Polyethylene unfilled

Note that, apart from the filler particle shape and size, the molecular mass of the base polymer may also have a marked effect on the viscosity of molten composites [182,183]. The higher the MM of the matrix the less apparent are the variations of relative viscosity with varying filler content. In Fig. 2, borrowed from [183], one can see that the effect of the matrix MM on the viscosity of filled systems decreases with the increasing filler activity. In the quoted reference it has also been shown that the lg r 0 — lg (MM)W relationships for filled and unfilled systems may intersect. The more branches the polymer has, the stronger is the filler effect on its viscosity. The data for filled high- (HDPE) and low-density polyethylene (LDPE) [164,182] may serve as an example the decrease of the molecular mass of LDPE causes a more rapid increase of the relative viscosity of filled systems than in case of HDPE. When the values (MM)W and (MM)W (MM) 1 are close, the increased degree of branching results in increase of the relative viscosity of filled system [184]. 

TABLE 2.11 Typical Properties of Unfilled Polyethylene terephthalate) (PET), Poly(trimethylene terephthalate) (PTT), and Poly(butylene terephthalate (PBT) Solid-State Polyester Resins... 

Fig. 7.17 Unmixed polyethylene superconcentrate (50% carbon black) in a mixture of superconcentrate and unfilled polyethylene as a function of viscosity ratio. [Reprinted by permission from V. W. Uhl and J. B. Gray, Mixing Theory and Practice, Vol. II, Academic Press, New York, 1967.]...

Fig. 4 The number of nitrogen atoms, which equals the number of sugar units, per cm2 (filled squares) and the number of polyethylene oxide) chains per cm2 (unfilled circles)...

Fig. 2. Dimensionless ratio AsM/fa] for various polymers. Open circles, polyisobutylene 148). Upright triangles, poly(raethyl methacrylate) 40, 47, 5V, 59). Inverted triangles, polyvinyl acetate (62, 233). Squares, polystyrene 35,71, 73,148,206,208). Filled circles, atactic polypropylene 138). Crosses, linear polyethylene 26,152,256), The unfilled points were selected as specially reliable in 1957 by Orofino and...

In general, plastics are superior to elastomers in radiation resistance but are inferior to metals and ceramics. The materials that will respond satisfactorily in the range of 1010 and 1011 erg per gram are glass and asbestos-filled phenolics, certain epoxies, polyurethane, polystyrene, mineral-filled polyesters, silicone, and furane. The next group of plastics in order of radiation resistance includes polyethylene, melamine, urea formaldehyde, unfilled phenolic, and silicone resins. Those materials that have poor radiation resistance include methyl methacrylate, unfilled polyesters, cellulosics, polyamides, and fluorocarbons. 

The sample of unfilled polyethylene (PE) was prepared by ethylene polymerization on VC13 activated with Al(i-Bu)3 at the same conditions as applied to the nanocomposite... 

Figure 5. Coefficient of friction of filled and unfilled high density polyethylene sliding against a ground steel disc. Sliding conditions 39 N load, 2.1 m/s speed.

Figure 6. Wear of filled and unfilled high density polyethylene...

In order to investigate the effect of free sulfur in the wear process, high density polyethylene was filled with 2% S and 2% 2-mercurobenzothiazole. This composition provided almost the same wear rate as that of the unfilled material and the coefficient of friction was also the same. It proves that the strengthening of the polymer from the filler material is important for the reduction of wear. 

Copolymers of ethylene with a small amount of vinyl acetate are often preferred for peroxide cross-linking because the latter promotes the cross-linking process. Large amounts of carbon black may be incorporated into polyethylene that is to be cross-linked. The carbon black is believed to take part in the cross-linking process, and the mechanical properties of the resulting product are superior to those of the unfilled material. 

Since the density of plastics highly depends on the presence of fillers or other additives, this property is far from being a characteristic feature. Unfilled polyolefines (polyethylene and polypropylene), a number of elastomers (natural rubber and silicone rubber), and foamed plastics come within the rare category of polymers which float on water. Some fluoropolymers exhibit a density around or greater than 2 g/cvo (see also Table 3.3). 

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