Poly fatigue

Nylon, an aUphatic polyamide, was introduced as a commercial tire cord in 1947 and grew in usage to - 5.4 billion kg/yr (- 2 billion Ib/yr) in the 1990s (10,11). Nylon-reinforced tires use nylon-6 poljmier (polycaprolactam) fibers as well as nylon-6,6 (poly(hexamethylenediainine adipamide)) fibers. Nylon tire cords are characterized by extremely good fatigue resistance in compression and good adhesion to most mbber compounds with simple RFL adhesives. 

By combining elastomeric and brittle glassy phases it is often possible to obtain improved properties over a range of temperature and frequency. However, relatively little attention has been given to fatigue in IPNs, and to energy absorption in polyurethane rubber/poly(methyl methacrylate) (PU/PMMA) systems. 

The polyurethane formulation Involved a proprietary crossllnkable system based on poly(propylene glycol) and methylene dllsocyanate (NCO/OH ratio = 1.0). For studies of viscoelastic, energy absorption, and fatigue behavior, the weight fractions of PUMA were 0, 0.25, 0.50, 0.75, and 1.0 for studies of tensile and tear strength, the ratios were 0, 0.10, 0.20, 0.25, 0.30, and 0.40. Reactants were mixed at room temperature, degassed, poured Into a mold, and cured at 60 C for 48 hr. 

The fibers of aromatic PODs are known to have a combination of good properties, such as strength and stiffness, fatigue resistance, and relatively low density, in the range of 1.2 to 1.4 g/cm3. PODs have been used to improve the heat resistance of many synthetic fibers. This is usually done by dissolving the POD in sulfuric acid and then treating the fibers with this solution. Poly( >-phenylene-l,3,4-oxadiazole) is the most commonly used commercial polyoxadiazole, and the fiber spun from this polymer is called Oksalon. 

Crazing inhibition by crosslinking explains the better fatigue resistance of thermosets compared with thermoplastics (this is not valid for semicrystalline thermoplastics such as polypropylene or poly (ether ether ketone). 

Kawagoe M, Morita M (1993) Fatigue failure of poly(methyl methacrylate) in alcohol environments. J Mater Sci 28(9) 2347-2352... 

Enokida et al. (1991) reported that ultraviolet-induced fatigue of a photoreceptor using poly(methylphenylsilylene) (PMPS) as the transport layer could be explained by photodecomposition of the transport layer. The PMPS was both decomposed and cross-linked by the ultraviolet exposures. 

The fatigue lifetime data for prenotched (knit-line) samples of poly butylene terephthalate (PBT), a semicrystalline polymer, were unrevealing in that no fatigue crack growth could be induced under any of the conditions teted (Fig. 34). At higher... 

Lauretti, F. Gargani, L. Fatigue resistance of poly butadiene. Paper at the 27 th Annual Meeting of the International Institute of Synthetic Rubber Producers, Jun 1987. 

Figure 15.12 shows the fatigue resistance of carbon and glass fiber filled poly(phenylene ether ketone).The flexural fatigue depends on tensile properties of the composite. The yield strength of the matrix and the quality of the interface affect the fatigue properties of composites. 

Fatigue Behavior of Interpenetrating Polymer Networks Based on Polyurethanes and Poly(methyl methacrylate)... 

Although interpenetrating polymer networks (IPNs) are now beginning to be commercially exploited, little is known about many types of engineering behavior, such as fatigue. In this paper, energyabsorbing simultaneous interpenetrating networks (SINs) based on polyether-type polyurethanes (PU) and poly(methyl methacrylate)... 

This paper addresses three topics of current scientific and technological interest poly(vinyl chloride) (PVC) toughening of brittle or ductile but notch-sensitive polymers by the inclusion of rubbery phases and the kinetics of fatigue crack propagation (FCP). 

This Is the linear additivity of damage law. In the following paragraphs, we examine how well the failure and fatigue of Poly(methyl methacrylate) (PMMA) are described by this law. 

Poly(4 -vinyl-fraws-benzalacetophenone) was prepared by Unruh 52> by condensation of poly(p-vinyhcetophenone) with benzaldehyde. In his studies Unruh s2> compared the photochemical behavior of poly(4 -vinyl-fraMS-benzalacetophenone) with that of the model compound, 4-ethylbenzalacetophenone. Both the polymer and its model showed typical photoisomerization behavior when irradiated in dilute solution. This behavior of the two species was consistent with the results reported for benzalacetophenone by Lutz, et al. 53<54>. Unruh found, however, that when the trans polymer was photoisomerized to the cis form, the expected complete return to trans form upon addition of acid failed to result. This fatigue or loss was attributed to small amounts of intrachain... 

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