摘要:

Quantities of high-quality rubber gumstock, well below the permissible contaminant levels established by the Federal Emergency Management Agency (FEMA) and the American Society for Testing Materials (ASTM), have been prepared in the Food Protein Research and Development Center's Industrial Crops Solvent Extraction Pilot Plant using a batch-processing approach. The basic unit operations of this approach are compatible with the infrastructure of screw press cottonseed oil mill operations in the United States. Process limitations in shrub preparation, mixing, miscella filtration, and removal of solvent from the finished rubber were identified and subsequently minimized or resolved. Different combinations of solvents and alcohols for rubber precipitation, antioxidants, extraction temperatures, shrub sources, storage conditions, and preparation methods were investigated; and their effects on rubber material properties were evaluated. Compounding studies and physical testing have shown that the center's guayule rubber is comparable to both hevea rubber and Mexican guayule rubber prepared by an aqueous extraction method. These results confirm the overall adequacy of the process. However, a number of processing steps require initial evaluation or further “fine tuning” to ensure development of a fully optimized processing scheme.

ISSN:0360-2559    

DOI:10.1080/03602558808070106

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The molecular mechanism of deformation and fracture of some poly-urethane thermoplastic elastomers under uniaxial tensile creep and vibratory milling conditions was investigated. By using chemical methods (reactions with radical acceptors, vinylic and diene monomers) the formation of free radicals, appearing as a consequence of chemical bonds splitting, was confirmed.

ISSN:0360-2559    

DOI:10.1080/03602558808070107

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

In the first part of this article, three examples of microdomain fixing in sequential copolymer films are reviewed. Two of them are examples of chemical fixation of the microdomains, and at the same time making the films insoluble in solvent. Quaternization by a gas-phase dibromo compound or photosensitizing polymerization was chosen in these cases. Another example is concerned with the crosslinking of isolated domains in graft copolymer matrix. By this reaction, small particles of the different materials of which the outside and the inner core are composed are expected to be obtained. Actually until a rather high crosslinking density (4.2 mol%), soluble products were obtained, and these materials differed from the original graft copolymer. In the second part, micelle formation with sequential copolymers in selective solvents, their dimensions, form, and so forth are reviewed with reference to the crosslinking of the core part. Finally, several results obtained with graft copolymers in recent years are reported.

ISSN:0360-2559    

DOI:10.1080/03602558808070108

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

First, existing research on diffusion of disperse, reactive, and ionic dyes in polymers and correlation of the rate of dyeing to the operating variables in the dyebath is reviewed. Second, to discuss the kinetic aspects of various dyeing processes, the dyeing of textiles is classified into two categories: adsorptive and reactive dyeings, and these two dyeing processes are modeled in terms of diffusion of dyes in polymers accompanied by some physicochemical interaction with the polymer substrates. The process of adsorptive dyeing was formulated on the basis of a dual-mode sorption and mobility model where the porelike region was conveniently invoked. The calculated profiles of the concentration of immobilized dye are similar to the measurments of dye distribution curves by means of film-roll, microdensitometric, and microspectrophotometric techniques. The outline of formulation of the process of dyeing with reative dyes (i.e., reactive dyeing) is given on the basis of diffusion of dye within the fiber accompanied by a fixation reaction incorporating hydrolysis of dye species. It is concluded from numerical analysis that the lower the bath ratio, the less the decrease of the final fixation due to hydrolysis of the dye and the less the influence of mixing in the dyebath on the fixation. When the fixation reaction is slow, the final futation is almost independent of the bath ratio and the degree of mixing.

ISSN:0360-2559    

DOI:10.1080/03602558808070109

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Unstabilized polyolefins are prone to several degradation reactions during the different stages of compounding/processing/fabrication, with catastrophic consequences on product stability and in-service performance. The level of protection afforded by a stabilizer system against the deleterious effects of mechanical, thermal, thermo-, and photoxidative degradation reactions is governed by several factors which include both physical and chemical characteristics of the substrate and stabilizer, the environment, and the application of stress. In considering the practical aspects for the selection of a stabilizer system, due regards must be given to the structural nonhomogeniety of polyolefins, and to stabilizer substantivity and stability as well as its intrinsic activity. The stabilizer function is examined here in the light of current understanding of the behavior of functions of antioxidants and stabilizers. Several examples are included to reinforce the mechanistic aspects of different classes of antioxidants. Further, growing demands for higher performance polyolefins for medical, food, telecommunication, automotive, and building applications places increasing demands on stabilizers and antioxidants under hostile and aggressive environments. In-situ binding of stabilizers is a practical approach which improves the performance of both the polymer and the stabilizer.

ISSN:0360-2559    

DOI:10.1080/03602558808070110

出版商:Taylor & Francis Group    

年代:1988

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:10.1080/03602558808070105

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor