Speciality thermoplastics

Whilst by far the bulk of polyamide materials are used in the form of fibres, they have also become of some importance as speciality thermoplastics of particular use in engineering applications. The fibre-forming polyamides and their immediate chemical derivatives and copolymers are often referred to as nylons. There are also available polyamides of more complex composition which are not fibre-forming and are structurally quite different. These are not normally considered as nylons (see Section 18.10). 

EVOHs (see Figure 4.28) are speciality thermoplastics copolymerized from ethylene and vinyl alcohol randomly distributed along the backbone. This is identical to polyolefin backbone but the pendant groups are different with a polar character and a random structure. 

EVOH is a speciality thermoplastic targeting specific applications and consumption is far smaller than for polyethylene and polypropylene. Worldwide production is estimated at 55 000 tonnes including 8000 tonnes consumed in Western Europe, that is to say, less than one thousandth of the total for plastics. Moreover, typical characteristics limit the applications and, consequently, relatively few grades are marketed, corresponding to the major applications ... 

Speciality thermoplastics polysulfone (PSU), PPS, fluoroplastics, PEEK, PEI, polyamide imide (PAI), liquid crystal polymers (LCP). 

For this comparison, a melt-spinning process was chosen. Each special thermoplastic process influences the structure and thus the properties of the obtained polymer samples differently. This is particularly pronounced for fibers, since especially melt spinning is a process which makes extremely high demands on the deformation ability of the polymer melts at high deformation speeds. Particularly the tensile stress within the fiber formation zone is a very important factor to reach a high orientation of the macromolecules along the fiber axis and a stress-induced crystallization. This crystallization should be discussed in relation to PLA and PHB multifilaments, and at the same time the general property spectrum of these polymers should be represented. 

Infusible ( )in- fyu-z9-b9l (1555) adj. Not capable of melting when heated, as are all cured thermosetting resins and a few special thermoplastics such as ultrahigh-molecular-weight polyethylene, polybenzimidazole, and aramid resins. 

Crystalline silicas are used where a coarse, high-wear finish is desirable. However, they are abrasive. These materials are used mostly in thermosets and highly specialized thermoplastics. Available types include screen grades, quartzite sand, sandstone, quartz rock, and novaculite. 

Polycarbonate blends with special thermoplastic elastomers, e.g., styrene-ethylene-butylene styrene-block-copolymers (SEES), provide excellent resistance to photo-oxidative degradation. 

Blends of polycarbonate and elastomers contain mostly graft copolymers based on butadiene and acrylate rubbers as the elastomeric component Polycarbonate blends with special thermoplastic elastomers, e.g., styrene/ethylene/butylene/styrene block copolymers (SEES) are another interesting product class. These blends exhibit improved resistance to gasoUne compared to polycarbonate, Figure 5.309. 

The procedure of dynamic measurement consisted of a sequence of records of interference patterns on a special thermoplastic plate, which then was fixed by a digital video camera. Afterward, the images were input into the computer and evaluated. For determination of the interference band center, the 10 points along the horizontal line of cuvette have been chosen. 

---