Plastic product design casting

In 1872, Baker found that the reaction between phenol and formaldehyde yielded a resinous product. The resin could be formed and cured and thus used for the production of a variety of moulded and cast plastic products. Baekland made the first successful commercial exploitation and the product entered the market in 1909 under the name of Bakelite. This was the first wholly synthetic polymer. Fillers and other additives were used to improve the product. From these first resins, other varieties have been developed so that phenol-formaldehyde resins now designate a group of resins with varying properties made from different phenols and aldehydes. 

In many cases design modifications can substantially improve the productibility of the products and reduce their cost with improved product quality. As an example if voids exist the problem can usually be corrected by modifying or changing the plastic s composition and/or the use of a vacuum system during the casting. Understanding the effects of the process on the product is essential in making successful products. 

Currently, these tests are of no practical value to the designer and the only approach to the problem of scratch, mar, and abrasion resistance is to simulate actual performance needs. For optical purposes, a cast sheet in the allyl family of plastics known as CR39 has been used as a standard of comparison in evaluating scratch and mar resistance of a material. The CR39 is used for eye lenses and other optical products where the advantages of plastics are a consideration. Coatings have been developed for polycarbonate, acrylics, and other plastics that dramatically improve the scratch and mar resistance of these materials. 

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