Scientific Technical Review

Two thermoplastic polycarbonate bisphenol A types were exposed to the influence of natural weathering at continental location and at marine location for a period of 8 years (96 months). Every six months the specimens of medium molecular weight polycarbonate and high molecular weight polycarbonate were taken from mentioned locations and tested. Seven characteristics were chosen for determination of quality before exposition and during the process of degradation of two mentioned polycarbonate types (tensile strength, elongation to break, Shore hardness, Vicat softening point, water absorption, density and Charpy impact resistance). Changes of these seven properties at continental location are similar to the changes of mentioned characteristics at marine location during specified period of time. Data obtained by testing specimens of medium molecular weight polycarbonate pointed out that there were two important changes of quality regarding elongation to break and Charpy impact resistance (first after 36 months and second after 54 months of exposure). After 96 months of natural weathering of the above-mentioned material at both locations meaningful drop of tensile strength, moderate change of water absorption and negligible changes of Shore hardness, Vicat softening point and density were recorded. The influence of molecular weight is very apparent because high molecular weight polycarbonate exhibited higher resistance to the degradation process in natural conditions. Two very important characteristics of this polycarbonate material (tensile strength and Charpy impact resistance) practically did not change during 96 months of exposition in an open air, while drop of elongation to break is meaningful, diminution of water absorption is moderate and changes of Shore hardness, Vicat softening point and density are very small.

Key words: Thermoplastic polycarbonate, degradation, natural conditions, tensile strength, elongation to break, Shore hardness, Vicat softening point, water absorption, density, Charpy impact resistance, natural weathering influence, continental location, marine location, molecular weight mass influence, results of investigations, tables, diagrams.

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