Liquid crystal polymers glass-reinforced

Ozel [86] studied the abrasive wear behavior of liquid crystal polymer, 30% reinforced polyamide 4,6, and 30% glass fiber-reinforced polyphenylene sulfide engineering polymers at atmospheric conditions. Pin-on-disc arrangement wear tests were carried out at 1 m/s test speed and load values of 4,6, and 8 N. Test durations were for 50,100 m and 150 m sliding distances. 

Some of the common types of plastics that are used are thermoplastics, such as poly(phenylene sulfide) (PPS) (see POLYMERS CONTAINING SULFUR), nylons, liquid crystal polymer (LCP), the polyesters (qv) such as polyesters that are 30% glass-fiber reinforced, and poly(ethylene terephthalate) (PET), and polyetherimide (PEI) and thermosets such as diallyl phthalate and phenolic resins (qv). Because of the wide variety of manufacturing processes and usage requirements, these materials are available in several variations which have a range of physical properties. 

Fig. 4.163 Flexural-creep modulus of glass fiber reinforced liquid-crystal polymer at different temperatures and stress levels [12Els].

The excellent electrical insulation property of E-glass has found many applications in this field. Fabrics made of textile glass yarn is the backbone of the printed circuit board of the modern electronic industry. Polybutene terephthalate, polyphenylene sulfide, and liquid crystal polymer reinforced with chopped glass fiber are also widely molded into electronic components (23). 

The specific wear rate for liquid crystal polymers, 30% glass fibre reinforced PA 4,6 and 30% glass fibre reinforced PPS increased with the increase in sliding resistance. 

Petra 140 (Allied Signal) is a 40 percent glass-reinforced polyethylene tereph-thalate from recycled soda bottles. It has a tensile strength of 26,000 psi and a heat-deflection temperature of 225°C at 264 psi. PC23MS-200 (MCR Polymers) contains at least 25 percent recyclate from personal computer compact disks and polyethylene terephthalate beverage bottles. DMDA-1343NT polyethylene (Union Carbide) contains 28 percent color-sorted recyclate and has physical properties similar to those of virgin stock. Encore resins (Hoechst Celanese) are a family of plastics based on 100 percent reclaimed thermoplastics such as acetal, polyester, polyphenylene sulfide, nylon 6/6, and liquid crystal polymer. 

Figure 1 Cost-related (specific) flexural strength of major thermoplastics, versus cost-related (specific) thermal tolerance. The unit cost is the market price in US cents (1992) of 1 cm plastics. The thermal tolerance is the temperature difference (AT) over room temperature (AT — T - room T), by which temperature (7 ) the flexural modulus is equal to 1 GPa. Designations, abbreviations WFRP-S, wood fiber reinforced PP (S type) of AECL, Canada (See Table 1) PMMA, polymethylmethacrylate PVC, pol)winyl chloride PS, polystyrene PP, polypropylene UP, unsaturated polyesters PA-GF, glass fiber (35%) reinforced polyamide PHR, phenolic resin EP, epoxy resin ABS, acrylonitrile/butadiene/styrene copolymer UF, urea/formaldehyde LDPE, low density polyethylene PC, polycarbonate POM, polyoxymethylene CAB, cellulose acetate butyrate LCP, liquid crystal polymers PEEK, polyether-etherketone PTFE, polytetrafluorethylene.

Li Youbing, Shi Wen, Li Jingyuan, et al. Structure and properties of glass fiber reinforced polypropylene/liquid crystal polymer blends. J. Macromol. Sci. Part B. 54 no. 9 (2015) 1144-1152. 

Figure 13.22 Tracking resistance and breakdown voltage of bulk samples of glass fiber-reinforced engineering plasties. TCP liquid crystal polymer UL Underwriters Laboratories.

Table 3.1 shows continuous use temperatures for engineering and high performance polymers. For comparative purposes, 30% glass fibre-reinforced grades have been selected. PEEK has the highest continuous use temperature of up to 260 C, followed closely by liquid crystal polymers. Other high performance polymers are polyphthalamide (PPA), polyamideimide (PAI), polyarylimide, polyphenylene sulfone (PPSU), polyphenylene sulfide (PPS), polyetherimide (PEI), polysulfone (PSU), polyethersulfone (PES). 

Table 3.12 presents a comparison of the performance properties for unfilled, 30% mineral filled and 30% glass fibre-reinforced grades of liquid crystal polymers. 

ELASTIC MODULI OF GLASS FIBER-REINFORCED POLYMER LIQUID CRYSTALS... 

The crystallisation kinetics of the composites are affected by the nucleating effects of the polymer liquid crystal interlayer and the glass fibre. When both components are present the glass fibres dominate the nucleation kinetics. This is also reflected in the degradation kinetics, where complete degradation of the matrix occurs at lower temperatures for the glass reinforced materials. 

These thermotropic liquid-crystalhne polymers have high melting points but can be melt-processed like other thermoplastics. The macroscopic orientation of the extended-chain crystals depends on the orientation imparted by flow during processing (molding, extrusion, etc.). Because of the fibrous nature of the extended-chain crystals, these plastics behave as self-reinforced composites, with excellent mechanical properties, at least in the chain direction. This is illustrated in Table 4.3 for molded specimens of a hquid-crystalline copolyester of ethylene glycol, terephthalic acid, and / -hydroxybenzoic acid [14]. In the direction parallel to the flow, the properties listed in Table 4.3 favorably compare with ordinary crystalline thermoplastics (nylons, polyesters) reinforced with up to 30% glass fibers. 

A liquid crystalline polymer contains rigid rod like structure as discussed earlier which forms the hquid crystal phases. This rod like molecular conformations and chain stiffness give LCPs their most important self-reinforcing properties that are close to that of glass fiber reinforced composites. 

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