摘要:

In the first part of this article, the method for preparation of heteroarm star (AnBnstar-block) copolymers from diblock macromonomers possessing central functional groups is reviewed. These diblock macromonomers formed a microphase-separated structure in the solid state. The central functional groups at the position of the block junction were located regularly at the domain interface. The microgelation of diblock copolymer films formed AnBnstar-block copolymers by organization effects. The second section reviews the methods for preparation of (AB)nstar-block copolymers from diblock macromonomers possessing a terminal vinylbenzyl group. The microgelation in micelles between diblock macromonomers and linking agent also formed (AB)nstar-block copolymers. Finally, the phase stability criteria of these star-block copolymers are reported briefly.

ISSN:0360-2559    

DOI:10.1080/03602559308021020

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The structure and properties of zinc-neutralized sulfonated EPDM (Zn-SEPDM) plasticized with modified glyptal resin (GR) were studied through mechanical property tests, capillary rheometry, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results show that GR can considerably reduce the glass transition temperature as well as the apparent melt viscosity of Zn-SEPDM, and that the mechanical properties of Zn-SEPDM plasticized with GR are much better than those of Zn-SEPDM plasticized with traditionally used zinc stearate (ZnSt).

ISSN:0360-2559    

DOI:10.1080/03602559308021021

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Information available from recent literature (1—6) is presented in this report on PVC-based, ABS-based, and PC-based polyblends. Property profiles of polyblends are superior to those of component homopolymers. Enhanced properties, combined with the low cost of polyblends, make them economically attractive for special markets (e.g., automotive engineering plastics) and result in better resin utilization. Blend resin attributes which result in a myriad of property improvements in different polyblends are highlighted. A survey of commercially available polyblends has been presented and their commercial utility is indicated. Much polymer science has gone into making polyblends a commercial success. Polyblend technology is a frontier area not only for current research; it will also continue to figure prominently in future developments. Polyblend technology provides attractive opportunities for reuse and recycling of polymer wastes. The discussion covers various compatibility criteria and the use of compatibilization additives in plastic scrap recycling and to enhance the commercial utility of phase-separated blends. Ways of achieving optimum performance in polyblends are discussed. Various criteria for impact modification of PVC have been laid out and the role of rubber morphology in polyblend toughening is pointed out. Polyblending can accomplish a permanent plasticization of PVC and improves its processability as well.

ISSN:0360-2559    

DOI:10.1080/03602559308021022

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Most polymeric sealants used in structural applications are organic and so some changes in the materials occur with passage of time: the material ages. The structural sealants function as a weather seal and when used with glazing also act as a binding agent for the glass to the substrate. As a weather seal, the sealants will be exposed to a wide variety of service conditions which include moisture. A question arises, therefore, as to the damage caused by moisture. When a structural sealant is exposed to moisture, a number of distinct phenomena are known to occur which can contribute to deterioration in the performance of the seal. In this study the moisture effect on the structural silicone sealant was correlated through crosslinking changes. A typical weathering event consisted of exposing the test coupons to moisture with pH levels ranging from 3 to 11, followed by drying. The extremes of the pH levels simulated acid rain (pH = 3) and cleaning solutions (pH = 11). Experimental data suggest that the moisture alone can trigger additional crosslinking in silicone sealants. Continued exposure, however, was observed to result in gradual deterioration of the physical properties of the sealants as reflected by changes in the crosslink density. Since it is advantageous to be able to predict the onset of failure due to moisture, it was decided to develop a chemical-kinetic model of the degree of crosslinking as a function of exposure time. A semiempirical approach was used to estimate the kinetic rate and other parameters from the experimental data. This paper also describes the development of the hypothetical mechanism used for modeling the time variations in crosslink density.

ISSN:0360-2559    

DOI:10.1080/03602559308021023

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The steady, fully developed, isothermal, incompressible laminar flow of power law fluids within a toroidal-type coiled tube has been studied for small ratio of tube radius to radius of curvature. Dean's constraint has been relaxed and the solutions of primary and secondary flows are obtained up to the second-order curvature ratio term. The expressions for primary and secondary flow of a Newtonian fluid are derived as special cases and are found to be in good agreement with published results. Comparison of the results with those of Newtonian fluids is made to bring out the effect of the power law index. The flow fields of dilatant and pseudoplastic fluids are found to differ significantly. The individual and collective roles played by the Reynolds number, curvature ratio, and power law index are discussed in detail. The results show that the flow rate of fluid in a curved tube is more influenced by curvature than by Reynolds number or power law index.

ISSN:0360-2559    

DOI:10.1080/03602559308021024

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The application of Taylor's dispersion theory to non-Newtonian laminar dispersion in a circular curved pipe wrapped in a coil is discussed. An analytical expression for the dispersion coefficient in laminar flow under two conditions, viz. Dean's constraint and relaxing Dean's constraint, is discussed along with system parameters. The present expression of dispersion coefficient under two different conditions reduces to the reported results in the literature for Newtonian fluids. The effect of power law index in combination with other process parameters on dispersion coefficient is studied. It is found that the dispersion coefficient decreases with decrease in power law index, and that it decreases with increase in Reynolds number and Schmidt number at a fixed curvature ratio.

ISSN:0360-2559    

DOI:10.1080/03602559308021025

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Melt blending of nylon 6 with chemically modified polypropylene (MPP) is carried out with a single-screw extruder over the whole range of compositions. The tensile, flexural, and impact properties are measured for the blend system. It is found that the MPP used as the second component has a profound effect upon the properties of the resulting blends. The addition of MPP decreases the tensile strength and flexural modulus whereas tensile modulus and flexural strength go through a minimum at the intermediate compositions. An improvement in impact strength is obtained only when nylon 6 is the basic resin and MPP is used as an additive. Microstructures of polyblends are studied by scanning electron microscopy.

ISSN:0360-2559    

DOI:10.1080/03602559308021026

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Polyphenylene sulfide (PPS) is an engineering plastic with excellent thermal, mechanical, and electrical properties, and has received considerable attention during the last few years. There are numerous reports on the crystallization behavior and physical properties of PPS (1-7). This polymer can be processed by conventional melt-processing techniques such as injection molding, compression molding, etc., and also by powder metallurgical technique. However, there are few reports on the powder processing of PPS (8, 9).

ISSN:0360-2559    

DOI:10.1080/03602559308021027

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The International Conference on Regulation of Polymeric Material Stability was held on October 12-15, 1992, in Moscow in the Institute of Chemical Physics of the Russian Academy of Sciences, mostly through the efforts of the Division of Chemical and Biological Kinetics of the aforesaid institute.

ISSN:0360-2559    

DOI:10.1080/03602559308021028

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0360-2559    

DOI:10.1080/03602559308021019

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor