Thermoplastic components

Thermal Oxidative Stability. ABS undergoes autoxidation and the kinetic features of the oxygen consumption reaction are consistent with an autocatalytic free-radical chain mechanism. Comparisons of the rate of oxidation of ABS with that of polybutadiene and styrene—acrylonitrile copolymer indicate that the polybutadiene component is significantly more sensitive to oxidation than the thermoplastic component (31—33). Oxidation of polybutadiene under these conditions results in embrittlement of the mbber because of cross-linking such embrittlement of the elastomer in ABS results in the loss of impact resistance. Studies have also indicated that oxidation causes detachment of the grafted styrene—acrylonitrile copolymer from the elastomer which contributes to impact deterioration (34). 

In most cases thermoplastic components are designed for use at room temperature. It might appear, therefore, that data on the impact properties at this temperature (approximately 20°C) would provide sufficient information for design. However, this approach would be rather naive since even indoors, temperatures may vary by an amount which can have a significant effect on impact behaviour. For components used outdoors of course, the situation can be much worse with conditions varying from sub-zero to tropical. In common with metals, many plastics exhibit a transition from ductile behaviour to brittle as the temperature is reduced. 

The manufacturing plants which produce thermoplastic components are located in Detroit, Michigan, Cleveland and Elyria, Ohio, Syracuse, New York, and Trenton, New Jersey. 

Several basic morphologies are observed in thermoplastic-modified epoxies and, indeed, other thermosets. Homogeneous [Fig. 6(A), in which no phase separation is observed] and particulate [Fig. 6(B), in which the modifier phase separates to produce small domains] morphologies occur at low concentrations of modifier. In these cases, the thermoplastic modifier is encapsulated within a thermoset matrix, whereas in the phase-inverted morphology, [Fig. 6(C)] the minor thermoplastic component is the continuous phase surrounding large, discontinuous domains of the major... 

Trantina, G. Nimmer, R. Structural Analysis of Thermoplastic Components, Hanster Gardner Publications, 1994. 

At the glass transition temperature (Tg), a thermoplastic material changes from a glassy state to a rubbery state. The properties of the material also change significantly. Tg values most often listed for polymers correspond to stiffening temperatures [3], The coefficient of thermal expansion usually doubles below Tg for these materials. Materials above the 7 , may be functional, but the performance may become unpredictable because most thermoplastic components are designed based on properties tested below 7 ,. 

The melting point, Tm, is the transition temperature at which a thermoplastic material changes from a rubbery state to a fluid state. Above Tm, a thermoplastic material completely loses its function. For a thermoplastic component, the optimum application temperature is the usage range below its Tg. 

One key factor for producing acceptable WPCs is the interaction between the wood and thermoplastic components (wood-polymer interface). It is difficult to achieve wood/plastic interaction because the hydrophobic thermoplastic (nonpolar) and hydrophilic wood (polar) are energetically different [2, 4]. During wood/plastic mixing, the thermoplastic must first coat or spread over the wood fiber surface to interact [4]. It is observed in Figure 26.2 that the polymer-fiber interface and a poor surface adhesion lead to fiber slipping from the matrix. 

Microscopic observations of decayed WPC specimens showed mycelium concentrated in the interfacial voids between the wood and the thermoplastic component. This observation supported the premise that the primary mode of fungal degradation was via hyphal penetration through the voids on the wood/polymer interfaces [10, 22], The materials used in these studies tended to have large wood particles, which resulted in lesser wood/plastic adhesion and more voids for fungal entry. 

These materials, known as polymer blends or polymer alloys (see Table 1.3), are generally prepared by mixing two or more thermoplastics. They combine, in an advantageous manner, the properties of the thermoplastic components, and in some cases, the properties of the blends are superior to those of the individual components. (Polymer mixtures also result from the recycling of mixed plastics which have to be identified before they can be reused.) Because of the large number of possible blend components, and the fact that usually so-called compatibilizers of often rather complicated chemical composition are present, a complete analysis of polymer blends is not possible with simple methods. However, by means of some screening tests and selected special tests, one can at least obtain qualitative information about the main components of such systems. 

Trdster S, Geiger O, Henning F, Eyerer P (2004) Added value for long-fiber reinforced thermoplastic components by in-line-compounding in the LFT-D-ILC process. SPE Paper 1121, ANTEC 2004, Chicago, IL... 

In most widely used two-polymer adhesives, the thermosetting component is phenolic. Phenolic resins are generally compatible, although not easily miscible, with a number of thermoplastic polymers. Particularly good compatibility is demonstrated between conventional alcohol-soluble phenolic resins and polyvinyl esters and acetals. Epoxies are important in two polymer adhesive systems. The most important thermoplastic components are the polyvinyl acetals (polyvinyl formal and butyral) and synthetic rubber, particularly nitrile rubber. Soluble nylons are also an important class. ... 

Figure 23.47 A selection of carbon fiber thermoplastic components, (a) Carbon fiber reinforced APC thermoplastic aircraft floorpanel (EH101 Merlin) Makes use of improved toughness and damage tolerance of thermoplastic materials, (b) Bulkhead or wing stiffener made from carbon fiber/PEEK thermoplastic Made in one piece apart from the ring stiffener, (c) Underslung carbon fiber APC2 reinforced thermoplastic tailplane. This item was made over 10 years ago and was the largest piece of flying thermoplastic in the world Fins are fabricated from Ultem 1000 (PEI). Source Courtesy of GKN.

Conventional thermal welding Welding is a thermal process requiring melting of fabric materials. A separate heat-activated adhesive material can also be used. Heating is achieved by direct contact of the fabric with a heated-tool surface or hot air. Fully or partially synthetic fabrics (woven and nonwoven) with thermoplastic components that are chemically and physically compatible when fused together. 

Thermoplastics used to blend with NR include PS, " polyamide 6, ethylene-vinyl acetate (EVA) copolymer, poly(methyl methacrylate) (PMMA), polypropylene (PP), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) " and high-density polyethylene (HDPE). To improve the properties of TPNR, modified NR is also used. ENR is the most frequently used modified NR. TPNR blends are prepared by blending NR and thermoplastics in various proportions. The role of rubber is to improve the impact strength and ductility of the plastic. Depending on the ratio, materials with a wide range of properties are obtained. The stiffness of the rubber is increased with the incorporation of plastic into the rubber matrix. The mechanical properties of TPNR again depend on the proportions of the rubber and thermoplastic components. The elastic properties of TPNR are considerably... 

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