摘要:

AbstractThe surface tension of a polymer liquid is a property of considerable practical importance. Within the past decade the experimental difficulties in accurately measuring the surface tension of viscous polymer melts have been overcome, and a considerable body of data is now available. This review discusses the measurement techniques which have proved useful, the results which have been obtained, and theoretical approaches which have been applied to them. A tabulation of surface and interfacial tension values which have been published up to mid‐1971 is include

ISSN:0032-3888    

DOI:10.1002/pen.760120102

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractAn improved theoretical model was derived for the solids conveying zone of a plasticating extruder. The model makes possible calculations in variable channel depth section. It also allows for a bulk density which is a function of pressure and for the non‐isotropic pressure distribution in the solid plug. An expression for maximum flow rate was also derived. Results simulated by the model on a computer indicate the effect of variables on extruder performance. The power consumption terms in the solids conveying zone of a plasticating extruder were also derived. Total power consumption is the sum of power consumptions on the barrel surface, screw surfaces and those due to pressure rise. Their relative importance was analyzed by computations. The effect of operating conditions and coefficients of friction on the various power terms was also analyze

ISSN:0032-3888    

DOI:10.1002/pen.760120103

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractDynamical mechanical relaxation spectra of a number of polyurethane‐polyether block copolymers have been studied as a function of composition, temperature and frequency. At low temperatures these copolymers are characterized by a high glass‐like modulus which decreases to a much lower typically elastomeric value in a narrow temperature range. The latter is a function in certain cases of the composition of the polymer. The rubbery plateau is maintained up to at least 140°C. In addition, a secondary relaxation is observed around −130°C. These observations can be interpreted in terms of an overall structure consisting of a polyether matrix containing segregated polyurethane domains, the latter serving as physical crosslinks in the system at ambient temperatures an

ISSN:0032-3888    

DOI:10.1002/pen.760120104

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe progress of interfacial debonding caused by the diffusion of boiling water to glass fibre/polyester resin interfaces has been followed by shining a He‐Ne laser beam along fibres and recording the changes in intensity of the emergent beam. Compared with measurements of electical conductivity arising from the presence of diffused water at the interface, it is concluded that the laser beam method provides more certain evidence of debonding.The glass/resin interface has also been investigated in partially cured composites and in filled composites, during exposure to boiling wate

ISSN:0032-3888    

DOI:10.1002/pen.760120105

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThis paper describes the use of an electron microprobe for characterizing filler and polymer dispersios in polymer composites. Examples described are: filler distribution in sisal reinforced polyester; aggregation of titanium dioxide in glassreinforced polyester; mixing behavior in a blend of silicone rubber, natural rubber, and titanium dioxide; and distribution of silica in a low‐gloss paint on an ABS plastic surface. The limitations of electron microprobe analyses for qualitative and quantitative studies, the use of back scattered electrons for surface topography, and techniques for preparing specimens are mentione

ISSN:0032-3888    

DOI:10.1002/pen.760120106

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractIn a study of the transient behavior of a series of nylon 6/6 yarns differing systematically in mechanical properties, the effects of high‐speed, transverse missile impact upon yarn specimens were observed by high‐speed photography. The loss in missile kinetic energy was determined directly from the reduction in missile velocity and was studied as a function of yarn tenacity and missile impact velocity. The shape of the missile energy loss curves was due to the partition of missile energy into yarn kinetic energy and yarn strain energy. The missile energy losses and yarn dynamic breaking strains were compared to static breaking energies and breaking strains for these yarns. The observed trends are discussed in terms of the differing yarn tenacities and test ra

ISSN:0032-3888    

DOI:10.1002/pen.760120107

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe structural utility of short, glass fiber‐reinforced epoxy composities is experimentally investigated for fiber volume fractions from 0.15 to 0.5. The strength and stiffness of systems with randomly oriented fibers are compared with those of similar composites with aligned fibers. The ultimate strength of both types of material increses in a reasonably linear fashion with volume fraction up to 0.5. For all volume fractions in this range, strength of the random composites is slightly higher than the longitudinal and much higher than the transverse strength of equivalent compsites with aligned fibers. The modulus of the random system is approximately two‐thirds the longitudinal and twice the transverse modulus of the unidirectional material. The structural utility of the flow molded material is greatest in uniaxial, stiffness critical situations. The greater strength and planar isotropy of the random composites make them preferable in all strength limited or multiaxial applicati

ISSN:0032-3888    

DOI:10.1002/pen.760120108

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractEvidence is presented of the main steps in the physical breakdown of glass‐fiber reinforced polyester (GRP) composites on outdoor weathering. The chronological sequence is fiber ridging, rupture of the resin layer covering ridging fibers or fibers running close to the surface, spalling of the resin at the site of failure and subsequent erosion, fiber prominence and formation of a network of microcracks. Breakdown is believed to be caused by a type of stress fatigue imposed on the composite by cyclic variation of humidity and temperature in conjunction with solar radiation, and by the action of water and oxygen. The under side of the exposed GRP sheeting shows only incipient breakdown, indicating that solar radiation is an important factor. Countermeasures suggested to reduce breakdown include techniques to keep fibers away from the surface, use of resins with better thermal and moisture characteristics, and use of resin formulations with the best light stabilit

ISSN:0032-3888    

DOI:10.1002/pen.760120109

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe melting of solids under shear conditions is an important operation in the processing of most thermoplastics. In this study, solid blocks of high density polyethylene were melted on a hot, moving surface over a range of surface temperatures and velocities. The conservation equations for mass, momentum, and energy were applied to the molten layer and then simplified by an order of magnitude analysis. A general model that included all significant terms gave rates of melting that agreed closely with the measured rates. A simpler model that was analogous to present extruder models predicted melting rates that were ten to twenty‐five percent lower than the experimental values. Models for polymers with low to moderate crystallinity should be modified to account for physical removal of amorphous material by shear force

ISSN:0032-3888    

DOI:10.1002/pen.760120110

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractPractical extrusion processes often involve geometrically complex dies. Such dies are usually tapered, or streamlined, to achieve maximum output rate under conditions of laminar flow. These converging flows may be analysed in terms of their extensional and simple shear components to calculate the relationships between volume flow rate, pressure drop, and post extrusion swelling. The analysis can also be extended to cover the free convergence as fluid flows from a reservior into a die. Comparisons between predicted and observed data for a series of coni‐cylindrical dies suggest that using this approach the pressure drop/flow rate relationship can be predicted within ±20% and the swell ratio/flow rate relationship within ±10%. Similar treatments have been in use for the last three years in solving such complex flow problems as radial flow in injection moulding and two‐dimensional annular convergence in blow moulding

ISSN:0032-3888    

DOI:10.1002/pen.760120111

出版商:Society of Plastics Engineers, Inc.    

年代:1972

数据来源: WILEY