Fibrous glass thermoplastics

Two specific areas are covered more comprehensively fibrous glass polyesters and fibrous glass thermoplastics. The advances in reinforced polyesters have been in the materials and process areas. These changes are more profound than those related to mechanical properties. Hence, a treatment of mechanical properties of reinforced polyesters is not attempted. On the other hand, the reinforced thermoplastics advances are essentially in terms of many new reinforced polymers as well as a greater variety of compounds. For these reasons, it seems appropriate to discuss advances in this area in terms of properties. 

Table VII. Theoretical Strength Model for Fibrous Glass Thermoplastics...

Tt always seems fitting at the start of a new decade to look back on the previous one. The topic of fibrous glass composites is no exception. As a clarification, the term fibrous glass composites as used here refers to thermosetting and thermoplastic molding resins reinforced with fibrous glass. 

The growth of these materials is reflected in the number of polymers which are being glass reinforced. These include polypropylene, polystyrene, styrene acrylonitrile, nylon, polyethylene, acrylonitrile-butadiene-styrene, modified polyphenylene oxide, polycarbonate, acetal, polysulfone, polyurethane, poly (vinyl chloride), and polyester. In addition, the reinforced thermoplastics available now include long-fiber compounds, short-fiber compounds, super concentrates for economy, a combination of long and short fibers, and blends of polymer and fibrous glass. 

Figure 5. Fibrous glass and impact strength of thermoplastics...

By definition, thermoplastics have limitations at elevated temperatures. It is in this particular property that fibrous glass can lead to remarkable improvements. However, a sharp division exists for reinforced thermoplastics. The various reinforced thermoplastics can be put in two groups relative to DTUL. These consist of amorphous and crystalline or semicrystalline polymers. The amorphous polymers such as styrene-acrylonitrile, polystyrene, polycarbonate, poly (vinyl chloride), and acrylo-nitrile-butadiene-styrene are generally limited to modest DTUL improvements, usually on the order of 20°F with 20% glass. However, crystalline polymers such as the nylons, linear polyethylene, polypropyl-... 

Figure 8 shows the effect of fibrous glass on linear coefficient of thermal expansion for ABS, one of the more dimensionally stable thermoplastics. The improvement in dimensional stability is on the order of... 

A typical unsaturated unreinforced polyester resin has an extremely low notched Izod impact strength. The addition of fibrous glass can change this extremely brittle material into a high impact strength composite. The same phenomenon occurs with some brittle thermoplastics, such as polystyrene and styrene—acrylonitrile. 

Thermoplastics. This segment of fibrous glass composites came out of its infancy in the 1960s. The potential of these materials is tremendous because no new molding process technology is required. Advances will be in the area of materials performance. 

A coupling agent for fibrous glass used in reinforced thermosetting and thermoplastic resins. 

The mechanical properties of plastics materials may often be considerably enhanced by embedding fibrous materials in the polymer matrix. Whilst such techniques have been applied to thermoplastics the greatest developents have taken place with the thermosetting plastics. The most common reinforcing materials are glass and cotton fibres but many other materials ranging from paper to carbon fibre are used. The fibres normally have moduli of elasticity substantially greater than shown by the resin so that under tensile stress much of the load is borne by the fibre. The modulus of the composite is intermediate to that of the fibre and that of the resin. 

Mandell 3.F., Darwish, A.Y. and McGarry F.3. (1981). Fracture testing of injection-molded glass and carbon fiber-reinforced thermoplastics. In Testing Methods and Design Allowable for Fibrous Composites, ASTM STP 734 (C.C. Chamis ed.), ASTM, Philadelphia, PA, pp. 73 90. 

As mentioned earlier, suspensions of particulate rods or fibers are almost always non-Brownian. Such fiber suspensions are important precursors to composite materials that use fiber inclusions as mechanical reinforcement agents or as modifiers of thermal, electrical, or dielectrical properties. A common example is that of glass-fiber-reinforced composites, in which the matrix is a thermoplastic or a thermosetting polymer (Darlington et al. 1977). Fiber suspensions are also important in the pulp and paper industry. These materials are often molded, cast, or coated in the liquid suspension state, and the flow properties of the suspension are therefore relevant to the final composite properties. Especially important is the distribution of fiber orientations, which controls transport properties in the composite. There have been many experimental and theoretical studies of the flow properties of fibrous suspensions, which have been reviewed by Ganani and Powell (1985) and by Zimsak et al. (1994). 

A reinforced structure of thermoplastics, named as the in situ hybrid composite, consists of three components in principle macroscopic fibers such as glass fiber, carbon fiber, or aramid fiber microscopic LCP fibrils and a matrix resin [157]. Macroscopic fibers are in their fibrous form before the fabrication of the reinforced composite, while LCP fibrils are generated in situ during the melt processing of the ternary composite. 

The reinforcement used with plastics, both thermosetting resins and thermoplastics, is usually a fibre or filament, used either on its own, or in mixtures. Non-fibrous materials can also be used in some cases. Reinforcing fillers are also used, including glass flakes, mica platelets, fibrous and finely divided minerals, and hollow and solid glass microspheres. 

Heating alkali metal or alkaline earth metal dihydrogen phosphates produces polymeric salts (cyclic metaphosphates and linear polyphosphates) and cross-linked polyphosphates (ultraphosphates), depending on temperature and the presence of other ingredients (11,12). This complex group of polymers includes materials with crystalline, glass-like, fibrous, or ceramic properties as well as some with thermoplastic and thermoset characteristics some are useful as binders for metals, ceramics, and dental restorations. Reviews are available on glasses (12,13), crystalline compounds (14), and polyphosphate fibers (15). 

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