Processing, thermoplastics Plastic product design

Morphology is the study of the physical form or structure of a material (thermoplastics crystallinity or amorphous) the physical molecular structures of a polymer or in turn a plastic. As a result of these structures in production of plastics, processing the plastics into products, and product designs, great differences are found in mechanical and other properties as well as processing plastics. 

There are many thousands of plastics, each with specific chemical and physical characteristics which will affect the performance of the product. There can be vast differences in processing these plastics. First the designer must choose between two basic types of plastic, thermosets and thermoplastics. 

Ogorkiewicz, R.M. (ed.). Thermoplastics Properties and Design, John Wiley, New York (1974). Ehrenstein, G.W. and Erhard. G., Designing with Plastics, Hanser [John Wiley] (1984). Morton-Jones, D.H. and Ellis, J.W., Polymer Products Design, Materials Processing, Chapman and Hall, New York (1986). 

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... 

Foamed plastics are used in helmets because of their very low density, their ability to crush and absorb energy and the possibility of economical mass production. There are many other applications of polymer foams for injury prevention, for instance the fascia padding in cars. Bicycle helmets are chosen because of the author s research experience, and because the typically 0.3 mm thick outer shell plays a minor part in energy dissipation. Consequently, the design process concentrates on the foam Hner (Fig. 14.11). In contrast, the deformation of the 4-5 mm thick thermoplastic shell of a motorcycle helmet absorbs energy of the order of 40 J, when the helmet hits a hemispherical anvil of radius 50 mm. 

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