摘要:

The concept of generating liquid crystalline polymer (LCP) reinforcing fibrils on an in situ basis has a number of potentially attractive advantages over the use of the more commonly used glass-reinforced composites. The potential advantages include a wider range of processing options, improved surface appearance, recyclability, and lower processing energy requirements. Many of these advantages have been discussed in previous reviews such as those written by Dutta et al. [1] and La Mantia and Valenza [2]. However, to successfully compete with glass-reinforced thermoplastics, in situ composites based on thermoplastics reinforced with thermotropic LCPs (TLCPs) should at least exhibit similar properties to injection-molded glass-reinforced thermoplastics. One purpose of this review is to address the advantages and disadvantages of in situ composites, and the other is to provide some standards for comparison against more commonly used composites.

ISSN:1532-1797    

DOI:10.1080/15321799508009637

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Some of the most important commercial polymers are diene polymers, e.g., natural rubber (polyisoprene, PI) and styrene butadiene rubber SBR). Their usefulness to scientists and engineers comes not only from their desirable physical properties, but also because they may be used as a base for a variety of chemical modification reactions that are made possible because of the presence of olefinic groups within the polymers.

ISSN:1532-1797    

DOI:10.1080/15321799508009638

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Polymer chain conformations can be described by many models. Some of the main ones are shown in Fig. 1. The rod-like model describes polymer molecules as rigid cylinders with high axis ratio. The axis ratio, X, is equal to the length of the polymer divided by the diameter. X = L/d for molecules in any conformation. Linear polymer chains that are not completely rod-like can be described by Kuhn chains, worm-like chains, or segmented rod-like and random coil chains. Kuhn chains are characterized by rigid segments connected by universal joints. The rod-like segment, known as the Kuhn segment, has a characteristic length, 2q. Worm-like chains have continuous deviation from rod-like behavior but are not necessarily completely flexible. The worm-like chains are characterized by a persistence length, q. Polymers of types a-d in Fig. 1 can all form liquid crystalline solutions under appropriate conditions. The final type of chain, the random coil, is not expected to form liquid crystalline solutions.

ISSN:1532-1797    

DOI:10.1080/15321799508009639

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Polyhydroxybutyrate (PHB) is an optically active polymer of D(−)3-hydroxybutyric acid. It is a naturally occurring polymer produced by a wide variety of bacteria. It serves as an intracellular storage material for carbon and energy and is accumulated as granules within the cytoplasm [1–4] of the bacteria. The chemical structure of PHB is shown in Fig. 1.

ISSN:1532-1797    

DOI:10.1080/15321799508009640

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Polymers in one form or another are basic constituents of every kind of living matter, whether plant or animal. It is only in the present century, however, that as a result of a wide range of scientific studies, their existence as a coherent group has come to be recognized and understood. Following this recognition and this understanding, the possibility has arisen of actually producing polymers by means of suitable chemical reactions. Originally these synthetic products, regarded as subsitituents for existing natural polymers such as rubber or silk, led to the introduction of a vast range of entirely new compounds in the field of plastics, rubber, and fibers, many of which have properties different from those of existing natural materials. At present, the study of polymers, though it includes the original natural polymers, tends to be dominated by these synthetic materials. It is from the industrial development of such polymers that the main stimulus to scientific research has arisen.

ISSN:1532-1797    

DOI:10.1080/15321799508009641

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor