摘要:

AbstractThe paper consides the effects of compatibilization with maleic anhydride grafted polypropylene (PP‐g‐MAH) on the propertie of immiscible blends of polypropylene (PP) and nylon 6 (N6). We prepared the blends by three different mixing processes; single‐step blending, two‐step blending with reactive premixing, and two‐step blending with nonreactive premixing, to determine the effective mixiing process for fine morphological structure thermal stability, and mechanical properties. Dynamic melt reheological properties were measured to examine the modification of elastic properties by the compatibilizer. In addtion, thermal analysis was also carried out to detect the change in crystallization and thereby to probe the degree of compatibilizaton. The results show that compatibilized blends prepared by teh single‐step process exhibit improved phase morphology, thermal stability, and mechanical properties fordriedconditions, compared with other blend types. Finally, the water absorption test indicates that the added compatibilizer yields enhanced water resistance in spite of the strong intrinsic hydrophilicity of N6. In particular, two‐step blending with reactive premixing is most effective in improving water resistance and reducing degradation of mechanical properties after moistu

ISSN:0032-3888    

DOI:10.1002/pen.760352302

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractA hybrid two‐/three‐dimensional solution technique is presentedto model 3‐D flow fields in resin transfer moeling using Darcy's low. The 3‐D flow field is only solved for regions where all three velocity components are significant, thus largely reducing the number of unknowns. Elsewhere, the commonly used 2‐D approximation for flow in thin gaps between plates is employe.d The method is applied to regions where the flow splits, such as T‐joints. Because of the uncertainties associated with an accurate determination of the permeability in these regions, a simplified decompled procedure is procesed, which reduces the computational complexity. In this procedure, the flow front is advanced using the 2‐D formulation. The 2‐D formulation also provides the boundary conditions for the subsequent computation of the 3‐D flow field without feedback of flow field information to the 2‐d model. The governing equations are solved using boundary fitted coordinate systems (BFCS) together with the finite difference method (FDM). Numerical as well as algebraic grid generation and domain decomposition are employe dto generate grids that always concide with the continuously deforming and enlarging flow domain. Results that include the trackingof numerical tracer particles to visualize the three‐dimensionality of the flow field are presented for isothermal flow of a Newtonian fluid through a T‐joint. This detailed flow field description is expected to form the basis for a rather accurate simulation of quantitities that largely depend on the fluid particle pathlines, such as the degree of cure. The method is also extendable to shear‐thinning fluids as well as to 3‐D flow in the

ISSN:0032-3888    

DOI:10.1002/pen.760352303

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe free and confined inflation of isotropic homogeneour membranes of general shape are considered. The material is assumed to obey the Mooney‐Rivin constitutive model, and the resulting partial differential equations, governing the deformation field, are solved using a Galerkin based finite‐element procedure. The method is illustrated through examples of both free and conflined inflation, as well as simulationeus stretch and inflation. Measurements were carried out on the final thickness distributionof containers blow‐molded inour laboratory. These containers typically cover a wide range of geometry adn size, including bottles with handles. Comparison between theory and experiment leads generally to good agreement, despite the limitation of the membrane hypot

ISSN:0032-3888    

DOI:10.1002/pen.760352304

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractExperiments were carried out in both sliding plate and capillary rheometers with a polypropylene resin to determine the conditions for the onset of slip, surface, and gross melt fracture. It was found that there was no distinction between surface and gross melt fracture, which is commonly observed in the case of polyethylenes. Furthermore, the flow curves determined by using capillaries having various diameters are diameter independent implying the absence of slip. However, experiments with slit dies having rough surfaces suggest wall slip. Further analysis has shown that the effect of viscous heating masks the detection of slip from the diameter‐dependency of the flow curves. The effect of a thin layer of fluoropolymer (Teflon PA, DuPont) on the critical shear stress for the onset of wall slip and melt fracture, as well as on the relationship between the wall shlip and the shear stress, were also examined. It was found that the presence of such layers increases the slip velocity, while it decreases the critical shear stress for the onset of sli

ISSN:0032-3888    

DOI:10.1002/pen.760352305

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Smoluchowski equation for the breakup and coalescence of dispersed droplets has been solved for flowing polymer blends. A scaling form for the distribution of droplet sized derived and published for a system of clusters with fragmentation and coagualation was used in our dervation. Equations are developed here for the average droplet size and for the characteristic time of transition to steady state flow of blends with a high content of the dispersed phase. Expressions reasonably describing the average size of droplets for all concentrations were obtained by a theory modification. Measured dependences of droplet size on the blend composition can be matched only if simultaneous collisions of three and more droplets are considered. The results of the theory indicate that the mechanism of droplet breakup (formation of pieces with the same or different volumes) has only a small effect on their average size in concentrated systems. The dependence of droplet size on the shear rate in flow is determined by properties of the blend components, and is generally nonmonotonic.

ISSN:0032-3888    

DOI:10.1002/pen.760352306

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractMultilayer LDPE/nylon‐6 films with an overall content of 71 wt% LDPE, 24 wt% nylon‐6, and 5 wt% PE‐based tie‐layer adhesive were reprocessed under both minimal and extensive mixing conditions. Thermal and mechanical properties, oxygen and water vapor permeability, and morphology of the reprocessed samples were determined. The modulus and yield stress of the reprocessed films fell between those of the pure homopolymers, whereas percent elongation at break and energy‐to‐break for all reprocessed films were less than those of the homopolymers. In minimally reprocessed film, layering of LDPE (low‐density polyethylene) and nylon‐6 was retained, whereas in extensively mixed samples, nylon‐6 domains were spherical and ranged from 0.2 to 7 μm. Minimally reprocessed film exhibited good O2and H2O vapor barrier properties, whereas extensively‐mixed samples had poor barrier properties. Properties of well‐mixed blends prepared both with and without adhesive showed that 5 wt% adhesive did not compatibilize the LDPE

ISSN:0032-3888    

DOI:10.1002/pen.760352307

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractTwo series of unsaturated polyesters (UPE from isophthalic acid, fumaric acid, and propylene glycol) were prepared. In series‐A resins, UPEs wee thickened with isocyanate‐terminated saturated aliphatic polyestes, i.e., an isocyanate‐terminated polycaprolactone diol (PE‐di‐OL), through reaction of the isocyanate group with the hydroxyl group of the UPE. In series‐B resins, the UPEs were mixed with saturated aliphatic polyesters i.e., PE‐di‐OL. The curing reaction of these two series of UPEs with styrene was studied by using differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). The DSC data show that for a fixed PE‐di‐OL molecular weight, the curing reaction rate of series‐A UPE is faster than that of series‐B UPE. The variation of microgel size during curing ws studied by GPC. These results revealed that microgel formation has a great effect on the kinetics of cure for the unsaturated polyester‐styrene system. The curing of these two series of UPEs is found to strongly depend on the compatibility of the compon

ISSN:0032-3888    

DOI:10.1002/pen.760352308

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractA new stress monitoring technique, a stress‐tracking device, is described here. It has been used to study some important properties of epoxy resin. Residual stresses, including a curing shrinkage stress and a cooling shrinkage stress, were measured automatically and continuously during curing and cooling. Simultaneously, information such as an apparent gelation time and glass transition temperature were obtained directly during the experiment. These epoxy resin properties were related to the extent of cure. Varying cure temperature produced changes of cure behavior, which resulted in different residual stresse

ISSN:0032-3888    

DOI:10.1002/pen.760352309

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractProcessing of microcellular foam was investigated for the feasibility of production of tough and lightweight polyurethanes. To increase the nucleation rate in a gas‐supersaturated resin, ultrasonic excitation was applied to the mixture of polyol(polyether‐based polyol) and isocyanate(diphenyl methane diisocyanate). A microcellular structure was produced by two sequential steps, i.e., supersaturationof the polyol resin with nitrogen gas at elevated pressure and ultrasonic bubble nucleation right after the impingement mixing of two components of the polyurethane system. Theoretical analyses based on nucleation theories were employed to predict the rate of nucleation in the gas‐supersaturated polyurethane. The rate of nucleatio in the resin was predicted by classical nucleation and cluster theories. In the experimental investigation, ultrasonic excitation was applied to increase the nucleation rate in the resin that had been saturated by nitrogen at a saturation pressure<2.

ISSN:0032-3888    

DOI:10.1002/pen.760352310

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractPrevious research and this research indicate that the mechanical melting for poly(vinylidene chloride) copolymers (PVDC) is complex. Mechanical melting is defined as the melting (or devitrification) of a polymer when a significant portion of the thermal energy originates from a mechanical energy dissipative process. PVDC mechanically melted on a moving metal surface at temperatures of the test instrument that were considerably lower than the differential scanning calorimetry (DSC) onset melting temperature. PVDC formulated with low levels of high density polyethylene (HDPE), however, melted at metal temperatures near the DSC onset melting temperature. Two different mechanical melting mechanisms are proposed to explan the data, and the frictional data are discussed with respect to solids conveying in a single‐screw, plasticating extrude

ISSN:0032-3888    

DOI:10.1002/pen.760352311

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY