Crystalline reinforced polymer

Hence polysaccharides have been viewed as a potential renewable source of nanosized reinforcement. Being naturally found in a semicrystalline state, aqueous acids can be employed to hydrolyze the amorphous sections of the polymer. As a result the crystalline sections of these polysaccharides are released, resulting in individual monocrystalline nanoparticles [13]. The concept of reinforced polymer materials with polysaccharide nanofillers has known rapid advances leading to development of a new class of materials called Bionanocomposites, which successfully integrates the two concepts of biocomposites and nanometer sized materials. The first part of the chapter deals with the synthesis of polysaccharide nanoparticles and their performance as reinforcing agents in bionanocomposites. 

The primary crystalline polymer based on CHDM is the terephthalate, poly(1,4-cyclohexylenedimethylene terephthalate) (PCT). This polyester was originally developed for fiber applications but has since found wider utility as a reinforced polymer for injection molding and (when copolymerized with a small amount of isophthalic acid) as a material for crystallized food packaging trays. The key property of PCT which sets it apart from other thermoplastic polyesters in these latter applications is its melting point. 

This chapter provides an overview of current researches on liquid crystalline polymers (LCPs). Topics include syntheses of main-chain and side-chain LCFs, structured characterization of LCFs and LCP networks and rheology and processing. Applications of LCP/polymer blends as self-reinforced polymers and electro-optical meterials are also discussed. 

The finding that the PEIs of 27b and monosubstituted hydro quinones form broad nematic phases, but show little propensity to crystallize, has prompted various modifications of their structures and properties. In this connection it should be stated that non-crystalline LC-polymers have found little interest in the past decades, but they may be attractive for various applications provided that the Tg can be varied between 90 and 250 °C. For instance, the absence of crystallinity has the advantage that the mechanical properties do not depend on the thermal history, and thus on the processing conditions. The temperature allowing a convenient processing may be reduced below 200 °C, which is of interest for the processing of LC-polymer reinforced blends and composites. Furthermore, non-crystalline nematic FC-polyesters are a useful basis for the synthesis of cholesteric lacquers, films or pigments (Sect. 5). 

Although composites are a very important class of polymeric materials they form a separate subject in their own right, in which it is necessary to assume an understanding of the properties both of the polymer matrix and of the reinforcing material. They are not discussed further in this book, but it is interesting to note that in some ways semi-crystalline polymers can be considered as self-reinforcing polymers, because the mechanical properties of the crystalline parts are different from those of the non-crystalline parts, which often effectively form a matrix in which the crystals are embedded. 

Tensile testing of single crystalline metallic microwhiskers can also be studied following the experimental tensile testing constructed by Brenner and (b) results of whisker fracture strength as a function of whisker size, showed the clear size dependence (Fig. 3.34). The chitin whiskers are usually incorporated into polymer matrix to prepare CWs reinforced polymer nanocomposite. Thus, the mechanical... 

A study of polystyrene and poly ether sulfone, with and without 20% glass reinforcement [45], found that, after one year s exposure in Saudi Arabia, strength and ductility were retained better in the reinforced polymers, although the values in all cases fell to 50-77% of their original values. Other studies have shown that short glass fibres cause a significant increase in as-moulded residual stress in such polymers as well as in semi-crystalline polymers [46,47]. This can lead to stress cracking in service. 

Before going any further, let us adopt the terminology introduced by Samulski [5]. We have already used above the abbreviation PLCs. Samulski contrasted PLCs to MLCs, and defined the latter as low molecular mass LCs— irrespective of the fact whether they can or cannot polymerize. His terminology is unequivocal and succinct. People unfamiliar with it use long and not necessarily well-defined terms, such as liquid-crystalline substances with low molecular weights —when they presumably mean MLCs. Other names such as liquid crystalline polymers (LCPs) for PLCs or LMMLCs for MLCs are also in use. The abbreviation SRPs for self-reinforcing polymers and the name in situ— composites [6] are used as weU. Moreover, PLCs are sometimes also called molecular composites. 

From a survey of the recent development in the field of self reinforcing polymers it appears clearly that the unique properties of the LCP make them primary candidates as reinforcing agent, added to engineering thermoplastic in the form of second phase. In the design of the blend several parameters have to be considered, but first let consider in close details the major features of liquid-crystalline compounds. 

Molecular Liquid Crystalline Polymers Reinforced Polymer Composites The Concept of Hairy Rods ... 

Crystalline morphology and aggregates of microfibril reinforced polymer-polymer composites... 

Electrical properties have been reported on numerous carbon fiber-reinforced polymers, including carbon nanoflber-modified thermotropic liquid crystalline polymers [53], low-density polyethylene [54], ethylene vinyl acetate [55], wire coating varnishes [56], polydimethyl siloxane polypyrrole composites [50], polyacrylonitrile [59], polycarbonate [58], polyacrylonitrile-polycarbonate composites [58], modified chrome polymers [59], lithium trifluoromethane sulfonamide-doped polystyrene-block copolymer [60], boron-containing polyvinyl alcohols [71], lanthanum tetrafluoride complexed ethylene oxide [151, 72, 73], polycarbonate-acrylonitrile diene [44], polyethylene deoxythiophe-nel, blends of polystyrene sulfonate, polyvinyl chloride and polyethylene oxide [43], poly-pyrrole [61], polypyrrole-polypropylene-montmorillonite composites [62], polydimethyl siloxane-polypyrrole composites [63], polyaniline [46], epoxy resin-polyaniline dodecyl benzene sulfonic acid blends [64], and polyaniline-polyamide 6 composites [49]. 

REINFORCED POLYMERS BASED ON BLENDS OF POLYMERS WITH THERMOTROPIC LIQUID CRYSTALLINE POLYMERS... 

Weiss A. Robert, Huh Wansoo, and Nicolais L. Novel reinforced polymers based on blends of polystyrene and a thermotropic liquid crystalline polymer. Polym. Eng. Sci. 27 no. 9 (1987) 684-691. 

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