Endurance polyethylene

The data presented in Figure 19.7 were obtained on a Sonntag-Universal machine which flexes a beam in tension and compression. Whereas the acetal resin was subjected to stresses at 1800 cycles per minute at 75°F and at 100% RH, the nylons were cycled at only 1200 cycles per minute and had a moisture content of 2.5%. The polyethylene sample was also flexed at 1200 cycles per minute. Whilst the moisture content has not been found to be a significant factor it has been observed that the geometry of the test piece and, in particular, the presence of notches has a profound effect on the fatigue endurance limit. 

Dukes WA (1961) The Endurance of Polyethylene under constant tension while immersed in Igepal. British Plastics 34 123... 

Based on the concentration dependence of adhesion (similar to that presented in Fig. 3.38) the formulation of an antirust coating has been calculated [79]. It is composed of polyethylene and a sulfuric 8-oxyquinalin Cl. At 5 wt% content of this Cl adhesion of the coating to a steel substrate shows a maximum adhesion A = 0.4kN/m corresponding to the antiplastification peak of polyethylene by Cl. It is peculiar to this composition that, after endurance in a 50% aqua solution of sulfuric acid for ten days, adhesion of the initial polyethylene coating drops almost to zero, while adhesion of the inhibited ones, though sure to reduce, remains at a level (0.1-0.2kN/m) sufficient for normal operation. 

About one-half of all symthetic resin produced worldwide is polyolefin. The two principal compositions are polyethylene (mainly its high density and linear, low-density forms) and polypropylene (mainly its isotactic form). The widespread and enduring commercial success of olefins derives from a combination of favorable properties they are inexpensive. 

Confirmation of the general fatigue superiority of semicrystalline polymers is implicit in studies of a-N behavior at frequencies low enough to minimize temperature rises (169). While the ratios of the endurance limit to tensile strength for typical amorphous polymers (polystyrene, PMMA, and cellulose acetate) are approximately 0.2, values for nylon-6,6, acetal resin, and polyterafluoroethylene are 0.3, 0.5, and 0.5, respectively. At a low frequency, polyethylene (Mw > 50,000) exhibits no failure after 5 x 10 cycles, even at the relatively high alternating stress... 

Acrylonitrile-butadiene-styrene terpolymer and low-density polyethylene generally cannot meet the fatigue endurance, dimensional stability, and heat and creep resistance requirements of precision gears. Such polymers are most often found in basic low-load or low-speed gears. 

Takala M, Ranta H, Nevalainen P, Pakonen P, Pelto J, Karttunen M, Virtanen S, Koivu V, Pettersson M, Sonerud B, Kannus K (2010) Dielectric properties and partial discharge endurance of polypropylene-silica nanocomposite. IEEE Trans Diel Electr Insul 17 1259-1267 Tanaka T, Kozako M, Fuse N, Ohki Y (2005) Proposal of a multi-core model for polymer nanocomposite dielectrics. IEEE Trans Diel Electr Insul 12 669-681 Vaughan AS, Swingler SG, Zhang Y (2006) Polyethylene nanodielectrics the influence of nanoclays on structure formation and dielectric breakdown. Trans lEE Jpn 126 1057-1063 Venkatesulu B, Thomas MJ (2010) Erosion resistance of alumina-filled silicone rubber nanocomposites. IEEE Trans Diel Electr fiisul 17 615-624 Weibull W (1951) A statistical distribution function of wide applicability. J Appl Mech Trans ASME 18 293-297... 

The Medtronic Endurant bifurcated stent graft was approved for commercial use by the FDA in December 2010 (FDA, 2013). It consists of two components, the main bifurcated body and the contralateral limb (Fig. 21.10). The main body consists of a multifilament polyester fabric coupled with laser-cut nitinol stents, sewn together using polyester sutures. A bare nitinol stent is affixed to the proximal end of the main body using ultra-high molecular weight polyethylene sutures. This stent allows the device to be fixed above the renal arteries without preventing arterial blood flow to the kidneys, and is referred to as the suprarenal stent. There are barbs on the top of... 

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