摘要:

AbstractThe thermal conductivities and the thermal expansion curves of glass fiber‐reinforced rigid polyurethane foams with various fiber lengths, various fiber volume fractions and various matrix densities were determined experimentally. Additionally the thermal expansion coefficients of these materials at room temperature were examined in terms of the interaction between fiber and matrix. The thermal expansion properties were analyzed successfully with the analogous treatment which is applied to the mechanical tensile behavio

ISSN:0032-3888    

DOI:10.1002/pen.760241202

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractPaper properties of the thermochemical pulp modified by ozonation and grafting with styrene, acrylamide or their mixtures have been studied. Paper sheets, prepared by hot pressing from ozonated and grafted pulps showed improvement in: wet breaking length; dry breaking length; burst and dimensional stability.

ISSN:0032-3888    

DOI:10.1002/pen.760241203

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractOrientation effects in amorphous polystyrene are studied using a uniaxial stretching experiment. The rheological properties of the polymer are determined from an analysis of creep data obtained from the tensile apparatus, and oriented polymer samples are prepared at different extension ratios and rates of stretching. From birefringence and tensile strength measurements on oriented samples of polystyrene, it is shown that the tensile strength is not a unique function of the birefringence. It is proposed that the tensile strength may depend not only on the average orientation, as reflected by the birefringence, but on which portion of the relaxation spectrum is preferentially oriented.

ISSN:0032-3888    

DOI:10.1002/pen.760241204

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractA method based on network theory is developed for characterizing molecular orientation in amorphous polymers. The proposed procedure gives not only the orientation distribution function for the chain segments in the polymer network (and hence the average orientation) but also a quantitative measure of how this orientation is distributed among the various types of entanglement junctions. The orientation of chain segments can be characterized by two parameters, one which gives the average orientation and another which reflects how much orientation is concentrated in long time entanglement junctions. The new method of characterizing orientation is used to interpret tensile strength data for both brittle and ductile failures.

ISSN:0032-3888    

DOI:10.1002/pen.760241205

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe simultaneous production of polyurethane (PUR) and polymethyl methacrylate (PMMA), starting from a mixture of polyol, polyisocyanate, and vinyl monomer, results in 2‐phase polymer alloys. A simultaneous crosslinking of the PMMA is unable to prevent phase separation during the curing reaction; interpenetrating polymer network (IPN) structures were not found, Grafting the PMMA onto the PUR through the incorporation of 2‐hydroxyethylacrylate resulted in single‐phase systems. Various material combinations did not show, with a relatively high PMMA content, any poorer properties than the straight PUR. A major advantage of incorporating low‐viscosity vinyl monomers lies in the fact that high‐viscosity polyurethane starting components that are otherwise difficult or impossible to process can be processed here withou

ISSN:0032-3888    

DOI:10.1002/pen.760241206

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe non‐isothermal flow of a power‐law fluid in a coal‐hanger flat die is studied. Equilibrium and thermal equations are solved by using an iterative finite difference method. The pressure distribution, the flow lines, the residence time distribution, the temperature distribution, and the flow uniformity at the end of the die are obtained, with a stress on the effect of thermal regulation and of temperature dependence of the visc

ISSN:0032-3888    

DOI:10.1002/pen.760241207

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThis paper addresses the apparent controversy surrounding the role of the solid bed mechanics in the Maddock melting mechanism. It is demonstrated that the inability of the melting models based on the freely deformable solid bed concept to predict accurately the pressure gradients in the melting zone is not exclusively due to the highly simplified isothermal Newtonian treatment of the melt pool as presumed previously. This study has shown that when using a non isothermal non‐Newtonian flow model for the melt pool, the freely deformable solid bed concept still results in unrealistically low pressure gradients while it may give good predictions of the melting rates. To the contrary, when a rigid solid bed is assumed, the pressure predictions tend to represent the experimental data more closely, whereas the theoretical melting rates seems to become less realistic. In view of the fact that both the freely deformable and the rigid solid bed concepts show such inconsistencies, it has been concluded that the mechanics governing the solids and melt transport in the melting zone require some additional examination, most notably, the influence of the constitutive behavior of the solid bed and of the cross‐channel melt circulation around the solid bed, and possibly of the melting kinetics for semicrystalline polym

ISSN:0032-3888    

DOI:10.1002/pen.760241208

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractFlexural stress relaxations were measured for rigid polyurethane foams (PUF) and glass‐fiber‐reinforced rigid polyurethane foams (FRU). The results were successfully analyzed in terms of the five element Maxwell model: (1) Samples reinforced with longer fibers exhibit reduced stress relaxation and reduced temperature dependency of stress relaxation; (2) The increased expansion ratio reduces the flexural modulus of both reinforced and non‐reinforced materials, but the stress relaxation tends to increase greatly at the higher temperature for PUF, while not so greatly for FRU; (3) The temperature dependency ofE1decreases as longer fibers are used to reinforce the polyurethane. The dependency is minimal for the polyurethane reinforced with continuous fibers, where the reinforcing effect is maximal; and (4) The activation energy calculated from τ2according to the Arrhenius plot is smaller for the longer fiber reinforced polyurethane

ISSN:0032-3888    

DOI:10.1002/pen.760241209

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760241201

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY