bluuebunny/crossref_metadata_2025 huggingface dataset:
Rubber‐ and thermoplastic‐toughened epoxy adhesive films
Authors: Romano A. M. , Garbassi F. , Braglia R.
Published: April 2003

Epoxy resins have been toughened using together two components: a liquid rubber (Hycar CTBN 1300 × 13) and a thermoplastic polymer (Phenoxy PKHH). Unsupported adhesive films have been obtained from blends. The effect of different curing cycles on morphology, fracture behavior, and adhesive strength has been studied, monitoring phase separation by dynamic mechanical analysis. The combination of the two moieties was found the most efficient toughening agent when a slow curing cycle was adopted. © 1994 John Wiley & Sons, Inc.
Controlled release of proteins from poly(L‐lactic acid) coated polyisobutylcyanoacrylate microcapsules
Authors: Park Tae Gwan , Alonso Maria J. , Langer Robert
Published: April 2003

Poly(L‐lactic acid)‐coated polyisobutylcyanoacrylate microcapsules containing protein molecules were prepared by a single‐step procedure based on either a double‐emulsion‐solvent evaporation method or a spray‐drying method. First, an aqueous protein solution was emulsified in an organic phase of methylene chloride containing a wall‐forming monomer (isobutylcyanoacrylate), various kinds of poly(L‐lactic acid), and a surfactant. An immediate polymerization process of isobutylcyanoacrylate takes place at the W/O interface upon contact with hydroxide ion in the aqueous phase, leading to the formation of a polyisobutylcyanoacrylate wall around the aqueous droplets. This W/O emulsion was reemulsified in an aqueous solution to promote the solvent removal and, consequently, the precipitation of poly(L‐lactic acid) onto polyisobutylcyanoacrylate microcapsules or was spraydried to directly deposit the poly(L‐lactic acid) on the wall. Three proteins, bovine serum albumin, horseradish peroxidase, and tetanus toxoid, were encapsulated in these poly(L‐lactic acid)‐coated polyisobutylcyanoacrylate microcapsules, and then their release profiles were examinedin vitroas a function of molecular weight of poly(L‐lactic acid) and its copolymers with glycolic acid. These formulations exhibited a low “burst” effect at initial incubation stages and released the proteins for extended periods of time. Subcutaneous injections of the tetanus toxoid‐loaded microparticles into rats showed that the time course of immunization (antibody titer) can be controlled by the type of polymer matrices used. © 1994 John Wiley & Sons, Inc.
Physical, thermomechanical, and rheological properties of bisphenol A–tetrabromobisphenol a copolycarbonates
Authors: Marks M. J. , Brewster S. L. , Sekinger J. K.
Published: April 2003

The physical, thermomechanical, and rheological properties of bisphenol A–tetrabromobisphenol A copolycarbonates (BA–TBBA coPCs) were studied as a function of copolymer composition. TBBA carbonate segments in the copolymer induce proportionally increased glass transition temperatures, heat distortion temperatures, ignition resistance, tensile and flexural moduli, and density. Properties that do not change proportionately with copolymer composition are coefficient of linear thermal expansion, ambient notched Izod and dart puncture impact strengths, and refractive index. Many properties of BA‐TBBA coPCs, including glass transition temperature, heat distortion temperature under load, and modulus, approach those of amorphous high‐performance thermoplastics such as polyetherimide and polyethersulfone. However, these copolymers have the possible advantage of melt blending with bisphenol A polycarbonate to form homogeneous alloys with variable and controllable properties. © 1994 John Wiley & Sons, Inc.
Time‐dependent fracture toughness measure for polyethylene
Authors: Strebel J. J. , Moet A.
Published: April 2003

Because of their extraordinary cracking resistance, medium‐density polyethylenes (MDPEs) do not fail in a brittle manner when tested with conventional fracture toughness procedures, but brittle fractures andJ1cvalues can be obtained for these materials by utilizing fatigue loading. However, because brittle fracture in polyethylene is a result of low stresses (energy) applied over long periods of time, and sinceJ1cneglects time,J1cis incapable of differentiating MDPEs on the basis of their fracture resistance. Thus, the power to fracture method, which incorporates both energy and time, has been developed. During increments of crack growth, the product of the potential energy and the number of elapsed cycles is used to calculate the power to fracture. Within limits that assure a similar failure mechanism, the power to fracture for a particular resin is constant despite varied fatigue conditions. The power to fracture is capable of differentiating between resins on the basis of their brittle cracking resistance. © 1994 John Wiley & Sons, Inc.
Wood‐induced catalytic activation of PF adhesives autopolymerization vs. PF/wood covalent bonding
Authors: Pizzi A. , Mtsweni B. , Parsons W.
Published: April 2003

The reaction of polycondensation of phenol‐formaldehyde (PF) resins in the presence of wood was confirmed to have a lower energy of activation than of the PF resin alone. Under the low temperature and short curing times characteristic of the application of PF resins as thermosetting wood adhesives DSC, TGA, chemical kinetics, and IR of PF resins and relevant model compounds were carried out. These indicated that two effects appear to be present when a PF resin cures on a wood surface, both induced by the polymeric constituents of the substrate, namely carbohydrates and lignin. These appear to be (1) the catalytic activation of the resin self‐condensation induced particularly by carbohydrates such as crystalline and amorphous cellulose and hemicelluloses and (2) the formation of resin/substrate covalent bonding, particularly in the case of lignin. The first appears to be, by far, the major cause of the lowering of the activation energy of PF resins curing. The contribution of the second has been found to be very small and often negligble under the conditions pertaining to thermosetting wood adhesives applications. Molecular mechanics results appear to indicate that the marked catalytic activation of PF resins autocondensation and curing appears to be induced by the strong set of PF adhesive/substrate secondary forces interactions which appear to weaken bonds which, by cleavage, lead to PF resins autocondensation. © 1994 John Wiley & Sons, Inc.
Aspects of surface characterization of polyurethane adhesives
Authors: Ulkem I. , Schreiber H. P.
Published: April 2003

The performances of adhesives is strongly dependent on the contributions to overall surface energies from dispersion and nondispersion forces. In this work, surface energies have been studied for polyurethanes representing the categories of aliphatic and aromatic polyethers and aliphatic polyesters. The surface energies of the polymers were measured by static and dynamic contact angle methods. In addition to determining the energy values for polymers as received, evaluations were also made on the polymers following modification by an aminopropyl silance (APS), present at concentrations ranging from 0.1 to 20 wt %. The dispersion surface energies of the three polymers were roughly equal; however, the nondispersive surface energies strongly differentiated among them. Organic liquids were used for calculations of energy parameters from static contact angles. Data for water failed to follow theoretical expectations and were used instead to compute a work of adhesion parameter for the polymer/water interface. This correlated with nondispersion surface energies of the polyurethanes. Somewhat different values of the nondispersion surface energy were obtained from static and dynamic contact angles, an effect attributed to the tendency of polyurethanes to restructure when their surfaces were in prolonged contact with water during dynamic analysis. This behavior may be important to the type of adhesive bond formed by the polymers and to variations in bond characterstics with time. The use of APS was found to influence both static and dynamic contact angle values, with primary changes occuring in nondispersion contributions. The effects of APS addition were fully developed at concentrations of 1 wt % or less, raising doubts about the efficiency of using this additive at higher concentrations. © 1994 John Wiley & Sons, Inc.
Kinetic study of pyrrole polymerization with iron (III) chloride in water
Authors: Planche M. F. , Thiéblemont J. C. , Mazars N. , Bidan G.
Published: April 2003

The chemical synthesis of polypyrrole in water, with FeCl3 as an oxidant of pyrrole, was investigated. During these experiments in ambient air, a large evaporation of pyrrole was observed. Moreover, a kinetic study of pyrrole disappearance by high‐performance liquid chromatography (HPLC), with various FeCl3 concentrations, proved that the polymerization is first order with respect to the pyrrole and second order with respect to the FeCl3. These kinetics can be explained by the formation of an intermediary FeCl3–pyrrole complex as the first step of the polymerization. The second step, which is rate‐determining, is the pyrrole oxidation by FeCl3, © 1994 John Wiley & Sons, Inc.
Melt viscosity of oligomeric triblock copolymers (type PEP) of ethylene and propylene oxides
Authors: S̆imek L. , Petr̆ik S. , Bohdanecký M.
Published: April 2003

Melt viscosity η at 25°C of four oligomeric triblock copolymers consisting of a central block of ethoxamer units and two end blocks of propoxamer units (PEP) (Mn × 10−3 = 1 and 2; mole fraction of ethoxamer units xE = 0.41, 0.57, and 0.74) was analyzed in terms of the theory advanced by Berry and Fox. The structure‐dependent factor F(X) was deduced from the intrinsic viscosity data, and the mean friction factor per friction center ζ was computed from η and F(X). At a fixed molecular weight, it increases with increasing xE. The dependence of ζ versus xE was compared with curves computed from the data for homopolymers. The best agreement was obtained if the following values of the inherent friction factor (log ζ0) were used: −10.25 for poly(ethylene oxide) PEO and −10.65 for PPO. © 1994 John Wiley & Sons, Inc.
Experimental testing of the polymer–filler gel formation theory. Part I
Authors: Karásek L. , Meissner B.
Published: April 2003

Experimental data were obtained on the concentration dependence of the fraction of total filler–bound polymer, fraction of polymer in a coherent polymer–filler gel, and fraction of solvent‐dispersed filler particles in compounds of fume silica (Aerosil OX50) with natural rubber (NR) and styrene butadiene rubber (SBR). Predictions of the polymer–filler gel formation theory were tested and a good formal description of the data was obtained. The two adjustable parameters of the theory assume reasonable values. While A0 is a characteristic of the filler interaction with polymer and has similar values in NR and SBR, the functionality f of the theoretically assumed filler particle acting as a polyfunctional crosslinker of polymer chains seems to depend on the polymer as well. Dimensions of the theoretical filler particle calculated from a comparison of experiment with theory are of the same order of magnitude but smaller than those of primary filler particles. © 1994 John Wiley & Sons, Inc.
Mechanical properties and morphology of PP/SEBS/PC blends
Authors: Srinivasan K. R. , Gupta A. K.
Published: April 2003

Rubber toughening of thermoplastic polymers always decreases the tensile and flexural properties. In this article, an attempt is made to improve the tensile and flexural properties of a rubber‐toughened polymer system viz., polypropylene (PP)/styrene‐ethylene‐butylene‐styrene tri‐block copolymer (SEBS) binary blend by blending a rigid polymer viz., polycarbonate (PC) with this binary system. The PP/SEBS blend with a blending ratio fixed at three levels, namely 95/5, 90/10, and 80/20, was melt mixed with 0–30 wt % PC to generate the various blend compositions studied. This choice of compositions enabled us to show how the mechanical properties varied as a function of (1) PP/SEBS ratio at a constant PC content and (2) PC content at a constant PP/SEBS ratio of the blend. Data on the corresponding binary blends, namely PP/SEBS and PP/PC, are also presented and discussed as reference systems. The data are discussed in detail for the effect of each component of the blend. As regards the morphology, some distinct changes were seen in the middle of composition ranges of the additives, i.e., around 10 to 20% PC level, and 95/5 and 90/10 PP/SEBS ratios. Variation of mechanical properties in the respective composition ranges are found consistent with the variations of blend morphology. Hence, a correlation of morphology and the properties is discussed. Furthermore, the results suggest stronger interfacial interaction between SEBS and PP than that between PC and PP. Scanning electron microscopic studies of appropriately etched impact fractured samples reveal the existence of composite droplets of SEBS and PC embedded in PP matrix, with SEBS forming the outer envelope around PC. © 1994 John Wiley & Sons, Inc.
Effect of aromatic diamine extenders on the morphology and property of RIM polyurethane–urea
Authors: Gao Yun , Xiu Yu‐Ying , Pan Zhao‐Qi , Wang De‐Ning , Hu Chun‐Pu , Ying Sheng‐Kang
Published: April 2003

An aromatic diamine, CMOMDA, was synthesized and used as a chain extender for reaction injection molding (RIM) polyurethane–urea. The morphology and properties of CMOMDA‐, DETDA‐, and MDA‐extended poly(ether–urethane–urea)s (PEUUs) were measured by IR, DSC, DMS, SEM, and tensile testing apparatus. Well‐matched values of Ch and Xut,b/Ch were necessary for aromatic diamine‐extended PEUU. DSC and SEM showed that the aggregation state of hard segments might undergo some changes with increasing hard‐segment content. © 1994 John Wiley & Sons, Inc.
Kinetics of radical polymerization of N‐vinylpyrrolidone by peroxidiphosphate–Ag+ system
Authors: Gupta K. C.
Published: April 2003

The kinetics of aqueous polymerization of N‐vinylpyrrolidone (N‐VP) was carried out using potassium peroxidiphosphate–Ag+ system under nitrogen atmosphere at 25°C. The rate of polymerization was directly proportional to the concentration of the N‐vinylpyrrolidone and showed a half‐order with respect to the concentration of the peroxidiphosphate (H2P2O) and Ag+ ions. The value of κp/(κt)1/2 was computed and its value found to increase on increasing the temperature of the reaction mixture. The energy of activation (Ea) was found to be 65.8 ± 0.1 kJ mol−1 within the temperature range from 20 to 50°C. Viscometric average molecular weight of polyvinylpyrrolidone was determined by measuring intrinsic viscosity of the polymer samples collected at different kinetic conditions. The effect of various additives was also studied. A suitable mechanism of polymerization has been proposed and a reaction rate law was derived considering experimental results. © 1994 John Wiley & Sons, Inc.
Enrichment of helium by asymmetric hollow‐fiber membrane of cellulose triacetate
Authors: Kumazawa H. , Sada E. , Nakata K. , Kawashima N. , Kataoka S. , Tada K.
Published: April 2003

The permeation behavior of pure He and separation characteristics of He–air mixtures were examined using asymmetric hollow‐fiber‐type membrane modules of cellulose triacetate. The module was operated in a feed‐outside mode. In permeation of pure He, the permeation rate coefficients slightly increased with increasing upstream pressure, and they agreed fairly well with those calculated on the basis of the assumption that the permeate flow inside the fiber is governed by the Hagen‐Poiseuille equation. In the single‐stage hollow‐fiber module used, the molar fraction of He in the permeate stream was increased to 0.99 and 0.999 at the stage cuts of lower than 0.3 when the molar fraction in the feed stream was 0.90 and 0.99, respectively. The molar fractions of He in the permeate stream were numerically evaluated for various combinations of operating conditions in terms of a countercurrent plug flow model. © 1994 John Wiley & Sons, Inc.
Structure and electrical properties of the oriented polyaniline films
Authors: Wan Meixiang , Li Ming , Li Junchao , Liu Zhenxing
Published: April 2003

The structure of oriented polyaniline (PANI) films were characterized by elemental analysis, FTIR, XPS, SEM, and X‐ray diffraction, and their electrical properties were measured as a function of the protonation state, elongation ratio, temperature, and applied pressure. A maximum conductivity at room temperature for oriented PANI films can be achieved up to 500 s/cm with conductivity anisotropy as high as 20 : 1. The temperature dependence of conductivity for both unoriented and oriented films at 77–300 K and applied pressure of 0–11.4 kbar is consistent with the 3‐D variable‐range hopping model; however, the hopping barrier of oriented films is one order magnitude lower than that of unoriented films. The mechanism of enhanced conductivity for oriented PANI films is discussed. © 1994 John Wiley & Sons, Inc.
Structure and properties of polyvinyl alcohol amidoxime chelate fiber
Authors: Lei Rao , Jie Xu , Jun Xu , Ruiyun Zhan
Published: April 2003

Polyvinyl alcohol amidoxime (PVAAO) chelate fiber prepared in our laboratory is a good adsorbent. Comparing with other adsorbents, it has many advantages, such as higher hydrophilicity, better adsorbability and easier synthesis. In this work, the synthesis course, structure and properties of PVAAO fiber have been studied by the means of FT‐IR, SEM, ESR, and TG. The structural changes of the fiber associated with adsorbed copper ions have also been investigated using ESR, FT‐IR, and XPS. In addition, chelating mechanisms of the fiber‐adsorbing copper ions have been discussed. © 1994 John Wiley & Sons, Inc.
Effect of corona modification on the mechanical properties of polypropylene/cellulose composites
Authors: Belgacem M. N. , Bataille P. , Sapieha S.
Published: April 2003

The effect of various corona treatment conditions on the mechanical properties of cellulose fibers/polypropylene composites was studied. The cellulose fibers and polypropylene were modified using a wide range of corona treatment levels and concentrations of oxygen. The treatment level of the fibers was evaluated using the electrical conductance of their aqueous suspensions. The mechanical properties of composites obtained from different combinations of treated or untreated cellulose fibers and polypropylene were characterized by tensile stress–strain measurements; they improved substantially when either the cellulose fibers alone or both components were treated, although composites made from untreated cellulose fibers and treated polypropylene showed a relatively small improvement. The results obtained indicate that dispersive forces are mostly responsible for the enhanced adhesion. The relationship between the electrical conductance of the fibers, the mechanical properties, and the mechanism of improved adhesion is discussed. © 1994 John Wiley & Sons, Inc.
Catalysts for the preparation of polybenzimidazoles
Authors: Choe Eui‐Won
Published: April 2003

The single‐stage preparation of poly[2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole] (PBI), from 3,3′,4,4′‐tetraaminobiphenyl (TAB) with isophthalic acid (IPA) in the presence of a catalyst, was explored and developed. The effects of a variety of catalysts on the polymerization of TAB with IPA and/or diphenyl isophthalate were screened and evaluated. Many organo phosphorus and silicon compounds catalyzed the PBI condensation reactions, increased the molecular weight, and improved the quality of PBI polymers. Fiber and reverse osmosis membrane properties of PBI prepared from TAB and IPA were comparable to those for commercial standard PBI prepared from TAB and diphenyl isophthalate. © 1994 John Wiley & Sons, Inc.
Impact modification of engineering thermoplastics
Authors: Kanai Hiroyuki , Sullivan Vince , Auerbach Andrew
Published: April 2003

Impact modification was studied for a variety of engineering thermoplastics to determine if notched Izod data obtained at various temperatures and modifier concentrations could be correlated with particle size or surface‐to‐surface interparticle distance of the modifier. Elastomers evaluated were characteristic of those used in commercial blend systems for those polymers, and both functionalized and nonfunctionalized materials were studied. For the single matrix polymer/elastomer‐modified blend systems studied [poly(phenylene sulfide) (PPS), polyoxymethylene (POM), poly(butylene terephthalate) (PBT)], elastomer interparticle distance provides a better correlation to brittle–tough transition temperature than does particle size, as predicted by the Wu model. In POM, the dispersion morphology of the samples used was not adequate to achieve the critical interparticle distance required for supertoughening at room temperature. In this study, the critical interparticle distance has been shown to depend on the degree of crystallinity (PPS) and the modulus of the impact modifier relative to the matrix (PBT). Actual adhesion of the polymer to the matrix (variation of functionality levels) was not found to have a strong influence (PBT). In POM, the increase in impact at the brittle–tough transition was dependent on the molecular weight of the base resin. This is examined with respect to the ratio of the molecular weight (Mn) to the entanglement molecular weight (Me), which determines the critical molecular weight necessary to achieve useful physical properties. In polyester (PET)/polycarbonate (PC)/elastomer blends, the molecular weight of the primary matrix resin (PET) determined impact properties within the molecular weight range of the resin studied. This was again related to the Mn/Me ratio for PET and PC. © 1994 John Wiley & Sons, Inc.
A thermally stimulated current/relaxation map analysis of the relaxation processes in aromatic polyester, liquid crystal polymer film
Authors: Collins George , Long Barbara
Published: April 2003

Thermally stimulated current (TSC) and relaxation map analysis (RMA) have been applied to the examination of dynamics of thermally induced relaxation processes in highly oriented, wholly aromatic, polyester liquid crystalline polymer films. Films of two compositions were examined. A primary distinction in composition was the difference in level of 6‐hydroxy‐2‐napthoic acid. Following an analysis protocol developed by Sauer et al., it was found that values of activation enthalpy were well above the zero entropy value at temperatures well below the Sauer “Tg.” This indicates a high level of cooperativity in rotational relaxation processes even at low temperatures. Cooperative rotational relaxation domains were postulated to account for this behavior. The persistence of cooperativity above the Sauer “Tg.” is evidence that these materials did not undergo a conventional glass transition at any temperature in the range–80 to 200°C. The behavior of these materials as a model system of “loosely bundled rods” was examined using a modified Barker–Crine analysis. This type of model behavior seemed to fall off at relatively low temperatures. The occurrence of rotational processes at high temperatures with little or no loss in orientation suggests that polymer chains are physically constrained to maintain their relative positions. © 1994 John Wiley & Sons, Inc.
Thermosetting cure diagrams: Calculation and application
Authors: Simon S. L. , Gillham J. K.
Published: April 2003

The time–temperature–transformation (TTT) isothermal cure diagram and the continuous‐heating‐transformation (CHT) cure diagram are calculated from a reaction model for a high‐Tg epoxy/amine system that has been developed to describe both epoxy/amine and etherification reactions in kinetically and diffusion‐controlled reaction regimes. The cure diagrams are applied to various processing operations. The optimization of processing and of material properties by exploiting gelation and/or vitrification during cure is discussed. © 1994 John Wiley & Sons, Inc.
Characterization of polyamide 6 made by reactive extrusion. I. Synthesis and characterization of properties
Authors: Hornsby P. R. , Tung J. F. , Tarverdi K.
Published: April 2003

The anionic polymerisation of ε‐caprolactam in a corotating, intermeshing twin‐screw extruder is discussed in terms of the materials formulation, extruder screw profile, and processing parameters such as temperature and screw speed. Using a variety of analytical characterization techniques, it is demonstrated that molecular mass, residual monomer content, and mechanical properties of the polyamide 6 are very sensitive to the reactive processing conditions employed. © 1994 John Wiley & Sons, Inc.
Studies on semiinterpenetrating polymer networks based on poly(vinyl chloride‐co‐vinyl acetate) and poly(alkyl methacrylates)
Authors: Mathew Annakutty , Deb P. C.
Published: April 2003

A number of semi‐interpenetrating polymer networks (IPNs) based on linear poly(vinyl chloride‐co‐vinyl acetate) and poly(alkyl methacrylates) were synthesized. The semi‐IPNs were found to be transparent, high strength materials. The IPNs show only one glass‐transition temperature and it is dependent on the composition as studied by differential scanning calorimetry and dynamic mechanical analysis. These IPNs are also characterized by high tan δ values. The tensile strength of the IPNs were found to be higher compared to the starting polymers. In order to compare the properties of these IPNs with the corresponding homopolymers and blends, the latter were synthesized and the properties were studied. © 1994 John Wiley & Sons, Inc.
Modification of isotactic polypropylene by a cold plasma or an electron beam and grafting of the acrylic acid onto these activated polymers
Authors: Poncin‐Epaillard Fabienne , Chevet Bruno , Brosse Jean‐Claude
Published: April 2003

Surface grafting of polymeric materials, such as films and fibers, may improve their reactive surface properties. Polypropylene active sites that should initiate a surface postgrafting can be formed by either nitrogen cold plasma or an electron‐beam irradiation. The plasmamodified polymer surface is cross‐linked and functionalized with primary amino groups and with oxidized groups, and it is almost not degraded. Electron‐beam‐modified polypropylene is also functionalized through an aging reaction, emphasized by a high radical concentration. In both cases, active surface films are susceptible to react with monomers in a postgrafting reaction. The grafting yield and rate of acrylic acid were shown to be dependent on the formed amino group concentration: The hydrophilic character of the modified polypropylene surface enhances the acrylic acid approach. The electron‐beam treatment leads also to a reactive surface that can initiate a grafting reaction. But its yield and rate are dependent on the radical concentration: radicals formed during the irradiation. © 1994 John Wiley & Sons, Inc.
Thermally induced crosslinking between polyacrylic acid and epoxidized natural rubber. III. Effect of carbon black filler and mixer rotor speed
Authors: Mallick A. , Tripathy D. K. , De S. K.
Published: April 2003

High‐temperature molding of Brabender‐mixed blend of polyacrylic acid (PAA) and epoxidized natural rubber (ENR) causes thermally induced crosslinking between PAA and ENR. Studies on Monsanto rheometry of the blend and physical properties, solvent swelling, and dynamic mechanical properties of the molded blend show that both mixer rotor speed and carbon black filler influence the crosslinking between the component polymers. For example, the extent of crosslinking for the 50–50 PAA–ENR blend was found maximum when the component polymers were mixed at 40 rpm, but the same blend filled with 30 phr HAF carbon black filler showed maximum crosslinking when mixing was carried out at 120 rpm. The results have been explained on the basis of formation of network on the filler surface, which in turn depends on two competing factors: increase in bound rubber formation with increase in filler loading at a fixed rotor speed and enhanced degradation of ENR at higher mixer rotor speed at a fixed filler loading. © 1994 John Wiley & Sons, Inc.
Decomposition behavior of polyurethanes via mathematical simulation
Authors: Chang Wally L.
Published: April 2003

A series of polyurethane elastomers with different hard‐segment contents of 24% (M24), 34% (M34), 50% (M50), and 100% (M100) have been investigated through thermogravimetric analysis (TGA) measurement and mathematical simulation. The fourth‐order Runge–Kutta method was used to solve the differential equations, and the solutions were obtained by running a written computer program. The activation energy and the frequency factor of polyurethane decomposition can be obtained by only one nonisothermal measurement of TGA. The same values of the activation energy and the frequency factor were obtained using the different constant heating rates under air for the elastomer with a hard‐segment content of 34%. The activation energy decreases as the hard‐segment content of polyurethanes increases. The polyurethane materials can be used at room temperature for several millennia failure through lifetime calculation. Comparison of the values of t1/2, the heat stability of polyurethanes decreases in the following order: M24 > M34 > M50 > M100; this phenomenon can be explained due to the heat instability of the urethane group. The highest concentration of the urethane group in the M100 structure results in the worst heat stability. © 1994 John Wiley & Sons, Inc.
Synthesis and evaluation of dialkyl furan‐2,5‐dicarboxylates as plasticizers for PVC
Authors: Sanderson R. D. , Schneider D. F. , Schreuder I.
Published: April 2003

Di(2‐ethylhexyl), di(2‐octyl), dihexyl, and dibutyl furan‐2,5‐dicarboxylate were synthesized from furfural and characterized for their plasticizing abilities toward PVC by dynamic mechanical thermal analysis (DMTA) with di(2‐ethylhexyl) phthalate (DOP) as the standard of reference. DMTA gave values for the depression of the glass transition temperature (Tg) per mass fraction of plasticizer, and it also yielded a set of parameters, relative to those for DOP, which describe the compatibility of the furan diesters with PVC. The efficiency in lowering Tg as exhibited by di(2‐ethylhexyl) furan‐2,5‐dicarboxylate is similar to that of its benzenoid analog, DOP, and was determined at 2.41 and 2.45°C per mass % plasticizer, respectively. All four furan diesters were found to be more compatible toward PVC than toward DOP, with dibutyl furan‐2,5‐dicarboxylate the most highly compatible. © 1994 John Wiley & Sons, Inc.
Effect of solvent precipitation on the crystallization behavior and morphology of nylon 6,6
Authors: Muellerleile Joan T. , Freeman John J.
Published: April 2003

This work describes the effect of solvent precipitation on the crystallization behavior and morphology of nylon 6,6. We found that solvent precipitation of nylon 6,6 induces elevated crystallization temperatures upon cooling from the melt (Tmc) and highly nucleated morphologies that rival those induced by rapid, thermal reprocessing such as melt reextrusion or heterogeneous nucleating agents such as CaF2. The primary techniques used to characterize these changes in crystallization behavior and morphology were differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide‐angle X‐ray scattering (WAXS). Several other supplementary techniques were employed for identifying the origin of the crystallization behavior and morphological changes after solvent precipitation. Our results are consistent with the hypothesis in which dissolved nylon reorients to form ordered H‐bonded regions that later serve as nucleation sites during melt processing. Finally, (Tmc) decreased with nylon 6,6 solution concentration prior to precipitation. These results suggest that polymer entaglements in solution also affect the crystallization behavior and morphology of the solvent‐precipitated nylon 6,6. © 1994 John Wiley & Sons, Inc.
Synthesis and properties of main‐chain liquid crystalline polyurethane elastomers
Authors: He Xiangdong , Jia Xudong , Yu Xuehai
Published: April 2003

Liquid crystalline polyurethane elastomers (LCPUE) have been synthesized by a two‐step block copolymerization reaction. The main‐chain LCPUEs are based on two biphenyl‐type mesogenic diol chain extenders (HB2 and HB6), a poly(tetramethylene oxide) (PTMO) soft segment, and different diisocyanates, icluding 4,4′‐diphencylmethane diisocyanate (HDI), and 1,4‐(3,5,5‐trimethyl)cyclohexane diisocyanate (IPDI). The polyurethanes were characterized by FTIR dichrosim, DSC, DMA, WAXD, and polarized optical microscopy. Most of the polyurethane samples exhibited nematic thermortopic liquid crystal behavior and had physical properties typical of thermoplastic elastomers. The liquid crystal properties are strongly related to the interaction between the hard and soft segments of the polyurethane. As the compatibility of the soft and hard segments increased, the thermal stability of the liquid crystal phase and the transition temperatures decreased and the range of the transition became narrower, Uniaxial extenstion analysis shows that two orientation mechanisms exist in the LCPUE systems. These samples had fairly high strength and modulus and good membrane‐forming ability. © 1994 John Wiley & Sons, Inc.
A novel TLCP blended with PET and PC matrices
Authors: Joslin Scott , Jackson Woodward , Farris Richard
Published: April 2003

This investigation focused on the potential of improving the performance of poly(ethylene terephthalate) (PET) and polycarbonate (PC) fibers by incorporating a novel thermotropic liquid crystalline copolymer (TLCP). The degree of mechanical enhancement obtained in the fibers incorporating 20 wt % TLCP depended upon the chosen matrix material and the processing conditions. The PET matrix systems did not exhibit any modulus improvements until after posttreatment of the fibers. Following posttreatment, the blends exhibited a modulus of 24 GPa, an increase of 40% compared to the PET control fiber. The PC systems exhibited a 1 GPa modulus increase in the as‐spun fiber blends, but improvement was negligible after fiber posttreatment. The morphologies of the as‐spun and posttreated fibers suggest that different mechanisms of reinforcement are occurring depending upon the matrix material selected. © 1994 John Wiley & Sons, Inc.
Preparation of zeolite filled glassy polymer membranes
Authors: Duval J.‐M. , Kemperman A. J. B. , Folkers B. , Mulder M. H. V. , Desgrandchamps G. , Smolders C. A.
Published: April 2003

The incorporation of zeolite particles in the micrometer range into polymeric matrices was investigated as a way to improve the gas separation properties of the polymer materials used in the form of membranes. The adhesion between the polymer phase and the external surface of the particles appeared to be a major problem in the preparation of such membranes when the polymer is in the glassy state at room temperature. Various methods were investigated to improve the internal membrane structure, that is, surface modification of the zeolite external surface, preparation above the glass‐transition temperature, and heat treatment. Improved structures were obtained as observed by scanning electron microscopy, but the influence on the gas separation properties was not in agreement with the observed structural improvements. © 1994 John Wiley & Sons, Inc.
Proton exchange membranes by radiation grafting of styrene onto fep films. III. Structural investigation
Authors: Gupta Bhuvanesh , Haas Otto , Scherer Günther G.
Published: April 2003

Structural investigation on proton‐exchange membranes, obtained by the radiation grafting of styrene onto FEP films and subsequent sulfonation, was carried out by differential scanning calorimetry. The membrane crystallinity was found to show a decreasing trend with increasing degree of grafting. The melting temperature of all the membranes also showed a slight decrease as compared to the ungrafted FEP. The results have been explained in terms of the cumulative effect of the decrease in the crystalline/amorphous ratio by the incorporation of amorphous polystyrene grafts and of disruption of spherulitic crystallites of the FEP component in the membranes. The glass transition temperature of the membranes with different water contents was also evaluated. A correlation of the glass transition temperature with the residual water in dried membranes was established. © 1994 John Wiley & Sons, Inc.
Rubber toughened styrene/methyl methacrylate/butyl methacrylate composites by the concentrated emulsion pathway
Authors: Ruckenstein Eli , Li Hangquan
Published: April 2003

Solutions of rubber in mixtures of styrene, methacrylate, and/or butyl methacrylate containing proper amounts of initiator have been polymerized to produce novel polymer composites—MBBS. In these composites, it is expected that tri‐component and bi‐component copolymers as well as homopolymers coexist. The tensile behavior of composites of various compositions was investigated. At certain weight ratio of monomers, excellent combinations of tensile strength, elongation, and toughness were obtained, which are better than those of most commercial engineering plastics. There is an optimum amount of butyl methacrylate, which is dependent upon the contents of the other monomers, for which the toughness acquires a maximum value. The concentrated emulsion polymerization was employed to prepare the MBBS composite latexes and the products were compared with those prepared via bulk polymerization. While the two polymerization methods provide high, comparable tensile properties and toughness, the concentrated emulsion method generates latexes which can be more easily processed in any desirable shape. © 1994 John Wiley & Sons, Inc.
Non‐markovian diffusion processes in polymers and a stretched exponential relaxation constitutive equation
Authors: Stastna J. , De Kee D. , Harrison B.
Published: April 2003

Non‐Markovian diffusion transport in polymers was studied. Applying the results of various researchers, a stretched exponential relaxation function was obtained and a linear viscoelastic constitutive equation formulated. Frequency dependent material functions, obtained from this constitutive equation were studied and the results successfully compared with experimental data for polyethylene oxide solutions. Sorption kinetics in a polymeric film were also studied. © 1994 John Wiley & Sons, Inc.
Through‐thickness distribution of LCP in PPS/LCP blends
Authors: Shonaike G. O. , Hamada H. , Yamaguchi S. , Nakamichi M. , Maekawa Z.
Published: April 2003

Through‐thickness distribution of liquid crystalline polymer (LCP) of blends containing polyphenylene sulfide (PPS) and LCP was investigated using differential scanning calorimetry and scanning electron microscopy. The effect of the LCP distribution on the mechanical test was checked through bending testing of the various compositions of the injection molded samples. These studies showed a nonuniform distribution of LCP in the PPS‐rich region where the LCP content in the skin layer was higher than in the core layer or boundary between the two layers. The LCP component was uniformly distributed in the LCP‐rich region. The increase of bending modulus with increasing LCP content was attributed to the reinforcing nature of the LCP fibrils in the skin layer. © 1994 John Wiley & Sons, Inc.
Effect of poly(vinylidene fluoride) on the ionic conductivity and morphology of PEO–salt polymer electrolytes
Authors: Whang Wha‐Tzong , Yang Li‐Huy , Fan Yu‐Wen
Published: April 2003

The high dielectric constant polymer poly(vinylidene fluoride) (PVDF) was blended with PEO–Salt polymer electrolytes to improve their ionic conductivity. PVDF did improve the room‐temperature ionic conductivity of the polymer electrolytes PEO–LiCF3CO2 and PEO–LiBF4, and the ionic conductivity at room temperature went up one order of magnitude with 10−5S/cm for LIB4M–PF4 being the most prominent. PVDF exhibited strong effects on the ionic conductivity and morphology of the polymer electrolytes, such as weakening the association of poly(ethylene oxide) (PEO) with the salt, hindering the formation of the PEO–salt complex, enlarging the crystalline PEO phase in LIAnM–PFm polymer electrolytes, and reducing the crystalline PEO phase in LIBnM–PFm polymer electrolytes. Both LIA4M–PF4 and LIB4M–PF4 polymer electrolytes formed a new PEO–PVDF–salt complex. The new complex in the former was crystalline, but that in the latter was amorphous. © 1994 John Wiley & Sons, Inc.
Ultraviolet curing acrylated chlorinated low‐molecular‐weight guayule rubber wood filler and finish
Authors: Thames Shelby F. , He Z. Alex
Published: April 2003

Acrylated chlorinated low‐molecular‐weight guayule rubber (ACLMWGER) has been systhesized and characterized with Fourier Tranform infrared spectroscopy, solid‐state nuclear magnetic responance spectroscopy, and differential scanning calorimetry, We have found that ACLMWGER is useful as a prepolymer in 100% solids ultraviolet (UV) curing wood coatings. The properties of the coatings are equal or superior to coatings prepared from acrylated chlorinted rubber synthesized from commerical masticated natural rubber. However, when low‐molecular‐weight guayule rubber (LMWGR) serves as the feedstock, the cost of producing ACLMMWGR is significantly reduced since no mastication is needed. © 1994 John Wiley & Sons, Inc.
Photochemically modified thin‐film composite membranes. II. Bromoethyl ester, dioxolan, and hydroxyethyl ester membranes
Authors: Trushinski B. J. , Dickson J. M. , Childs R. F. , McCarry B. E. , Gagnon D. R.
Published: April 2003

A photochemically active thin‐film composite membrane was made by the interfacial copolymerization of a mixture of 3‐diazo‐4‐oxo‐3,4‐dihydro‐1,6‐naphthalene disulfonylchloride and naphthalene‐1,3,6‐trisulfonylchloride in CCl4 with aqueous 1,6‐hexanediamine on the surface of a polysulfone ultrafiltration membrane. The chemical functionality of the resulting polysulfonamide membrane surface was modified via a photochemical reaction in the presence of various nucleophiles to form membranes containing bromoethyl ester, dioxolan, and hydroxyethyl ester functionality. Surface analysis techniques of attenuated total reflectance–FTIR, scanning electron microscopy (SEM), energy disperse spectral analyzer (SEM/EDS), and electron spectroscopy (ESCA) were used to confirm the changes in the chemistry of the thin‐film composite membranes. Changes in chemistry, on irradiation, were also examined with model compounds. The reverse osmosis flux and separation of various solutes with these membranes are reported and discussed in terms of the photochemical modifications of the membrane surface. © 1994 John Wiley & Sons, Inc.
Modulus evaluation of particulate composites using generalized viscosity model for solutions with suspended particles
Authors: Sudduth Richard D.
Published: April 2003

The theoretical relationship between the shear modulus of a particulate reinforced composite and the viscosity of a solution with suspended particles was first proposed by Goodier. Since that time several partially successful attempts have been made in the literature to derive equations to describe the available relative shear modulus–particulate concentration data. Recently a new generalized suspension viscosity equation appeared in the literature which for the first time addresses the detailed effects of particle size, particle size distribution, and packing fraction. This new viscosity equation was applied to available modulus literature on particulate composites in this study. Four significant particulate composite modulus derivations in the literature were all shown in this study to yield the same theoretical “intrinsic modulus” of a particulate composite. The generalized viscosity–modulus equation yielded an excellent fit of the shear modulus–particulate concentration data of both Smallwood and Nielsen using a variable intrinsic modulus. Some fillers predicted the Einstein limiting value of the intrinsic modulus while other fillers yielded intrinsic modulus values that were either larger or smaller than this value. The intrinsic modulus for carbon black in rubber was much larger than Einstein's predicted value. However, intrinsic modulus values smaller than Einstein's prediction were obtained at temperatures below the glass transition temperature of the matrix. Unfortunately, the previously obtained direct relationship between the particle interaction coefficient and particulate size for suspension viscosities with a constant intrinsic viscosity was not obtaind for shear modulus—particulate concentration data using a variable intrinsic modulus. © 1994 John Wiley & Sons, Inc.
Epoxy resin based on 4,4′‐dihydroxydiphenysulfone. I. Synthesis and reaction kinetics with 4,4′‐diaminodiphenylmethane and 4,4′‐diaminodiphenylsulfone
Authors: Sýkora V. , Špaček V. , Dobáš I.
Published: April 2003

Epoxy resins based on 4,4′‐dihydroxydiphenylsulfone (DGEBS) and diglycidyl ether of bisphenol A (DGEBA) were prepared by alkaline condensation of 4,4′‐dihydroxydiphenylsulfone (bisphenol S) with epichlorohydrin and by recrystallization of liquid, commercial bisphenol A‐type epoxy resin, respectively. Curing kinetics of the two epoxy compounds with 4,4′‐diaminodiphenylmethane (DDM) and with 4,4′‐diaminodiphenylsulfone (DDS) as well as Tg values of the cured materials were determined by the DSC method. It was found that the SO2 group both in the epoxy resin and in the harener increases Tg values of the cured materials. DGEBS reacts with the used hardeners faster than does DGEBA and the curing reaction of DGEBS begins at lower temperature than does the curing reaction of DGEBA when the same amine is used. © 1994 John Wiley & Sons, Inc.
Studies upon the fine structure and selected physical and physicochemical properties of butrylchitin membranes
Authors: Urbańczyk G. , Lipp‐Symonowicz B. , Jeziorny A. , Urbaniak‐Domagala W. , Wrzosek H.
Published: April 2003

The effect of varying the molecular weight of butyrylchitin membranes cast from methylene chloride on their properties has been investigated. Characterization analyses include X‐ray, scanning calorimetry and tensile stress‐strain. The crystal structure of the butyrylchitin was shown to consist of fringed micelles, irrespective of the molecular weights examined, and of lower crystal volume fraction than usually found for chitin membranes, 0.3 versus 0.5, respectively. The membranes exhibit greater ductility and less swelling in physiological salt solution with increasing molecular weight. © 1994 John Wiley & Sons, Inc.
Polylactide. I. Continuous dry spinning–hot drawing preparation of fibers
Authors: Horáček I. , Kalíšek V.
Published: April 2003

The mechanical properties and in vitro degradability of gamma‐rays sterilized and non‐sterlized PLLA fibers prepared by a continuous dry spinning–hot drawing process were studied in relation to the spinning solution composition. Chloroform/cyclohexane mixtures of different volume ratios were used for dissolution either purified or as polymerized (with a residual monomer) PLLA. The fibers obtained had average or poor mechanical properties and a porous structure with a pointed outer skin. No increase of the degradation rate was observed except for the fibers formed from pure chloroform with a residual monomer at a drawing temperature of 110°C. At chloroform/cyclohexane volume ratio of 6:4 the process resulted in nearly hollow fiber formation. © 1994 John Wiley & Sons, Inc.