Polycarbonates (PCs) are known for their high impact resistance property. Engineers and equipment designers are always interested in this intrinsic property of PCs since it affects their performance. Remember, a high performance material can be used as a perfect alternative in high temperature and harsh chemical environment applications.
Generally, polycarbonate sheets are used to make safety glasses, green houses and compact discs due to their exceptional properties such as tensile strength, optical clarity, impact resistance and dimensional stability. It is considered a special type of plastic material.
The chemical and physical properties of PCs solely depend on their molecular structure. The most basic molecule of a polycarbonate sheet is formed by reacting a carbonic acid and alcohol. During this chemical reaction, molecules of water are given off. The various molecules of the PCs are held together by strong covalent bonds, which are also responsible for their strength and durability. Nevertheless, this reaction alone is not enough; it is used as a copolymer in a polymerization reaction with a number of phthalates to make it heat resistant. At the same time, to achieve other desirable properties such as a high degree of flexibility and fracture resistance; it can be blended with other plastic materials such as Anhydride, ABS, PET, amongst other materials.
It is important to note that its flexibility is one key property which is also responsible for the superb impact resistance feature which is a key feature in polycarbonate sheets. This does not imply that this material is strong in all aspects; PCs do not scratch. They must be coated with a scratch resistant coating.
Although a number of people tend to believe that polycarbonate materials have high impact resistance and hence they cannot be broken; the possibility of cracking must not be overlooked. When PCs are exposed to higher magnitude of stress corrosion, unexpected cracking may be experienced. This stress could be either residual stress or applied stress. At times, cracking can also be due to the two types of stresses (when they act simultaneously). Therefore, you need to examine the polycarbonate sheet to be sure that none of these types of stresses exist. You can use a polarized filter or a polarized sunglasses to check the presence of residual stress.
This may at times call for failure analysis. You can examine the PC using an optical microscope. This involves analyzing this product for crack, hydrolysis and chemical attack. It is important to note that even though these materials can withstand a lot of impact; the PC’s vulnerability to certain chemical and solves besides its hygroscopic nature should be scrutinized keenly at all times.
