摘要:

AbstractDGEBA‐DDM (diglycicyl ether of bisphenol‐A‐diamino diphenyl methane) networks of various epoxide/amine molar ratios ranging from 0.7 to 1.4, were studied by density, quasi static (10−4s−1), and ultrasonic (5 106s−1) modulus, and thermostimulated creep measurements. Any step aside stoichiometry leads to an antiplasticization, e.g. an increase of the quasi static modulus, whereasTgdecreases. The previous interpretations (based on volumetric property considerations), of this phenomenon are questionable. The only common feature of all the antiplasticized systems is an unexplained decrease of the population of macro‐molecular segments involved in

ISSN:0032-3888    

DOI:10.1002/pen.760300602

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractBulk compression flow of high density polyethylene (HDPE) and low density polyethylene (LDPE) have been measured at temperatures of 423 to 463K, pressure up to 150 MPa, and bulk compression rates of about 1.0 to 200.00 × 10−5s−1. Bulk and surface compression modulus of elasticity (LandKs), longitudinal bulk compression viscosity (ηL), and surface compression viscosity (η Ks) are described as a function of compression rates (kvandks), compression deformations (kvpercent andKspercent), and temperature (T). Bulk and surface compression flow activation energies are of the order of 40 to 100 KJ/mol and 3.84 KJ/mol, resp

ISSN:0032-3888    

DOI:10.1002/pen.760300603

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe cast film process is studied and a numerical simulation is performed using a finite element method. Two dimensional equations involving the thickness and a mean velocity are used by considering the film as a thin layer. The process is assumed to be isothermal between the die exit and the quick cooling on the chill roll. The width of the film is computed iteratively as a free surface problem by means of a finite element method. The thickness distribution of the film is obtained by a finite volume method. This approach allows modeling of the well known “dog‐bone” or “edge bead” defect with a reasonable computa

ISSN:0032-3888    

DOI:10.1002/pen.760300604

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractBinary blends of ethylene vinyl alcohol copolymers, containing 62 (EVOH‐62) and 71 (EVOH‐71) mole percent vinyl alcohols, with nylons (nylon‐6, nylon‐6/12, and nylon‐12) have been prepared from melt mixing in a twin screw compounding machine. Morphological, thermal, rheological, and mechanical properties were determined. EVOH‐62/nylon‐6 and EVOH‐71/nylon‐6 blends showed homogeneous phase morphologies in the nylon‐6‐rich region, and fine phase separations (c.a. 2 × 10−7m) in the EVOH‐rich region. Melting point depression, positive deviations in viscosity and flexural modulus, and negative deviation in impact strength from the simple additive rule were generally observed. And the results were possibly interpreted in terms of compatibility and increased nylon/EVOH interactions over the nylon/nylon interactions. On the contrary, clean phase separations in large domains were observed from EVOH‐71/nylon‐6/12 and EVOH‐71 /nylon‐12 blends. Fibrillation was also obtained from EVOH rich blends. Probably due to the incompatible nature of these blends, yield at low rate of shear and a mechanica

ISSN:0032-3888    

DOI:10.1002/pen.760300605

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractChawla,et al.(2) recently described a new SISO control algorithm called the Conservative Model Based Control (CMBC). In this paper, we assess the feasibility of implementing CMBC as a multiloop controller on a simulated reactor used for the polymerization of methyl methacrylate. Both servo and regulatory behavior of the controller are studied. Despite the non‐linearities and coupling between the two controlled variables, the easy‐to‐implement CMBC algorithm has been shown to give good control perfor

ISSN:0032-3888    

DOI:10.1002/pen.760300606

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractIn attempts to improve the compatibility of polypropylene with polyethylene terephthalate, an acrylic acid functionalized polypropylene was evaluated as the blend component in polyblends containing 40 percent by weight polyethylene terephthalate and compared with an unmodified polypropylene. The preliminary experiments in a batch laboratory mixer were followed by compounding in a co‐rotating twin‐screw extruder. Additives such as magnesium acetate and p‐toluenesulfonic acid were evaluated as catalysts for potential interchange or esterification reactions that could occur in the melt. The blends were characterized through scanning electron microscopy, infrared spectroscopy, differential scanning calorimetry, and for mechanical properties. The results show that the functionalized polypropylene promotes a fine dispersed phase morphology, improves processability and mechanical properties, and modifies the crystallization behavior of the polyester component. These effects are attributed to enhanced phase interactions resulting in reduced interfacial tension (calculated as a 4‐fold decrease). The presence of the additives does not, in general, improve any further the blend morphology and properties, or its process

ISSN:0032-3888    

DOI:10.1002/pen.760300607

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe cure process of a BADGE (diglycidyl ether of bisphenol‐A) resin (Epon 828) and ethylenediamine has been investigated by means of calorimetry and dielectrometry in the microwave region (107–1010Hz) in the temperature range 50 to 70°C. Kinetic data from calorimetry were analyzed in detail. An overall kinetic order of 2.5 has been obtained. The time domain reflectometry (TDR) has been used to characterize pure components and their mixtures. Cure monitoring was carried out with both TDR and a cavity method at fixed frequency (9.5 × 109Hz). A very good agreement was obtained between the reaction rate as measured by calorimetry and the rate of decrease of dielectric constants up to very high conversion. This was explained by admitting that the rates of disappearance of dielectric dipoles and of reactive species coin

ISSN:0032-3888    

DOI:10.1002/pen.760300608

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractAC dielectric properties and thermally stimulated polarization (TSP) and depolarization (TSD) currents were studied in a series of CaCO3‐filled polypropylene composites. The filler content (0 to 50 weight percent) and the average particle size (3.0 to 16.1 μm) at constant filler content (30 weight percent) were varied in separate groups of samples. In a third group of samples the filler (20 to 40 weight percent) was surface treated with stearates. The AC dielectric behavior of composites containing untreated fillers is largely determined by a small amount of adsorbed water. Upon heating, the dielectric properties show maxima (increasing with decreasing frequency) which disappear on cooling. In the case of stearate‐treated fillers the dielectric loss level is higher, the dispersion and loss curves on heating reflect a combination of dipolar and protonic processes with water desorption. In the dry state the onset of an audio frequency relaxation process is observed in the pre‐melting zone. The thermally stimulated currents of the composites containing treated and untreated fillers are also different. In the case of the untreated fillers the TSP curves show maxima indicating water desorption which are increasingly intense and roughly exponential with filler content. The high temperature conductivity and the intensity of the pre‐melting depolarization peak pass through a minimum as a function of filler content. Above 20 weight percent filler content the activation energy of high temperature conductivity decreases. In the case of the surface treated samples, the thermally stimulated response is different for “wet” and dried samples. The dry samples exhibit a relaxation between the amorphous and crystalline transitions of the matrix polymer which is probably due to interfacial relaxation caused by the enhanced surface conductivity of the stearate‐t

ISSN:0032-3888    

DOI:10.1002/pen.760300609

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760300601

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY