Polypropylene unfilled

Some thermoplastics, notably polypropylene, are relatively unstable to heat and light unless stabiliser additives are present [30]. In the early days, these additives comprised a significant proportion of compound raw material costs, but over time the polymers and the stabiliser systems have been improved until they have only a relatively small effect on the costs of unfilled polymers today. 

Fig. 9. The effect of magnesium hydroxide filler type on the dynamic storage modulus G of polypropylene (PP) at 200 °C (strain amplitude 10%, filler level 60% by weight). Magnesium hydroxide fillers differed in origin particle size and treatment. Mean particle size (pm) type A ( ), 7.7 type B (+), 0.9 type C ( ), 4.0 type D ( ), 0.53 type E, stearate-coated version of type A, (X), 3.7 unfilled PP (O) [36]...

Gay is used as a filler in compounding paper and rubber. Talc, a naturally occurring fibrouslike hydrated magnesium silicate, is used to improve the thermal resistance of polypropylene (PP). Since talc-filled PP is much more resistant to heat than unfilled PP, it is used in automotive accessories subject to high temperatures. Over 40 million tons of talc are used annually as a filler. 

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...

Attempts to improve flexural strength by surface treatment of fillers have not, to date, been successful. A variety of silanes, titanates, and fatty acids and their derivatives have been used to coat magnesium hydroxide for use as a filler in polypropylene. " Almost all composites had inferior flexural properties. In the few cases where some improvement was seen, it was 10% more then the unfilled material. 

There are several reports on the influence of fillers on shrinkage. " Figure 8.56 shows mold shrinkage vs. concentration of filler. Mold shrinkage can be reduced to half of the value for unfilled resin by the incorporation of mica. Additional reduction of shrinkage is possible if the interaction between filler and the matrix can be increased. This can be achieved by reacting polypropylene with maleic anhydride. ... 

Talc is always an attractive subject of such studies due to its platelet structure. In thermoforming and compression molding processes of three resins (PP, HDPE, and PPS), each containing 20% talc, the talc particles were always parallel to the specimen surface, regardless of the resin used. Crystallites grew in a direction normal to the surface of talc particles and thus were perpendicular to the specimen surface. But in the case of unfilled HDPE, crystallites grew parallel to the specimen surface. There was no difference in crystallite growth direction in the case of polypropylene with and without talc. 

Decomposition of PA-6 and PA-66 produces NH3, H2O, CO, CO2, and hydrocarbons. The addition of magnesium hydroxide decreases the amounts of volatiles produced but the chemical components and their proportions are very similar to unfilled polymers. The addition of zeolites to polypropylene changes the mechanism of degradation depending on the zeolite type, its morphology, and dispersion but, in the investigation, the composition of the decomposition products was not determined. ... 

Melt blending of PA-6 (or 66) with such an anhydride functionalized polypropylene causes a fast graft copolymer reaction between the polyamide and PP at the interface, which subsequently compatibilizes the blend. Some commercial polyamide/polypropylene blends may utilize such types of reactive compatibilization techniques. Properties of commercial PA/PP blends, both unfilled and glass filled grades, are shown in Tables 15.18 and 15.19. Typically, these blends... 

A comparison [32] of standard (ASTM and DIN) Charpy notch-impact test results with those of critical strain energy release rates G... obtained in accordance with LEFM criteria under the condition of small-scale yielding, were made for various unfilled polypropylenes. blends of PP with ethylene-propylene random copolymer (EPR) and also with... 

Polypropylene (PP) in various forms (filled, unfilled, reinforced, rubber blended) finds the greatest usage of all automotive plastics. Its consumption is likely to accelerate as a result of new laws requiring recyclability, and because of the weight and cost reductions it offers. New fabrication techniques may also contribute to growth. For example, the monomaterial sandwich construction techniques developed by fabricators yield rugged and lightweight PP-based instrument and door panels. These parts consist of a sandwich of reinforced or neat PP substrate, a cross-linked PP foam, and a thermoplastic polyolefin elastomer (TPO) cover. 

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). 

By 1993, there was widespread industry acceptance of engineered polypropylene, with nearly eveiy OEM (foreign and domestic) having specifications for and using at least one grade. A great deal of effort was channeled into the development and certification of these resins, however, much of the color technology was carried over from unfilled polyolefins. In... 

The end result is that there can be density overlap between two resins even though the densities of the base resins differ significantly (Fig. 14.18). A classic example is common talc-filled polypropylene (PP) that can have a density very similar to that of unfilled acrylonitrile-butadiene-styrene (ABS) resin. These... 

Table 2.8 Properties of a Typical Filled and Unfilled Polypropylene (1)...

Particulate fillers can be incorporated into one of the layers, producing novel structures. Nazarenko et al. incorporated nickel, Ti02, and talc in LLDPE/low-density polyethylene (LDPE) combinations. Novel structures can also be prepared by combining filled and unfilled layers of the same material, such as filled and unfilled polypropylene (PP). Microlayered structures using poly(ethylene terephthalate)(PET) and talc filled PET have also been prepared. ... 

Studies on a similar group of materials - polymeric composites reinforced with sisal fibers - were conducted by Manchado et al. [35]. They analyzed the presence of different fibers, such as sisal, on crystallization of polypropylene. The composites were prepared in special chamber for mixing where the matrix was plastified at 190°C. Obtained materials were subjected to thermal analysis by DSC. The analysis of thermograms allowed for a similar finding like in Joseph s studies [34], The presence of sisal fibers, as well as other fibers used in the study, accelerated crystallization of polypropylene. This was explained by the nucleating effect of sisal filler. Also, the half-time crystallization (ti/2) decrease was observed for polypropylene with the addition of sisal fibers in comparison with unfilled polypropylene. The analysis of nonisothermal crystallization showed that the degree of polypropylene crystallinity is higher for the composites filled with sisal fibers than for unfilled polymer. 

The addition of talc to polypropylene does not seem to have a significant effect on melt flow rate. Because of its higher specific gravity (2.78 versus 0.91-0.94 for unfilled polypropylene), talc causes a slight increase in measured melt flow... 

In Chapter 3, mechanical properties of glass fiber-reinforced polypropylene are improved by addition of a coupling agent. Likewise, the in situ generation of modified polypropylene by grafting acrylic acid onto the polymer backbone in the Nichols and Kheradi investigation yields enhanced tensile strength compared with unfilled polypropylene and uncoupled composite (Fig. 10.2). 

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