Processing Glass-Reinforced Thermoplastics

Bulletin JIA Properties and Processing Glass Reinforced Grades—Celanex Thermoplastic Polyester", Celanese Corporation, Chatham, NJ, May 1974. 

Walter Lachowecki, Fiber Glass Reinforced Thermoplastics Part 1—Properties, Design Tip and Applications Part 2—Processing and Fabricating . Plastics Design and Processing (June and July 1969). 

J. P. Nunes, J. R Silva, L. Silva, A. T. Marques, P. J. Novo (2000) The development of a dry coating process to produce glass reinforced thermoplastic matrix towpregs, Proc. 9 European Conf. Composite Materials ECCM-9, Brighton. 

Lightweight reinforced thermoplastics materials with great strength and stiffness are needed in a number of so-called technical applications. Therefore short glass fibers are used to stiffen thermoplastics, for instance polypropylene, polyamides and also more technical polymers such as polybutylene terephthalate. Thermoplastic processors do not compound themselves their materials and consequently there is quite a large choice of ready-to-be-processed SGF reinforced thermoplastic composites. Table 7.6 gives the average properties of typical commercial PP-SGF composites, as compiled from manufacturers data sheets (when available). 

Reinforced Thermoplastic Sheet. This process uses precombined sheets of thermoplastic resin and glass fiber reinforcement, cut into blanks to fit the weight and size requirements of the part to be molded. The blanks, preheated to a specified temperature, are loaded into the metal mold and the material flows under mol ding pressure to fiU the mold. The mold is kept closed under pressure until the temperature of the part has been reduced, the resin solidified, and demolding is possible. Cycle time, as with thermosetting resins, depends on the thickness of the part and the heat distortion temperature of the resin. Mol ding pressures are similar to SMC, 10—21 MPa (1500—3000 psi), depending on the size and complexity of the part. 

Glass fibres dominate this field either as long continuous fibres (several centimetres long), which are hand-laid with the thermoset precursors, e.g., phenolics, epoxy, polyester, styrenics, and finally cured (often called fibre glass reinforcement plastic or polymer (FRP)). With thermoplastic polymers, e.g., PP, short fibres (less than 1 mm) are used. During processing with an extruder, these short fibres orient in the extrusion/draw direction giving anisotropic behaviour (properties perpendicular to the fibre direction are weaker). 

Grades reinforced with fibres 20 mm and more in length cannot be processed on conventional equipment. It is necessary to use, for example, the extrusion-compression technique. The process differs too much from conventional injection used for short glass fibre reinforced thermoplastics to measure the influence of fibre length alone. 

The integration of the compounding of long glass fibre reinforced thermoplastics on the process line is an example of the globalization and automation of the process. 

POLYCYCLO-ITEXYLENE-Dl METHYLENE TEREPHTHALATE. PCT is 1,4-cyclohexvlene-dimethylene terephthalate and is a high-temperature. semicrystalline thermoplastic polyester. PCT possesses excellent thermal properties. Injection molding is the predominant method of processing glass fiber-reinforced grades of PCT. It is widely used for... 

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. 

Fig. 11.30 Effect of preheating 50% by weight E-glass fiber-filled polyamide pulltruded pellets on fiber lengths at the screw tip of a 300-ton 23.86-oz reciprocating injection molding machine. [Reprinted by permission from C. G. Gogos, C. K. Yoon, and J. Brizzolara, Injection Molding Process Development for Long Fiber Reinforced Thermoplastics, SPE ANTEC Tech. Papers, 40, 384 (1994).]...

The process of injection molding (IM) is used principally for processing unreinforced or glass fiber reinforced thermoplastics (TPs) and thermosets (TSs) (Figure 4.1). Up to at least 90wt% of all plastics processed are TPs. There are many different types or designs of IM machines (IMMs) that permit molding many different products based on factors such as quantities, sizes (such as auto bumpers to medical micro products), shapes (simple to complex), product performances, and/or economics.1,150>157,173 176 476... 

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