摘要:

AbstractThe free‐radical copolymerization of propyl, pentyl, hexyl, heptyl, octyl, and dodecyl methacrylates with triallyl cyanurate was investigated. The reactivity ratios were determined using the methods of Fineman‐Ross and Kelen‐Tüdös. The Alfrey‐PriceQandevalues for the methacrylates were also evaluated. The effect of the length of alkyl group in methacrylates on reactivity ratios is

ISSN:0021-8995    

DOI:10.1002/app.1991.070420601

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractGraft copolymers composed of water‐soluble cellulosic backbones and>0.4% (by weight) alkyl grafts are insoluble in water but soluble in surfactant solutions. Studies of the bulk viscosity and stability of polymer‐surfactant solutions at 49°C indicate that the mechanism for solubilization of the polymer is the incorporation of the alkyl side chains into surfactant micelles. The tendency for side chains to combine with micelles appears to depend at least in part on the geometry of the surfactant tail group such that surfactants containing straight‐chain tail groups solubilize alkyl side chains more readily than olefinic surfactants. The presence of small solutes near the surface of the micelle also inhibits incorporation of side chains from the polymer. Unsolubilized side chains remain in the aqueous phase of the solution, where they form thermally unstable intermolecular aggr

ISSN:0021-8995    

DOI:10.1002/app.1991.070420602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe process of depolymerization of PET resin by EG glycolysis under pressure is investigated. The kinetics of this pressurized depolymerization of PET resin is discussed. It was found that the rate of depolymerization is dependent of temperature, pressure, and concentration ratio of EG to PET. The rate of depolymerization is proportional to the square of EG concentration and faster than that under atmospheric pressure. Glycolyzed products under pressure consist of the PET monomer, BHET, and oligomers, mostly dimer and trimer. An equilibrium between BHET and oligomers is attained quickly soon after the depolymerization step is completed in the case of a higher ratio of EG/PET used. In the case of lower ratio of EG/PET, the final product now consists of higher molecular weight of oligomers rather than monomer, dimer, and trimer.

ISSN:0021-8995    

DOI:10.1002/app.1991.070420603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractUltrahigh speed spinning of poly(ethylene terephthalate) (PET) was carried out at various take‐up velocities from 5 to 10 km/min. The superstructure of as‐spun fibers was characterized by small‐angle X‐ray scattering (SAXS), wide‐angle X‐ray diffraction (WAXD), viscoelastic properties, and scanning electron microscopy (SEM). Above 6 km/min the peaks or shoulders that are due to the interference between microfibrils appear on the equatorial SAXS intensity curves. The interfibrillar spacing estimated from the peak position increases with increasing take‐up velocity. Comparison of the spacing with the lateral crystal sizes estimated from the broadness of the crystal (hk0) WAXD peaks indicates that the microfibril diameter becomes thick with increasing take‐up velocity. Although the orientation and density in amorphous region for high‐speed spun fibers are very low on the average, it can be seen that a few highly extended tie molecules exist in that region, and the number of these molecules increases with increasing take‐up velocity. The modes and mechanisms of fibrillation induced by a rubbing test are discussed relati

ISSN:0021-8995    

DOI:10.1002/app.1991.070420604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe literature reveals no equation that expresses the influence of the diffusional boundary layer on diffusion‐controlled sorption of dyes or other material by polymeric substrates fromfinitebaths. In view of this mathematical void, a technique is proposed that approximates dimensionless sorption time as a function of fractional equilibrium uptake of diffusant by polymer, dimensionless dye bath exhaustion, and dimensionless boundary layer. The computational technique is based on relationships found in transitional kinetics and is shown to be applicable for sorption systems involving polymeric material of different geometrical shapes. To illustrate the technique, dimensionless half‐times of sorption are computed for the case of diffusant uptake by a cylin

ISSN:0021-8995    

DOI:10.1002/app.1991.070420605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractStyrene‐acrylic acid copolymers exhibit miscibility with various aliphatic, crystalline polyamides (e.g., nylon 6, 11, and 12) at 20% acrylic acid content in the copolymer. At 8% acrylic acid, phase separation is observed with the crystalline polyamides. At 14% acrylic acid, partial miscibility is observed with each polyamide, resulting in theTg's of the constituents shifted toward the other constituent. The miscibility of the styrene‐acrylic acid copolymers (>14 wt % AA) can be ascribed to hydrogen bonding interactions with the polyamides. Styrene‐acrylic acid (20% AA) copolymers are miscible with other nylons with alternating amide orientation along the chain (e.g., nylon 6,6 and nylon 6,9). These samples tend to crosslink upon exposure to temperatures above the polyamide melting point unlike the nylon 6, 11, and 12 blends in which branching may only occur. Nylon 11/styrene‐acrylic acid blends were chosen for crystallization rate studies. A melting point depression of nylon 11 occurs with addition of the styrene‐acrylic acid (20% AA). The Flory‐Huggins interaction parameter from the melting point depression is calculated to be ‐0.27. The crystallization rate of nylon 11 is significantly reduced with the addition of the miscible SAA copolymers (20% AA). The spherulitic growth rate equation predicts this behavior based on aTgincrease with

ISSN:0021-8995    

DOI:10.1002/app.1991.070420606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA bisphenol A based epoxy adhesive (EP) was modified by polyblending with Kraft Lignin (L). A systematic investigation of the thermally cured EP‐L polyblends with up to 40% by weight L was undertaken. Adhesive shear tests, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and solid‐state CP‐MAS NMR spectroscopy were performed to establish the effect of L on the mechanical properties of the polyblends and on the morphology of these crosslinked structures. The possibility of an enhanced degree of bonding between L and the EP network is discussed. This bonding can arise from a chemical reaction between L and some unreacted amine groups present in the har

ISSN:0021-8995    

DOI:10.1002/app.1991.070420607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA UV‐curable coating for plastics that is abrasion resistant and weatherable is described. The coating consists of colloidal silica functionalized with methacryloxypropyltrimethoxy‐silane (MAPTMS) in a matrix of acrylic monomers. The formulation employs diethoxyacetophenone (DEAP) as a photoinitiator and a sulfonated benzotriazole as a UV absorber. It has been found that the adhesion of the coating depends greatly on the type of acrylic monomers used and the application parameters. Transmission electron microscopy (TEM) analysis shows that improved adhesion is due to the formation of an interpenetrating layer between coating and substr

ISSN:0021-8995    

DOI:10.1002/app.1991.070420608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe physical and chemical properties of the diglycidyl ether of bisphenol A (DGEBA) cured with different concentrations of bisphenol A (BPA) and 2‐ethyl‐4‐methylimidazole (EMI‐24) were examined using Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical and dielectric analyses, and solvent extraction studies. The effects of the phenol‐epoxide and the secondary hydroxyl (R‐OH)‐epoxide reactions on the network formation process were analyzed using a recursive modeling technique to obtain expressions for the weight‐averaged molecular weight, the weight fraction solubles, and the gel point as a function of the extent of cure and the epoxide‐phenol reactant ratio. The sol fraction and the gel point predictions from recursive modeling studies of the network formation process agreed with the results obtained from the extraction studies. The results from the network modeling studies were also related to the thermal and rheological properties of the

ISSN:0021-8995    

DOI:10.1002/app.1991.070420609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractNa+and Cl‐transport across 2.4‐ and 5.2‐μm‐thick polyimide (PI) PMDA/ODA and 7.5‐μm‐thick du Pont Kapton films was studied in a diffusion cell using ion‐selective electrodes. The temperature was 30°C. Diffusion coefficientsDm(in cm2/s), permeability coefficientsP(in cm2/s), and distribution coefficientsKwere obtained by applying the time lag analysis on the ion uptake transient in the acceptor compartment of the diffusion cell. Both Na+and Cl‐were observed to diffuse across PI. Diffusion coefficients varied in the range 10‐12‐10‐13cm2/s whereas ionic permeability results showed more scatter ranging from 1 X 10‐11to 8 X 10‐14cm2/s. The latter discrepancy was ascribed to diffuse heterogeneities on the order of 0.5 μm. No significant ionic selectivity between Na+and Cl‐was observed. This result indicates the absence of ionic fixed charge (unreacted polyamic acid) in the polymeric matrix. An attempt is made to determine the effect of water sorption mode and contaminants in the film o

ISSN:0021-8995    

DOI:10.1002/app.1991.070420610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY