摘要:

AbstractIt is shown that the liquid‐liquid transitionTllin polymer melts need not be a true polymer transition but can be an artifact of the torsional braid analysis technique. The shift inTllwith molecular weight then is due to the variation of viscosity with molecular weigh

ISSN:0032-3888    

DOI:10.1002/pen.760171002

出版商:Society of Plastics Engineers, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractDimethylaminoethyl methacrylate (DMAEMA) was investigated as a prospective coupling agent for mica‐reinforced polypropylene. Composites prepared with the widely‐used silane coupling agent, N‐(4‐vinylphenyl) methyl‐N′‐(3‐trimethoxysilylpropyl)ethylenediamine monohydroehloride (Z‐6032), were compared with the amino‐coupled composite. Improvements in the flexural properties at room temperature were observed with the two coupling agents: a 22 percent increase in the strength with the silane compared to a. 16 percent increase with DMAEMA. Cone‐and‐plate viscometry at 220°C showed that the addition of coupling agents greatly, reduces the viscosity of the composite: a 50 percent decease was obtained with the silane‐treated composite and a 20 pe

ISSN:0032-3888    

DOI:10.1002/pen.760171003

出版商:Society of Plastics Engineers, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractThe series of olefin‐SO2copolymers prepared from the C8‐C18even‐numbered carbon series of alpha‐olefins and sulfur dioxide have been studied. The C16polymer especially has high gas permeability, good biocompatibility, low, toxicity, low thrombogenicity, ease of fabrication and potential low cost. Maximum permeabilities, maximum percent elongation at the yield point and minimum density are obtained with the C16based polymer. An explanation is proposed involving a competitive plasticizing/side chain crystallization

ISSN:0032-3888    

DOI:10.1002/pen.760171004

出版商:Society of Plastics Engineers, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractThe mechanistic origins of the post extrusion swelling phenomenon have been the subject of considerable debate. Conflicting theories have postulated that it is caused either by (1) deformations at the die entrance which are recovered upon die exit as a consequence of viscoelastic memory or (2) elastic enorgy, which is stored during capillary flow by the action of normal stress, and subsequently released upon die exit or by both (1) and (2). We have described these situations by mathematical models and show that the resulting equations are similar despite different origins. The difficulties in interpreting the results mechanistically are discussed. Empirically, the results can be described as being exponential in capillary residence irrespective of cause.

ISSN:0032-3888    

DOI:10.1002/pen.760171005

出版商:Society of Plastics Engineers, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractThe influence of mechanical forces on structural changes in commercial grades of high and low density polyethylenes was investigated by using extremely high shear rates (>2 × 104S−1) during processing in a special injection molding machine and by long‐term loading at ambient temperature. Changes in molecular weight distribution (MWD) and the degree of long‐chain branching (LCB) were followed by gel permeation chromatography and viscometry. No effect of the mechanical forces was observed either in the long‐term loading or in the processing. At temperatures exceeding 280°C the small changes noted in MWD and LCB wrere found to be entirely due to thermal de

ISSN:0032-3888    

DOI:10.1002/pen.760171006

出版商:Society of Plastics Engineers, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractThis paper describes a simple miss‐spring model of Charpy's classical impact bending test. In this model, the mass represents the striker, and the spring the bent specimen. The stiffness of the latter is calculated from the formulas for static bending. The model has been tested by experiments on polymethyl methacrylate at room temperature. First, it is shown that the model correctly describes the effect of the dimensions of the specimen (span, width and thickness) on the fracture impact energy Secondly it is shown, that the fracture energy calculated from the measured fracture time agrees with the fracture energy determined experimentally. Third it has been found that the fracture energy in impact can be predicted by extrapolation of the results of slow bending tests at various deformation rates. Lastly, it has been proven experimentally that any stress waves generated by the impact of the striker have little effect on the measured fracture energ

ISSN:0032-3888    

DOI:10.1002/pen.760171007

出版商:Society of Plastics Engineers, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractIt has long been known that elastomeric solids could be used as the working “fluid” in engines designed to convert heat into mechanical work. In the past rubber heat engine cycles were not given serious consideration since energy alternatives were not in demand and a majority of the scientific community is unaware of their gas‐like thermodynamic behavior. Consequently, past work has dealt with the subject primarily as a novelty or as a demonstrative proof of thermodynamic behavior. This paper provides an idealized mechanical and thermodynamic analysis of the rubber cycle and compares it to an equivalent cycle wherein a gas is the working fluid. Experimental data on a small rubber fiber engine is included which confirms the high power potential of these engines when they are designed using modern elastomeric fibers. These materials have remarkable properties and can respond rapidly to cyclic thermal disturbances. Power densities of roughly one watt/g of rubber have been attained using only a 30°C difference between the heat source and heat sink. Engine speeds well over 1000 RPM have also been attained when atmospheric pressure steam was used as the heat source. The analyses demonstrate that elastomers are ideally suited for energy conversion when only small temperature differences are ava

ISSN:0032-3888    

DOI:10.1002/pen.760171008

出版商:Society of Plastics Engineers, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractThe rheological properties of high atomic number metal‐low density polyethylene composites were investigated. Tungsten, tungsten carbide, and lead powders were studied at concentrations up to 10 volume percent. Viscosity‐shear rate, die swell‐shear rate, and melt draw down to break data were, determined as functions of filler type, filler concentration, and particulate size at 200°C. The viscosity data were found to fit the Einstein relationship over the range of filler loadings and shear rates investigated. Tanner's equation was used to calculate the first normal stress difference from the die swell data. The effect of the fillers on the predicted first normal stress difference was contrary to previously observed experimental evidence. Melt draw down to break data was found to be very sensitive to filler contamination and correlated quite well with wire coating experiments. During low‐speed wire coating runs coating quality was found to be seriously affected by small levels of contamination present in the fillers. Coating duality was determined by surface smoothness and un

ISSN:0032-3888    

DOI:10.1002/pen.760171009

出版商:Society of Plastics Engineers, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractExperiments were carried out to study the effects of cutting speed, feed, depth‐of‐cut and tool‐nose‐radius on the cutting force and surface roughness produced during turning of the thermoplastics Nylon‐6 and Teflon. Generalized equations for the cutting force and surface roughness in terms of processing factors have been established using the statistical technique of multiple regression analysis. The equations have been tested for acceptability by theF‐test and the degree of significance of various factors has been assessed b

ISSN:0032-3888    

DOI:10.1002/pen.760171010

出版商:Society of Plastics Engineers, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractIn the processing of thermoplastics, the economy of the process and the quality of moldings are decisively influenced by material thermal properties. Therefore, it is particularly important for the processor to know and consider such properties. Process analyses have revealed that the processing conditions can be set to achieve optimum results by the application of pressure‐volume‐temperature diagrams, particularly if used in conjunction with computer control of the process. A new measuring instrument is described which makes it possible to determine such diagrams under normal processing conditions, that is, at normal cooling rates and pressures. The results contrast with values heretofore quoted in the literature, where values have been measured at very slow heating and cooling rates. Some experimental results and their practical use are discus

ISSN:0032-3888    

DOI:10.1002/pen.760171011

出版商:Society of Plastics Engineers, Inc.    

年代:1977

数据来源: WILEY