摘要:

AbstractBlends of a poly(ethylene 2,6‐naphthalate) (PEN) and a liquid crystalline copolyester (LCP), poly(benzoate‐naphthoate) were prepared in a twin‐screw extruder. Specimens for thermal properties were investigated by means of an instron capillary rheometer (ICR) and scanning electron microscopy (SEM). The blend viscosity showed a minimum at 10 wt% of LCP and increased with increasing LCP content above 10 wt% of LCP. Above 50% of LCP and at higher shear rate, phase inversion occured and the blend morphology was fibrous and similar to pure LCP. The ultimate fibrillar structure of LCP phase appeared to be closely related to the extrusion temperature. By employing a suitable deformation history, the LCP phase may be elongated and oriented such that a microfibrillar morphology can be retained in the solid state. Thermal properties of the LCP/PEN blends were studied using DSC and a Rheovibron viscoelastomer. These blends were shown to be incompatible in the entire range of the LCP content. For the blends, theTgandTmwere unchanged. The half time of crystallization for the LCP/PEN blends decreased with increasing LCP content. Therefore, the LCP acted as a nucleating agent for the crystallization of PEN. The dimensional and thermal stability of the blends were increased with increasing LCP content. In studies of dynamic mechanical properties, the storage modulus (E′) was improved with increasing LCP content and synergistic effects were observed at 70 wt% of LCP content. The storage modulus for the LCP/PEN 70/30 blend is twice that of PEN matrix and exceeded p

ISSN:0032-3888    

DOI:10.1002/pen.760351802

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe fracture toughness of acrylonitrile‐butadiene‐styrene (ABS) was determined by threeJ‐integral methods, ASTM E813‐81, E813‐87, and by hysteresis. The criticalJvalues (J1c) obtained are fairly independent of the specimen thickness, ranging from 10 to 15 mm. ASTM E813‐81 and hysteresis methods result in comparableJ1cvalues, whereas the ASTM E813‐87 was ∼40% to 50% higher. The critical displacement determined from the plots of hysteresis (energy or ratio) and the true crack grow length vs. displacement are close. This indicates the critical displacement determined by the hysteresis method is indeed the displacement at onset of crack initiation, and the correspondingJ1crepresents a physical event of crack initiation. The elastic storage energy. The input energy minus the hysteresis energy, is the most important factor in determining the onset of crack initiation. The critical elastic storage energy (at the beginning of crack growth) was found close to theJ1cobtained from the E813‐81 or the

ISSN:0032-3888    

DOI:10.1002/pen.760351803

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractA combined finite element and finite difference approach has been developed to include the capability to model fluid and thermal transport for the filling of a die cavity by a fluid that has differing sensitivities to extensional and shear deformation rates. This is referred to here as a dual viscosity fluid. For the case of mildly convergent or divergent quasi two‐dimensional flows, a viscosity model is described that has such a dual‐viscosity character and in which shear and extension rate sensitivities are nearly separated. Filling simulation results can be generated rapidly in a modest computational environment. The range of cavities and molding materials that may be modeled realistically is widened by the inclusion of a dual viscosity model. The effect of wall quenching (freezing) increased with decreasing filling rate, while the effect of dual viscosity increased with increasing filling r

ISSN:0032-3888    

DOI:10.1002/pen.760351804

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe influence of mean strain Changes in the range from 0 to 4% on the cyclic deformation and stress‐relaxation properties is investigated using rod specimens of polypropylene. An extensometer measures and controls the axial strain in a closed‐loop, electrohydraulic, servocontrolled mechanical testing machine. The hysteresis loop at different numbers of cyclesNofN= 35, 45, and 50 are irregular in shape, and the tensile portion decreases in size as the number of cycles was increased. The stress value of the tensile portion for three mean strains of ϵm= 1.0%, 2.0%, and 4.0% remains constant, but the value of the compressive portion decreases as the mean strain was increased. The stress level at a strain width of 3% changes little with mean strain. For the strain widths of 5% and 7%, however, the minimum stress levels atN= 35, 45, and 50 increase with increasing mean strain, in contrast to the behavior of maximum stress level. The stressrelaxation tests show that the drop of stress decreases with an increase in number of cycles. The discrepancy in the results of relaxation tests is due to the effect of the difference in strain r

ISSN:0032-3888    

DOI:10.1002/pen.760351805

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe shape of the hysteresis loop has been studied for polypropylene subjected to different cyclic loadings. Cyclic tests were performed under different sets of cyclic strain amplitude and number of cycles, using a closed‐loop, electrohydraulic, servocontrolled testing machine. A constitutive theory is developed for the interpretation of loop shape behavior in terms of elastic, perfectly plastic materials of different yield strengths. The constitutive equation is based on a simple overlay model of bar elements. The calculated results agree well with experiments, which indicates the distictive shape of the hysteresis loop, termed a propelled‐like shape. The truss model reasonably explains the cyclic deformation behavior in polypropyl

ISSN:0032-3888    

DOI:10.1002/pen.760351806

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractPhenolic hydroxyl‐terminated (HTPU) and aromatic amine‐terminated (ATPU) PU modifiers were prepared by reacting two different macroglycols (PTMG, polytetramethylene glycol,Mn= 2000, and PBA, Polybutylene adpate,Mn= 2000) with 4,4′‐diphenylmethane diisocyanate (MDI), then further coupling with two different coupling agents, bisphenol A or 4,4′‐diaminodiphenyl sulfone (DDS). These four types of PU prepolymers were used to modify the epoxy resin with 4,4′‐diamino‐diphenyl sulfone as a curing agent. From the experimental results, it was shown that the values of fracture energy,GIC, for PU‐modified epoxy were dependent on the macroglycols and the coupling agents. Scanning electron microscopy (SEM) revealed that the ether type (PTMG) of PU‐modified epoxy showed the presence of an aggregated separated phase, which varied between 0.5 μm and 4 μm in the ATPU (PTMG) and between 1 μm and 1.5 μm in HTPU (PTMG) modified system. On the contrary, the ester type (PBA) PU‐modified epoxy resin showed a homogeneous morphology and consequently a much smaller effect on toughening for its good compatibility with the epoxy network. In addition, it was found that the hydroxyl‐terminated bisphenol A as a coupling agent improved fracture toughness more than the amine‐terminated DDS because of effective molecular weight buildup by a chain extension reaction. The glass transition temperature (Tg) of modified epoxy resin as measured by dynamic mechanical analysis (DMA) was lower in PTMG‐based PU than in a PBA‐based PU seri

ISSN:0032-3888    

DOI:10.1002/pen.760351807

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe snall angle neutron scattering (SANS) technique has been used to study the interfacial structure development in poly(methyl methacrylate)/polycarbonate (PMMA/PC) blends through transesterification. We found: (1) Development of interfacial structure through transestrification at the phase separated domain interfaces are observed atT≤ 200°C. AtT≥ 215°C, because of a higher transesterification rate, the melting of domains is observed together with very weak scattering by interfacial structure. (2) Interfacial thicknesstiincreases with time and reaches a plateau value oftiat 32.5 ± 2.4 Å and 29.6 ± 3.7 Å for 180°C and 200°C, respectively. (3) The internsity profiles at 190°C and long times shows the formation of spherical domains similar to those reported by Rabeonyet al.(1). These may be caused by the crosslinking effect of the transesterification reaction between

ISSN:0032-3888    

DOI:10.1002/pen.760351808

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760351809

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760351810

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760351801

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY