly(butyl acrylate) (PBA) phases, the site of styrene polymerization and thus the PS phase morphology is influenced by seed particle size, seed crosslinking, and S/BA ratio. The morphology of as‐dried films consists of finely dispersed PS domains in a continuous PBA matrix. Thermal annealing above the PS Tg causes coalescence of the PS domains, resulting in significantly improved mechanical properties. The extent of PS phase coalescence is also influenced by the level of seed crosslinking.
Radiation‐induced grafting of N,N‐dimethylacrylamide onto polytetrafluoroethylene
Authors: Razzak Mirzan T. , Otsuhata Kazushige , Tabata Yoneho
Published: April 2003

Grafting of N,N‐dimethylacrylamide (DMAA) onto polytetrafluoroethylene (PTFE) has been carried out by using gamma rays from a 60Co source. Degree of grafting was affected by grafting conditions. Especially, solvent for the grafting was found to be a very significant parameter to obtain a higher grafting yield. When ethylacetate or acetone was used as the solvent, grafting yield greater than 5% was obtainable while the graftcopolymerization scarcely occurred in the presence of other kinds of solvent such as ethanol or water.

Apparent activation energy of the grafting in ethylacetate was calculated to be 7.90 Kcal/mol, and initial grafting rate of it was proportional to 0.55 power of dose rate.
Production and properties of highly oriented polypropylene by die drawing
Authors: Taraiya A. K. , Richardson A. , Ward I. M.
Published: April 2003

A comprehensive examination of the die‐drawing behavior of polypropylene has been carried out, examining the effects of draw temperature, haul‐off speed, and initial billet size. A range of oriented products was obtained and characterized, primarily by the determination of Young's modulus at room temperature, the maximum modulus being 20 GPa for a draw ratio RA of 23.2. Using a large‐scale machine, it was found possible to produce drawn products at speeds up to 2 m min−1 at a draw temperature of 155°C and RA of 19.3. The dynamic mechanical behavior of several drawn materials was studied over the temperature range −30 to +80°C. It was of particular interest that the β relaxation was found to be absent in samples of high draw ratio.
Concentrated polymer solution between plates
Authors: Ronca G.
Published: April 2003

Geometric requirements, avoidance of boundary conditions, and focus on configurational properties have suggested mean field formulation of the many chain problem using discrete single chain Gaussian partition functions. Mean field account of energetic, combinatorial, and configurational contributions to the free energy provides correct reduction in the limit of remote confinement and avoidance of double counting of interactions. Strong influence of surface adsorption on configurational and global properties of spatial distribution is predicted to occur at lower concentrations. The interplate surface tension has been calculated in decoupled conditions (large separation distances between plates). Numerical results predict an approximate power law dependence of the surface tension on the concentration with exponent ∼ 1.3. Perfectly repulsive boundaries and athermal solvent conditions have been assumed for this calculation.
Gas permeation in miscible homopolymer‐copolymer blends: II. Tetramethyl bisphenol‐A polycarbonate and a styrene/acrylonitrile copolymer
Authors: Chiou J. S. , Paul D. R.
Published: April 2003

Gas sorption and transport properties for He, H2, O2, N2, Ar, CH4, and CO2 at 35°C near atmospheric pressure have been obtained for miscible blends of tetramethyl bisphenol‐A polycarbonate (TMPC) and a random copolymer of styrene with acrylonitrile (SAN) containing 9.5% by weight of acrylonitrile. All gas permeability, diffusion, and solubility coefficients obtained are lower than that calculated from the semilogarithmic additivity rule. These results are qualitatively interpreted by ternary solution theory and activated state theory which have been proposed to describe gas sorption and diffusion in miscible blends. The negative deviation of gas permeabilities for the blends from this rule can be explained semiquantitatively by free volume theory which takes volume contraction on mixing into account. The negative deviation increases with gas molecular size which results in larger ideal gas separation factors than that calculated from the additivity rule. For He/CH4 and H2/CH4 pairs, the permselectivities for the blends are higher than that for either pure TMPC or SAN. The deviation from additivity for gas transport properties of TMPC/SAN blends is the opposite of that observed in the first paper of this series for PMMA/SAN blends. This can be attributed to the stronger interactions in TMPC/SAN blends than in PMMA/SAN blends.
The influence of resin characteristics on the high speed melt spinning of isotactic polypropylene. I. Effect of molecular weight and its distribution on structure and mechanical properties of as‐spun filaments
Authors: Lu Fu‐Min , Spruiell Joseph E.
Published: April 2003

The fine structures and tensile mechanical properties were characterized for high speed melt spun filaments prepared from three polypropylenes with melt flow indices in the range 12–300. It was found that spinnability and the resulting structure and properties are affected by both the weight average molecular weight and the polydispersity of the polymer. Higher tenacities, with consequent lower percent elongation to break, could be achieved by spinning the narrow molecular weight distribution polymers at high spinning speeds. This effect was associated with the development of higher birefringence in these samples. Modulus did not correlate with birefringence in the present study, but it was found to be controlled by the nature and level of crystalline order developed in the filaments.
Low pressure CO2 sorption in poly(vinyl cyclohexane‐carboxylate)
Authors: Hirose Takuji , Mizoguchi Keishin , Kamiya Yoshinori
Published: April 2003

A gravimetric method was applied to determine the solubility of CO2 in poly(vinyl cyclohexanecarboxylate) below 1 atm. The temperatures were varied from 5 to 85°C, above and below the glass transition temperature. The sorption isotherms were concave to the pressure axis below Tg and they were tentatively analyzed by the dual‐mode sorption model. Above Tg, the isotherms were linear and described by the Henry's law. Below 75°C, the diffusion coefficients of CO2 were also obtained from the half‐time of the sorption process.
Numerical simulation of coextrusion from a circular die
Authors: Mitsoulis E. , Heng F. L.
Published: April 2003

A numerical simulation of coextrusion flow in a capillary die has been undertaken for polymer melts used in a previously reported experimental study of coextrusion. Viscosity data are used for PS, HDPE, and LDPE melts. A Newton–Raphson scheme is employed to solve the equations for a fully developed pressure‐driven flow of two concentric layers in a capillary. A finite element method is used to simulate the full flow field behavior, including determination of the interface and free surface of the exiting stream. Double nodes have been used at the interface to ensure continuity of velocities and stresses and to capture the pressure discontinuities. Pressure gradients, extrudate swell, interface swell, and other relevent flow characteristics are presented and compared with the experimental findings. The finite element analysis revealed that satisfactory convergence of the interface location is found for the cases when the less viscous material wets the capillary walls, which is also the preferential configuration in coextrusion. For the opposite configuration, convergence proved either difficult or impossible depending upon the viscosity ratio. Discrepancies were found to exist between the theoretically predicted and experimentally measured pressure gradients.
Structure of skin layer in injection‐molded polypropylene
Authors: Fujiyama Mitsuyoshi , Wakino Tetsuo , Kawasaki Youtoku
Published: April 2003

The structure of skin layer in injection‐molded polypropylen which displayed a clear two‐phase structure of skin and core has been studied by means of wide‐angle x‐ray diffraction, small‐angle x‐ray scattering, melting behavior, density, dynamic viscoelasticity, and tensile test. In skin layer, the c‐axis and a*‐axis were highly oriented to the machine direction (MD), and the plane of the lamellar structure of about 160 Å in thickness was in normal to MD. The density was about 0.907 g/cm3, which was nearly the same as that of core layer. Although the majority of crystallites melted in the same temperature range as in that of the core layer, there was about 5.3% higher temperature melting structure (Tm = 182°C). The dynamic tensile modulus E′ in MD decreased more slowly with increasing temperature than that of the core layer and held high modulus in the range of ca. 30°C, just above the temperature at which E′ of the core layer suddenly dropped. E′ in MD was higher than that in TD in the temperature range below 33°C, which was slightly higher than the primary absorption temperature, and the order reversed above 33°C. The tensile yield stress in MD was 1.5 times higher than that of the core layer. The skin layer in MD ruptured just after yielding and did not show necking. The tensile yield stress in TD was about half of that in MD about 0.7 times that of the core layer. The necking stress in TD was about 0.6 times that of the core layer. In general, a polypropylene melt crystallizes under a high shear stress in injection molding. From these facts, it was concluded that the skin layer is composed of so‐called “shishkebab”‐like main skeleton structures, whose axis is parallel to MD, piled epitaxially with a*‐axis‐oriented imperfect lamellar substructure.
Common thermoanalytical characteristics of durable press reactants based on cyclic ureas
Authors: Trask‐Morrell B. J. , Andrews B. A. Kottes
Published: April 2003

Thermal analyses, including differential scanning calorimetry (DSC), thermogravimetry (TG), and differential thermogravimetry (DTG), were performed on a series of derivatives of cyclic ureas under nitrogen. Such compounds are used extensively for durable press finishing of cotton textiles. Three common features were discovered in 15 compounds analyzed. Two features related to the presence of an oxygen‐containing substituent on the ring carbons or the ring nitrogens. The former substitution was expressed as an exothermic response between 200 and 300°C and the latter as an endotherm between 300 and 400°C. Specific substituent modifications that changed these responses are described. A final feature was identified. The presence of N‐methylol groups was recognized. This represented the first evidence that compounds capable of releasing formaldehyde have a thermoanalytical marker. The amount of residue produced in TG analyses was related to structure and indicated that thermally induced polycondensations were occurring.
Electrical conduction of CuxS‐treated films
Authors: Im Sung Soon , Kang Eun Young
Published: April 2003

Electrical conductivity measurements have been made on CuxS‐treated PET and nylon 6 films in the temperature region between 20 and 200°C. CuxS‐treated films have been observed to have two transition temperatures at about 100 and 180°C, respectively. It should be reasonable to consider that the conductivity behavior between 100 and 180°C is attributed to the character of a metastable structure of the cuprous sulfide. Temperature dependence of conductivity of the CuxS‐treated PET and nylon 6 films was investigated and compared with that of original PET and nylon 6 films. The current–voltage characteristics and time dependence of conductivity of samples were investigated. Conduction mechanism of the CuxS‐treated films was not dependent on matrix polymers but dependent on CuxS crystal, and the conduction is mainly electronic.
Polyanhydride microspheres as drug carriers. II. Microencapsulation by solvent removal
Authors: Mathiowitz E. , Saltzman W. M. , Domb A. , Dor Ph. , Langer R.
Published: April 2003

A new method to prepare polyanhydride microspheres, namely via solvent removal, is presented. Polyanhydrides composed of the following diacids were used: sebacic acid (SA), bis(p‐carboxy‐phenoxy) propane (CPP), and dodecanedioic acid (DD). Polymers were characterized by infrared (IR) spectroscopy, X‐ray diffraction, viscosity, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Drug release was affected by polymer composition, physical properties of the microspheres, and type of drug. The potential for injectable microspheres (size range 1–300 μm) made of copolymer (CPP‐SA 50:50), as biodegradable polymer carriers for the controlled release of insulin in treating diabetes mellitus, was assessed. Both 5% and 10% w/w insulin‐loaded microspheres were prepared. The 10% loaded microspheres produced the best clinical response, demonstrating five days of urine glucose control and four days of serum glucose control in diabetic rats.
The microstructure of stabilized fibers
Authors: Ko Tse‐Hao , Ting Hsing‐Yie , Lin Chung‐Hua , Chen Jia‐Chyuan
Published: April 2003

The morphology and microstructure of a stabilized fiber, nonburning fiber, has been investigated under optical and electron microscopes, and a model for the structure of the stabilized fiber is presented. Skin‐core morphology was found in the cross section of the stabilized fiber. The proposed model is consistent with the lamellar‐plate‐like structure, measuring about 400–700 Å in thickness, 500–4000 Å in breadth and 0.1–0.5 μ m in length along the fiber axis, which is composed of microfibrils. The structure has some circumferential distribution in the outer zone, while the inner zone has a radical distribution. Evidence for the lamellar‐plate structure, including two chemical structures and having two different crystalline phases, which are the original AN units and the ladder polymer, were obtained from electron microscopy, wide‐angle X‐ray, and electron diffraction analyses.
Highly sensitive self‐developing soft X‐ray resists of silicon‐containing aldehyde copolymers and sensitive novolac‐based composite resists containing aldehyde copolymer
Authors: Nate Kazuo , Inoue Takashi , Yokono Hitoshi , Hatada Koichi
Published: April 2003

Copolymers of aliphatic aldehydes containing a trimethylsilyl group were prepared at −78°C in toluene using diethylaluminum diphenylamide as an initiator. The copolymer depolymerized into monomeric aldehydes on exposure to soft X‐rays. When the copolymer was used as a soft X‐ray resist, almost complete development was accomplished by exposure alone. No development step was required. The soft X‐ray sensitivity of poly(3‐trimethylsilylpropanal‐co‐propanal) was 50 mJ/cm2 at the film thickness of 1.0 μm. A composite resist system consisting of a novolac resin and an aldehyde copolymer containing trimethylsilyl groups has also been developed and used as an alkaline‐developable positive electron‐beam and soft X‐ray resist.
Rhodium (1) catalyst supported on polyethylene hollow fibers: Preparation and hydrogenation studies
Authors: Butler Jacqueline S. , Gordon Bernard , Harrison Ian R.
Published: April 2003

In recent years polymers have been utilized as binding sites for transition metal catalysts (e.g. crosslinked polystyrene beads). However, general problems exist with the above system. The rate of reaction depends on the presence of solvents that adequately swell the polystyrene bead in order to allow access to the catalyst sites. Differences in polarity and reactant size can inhibit diffusion into the bead. Recently a new system has been developed where the catalyst is bound to polyethylene single crystal surfaces, this has solved the above problems. However, polyethylene single crystals are small and plate‐like causing a new problem, when trying to filter the separate product the crystals cause clogging of the filtering system and limit the reactions to batch process. This paper describes the use of fine microporous polyethylene hollow fibers as the supporting polymer. This gives the advantages of the single crystal support, plus allows for the use of a fixed‐bed flow reaction system.
Laser marking of microporous films
Authors: Kuder James E. , Taskier Henry T. , Hamer E. Geoffrey
Published: April 2003

The potential for microporous films as optical recording media is explored in this report. Irradiation of metallized films of microporous polypropylene and polyethylene with a HeNe laser produced marks having high contrast and which could be read without the aid of polarizing optics. The novel marking process involves melting, collapse of the microporous structure, and thinning of the film as the built‐in strain relaxes.
Modeling of diffusion‐controlled free‐radical polymerization reactions
Authors: Achilias D. , Kiparissides C.
Published: April 2003

The present paper introduces a new fundamental approach to the modeling of diffusion‐controlled free‐radical polymerization reactions. Our analysis follows the original work of Chiu, Carratt, and Soong (CCS), according to which the termination and propagation rate constants are expressed in terms of both a purely reaction‐limited term and a diffusion‐limited one. The contribution of the latter term to the apparent rate constants is described in terms of the polymer and monomer effective diffusion coefficients and an effective reaction radius. It is shown that all parameters appearing in the original CCS model can be calculated from first principles using available data on the physical and transport properties of a particular monomer–polymer binary system. The generalized free volume theory of Vrentas and Duda and the theory of excess chain end mobility are invoked for the calculation of the effective diffusion coefficients and the reaction radius, respectively. The approach followed in this study is general and needs only the specification of one unknown parameter with a clear physical meaning. All other parameters can be readily calculated from available data. The ability of the new model to predict molecular weight developments and monomer conversion in diffusion‐controlled reactions is demonstrated by application of the proposed model equations to the bulk polymerization of MMA.
The effect of steric hindrance on physical properties in an amine‐cured epoxy
Authors: Duffy James V. , Lee Gilbert F.
Published: April 2003

A pair of aliphatic amines were synthesized in order to study the effect steric hindrance has on the physical properties of an amine‐cured epoxy resin. The hindered amine (TMSiDA) has NH2 groups that are obstructed by the presence of adjacent methyl groups while the unhindered amine (SiDA) does not contain any NH2 steric hindrance. DGEBA cured with TMSiDA is less dense, absorbs less moisture, and has a higher Tg than does SiDA/DGEBA. Torsional pendulum results show that TMSiDA/DGEBA has a slightly higher rubbery modulus and a secondary transition at a lower temperature than DGEBA cured with SiDA. Activation energies for the secondary transition were determined for TMSiDA/DGEBA and SiDA/DGEBA and are 19 and 14 kcal/mol, respectively.
Photovoltaic effect based on wet poly(vinyl alcohol)/merocyanine dye junction
Authors: Uehara Kaku , Takagishi Kenji , Tanaka Makoto
Published: April 2003

The sandwich cell, Au/wet poly(vinyl alcohol) (PVA)/merocyanine (MD)/Au, based on the PVA/MD junction exhibited photovoltaic and rectifying effects. Forward dark current from the MD/Au electrode to the counter PVA/Au electrode through the cell was observed. The Au/MD electrode showed a positive photovoltage with respect to the PVA/Au electrode regardless of the direction of the incident light. It was suggested that a heterojunction barrier similar to the Schottky type formed at polymer/dye interface was responsible for the photo charge separation.
Mechanical properties of HDPE/(PEC/PS)/SEBS blends
Authors: Schwarz M. C. , Barlow J. W. , Paul D. R.
Published: April 2003

Various amounts of a styrene‐butadiene‐based triblock copolymer (SEBS) was used to compatibilize immiscible blends of high density polyethylene (HDPE) and an amorphous glassy phase consisting of either pure polystyrene (PS) or a miscible blend of PS and a polyether copolymer (PEC). PEC is structurally similar to poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO). Mechanical properties were determined for blends fabricated by injection and compression molding. The inherently brittle two‐phase HDPE/(PEC/PS) blends show significant increases in ductility and impact strength resulting from addition of SEBS. These improvements coincide with a slight loss in modulus and yield strength. If the amount of HDPE and SEBS is held constant, impact strength and ductility increase with the amount of PEC in the glassy phase. These trends evidently result from the added ductility of glassy phases containing PEC and perhaps from better interfacial adhesion in blends after adding SEBS. The latter stems from the thermodynamic miscibility between PEC and PS endblocks of SEBS which provide an enthalpic driving force for compatibilization. Differences between the properties of compression and injection‐molded blends can be attributed to the degree of crystallinity and orientation induced during molding.
Solvent penetration and photoresist dissolution: A fluorescence quenching and interferometry study
Authors: Limm William , Stanton Deirdre , Dimnik Gerald P. , Winnik Mitchell A. , Smith Barton A.
Published: April 2003

A novel method, based upon fluorescence quenching measurements, is described for the study of the mechanistic details of solvent penetration into thin polymer films. Here poly(methyl methacrylate) (PMMA) labelled with phenanthrene (Phe) groups was coated as a film (0.8 μm thick) onto quartz disks. Diffusion of solvent (1 : 1 2‐butanone/2‐propanol) into the film was followed by a decrease in Phe fluorescence, while film dissolution was monitored simultaneously by laser interferometry. In the case of PMMA (Mw = 411,000, films annealed at 160°C) both processes occur at approximately the same rate and exhibit non‐Fickian (relaxation‐controlled) diffusion behavior. Correlating the results of these two experiments shows that, once the steady state is reached, the dissolution rate is controlled by the advance of the solvent front into the PMMA film. The “transition layer,” an important dissolution parameter, increases its thickness from 50 to 90 nm during the plasticization stage of solvent penetration and maintains its thickness until the solvent front reaches the quartz substrate.
Improved dispersive mixing through reduction in flow field vorticity
Authors: Roland C. M. , Nguyen M.
Published: April 2003

Dispersive mixing is most efficiently accomplished with pure straining flow. Vorticity in the flow field inhibits this extending action; accordingly, the presence of shearing flow will decrease the overall effectiveness of dispersive mixing processes. A method to reduce the vorticity by inducing lubricated flow through development of a nonuniform distribution of the components of a polymer blend is described.
Effect of pressure on the precipitation and sol‐phase aqueous polymerization of methyl methacrylate
Authors: Mohanty Baijayantimala , Palit Sunanda K. , Biswas Mukul
Published: April 2003

Effect of pressure (atmospheric to 120 kg/cm2) on the K2S2O8–Na2S2O4‐initiated aqueous polymerization of methyl methacrylate has been studied at 25°C. When the concentrations of the redox initiator are so adjusted as to obtain the separating polymer phase as a coarse coagulum, the conversion, rate, and molecular weight of polymerization tend to rise initially with increase of pressure up to a certain value and fall subsequently to a limiting value. However, these parameters fall monotonously with an increase in pressure when the polymer phase separates out as a fine colloid at a lower concentration of the initiator. The initial rise in rate is consistent with an increase in kp and or a decrease in kt under high pressure; the ultimate fall in rate may be due to a decrease in the diffusion of monomer from the aqueous phase to the growing polymer radical site. The fall in the molecular weight with pressure is explained on the basis of enhanced monomer transfer. In the colloidal range the pressure dependence trend is related to the stability of the colloidal phase. The rate is proportional to the square root of the product of K2S2O8–Na2S2O4 and varies linearly as the first power of the monomer concentration as also observed under normal pressure conditions. The MWD values of the polymers are ca. 2.5 and do not change with applied pressure.
Thermal and crystallization behavior of engineering polyblends. I. Glass reinforced polyphenylene sulfide with polyethylene terephthalate
Authors: Shingankuli V. L. , Jog J. P. , Nadkarni V. M.
Published: April 2003

The thermal and crystallization behavior of blends of glass fiber reinforced polyphenylene sulfide (PPS) with polyethylene terephthalate (PET) has been reported. The blends showed two overlapping melting peaks and two separate crystallization peaks. The heat of crystallization of PPS was found to decrease continuously with increasing PET content, whereas the heat of crystallization of PET was found to increase with increasing PPS content. This indicates that the degree of crystallinity of PPS is reduced whereas that of PET is increased as a result of blending. It is interesting to note that the combined heats of fusion of the blends were marginally higher than those calculated by proportional additivity rule in spite of the drop in the heat of crystallization of PPS. The temperature onset of crystallization of PET in the blends shifted to higher temperature whereas there was no significant change in the crystallization temperature of PPS. The increase in the temperature of crystallization of PET indicates enhanced nucleation. The isothermal crystallization studies of the component polymers revealed that both the component polymers crystallized at a relatively faster rate in the blend. The crystallization rate of PPS was found to increase significantly with increasing PET content. A significant increase in the rate of crystallization of PET was also observed in the blends. The acceleration of crystallization rate of PET in the blends was more pronounced as compared to that of PPS. The acceleration in the PET crystallization rate was attributed to the presence of glass fibers and crystallized PPS.
Modeling high‐pressure gas–polymer mixtures using the sanchez‐lacombe equation of state
Authors: Kiszka M. B. , Meilchen M. A. , McHugh M. A.
Published: April 2003

The Sanchez‐Lacombe equation of state was used to model the sorption of high‐pressure gases into solid, amorphous polymers and molten polymers. Only one adjustable parameter per binary pair, δ12, was used in the mixing rules to correct the deviation of the characteristic pressure of the mixture, P12*, from the geometric mean. The values of δ12 which gave the best fit of the available literature data for the carbon dioxide–polymethyl methacrylate, carbon dioxide–silicone rubber, ethylene–low density polyethylene, methane–polyisobutylene, methane–low‐density and high‐density polyethylene, and methane–polystyrene systems ranged from −0.019 to 0.136. In all cases, the calculated sorption isotherms were in reasonably good agreement with the experimental data. The resultant swelling of polymethyl methacrylate and silicone rubber was also well represented by the Sanchez‐Lacombe equation of state. Because the Sanchez‐Lacombe theory is based on lattice‐fluid theory, the sorption calculations are limited to polymers which are noncrystalline, not cross‐linked or slightly crosslinked, above their glass transition temperature, or above their melting temperature. The sorption data for the amorphous polymers considered in this study were either at temperatures above the glass transition temperature of the polymer or were at sufficiently high pressures that the temperature was above the effective glass transition temperature as predicted from a theoretical relation presented by Chow.
Engineering plastics from lignin. XV. Polyurethane films from chain‐extended hydroxypropyl lignin
Authors: Kelley Stephen S. , Glasser Wolfgang G. , Ward Thomas C.
Published: April 2003

A series of polyurethane (PU) films was prepared from chain‐extended hydroxypropyl lignins (CEHPL). In appearance, these films ranged from brittle and dark brown to rubbery and bronze. The thermal, mechanical, and network properties of these PUs were investigated by DMTA and DSC analysis. All films exhibited single Tg's which varied between −53° and 101°C, depending on lignin content. From swelling experiments, molecular weight between crosslinks (Mc) was determined and found to vary over 2.5 orders of magnitude. The Mc's were related to the change in Tg that accompanied network formation. Stress–strain experiments showed a variation in Young's modulus between 7 and 1300 MPa. Most of the variation in material properties was related to lignin content and to a lesser extent to diisocyanate type, hexamethylene diisocyanate, or toluene diisocyanate. The source of the CEHPL had no effect on the observed properties. From these results it was concluded that the properties of PUs can be controlled and engineered for a wide variety of practical uses.
Study on rough‐surface biaxially oriented polypropylene film. VII. Roughening by blending low melting point polymers
Authors: Fujiyama Mitsuyoshi , Kawamura Yoshimasa , Wakino Tetsuo , Okamoto Tomomi
Published: April 2003

The roughening of biaxially oriented polypropylene film using polypropylene (PP) blended with low melting point polymers such as polybutene‐1 and high‐density polyethylene as raw resin in a successively stretching tenter method has been studied for the same reasons as has the roughening of BOP utilizing β crystals. Rough‐surface BOPs with a low depth and a high density of roughness were obtained by using the blended PPs as raw resins. By combining this roughening method with the roughening method utilizing the β crystals, rough‐surface BOPs with a crater‐like large roughness and a fine roughness on the ground were obtained. These rough‐surface BOPs showed excellent impregnation properties of insulating oils.
Graft polymerization of acrylamide onto UV‐irradiated films
Authors: Uyama Y. , Ikada Y.
Published: April 2003

Graft polymerization of acrylamide was attempted onto the surface of films preirradiated with UV radiation. The films employed are nylon 6, polypropylene, and ethylene–vinyl acetate copolymers. Following UV irradiation in air on films without photosensitizer, they were placed in monomer solution, degassed, and then heated to 50°C to effect the graft polymerization. After rigorous removal of homopolymers, polyacrylamide chains were found to be grafted in the surface region of the films to amounts up to several hundred micrograms per square centimeter of films. An ESCA study revealed the UV‐irradiated but not yet grafted surfaces to be oxidized, and formation of peroxides was strongly suggested by the reaction of irradiated films with 1,1‐diphenyl‐2‐picrylhydrazyl. It is likely that the initiator responsible for the graft polymerization is peroxides generated at and near the film surfaces upon UV irradiation. The grafted films became very slippery when contacted with water, in contrast with the films UV‐irradiated but not yet grafted.
Adsorption at the solution‐solid interface: Alkyd resin on TiO2 pigment
Authors: Janardhan R. , Gedam P. H. , Kumaran P. S. Sampath , Narasimha R. , Hussain Sajid
Published: April 2003

Gel permeation chromatography results obtained from the adsorption of alkyd from different solutions on anatase TiO2 surfaces are reported, and the influences of the solvent–resin interactions in the adsorption process are discussed, covering the thickness of the adsorbed layer, the type of molecular weight species adsorbed, and its dependence on the concentration of the solution. Resin–pigment interaction was found to be influenced by the type of solvents used.
Persulfate initiated aqueous polymerization of acrylonitrile at 50°C in an inert atmosphere of nitrogen gas
Authors: Sarkar S. , Adhikari M. S. , Banerjee M. , Konar R. S.
Published: April 2003

The rate of aqueous polymerization (Rp) of acrylonitrile (AN) initiated by potassium persulfate at 50°C, is given by:

where (M) stands for monomer concentrations. It has been suggested that persulfate ions in aqueous solution (pH 4 to 7) decompose not only via the well established paths viz.: (A) and (B)

but also via (C) and (D) in the presence of AN monomer:

where (M˙j)w is a water‐soluble monomeric/oligomeric free radical. The separating polymer phase remains in aqueous solution as a stable colloid, or a precipitate, depending on the ionic strength of the medium. At high conversions in general, and even at low conversions at relatively higher monomer concentrations, (1.20 m/dm3), the colloidal latex polymer was found to have a tendency to form gel, and the viscosity of the medium was found to increase with conversions. The distribution coefficient of the monomer between the polymer and the aqueous phases was found to be (0.50 ± 0.10) at 50°C in the presence and absence of electrolytes (K2SO4 7.5 × 10−3 m/dm3). The termination rate constants in the aqueous phase (ktw) and in the polymer phase (ktp) have been estimated as given below:

taking kp of Dainton et al. as 6.22 × 04 (dm3/m/s) at 50°C.
Characterization of some poly(methyl methacrylate)s prepared by emulsifier‐free emulsion polymerization in presence of some organic ligands and their nickel complexes
Authors: Sayyah S. M. , El‐Hamouly S. H. H. , Abd El‐Ghaffar M. A.
Published: April 2003

The aqueous polymerization of methyl methacrylate (MMA) was studied using sodium bisulfite as initiator in absence and presence of tetraoxalyl urea (TOU), tetraoxalyl thiourea (TOthioU) and tetraoxalyl paraphenylene diamine (TOp‐phD). The effect of their nickel complexes on the polymerization rate has also been studied. Ligands with free carboxyl groups have a retarding effect on the polymerization reaction, while their nickel complexes have a catalytic effect. The polymers obtained in presence of nickel complexes were found to have wider molecular weight distribution than those obtained in their absence; this was deduced by thin layer chromatographic analysis in a binary mixture (benzene/methanol). The apparent energy of activation was found to be 5.83 × 104 J/mol, 1.87 × 104 J/mol, 2.11 × 104 J/mol, and 3.95 × 104 J/mol in absence and in presence of 0.5 g of Ni complex of TOp‐phD, TOthioU and TOU, respectively.
Immobilization of poly(ethylene oxide) on poly(ethylene terephthalate) using a plasma polymerization process
Authors: Gombotz W. R. , Guanghui W. , Hoffman A. S.
Published: April 2003

Poly(ethylene oxide) (PEO) has been covalently immobilized on poly(ethylene terephthalate) (PET) films using a radio frequency glow discharge polymer deposition process, followed by chemical coupling. Amino or hydroxyl groups were introduced onto the surface of the PET by exposing the films to allylamine and allyl alcohol plasmas. These functional groups were activated with cyanuric chloride, and then they were reacted with PEO. ESCA and water contact angle studies were used to characterize the surfaces of these films during the different stages of the reaction. The films containing the higher molecular weight PEO exhibited an increase in the CO peak of the Cls ESCA spectrum and an increase in oxygen content on the film surfaces. Increasing the molecular weight of the PEO attached to the PET also resulted in an increased wettability of the films.
Addition polyimides. II. Synthesis and characterization of bisitaconimide prepolymers
Authors: Ninan K. N. , George Rene , Krishnan K. , Rao K. V. C.
Published: April 2003

N,N′‐bis(3,3′‐itaconimidophenyl) sulfone has been synthesized by reacting itaconic anhydride with 3,3′‐diamino diphenyl sulfone. The bisitaconimides and the intermediates were characterized by chemical analysis, IR, NMR, TG, and GPC. The degree of polymerization (DP) of the prepolymers of the bisitaconimide was followed by GPC and from the NMR data on vinylidene and aromatic proton ratios. The correlation between DP and intrinsic viscosity of the prepolymers was made use of to determine the Mark–Houwink constants (K and α). The thermal stability and the decomposition kinetics of the prepolymers were evaluated from TG data. The kinetic parameters, viz. energy of activation, E, and preexponential factor A, were computed using four nonisothermal integral equations, and their values are not appreciably affected by the degree of polymerization, within the range studied.
Suspension polymerization of vinyl chloride. I. Influence of viscosity of suspension medium on resin properties
Authors: Cebollada A. F. , Schmidt M. J. , Farber J. N. , Capiati N. J. , Vallés E. M.
Published: April 2003

The suspension polymerization of vinyl chloride is studied in a bench‐scale reactor adequately reproducing reaction conditions and resin properties of industrial relevance. The evolution of particle morphology is analyzed at different stages of conversion, and a model for particle formation is verified. The influence of viscosity of the suspension medium is analyzed in relation to molecular weight distribution and particle morphology.
Effect of ultraviolet irradiation on the selective transport of alkali metal ions through 2,3‐epithiopropyl methacrylate–methacrylic acid copolymer membrane
Authors: Nonaka Takamasa , Maeda Hirotoshi , Nakayama Morio , Egawa Hiroaki
Published: April 2003

Cationic exchange membranes were prepared with 2,3‐epithiopropyl methacrylate (ETMA)–methacrylic acid (MAc) copolymer. Transport of alkali metal ions against their concentration gradient through the membranes was investigated by using the system which contains HCl (left side) and alkali metal solution including two kinds of alkali hydroxides (right side). The effect of ultraviolet (UV) irradiation on the selective transport of alkali metal ions through the ETMA–MAc copolymer membranes was investigated. The membranes were irradiated with a 6‐W low pressure mercury lamp at a distance of 10 cm at room temperature in air. The transport selectivity could be increased by using UV‐irradiated membranes and the selectivity increased with increasing irradiation time up to 2–3 h, although the transport rate of alkali metal ions decreased with increasing time of UV irradiation. The maximum selectivity of K+/Na+, Na+/Li+, and K+/Li+ were 1.7, 2.0, and 4.2, respectively. In order to explain this phenomena, the effect of UV irradiation on the properties of the membranes was studied. It was concluded that the increase of the selectivity is attributed to the formation of the dense membrane by photocrosslinking of the membrane by UV irradiation.
Characterization of poly(3,3‐bisethoxymethyl oxetane) and poly(3,3‐bisazidomethyl oxetane) and their block copolymers
Authors: Murphy E. A. , Ntozakhe T. , Murphy C. J. , Fay J. J. , Sperling L. H. , Manser G. E.
Published: April 2003

The homopolymers, poly(3,3‐bisethoxymethyl oxetane) (polyBEMO), poly(3,3‐bisazidomethyl oxetane) (polyBAMO), and triblock copolymers based on these homopolymers and a statistical copolymer center block composed of BAMO and 3‐azidomethyl‐3‐methyl oxetane AMMO were synthesized and characterized by differential scanning calorimetry, modulus‐temperature, optical microscopy, membrane osmometry, and solution and melt viscosity. The values of K and a for the Mark‐Houwink equation were found to be 7.29 × 10−3 mL/g and 0.80, respectively, for polyBEMO at 25°C using number‐average molecular weights. Glass transition temperatures were in the range −25 to −40°C and melting temperatures were between 65 and 90°C for all polymers. The melting temperature was found to increase as expected with molecular weight. Melt viscosities of triblock copolymers with polyBAMO end blocks were at least an order of magnitude lower than those with polyBEMO end blocks and clear optically, suggesting that the polyBAMO‐based triblock copolymers formed one phase in the melt, while the polyBEMO‐based triblock materials (milk white) phase separated. The addition of filler raised the melt viscosity to a level between that predicted by the Guth‐Smallwood and the Mooney equations.
Long term oil‐seal embrittlement
Authors: Lawandy S. N. , Wassef M. T.
Published: April 2003

The effect of antioxidant concentration in mineral oil on polychloroprene rubber vulcanizate, based on different types of carbon black, has been studied. This study shows that, with the increase of antioxidant, the percentage volume swelling of the rubber increases, the hardness of the rubber decreases, and the embrittlement time is prolonged. The properties achieved are important for oil seal manufacturers.
Multiple transitions in atactic 1,2‐polybutadienes observed from dynamic mechanical and dielectric relaxation data
Authors: Ni Shaoru , Yu Fusheng , Shen Lianfang , Qian Baogong
Published: April 2003

Detailed investigation by dynamic mechanical, dielectric and 13C‐NMR relaxation spectroscopies over a temperature range from −180 to 100°C reveals the multiple transitions in atactic 1,2‐polybutadienes, which are denoted as T11, α, β, γ, and δ in conformity with reducing temperature. The spectroscopic data obtained show that α transition is the glass transition of the samples, β‐and γ‐relaxations are likely to be related to the flexibility of the main chain and the side chain motion, respectively, and δ loss process seems to be associated with the defects and inhomogeneity in structure. T11 transition observed in the dielectric relaxation spectra may be manifested by the abrupt broadening of the resonance peaks in solid‐state 13C‐NMR spectra.