摘要:

AbstractThe hydrolytic stability of glass fiber reinforced poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET) and polycarbonate (PC) was studied. The activation energies in kcal/mole for hydrolysis are 26 for PBT and 23 for PET. Both PBT and PET contain 30 percent glass fiber reinforcement. The hydrolysis rates for a series of experimental PC's containing 10, 30 and 40 percent glass were obtained from GPC data. These increase with glass concentration but are lower than that of the unreinforced PC. Melt flow rate changes are a good measure of the hydrolytic degradation of PET. However, in the time scale of these experiments, the tensile properties of glass reinforced PBT and PC do not correlate well with M̄wchanges, unlike unreinforced PBT and PC polymers. Consequently, to compare these three glass fiber reinforced polymers, estimates of failure time must be based on changes in tensile strength rather than melt flow rate

ISSN:0032-3888    

DOI:10.1002/pen.760231002

出版商:Society of Plastics Engineers, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractInfrared spectroscopy (4000–50 cm−1) was used to characterize the two crystalline modifications of poly(p‐phenylene terephthalamide). Polarized studies revealed that hydrogen bonds are oriented primarily perpendicular to the film plane in both forms. We also found that the crystalline modification coagulated in water could be transformed into the other form by annealing at high tempera

ISSN:0032-3888    

DOI:10.1002/pen.760231003

出版商:Society of Plastics Engineers, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractSolubility (sorption) and transport measurements with water in solvent‐free poly (acrylonitrile)(PAN) (23) have been interpreted in terms of an extension of the “dual‐sorption” model for transport of small molecules in glassy polymers. Satisfactory agreement has been obtained between theory and experimental data. An earlier analysis of similar data for water in PAN containing 0.26 percent (by weight) of a residual solvent (1) has been compared with the present results in order to investigate the effects of residual solvent on the dual‐sorption and transport parameters for the water

ISSN:0032-3888    

DOI:10.1002/pen.760231004

出版商:Society of Plastics Engineers, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe striation thickness distribution developed in an impingment T‐mixer is predicted using the statistical theory of turbulent diffusion. The predicted distribution is independent of the mixing nozzle Reynolds number, in agreement with some experiments, and is primarily a function of the mixing head geometry, the ratio of the reagent flow rates and the residence time distribution of the flow in the mixing head. Mixing is described as the result of fluid deformation in the intertial subrange of turbulent flow. The relationship of deformation to time and energy dissipation rate ϵ is examined. In the impingement T‐mixer ϵ is related to the kinetic energies of the streams entering and leaving the head. (There are no surface tension effects and pressure is relatively uniform in the mixing head, so that the kinetic energy is dissipated by viscous forces.) The distribution of residence times of fluid elements in the T‐mixer is responsible for varying degrees of deformation and hence a distribution of striation thickness. This residence time distribution does not seem to have been studied and the flow pattern was thus modeled as perfect macromixing, having an exponential distribution. The procedure developed in this paper to calculate the distribution of striation thickness allows reasonable estimates of its parameters from fluid mechanical information and showed good agreement with experimental values, without having to fit any quantities. This new approach to striation thickness distribution is worth further eva

ISSN:0032-3888    

DOI:10.1002/pen.760231005

出版商:Society of Plastics Engineers, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractIn order to analyze the failure phenomenon of plastic liners in freezers and refrigerators the mechanical properties of the freon blown polyurethane (PU) foam insulator material and the acrylonitrile‐butadiene‐styrene (ABS) plastic liner are determined. The properties considered essential for this problem are the elastic modulus, the tensile strength and the fracture toughness over the temperature range −40 to 20°C. By laminating a layer of the polyurethane foam to the ABS liner and depending on the test temperature brittle to semi‐brittle fractures are promoted and the maximum load fracture toughness of the liner material is reduced. The reduction is more severe for notched bend than for single‐edge notched tension specimens. Based on these mechanical properties plausible reasons for liner fractures are

ISSN:0032-3888    

DOI:10.1002/pen.760231006

出版商:Society of Plastics Engineers, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe resistance and resistivity of Ketjenblack EC/silicone rubber compounds were studied as function of strain in constant strain rate experiments. Both strain and rate of strain affect the electrical resistivity of the compounds. Such effects are carbon black concentration dependent. Ketjenblack EC, a low structure black, is shown to behave differently than other blacks of high structure in the electrical resistivity‐strain experiments. The resistivity in the straining experiments is determined by the transient distribution of the conductive particle arra

ISSN:0032-3888    

DOI:10.1002/pen.760231007

出版商:Society of Plastics Engineers, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe rheology of a variety of polyolefin resins, and resin blends, has been examined under conditions of constant strain rate elongation. These include high, low, and linear low density polyethylene, as well as polypropylene, commercially modified polypropylene, and elastomer blends with polypropylene. Two distinctly different classes of behavior are apparent in the viscosity growth patterns during uniaxial extension. Some resins display unbounded stress growth even at low strain rates. Others quickly attain a time independent value of extensional viscosity even at increased strain rates. The former behavior is identified with favorable blow molding behavior, while the latter was characteristic of resins unsuitable for such processing. The class of elongation behavior depends not only on resin type, but may be influenced by molecular weight distribution or blend morphology.

ISSN:0032-3888    

DOI:10.1002/pen.760231008

出版商:Society of Plastics Engineers, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractReactive polymer processing is the combined polymerization and processing of reactive prepolymers in a single operation. It encompasses a wide variety of processing methods including Reaction Injection Molding (RIM), a relatively new and growing fabrication method. Reaction Injection Molding utilizes impingement mixing of low viscosity fluids, injection of the reactive mixture into a mold, and polymerization therein to enable the molding of large plastic items. Polyurethane is currently the most commercially utilized RIM material although a number of other systems such as epoxy, nylon, and polyester are also suitable. Non‐urethane systems such as epoxy are often not as amenable to the process, however, since they are slower reactions and have a potentially damaging exotherm. A comprehensive analysis was developed to determine if a molding system is processable by RIM. Criteria for processability were established and include the ability to mix on impingement, fill large molds characteristic of the process, and provide a short cycle time without promoting a damaging exotherm. The treatment, consisting of both experimental and numerical techniques, was applied to identify potential epoxy molding systems, establish their processing window, and conduct an optimization of the process parameters to evaluate productivity. The analysis and its conclusions are applicable to most reactive polymer processing operations that employ a rapid, exothermic, polymerization reactio

ISSN:0032-3888    

DOI:10.1002/pen.760231009

出版商:Society of Plastics Engineers, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractA recent development suggests an approach to measure the equilibrium modulus through an impulse method. This paper is to report an attempt to apply such methods in measuring the changes of the equilibrium modulus of a thermosetting system during isothermal cures. Dynamic modulus changes were also measured and the results were correlated with that from the impulse method. At two different temperatures of cure, the equilibrium modulus values measured were very similar when the dynamic measurements showed tan δ = 1. At this point, it is not certain if the measured modulus is the real time independent portion of the elastic modulus, or contains the long relaxation time constant portion of the relaxation spectrum which appears to be pseudo‐time independent at the time scale and the instrumental sensitivity of the present experimental set‐up. This paper demonstrates the ease with which the impulse technique can be applied and suggests possible limitations or refinem

ISSN:0032-3888    

DOI:10.1002/pen.760231010

出版商:Society of Plastics Engineers, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractWhen injection molding complex parts, often knit‐lines are formed during the mold filling stage. These knit‐lines are well‐known as particularly critical regions in the mold when mechanically loaded. Using three test materials, polystyrene (PS), polycarbonate (PC) and polyoxymethylene (POM), the relationship between a design and a processing parameter and the effects of the knit‐lines on the tensile properties of injection molded plates with holes is quantified by the variation of a socalled knit‐line‐factorak1. Finally, for PS a comparison of the influence of knit‐line‐formation by a splitted melt stream and by multi‐gating on the mechanic

ISSN:0032-3888    

DOI:10.1002/pen.760231011

出版商:Society of Plastics Engineers, Inc.    

年代:1983

数据来源: WILEY