Polypropylene reinforcement with mineral

Polypropylene that is reinforced with mineral fillers, such as talc, mica, and calcium carbonate, as well as with glass and carbon fibers. The maximum concentration is about 5 wt%, although concentrates with higher levels of filler or reinforcement are available. 

Long Glass Fiber-Reinforced Polypropylene with Mineral Fillers... 

Crystalline polymers show the greatest interaction with minerals. In amorphous polymers, minerals merely increase stiffness, with little or no reinforcing effect. Polypropylene, high density polyethylene, thermoplastic polyester and polyamides are crystalline polymers. Low density polyethylene, polystyrene and polycarbonate are amorphous. 

It is well accepted that the good properties of the isotactic polypropylene as an engineering polymer matrix in thermoplastic composite materials and engineering blends are seriously affected by the inability of this polymer to develop an adequate level of interfacial interaction with polar components such as mineral fillers (calcium carbonate) and reinforcements (talc, mica, wollastonite), synthetic reinforcements (glass fibers, carbon fibers, and nanotubes), or engineering polymers such as polyamide, aliphatic polyesters, and so on. 

The presence of mineral reinforcements such as talc or mica, as foreign solid particles embedded into a polypropylene matrix, usually induces a nucleation effect. A signihcant increase in the crystalline content of the polymer is evidenced if compared with the neat polymer when processed at the same setup conditions that are necessary to ensure a good accommodation of the solid particles into the amorphous phase of the polymer in order to obtain a material with a good mechanical performance (27). The comparison between PP/mica and PP/talc composites in terms of their mechanical behavior under dynamic conditions in the solid state agrees with the morphological features derived from their chemical structures of both minerals (28). 

Thermoplastic polyolefin (TPO) is a generic name that refers to polyolefin blends usually consisting of some fraction of polypropylene (PP), polyethylene (PE) or polypropylene block copolymer (PP-b-EP or BCPP ), and a thermoplastic olefinic rubber, with or without a mineral reinforcing filler such as talc or wollastonite. Common rubbers include ethylene propylene rubber (EPR), EPDM rubber, ethylene-octene (EO) copolymer mbber, ethylene-butadiene (EB), and styrene-ethylene-butadiene-styrene (SEBS) block copolymer rubbers. Currently, there are a great variety of commercial polypropylene homopolymers, PP block copolymers, and olefinic rubbers available to make a wide range of TPO blends with densities ranging from 0.92 to 1.1. 

The multiple functions of mica have been outlined in Chapter 1 of this book, along with an example of its role in the search of multifunctional fillers for polypropylene compounds for automotive applications. Mica-reinforced thermoplastics such as polypropylene, polyethylene, nylon, and polyesters are now established in a variety of automotive applications and consumer products where mica supplements or replaces glass fibers and other mineral fillers. The wider use of mica in many applications has been limited by low impact strength and low weld-line strength in certain plastics. These issues are the focus of continuing R D efforts by materials suppliers and compounders/molders. 

The special grade of polypropylene, with rubber reinforcement to improve impact resistance, and mineral filler to increase stiffness, creeps sufficiently to give imbalance, and possible contact with the housing, under service conditions. This material was tried as a cost-saving exercise, which illustrates the importance of cost, but had to be eliminated for the reason given. 

General Motors fan assembly, with fan in reinforced polypropylene and support in mineral filled nylon (courtesy ICI). 

Talc has been the second mineral of choice to fill polypropylene. Such applications have usually been automotive and industrial. Talc is a general purpose filler mineral and is highly compatible with polyolefins. It is widely used to increase stiffness and heat resistance in polypropylene automobile trim parts that do not require high reinforcement. 

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