摘要:

While it is true that preform processes involving the use of long or continuous fibers are known and used in the manufacture of reinforced thermoplastic articles–Azdel [1] or STX sheet [2], for example–it is generally the case that such articles are formed by injection molding. Both the feedstock requirements for this process and the occurrence of high melt shear during it ensure that only short fibers will be present in the finished article. Although the use of slow screw speeds, slow injection rates, low back pressure, wide sprues, runners, and gates, and large radii of curvature avoids fiber breakage during molding, such conditions are not often found in practice. Furthermore, the necessity of incorporating reground material into the feedstock also ensures short fiber lengths in the final part, lengths not greatly in excess of the critical length required for effective stress transfer from polymer matrix to reinforcing fiber. In a practical part, design uncertainties caused by fiber length attrition are further compounded by the effects of fiber orientation. Although length distribution effects have been studied by a number of workers, both experimentally [3] and theoretically [4], relatively little has been reported on orientation effects in short fiber reinforced thermoplastics.

ISSN:0360-2559    

DOI:10.1080/03602557708545033

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The general theory of permeation of a gas or liquid through a polymer matrix [1] states that permeation is the product of a diffusion term and a solubility constant of the permeant in the polymer matrix, both of which are often independent of each other. The process of permeation through a polymeric barrier involves four steps: absorption of the permeating species into the polymer surface, solubility into the polymer matrix, diffusion through the wall along a concentration gradient, and finally desorption from the outer surface.

ISSN:0360-2559    

DOI:10.1080/03602557708545034

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The various aspects of the degradation of poly(vinyl chloride) (PVC) have been extensively studied [1-10]. This is to be expected considering the wide-spread use of the material in both rigid and flexible plastics, in foams, and in thin films. An understanding of the effects of heat, light, and high-energy radiation on the polymer's performance is necessary so that precautionary measures may be taken to allow its end use potential to be realized.

ISSN:0360-2559    

DOI:10.1080/03602557708545035

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor