Liquid crystalline polymers LCPs composites

Specific blends, which could offer an interesting combination of properties with proper com-patibilization, include PPS/PSE, PEl/PPS, PA/PSE, PA/PEI, and PC/PPS. Patent activity has been noted for most of these blend combinations as well as other selected blends involving engineering polymers as noted in Table 17.3. A number of recent patent and published papers have discussed blends of engineering polymers with various specialty polymers including high temperature polymers, liquid crystalline polymers (LCP s), conductive polymers, and as matrix materials for molecular composites. These will be discussed in the following sections. 

E. Shiva Kumar, C. Das, K. Banik, and G. Mennig. Viscoelastic properties of in situ composite based on ethylene acrylic elastomer (AEM) and liquid crystalline polymer (LCP) blend. Compos. Sci. Tech., 67(6) 1202-1209, May 2007. 

J. Kettunen, E. A. Makelaa, H. Miettinen, et al., Mechanical properties and strength retention of carbcm fiber-reinforced liquid crystalline polymer (LCP/CF) composite An experimental study on rabbits, Biomaterials 19 1219-1228 (1998). 

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. 

Keywords polymer blend, liquid crystalline polymer (LCP), morphology, compatibilization, processing, polymer reinforcement, in situ composites. 

It has been well recognized that melt blending of a thermotropic liquid crystalline polymer (LCP) and an isotropic polymer produces a composite in which fibrous LCP domains dispersed within the blend act as a reinforcement il ). The so-called insitu composite possesses several advantages in comparison with the inorganic reinforced thermoplastic composites. Firstly, LCP lowers the blend viscosity in the actual fabrication temperature range (3-5), Hence, the enhanced processability endows moldability for fine and complex shaped products. 

The preparation methods and the novel permselective characteristics of (polymer/LC) composite films have been extensively studied (1-3). Also, various types of (polymer/LC) composite systems have been reported as large area and flexible light-intensity controllable films (4-11). Since thermotropic liquid crystalline polymers (LCPs) with mesogenic side chain groups exhibit both inherent mesomorphic properties of LC and excellent mechanical characteristics of polymeric materials, LCPs... 

With some approximation, liquid crystalline polymer (LCP) containing composites can be considered to be the closest example of molecular composites. By virtue of their molecular structure and conformation, the LCP reinforcements tend to form in situ, during processing, very fine fibers having similar or better reinforcing efficiency as compared to that of conventional inorganic fibers [9]. A substantial amount of work has also been performed in the area of LCP-containing composites described in numerous publications [10-13] and also in Chapter 9 of this book. 

High modulus fibers and films are produced from extended chain crystals in both conventional polymers, notably PE, and in liquid crystalline polymers (LCPs). The topic of high modulus organic fibers has been described and reviewed [15-17, 25] providing information on their preparation, structure, and properties. High modulus fibers are found in applications such as fiber reinforced composites for aerospace, military, and sporting applications. Industrial uses are for belts, ropes, and tire cords. Extended chain crystals can also form when polymers are crystallized very slowly near the melting temperature, but they are weak and brittle. 

Formation of composite materials is the effective route to improve the performances of polymeric materials through appropriate stmctural modifications. Remarkable improvement can be obtained in mechanical, thermal, electrical, optical and catalytic properties of the composite materials. Therefore it can be stated that synthesis of composite materials is an efficient way to synthesize newer smart materials (Sun et al. 2013). Liquid crystalline polymers (LCPs) are considered as an important class of high performance engineering materials because of their... 

Liquid crystalline polymers (LCP) have excellent mechanical properties in addition to dimensional and chemical stability. These materials form in-situ composites during processing under elongational flow and are starting to replace traditional fiber reinforced systems [1, 2]. Combined with their ease of processing, LCPs are ideal for applications in aerospace, automobile, marine and other markets requiring high performance composites [2, 3]. 

The objective of this work has been to generate films, tapes or ribbons which might serve as a prepreg from blends of either an Ultem or a PEEK or a high molecular weight PPS with various liquid crystalline polymers, to identify the parameters that control the formation of reinforcing microfibrils of LCP phase, and to study the mechanical properties of the composite films. 

Saikrasun S and Saengsuwan S (2009) Thermal decomposition kinetics of in situ reinforcing composite based on polypropylene and liquid crystalline polymer, J Mater Proc Technol 209 3490-3500. Saikrasun S, Limpisawasdi P and Amornsakchai T (2009) Effect of LCP and rPET as reinforcing materials on rheology, morphology, and thermal properties of in situ microfibrillar-reinforced elastomer composites, J Appl Polym Sci 112 1897-1908. 

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