High performance polymers LCPs

In order to tap the commercial applications of LCP in packaging, processing must achieve efficient use of the high-performance polymer. There are many high value polymers and other materials that are used in thin layers. A prime example is ethylene vinyl alcohol (EVOH), a super barrier material used as a thin layer in coextruded film and multilayer containers such as ketchup bottles. Other examples are coatings, such as metal, glass, and polymeric coatings. LCP used in thin multilayer constructions should compete well with these other materials. 

This section of the chapter will focus on two applications of immiscible blends that contain high performance polymers. The first will be on the use of LCP s as processing aids and reinforcements of thermoplastics. There has been a great deal of both open literature and patents devoted to that topic. The second focus area will be on the use of polysulfone to enhance the fracture toughness of other thermoplastics. In that case, immiscibility is the desired phase structure for the observed effect. 

Synthetic thermosetting polymers used in the construction industry are polyester, vinylester and epoxies these materials are generally used to manufacture parts of the machines that produce sustainable energy generators. In addition, thermoplastic resins, such as polyetheretherketone (PEEK), polyethersulphone (PES) and various liquid crystal polymers (LCP) are also used. The latter high performance polymers also meet stringent out-gassing (relevant to space environments) and flammability requirements. 

LCP are fully aromatic copolyesters or copolyesteramides which have become the standard high performance polymers used in certain new electrical/electronic applications notably fuel cells. Thermosetting LCP are also available. 

Table 2.2 Comparison of Mctirai and wear properties of HP-LCP with other high performance polymer composites, polyethtaethtaketone (PEEK) and polyimide (PI) at a pressure of 1 MPa and velocity of 1 m/s at low and high counterpart temperatures...

A very high, price and performance family of polymers called liquid crystal polymers (LCPs) exhibit extremely high mechanical and thermal properties. As their ease of processing and price improve, they may find appHcation in thin-waH, high strength parts such as nails, bolts, and fasteners where metal parts cannot be used for reasons of conductivity, electromagnetic characteristics, or corrosion. 

Another natural polymer that needs a fresh look into its structure and properties is bitumen [123], also called asphaltines, that are used in highway construction. Although a petroleum by-product, it is a naturally existing polymer. It primarily consists of polynuclear aromatic and cyclocaliphatic ring systems and possesses a lamellar-type structure. It is a potential material that requires more study, and high-performance materials such as liquid crystalline polymer (LCP) could be made from it. 

Non-compatibilized blends of PS with either PEST or PEST and PMMA have been used for decorative applications or as the so-called plastic paper [Kamata et al., 1980]. Similarly, PAr blends with either SAN [Brandstetter et al, 1983], or high performance blends of LCP with thermoplastic polymers e.g., PP, PS, PC, PI) [Haghighat... 

Another rod like TP is self-reinforcing polymers (SRPs) that has exceptional high performance properties but very difficult to process. Unlike LCPs they are amorphous, isotropic, and transparent. Research on SRPs was sponsored during the 1960s by Wright-Patterson Air Force Base, Dayton, OH. 

The engineering polymers that have already reached maturity consist of the Nylons (PA), polycarbonate (PC), acetal (POM), polyesters (PBT and PET) and Noryl (PPO). Their relative price is aroxmd 3. Including very novel polymers, a prestigious high priced group consists of the advanced engineering polymers (high performance) polysulfone (PSU), polyphenylene-sulfide (PPS), fluoroethylenes (PTFE and its derivatives), polyamide-imide (PAI), polyether-imide (PEI), polyethersulfone (PES), polyether-ether-ketone (PEEK), aromatic polyesters and polyamides, polyarylates and liquid-crystal-polymers (LCP). 

Non-compatibilized blends of PS with either PEST or PEST and PMMA have been used for decorative applications or as the so-called plastic paper (Kamata et al. 1980). Similarly, PAr blends with either SAN (Brandstetter et al. 1983a, b, c) or high-performance blends of LCP with thermoplastic polymers (e.g., PP, PS, PC, PI) (Haghighat et al. 1992) showed adequate performance for the envisaged applications. However, most PS blends with engineering resins require compatibi-lization. Thus, for example, PS with PA-6 was compatibilized by addition of either methylmethacrylate-styrene copolymer (SMM) (Fayt et al. 1986b) or SMA (e.g., used in PARA/PS blends) (Lee and Char 1994). POM was blended with a small amount of either PS poly(a-methyl styrene) (MPS) or SAN and with particulate fillers (Tajima et al. 1991). PAr/PS blends were compatibilized with PAr-PS segmented copolymer (Unitika Ltd. 1983). 

There are two types of disparities between the steady-state and dynamic flow behavior, one related to the interlayer slip (Eq. (2.56)) and the second to the flow engendered migration of the low viscosity component to the high stress location. Blends of liquid crystal polymer (LCP) with polycarbonate (PC) or poly(ethylene-terephthalate) (PET) may serve as an example of the first type [321,322], whereas those of EPDM (ethylene-propylene-diene terpolymer) with poly(vinylidene-co-hexafluor-opropylene), Viton , exemplify the second [323-325]. In both cases the steady-state shearing was performed in a capillary viscometer- the viscosity ratio of the dynamic to the steady-state data for these two blends was about two and six, respectively. 

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