Polyolefins, additives Fillers

One would expect that addition filler of similar structure would reinforce the hard segments. It was found that the addition of thermoplastic polyolefins of high melting point did improve the physical properties. 

Polyolefin + mineral filler Polyolefin copolymer + Br additives... 

A manufacturer considering using a thermoplastic elastomer would probably first consider one of the thermoplastic polyolefin rubbers or TPOs, since these tend to have the lowest raw polymer price. These are mainly based on blends of polypropylene and an ethylene-propylene rubber (either EPM or EPDM) although some of the polypropylene may be replaeed by polyethylene. A wide range of blends are possible which may also contain some filler, oil and flame retardant in addition to the polymers. The blends are usually subject to dynamic vulcanisation as described in Section 11.9.1. 

Chlorinated polyether is formulated particularly for products requiring, good chemical resistance. Other materials exhibiting good chemical resistance include all of the fluorocarbon plastics, ethylpentenes, polyolefins, certain phenolics, and diallyl phtha-late compounds. Additives such as fillers, plasticizers, stabilizers, colorants, and type catalysts can decrease the chemical resistance of unfilled plastics. Certain chemicals in cosmetics will affect plastics, and tests are necessary in most cases with new formulations. Temperature condition is also very important to include in the evaluation. Careful tests must be made under actual use conditions in final selection studies. 

Demand for the different classes of polymer additives varies by resin. Modifiers and processing aids rely heavily on PVC while the property extenders are primarily used in non-PVC resins. PVC is by far the largest consuming resin for polymer additives (excluding fillers), accounting for some 80% of the world-wide volume or 60 % in total value. Polyolefins are a distant second accounting for 8% and 17%, respectively [36]. 

In addition to its role as a pigment, carbon black may be incorporated into polymers as a reinforcement for elastomers, as a UV stabiHser in polyolefins, or as an electrically conducting additive. In each case the physiochemical properties of the filler and its ultimate state of dispersion is critical in order to achieve... 

Zinc oxide (ZnO) is widely used as an active filler in rubber and as a weatherability improver in polyolefins and polyesters. Titanium dioxide (TiOj) is widely used as a white pigment and as a weatherability improver in many polymers. Ground barites (BaS04) yield x-ray-opaque plastics with controlled densities. The addition of finely divided calcined alumina or silicon carbide produces abrasive composites. Zirconia, zirconium silicate, and iron oxide, which have specific gravities greater than 4.5, are used to produce plastics with controlled high densities. 

The combination of melamine with hydrated mineral fillers can improve the fire retardancy behavior of PP, eliminating at the same time the afterglow phenomenon associated with these fillers used in isolation.70 Similarly in EVA copolymer, antimony trioxide used in combination with metal hydroxides has been reported to reduce incandescence.56 Chlorinated and brominated flame retardants are sometimes used in combination with metal hydroxides to provide a balance of enhanced fire-retardant efficiency, lower smoke evolution, and lower overall filler levels. For example, in polyolefin wire and cable formulations, magnesium hydroxide in combination with chlorinated additives was reported to show synergism and reduced smoke emission.71... 

Monoalkoxy titanate Chelate titanate Quat titanate Neoalkoxy titanate Cycloheteroatom titanate Stearic acid functionality aids in dispersion of mineral fillers in polyolefins Greater stability in wet environments Water-soluble, aids adhesion of water-soluble coatings and adhesives Eliminates pretreatment associated with fillers, can be used as a concentrated solid additive Ultrahigh thermal properties for specialty applications... 

TPOs are basically two-component elastomer systems consisting of an elastomer finely dispersed in a thermoplastic polyolefin (such as polypropylene). The thermoplastic polyolefin is the major component. Thermoplastic elastomers (TPEs) include TPOs, TPVs (thermoplastic vulcanizates), etc. Properties of TPOs depend upon the types and amounts of polymers used, the method by which they are combined, and the use of additives such as oils, fillers, antioxidants, and colors. Blends and reactor-made products compete primarily with other TPEs and metals. There are vulcanizates (TPVs) that have higher elastomeric properties. They compete primarily with TS elastomers. 

With metallocene catalysts, not only homopolymers such as polyethylene or polypropylene can be synthesized but also many kinds of copolymers and elastomers, copolymers of cyclic olefins, polyolefin covered metal powders and inorganic fillers, oligomeric optically active hydrocarbons [20-25]. In addition, metallocene complexes represent a new class of catalysts for the cyclopolymerization of 1,5- and 1,6-dienes [26]. The enantio-selective cyclopolymerization of 1,5-hexadiene yields an optically active polymer whose chirality derives from its main chain stereochemistry. 

Films containing filler may have a substantially improved UV stability due to the addition of carbon black. It is also possible to produce films which will be biodegradable by the combined action of UV degradation and biodegradation. It was confirmed that china clay increases the degradation rate of polyolefins by consuming stabilizers and thus reducing polymer stability... 

The addition of pigments to polymers is a very effective practical method for increasing the resistance to photodegradation. Carbon black is by far the most effective. It has been used for years as a filler in rubber vulcanites, but in thermoplastic materials such as polyolefins it also has a protective effect against photodegradation. This was shown for the first time in 1950 by Wallder et al. [126] they demonstrated that the weathering properties of polyethylene are improved by the addition of about 2% carbon black. The effect is dependent on the degree of dispersion and on the size of the particles. Channel Black (particle size about 30 nm), for instance, is more efficient than Furnace Black (particle size 80 nm). The role of carbon black is not only to prevent the absorp-... 

U.S. Pat. No. 6,632,863 [115] (by Crane Plastics Company, Timber-Tech) discloses a wood-plastic composition manufactured as feedstock pellets comprising 55-90% cellulosic material such as wood flour and wood fiber, 10-40% of polyolefin such as HDPE, LDPE, and polypropylene, and 0-35% total of additive(s), such as lubricants and inorganic fillers, such as talc and mica. 

Effect of talc on mechanical properties of polyolefins fypically depends on particle size of the filler. If is generally considered thaf fhe finer fhe falc particles, the better its effect on impact resistance, which generally suffers with addition of minerals. However, data in Table 4.7 show that it is not always so. Although introduction of talc indeed reduced impact resistance of the filled polypropylene regardless of particle... 

Additives in polyolefins which improve their application properties affect the crosslinking whenever they take part in the generation of free radicals or enter the propagation reactions.With the presence of fillers with acid sites, peroxides are, e.g., decomposed by an ionic medmnism and formation of a crosslinked structure in polyethylene is suppressed. To remove such an eff t, acid centres should be neutralized by basic substances. 

The reactive methods of compatibili2ation developed subsequently allowed the second generation Noryl (a blend of PPO with PA) to be developed. The compositions claimed usually cover 30-70% of each of the main ingredients, PPO and PA, with additionally up to four parts of such modifier as polycarboxylic acid, trimellitic anhydride acid chloride, quinine, oxidized polyolefin wax, and so on. In most cases, PA forms a matrix with spherical inclusions of PPO acting as compatibilized low-density filler. 

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