摘要:

AbstractThe bulk surface and thermal properties and chemical conformation of several poly(methyl methacrylate) samples have been characterized. The results of the analysis have correlated well with the suitability of the thermoplastic sheets for optical coating or thermal forming operation. Techniques for inspection of the plastic sheets appropriate for such special applications have been recommended.

ISSN:0032-3888    

DOI:10.1002/pen.760180802

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractIn coextrusion of multilayer film and sheet, one type of flow instability which can occur is a wavelike distortion of the interface under certain coextrusion conditions. Severe instability can cause intermixing of the layers, particularly in thin skin coextrusion. Observations have shown that the onset of instability is associated with a “critical interfacial shear stress”. This paper describes a mathematical model of non‐Newtonian multilayer flow which was used to correlate experimental observa

ISSN:0032-3888    

DOI:10.1002/pen.760180803

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractIt is shown that the technique of dynamic spring analysis (DSA) gives rise to a dynamic mechanical loss dispersion well above the glass transition temperature,Tg, analogous to theTuprocess observed in torsional braid analysis. A mechanical model is proposed which explains why any composite sample consisting of an elastic support coupled to a viscous liquid must necessarily produce such a relaxation regardless of whether the liquid is monomeric or polymeric in nature. Loss tangent measurements performed on a series of polystyrenes of varying molecular weight and on glycerol using both DSA and a Rheometrics mechanical spectrometer show that the relaxation observed in DSA is not of molecular origin.

ISSN:0032-3888    

DOI:10.1002/pen.760180804

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractDivalent metal salts of ethylene glycol‐methacrylate‐maleate in the amorphous state were easily soluble in styrene, methyl methacrylate and ethyl acrylate, to give homogeneous, curable mixtures with high metal content. The viscosities of the mixtures varied depending on the metal present. The mixtures were copolymerized to give metal‐containing cured resins of increased compressive strength and Rockwell hardness. Moreover, heat distortion temperature could be improved by introducing Mg or Ca. Of the cured resins studied, the Mg‐containing resin showed the best physical properties. Resistance of the metal‐containing resins to attack by organic solvents was generally high, whereas greater degradation by aqueous reagents was noted. The thermal behavior of the resins is

ISSN:0032-3888    

DOI:10.1002/pen.760180805

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe fatigue lives of graphite fiber reinforced nylon composites were related uniquely to the tensile strengths of the materials. The distributions of tensile strength and fatigue life were measured and correlated with either two‐ or three‐parameter Weibull functions. For a specific population, there existed a unique relationship between the two cumulative distributions. Thus, if the effect of an environmental variable on the distribution of strength is measured, the effect on the fatigue life can be estimated. It was also found that the mechanism of fatigue failure was influenced by the technique of fabrication. Compression molded materials failed through an isothermal, brittle mode of fracture, while injection molded materials failed in a ductile, thermal m

ISSN:0032-3888    

DOI:10.1002/pen.760180806

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractUpper and lower bounds for the die swell ratio are derived for all simple fluids in the presence of surface tension and under the assumptions that the flow remains viscometric up to a finite distance from the exit and that bounds on the shear stress distribution in this length exist. Both circular and plane jets are considered and the bounds so derived depend on the normal stress on the wall in the viscometric region. For Newtonian and power law fluids, this stress can be determined,a priori, from existing theories. However, for viscoelastic liquids, it is an open question at present.

ISSN:0032-3888    

DOI:10.1002/pen.760180807

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractResistivity and dielectric constant of polyethylene/carbon black compounds were measured from room temperature to 140°C. Within the polyethylene melting region a PTC/NTC (positive followed by negative temperature coefficients) phenomenon is observed, whose intensity depends on the type of carbon black, its concentration and other parameters. Reproducibility of the PTC phenomenon in polyethylene compounds containing a single type of carbon black is rather low. However, by using mixtures of carbon blacks differing appreciably in their particle size, remarkable reproducibility improvements can be achieved. Several other aspects are also discussed in the present paper covering current‐voltage relationships in these materials, comparison of PTC curves with DSC thermograms upon heating and cooling, and dielectric constant‐temperature relations. The carbon black concentration giving the optimum PTC intensity can be predicted approximately from room temperature

ISSN:0032-3888    

DOI:10.1002/pen.760180808

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractModel blends of glassy amorphous polystyrene and each of four different crystallizable and rubbery polyolefins of varying side‐chain molecular weight (polyethylene, polypropylene, poly(1‐butene), poly (4‐methyl‐1‐pentene)) have been prepared by melt extrusion of the polymeric components. Density measurements, differential scanning calorimetry (DSC), swelling measurements, and X‐ray diffraction have been performed on the extruded fibers. In all cases, over the entire range of blend composition, the polymeric blends are immiscible and incompatible. The DSC measurements indicated that the polystyreneTgwas not decreased after blending and that the small reductions in the crystallinity and melting point of the respective polyolefins was best explained by thermal and kinetic interference with homo‐crystallization of the respective polyolefins in the blends. The volumetric swelling and gravimetric sorption of n‐hexane in the various blends increased monotonically with polystyrene content. The companion experiments, relating axial swelling with polystyrene content, indicated that this particular mode of distension actually decreased with increasing polystyrene content. The composite results, including DSC, X‐ray, density, volumetric swelling and axial swelling suggest that the polystyrene phase is essentially microfibrillar and oriented in the direc

ISSN:0032-3888    

DOI:10.1002/pen.760180809

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe operation of a twin screw extruder processing a powder or granular solid is reviewed. The operating variables of screw speed and barrel temperature profile interact with a number of design parameters— screw design, die geometry, feed zone geometry and with the material properties, in determining machine performance. The factors that determine output and pressure development are specified in a sequence of block diagrams. The dynamic response of an operating machine to disturbances in the steady state conditions is explained in the light of the established relationships and interpreted in conventional control theory terms. Attention is drawn to the importance of mixing in the chambers formed by the screw channels and of the residence time distribution in determining the quality of the final produc

ISSN:0032-3888    

DOI:10.1002/pen.760180810

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractLength‐temperature measurements were made on unfilled and carbon‐black filled vulcanizates of styrene‐butadiene rubber. As in earlier experiments on polybutadiene, transients in thermal expansion behavior were observed following abrupt changes in the temperature. The nature of this time dependence was not dramatically affected by either the level of equilibrium strain or the structure and loading of the carbon‐black filler. Both the magnitude of the linear coefficient of thermal expansion and the point of thermoelastic inversion were sensitive to the presence of carbon‐black. A model based on considerations of occluded rubber and strain amplification in the free rubbery matrix was used successfully to rationalize the observed behavior of the filled

ISSN:0032-3888    

DOI:10.1002/pen.760180811

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY