摘要:

AbstractA statistical study of the strength of unmodified and modified uniaxially drawn polypropylene tapes was carried out. The results show that the curve representing the distribution of strength for unmodified tapes reveals seven discrete levels corresponding to microdefects in the form of microcrazes and submicrocrazes. On introduction of modifying additive, three discrete strength levels were observed, corresponding to submicrocrazes. The strength of the modified polypropylene tape increase approximately twice compared to the strength of the initial material. The polyfunctional effect of the additives as artificial nucleators and regulators of the structure leads to an increase of the degree of crystallinity which in turn restrains the submicrocrazes development into microcrazes. The method used could be applied for objective analysis of the tensile characteristics of polymeric materials.

ISSN:0032-3888    

DOI:10.1002/pen.760351402

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractMechanical properties of the ternary blends of poly(ethylene terephthalate) (PET), polycarbonate (PC), and thermotropic liquid crystalline (TCLP, Vectra A950) were investigated. The ternary blends were prepared by varying the amount TLCP but fixing the ration of PET and PC. The fiber fallen freely through the capillary die had the highest initial modulus (1.46 GPa)/tensile strength (73 MPa) when 10% of TLCP was added. Above this TLCP content, however initial modulus and tensile strength decreased. The scanning electron microscope (SEM) micrographs of the TLCP phase which was extracted by dissolving PET/PC matrix from the blend showed the fine fibrils formed at 5 and 10% of TLCP, while the aggregated TLCP phases at 20 and 30% of TLCP. It was suggested that the decrease of the mechanical properties of the resulting blend was caused by the aggregation of TLCP phase above 10% of TLCP. A high draw ratio gave a rise to the formation of highly oriented fibrils of TLCP phase in thePET/PC matrixand the improvement of mechanical properties of the ternary blend.

ISSN:0032-3888    

DOI:10.1002/pen.760351403

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe physical aging characteristics of oriented poly(ethylene terephthalate) (PET), have been studied ad functions of storage time and temperature below the glass transition temperature (Tg) of PET. The free volume relaxation, associated with aging, has been characterized by the enthalpy atTg, as measured by differential scanning calorimetry. The effects of the free volume relaxation on mechanical properties and the mode of failure have been investigated. It has been determined that a correlation exists between the enthalpy of relaxation and the ductile‐to‐brittle failure transition. Molecular orientation reduces significantly the enthalpy of relaxation, resulting in the disappearance of the ductile‐to‐brittle transition when highly oriented samples are aged over time. It has been established that a minimum amount of orientation is required to reduce or eliminate the effects of PET aging. Molecular orientation has also been found to reduce craze formation when oriented PET is exposed to a stress‐cracking medium at consta

ISSN:0032-3888    

DOI:10.1002/pen.760351404

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractAn experimental study of the effect of crystallinity on the light scattering of regenerated cellulose tubular films is reported. Several films were prepared by varying manufacturing conditions, so that thickness and surface roughness were maintained approximately constant and the degrees of crystallinity varied between 38 and 66%. The scattered radiation intensity, measured between 220 and 550 nm decreases with the increasing wavelength. It was demonstrated that for the polymeric films studied, there was excellent agreement between crystallinity and scattering radiation intensity for a given wavelength. It was found that for crystallinity values less than around 57%, scattered radiation intensity decreases with increasing crystallinity, the reverse of that for crystallinity values greater than that percentage.

ISSN:0032-3888    

DOI:10.1002/pen.760351405

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of temperature over the range −196 to 150°C on the crosslinking of polyethylenes irradiated by electron beam has been investigated on the basis of gel content determination and Fourier transform infra‐red (FTIR) spectroscopy. The crosslinking efficiency increases significantly with increasing irradiation does and at elevated irradiation temperature. The crosslinking rates of high density polyethylene (HDPE) and low density polyethylene (LDPE) samples above the melting point (TM) are much higher than those belowTm. The FTIR data give positive evidence: (i) that trans‐vinylene double bonds in cross linked HDPE and LDPE samples increase with increasing irradiation dose temperature (ii) that vinyl double bonds in HDPE decrease rapidly with increasing irradiation dose and temperature, and (iii) vinylidene groups in LDPE decrease slowly with increasing temperature at the lower dose and are almost independent of the irradiation temperature at above room temperature and the higher dose of more than 100 kGy. Gas bubbles are observed in LDPE samples irradiated at 100 and 150°C with high dose (200 to 250 kGy). The size of the bubbles increases gradually at high tempe

ISSN:0032-3888    

DOI:10.1002/pen.760351406

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper reports on the tensile properties of microcellular foams of three different thermoplastics, since there have been several reports in the literature, but with indefinite conclusions so far, that microbubbles act in a manner similar to rubber particles in toughening thermoplastics. Polystyrene (PS), styreneacrylonitrile copolymer (SAN), and polycarbonate (PC), were selected based on their different intrinsic ductilities. The gas supersaturation technique was used to generate samples with microbubbles. The effect of the presence of microbubbles inside the polymer matrix was separated from the effects of the pressure and thermal history experienced by the samples. Nitrogen gas dissolved into PS, and to a lesser extent into SAN, caused and increase of the tensile toughness, but this increased decayed with time as nitrogen gas diffused out of the samples. Furthermore, microcellularly foamed PS samples showed some limited improvement in terms of tensile toughness after all the nitrogen gas diffused out. SAN and PC showed deterioration of the tensile toughness in the presence of microbubbles.

ISSN:0032-3888    

DOI:10.1002/pen.760351407

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractIn the first part of this series of papers, the tensile properties of microcellular foams of polystyrene (PS), styrene‐acrylonitrile copolymer (SAN), and polycarbonate (PC) were reported. In this part, the impact properties of unnotched, sharply and bluntly notched samples of microcellularly foamed PS and SAN samples were studied. Furthermore, the effects of the sharpness of the notch as well as of the speed of the test were studied by comparing the impact tests with the single‐edge‐notched (SEN) tensile tests, which were carried out for the PS, SAN, and PC sample. Some limited improvement in impact and SEN tensile properties was exhibited in some experimental conditions. The impact properties of microcellularly foamed PC samples are reported else

ISSN:0032-3888    

DOI:10.1002/pen.760351408

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe kinetics of water sorption by starch filled polyolefins has been investigated using blends of commercial starch masterbatch with low density polyethylene (LDPE), high density PE (HDPE), and copolymers of ethylene with methyl acrylate (EMA), ethyl (EEA), AND n‐butyl acrylate (EBA). Transient state diffusion coefficients (D) of water in the blends were determined using Fickian analysis of the initial stages of the sorption isotherms. Measured D values were several orders of magnitude lower than values reported for either pure starch of LIDPE by various investigators. Resin effects on D were on the order DHDPE

ISSN:0032-3888    

DOI:10.1002/pen.760351409

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractExtruded microlayer sheets of Polycarbonate/Polyester (PC/PCTG) and Polycarbonate/Styrene‐acrylonitrile (PC/SAN) were tested for ballistic performance. Composition of the microlayer sheets ranged from 60 to 100 percent polycarbonate. The number of layers in the approximately 3 mm thick sheets ranged from on for the blend control samples to 3713 layers in the PC/PCTG sheets. The normalized ballistic test results showed that some samples performed as well as as and slightly better than injection molded polycarbonate samples. The failure mechanism was affected by the composition and the number of layers. Increasing composition of polycarbonate and number of layers decreased the percent of brittle failure

ISSN:0032-3888    

DOI:10.1002/pen.760351410

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760351401

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY