Thermal degradation reinforcement

Thermal and Chemical Stability. In addition to load-bearing properties, tire reinforcement must be able to resist degradation by chemicals in cured mbber and heat generation. The most critical degradant depends on the material in use. Most thermoplastic reinforcements are either modified directiy or stabiH2ed with additives to offset some, mostiy thermal, degradation (32,33). 

PEI resins reinforced with up to 40 wt % fiber glass are available. The American Cyanamid Co. uses an Ultem-type resin with carbon fibers to form their Cypac 1000 series prepregs (31). The moisture content of the resin must be less than 0.05% prior to melt processing to minimise thermal degradation. 

The increasing use of light ceramic composites for high temperature and space applications has stimulated the development and optimization of the Chemical Vapour Infiltration technique. The use of conventional ceramic techniques for the fabrication of fibre-reinforced composites damages the fibres both mechanically as chemically. Also, the high process temperature causes a thermal degradation of the fibres. 

Recycling as new plastics materials. TP matrices can be re-melted and re-compounded, with some possible loss of mechanical properties due to thermal degradation of the matrix and breakage of the fiber reinforcement into shorter lengths. On the other hand, TSs have been crosslinked and therefore cannot be re-melted, but can be ground to fine powder that is an effective filler in new compounds... 

Figure 12.10 shows the release of volatiles during thermal degradation of polypropylene. Mica reinforces the polypropylene stability, while halogenated flame retardant reduces it. Both composite polymers are compared with the pure polymer. The thermal stability of low, medium and high-density polyethylenes has its linkage to the number of branches in the main polymer chain. It is of interest that the flammabihty expressed in the amount of oxygen consumed follows the similar tendency (Fig. 12.11). 

The thermal degradation of natural fibers results in poor physico-mechanical properties and in the discoloration of the fibers. Therefore, reinforcing high temperature melting thermoplastics which melt above 200°C with natural fibers has turned out to be a challenging task (26). 

Seo, M. K. and Park, S. 2004. A kinetic study on the thermal degradation of multi-walled carbon nanotubes-reinforced poly(propylene) composites. Macromolecular Materials and Enoineerino 289 368-374. 

To the category of amorphous, aromatic polyamides (PARA) belong polyphthalamides (PPhA), e.g., AmodeF (Tg = 127 °C, T = 310 C, HDT = 285 °C, CUT = 180 °C). PPS/PARA blends were formulated to increase the reinforcing effects of GF on PPS. They show good processability, mechanical performance, and resistance to thermal degradation. 

Acrylonitrile-butadiene-styrene terpolymer (ABS), as well as its fiber reinforced composites and blends, is a very important and widely used engineering material. The demand for and production of this family of materials increase year by year however, there is only little work on the thermal degradation of ABS terpolymer (Dong et al. 2001 Luda di Cortemiglia et al. 1985 Suzuki and Wilkie 1995). 

The peak temperatures for thermal degradation of the composites and the PP matrix occurred at approximately 458°C and 450°C, respectively. Table 6.4 shows that the addition of fibers caused a significant increase in the peak temperature for composite degradation, reaching 466°C for the composites reinforced with 20 wt% fibers treated with hot water. 

A.K. Gupta, M. Biswal, S. Mohanty, and S.K. Nayak, Mechanical, thermal degradation, and flammability studies on surface modified sisal fiber reinforced recycled polypropylene composites. Adv. Mech. Eng. 2012, Article ID 418031, http //dx.doi. org/10.1155/2012/418031 (2012). 

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