The Oxidative Degradation of Styrenic Copolymers: A Comparison of Photoproducts Formation Under Natural and Accelerated Conditions R. P. SINGH, A. VISHWA PRASAD, S. S. SOLANKY Polymer Chemistry Division, National Chemical Laboratory, Pune-411008, India Received 11 July 2001; accepted 13 November 2001 Published online 6 June 2002 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/app.10794 ABSTRACT: Natural and accelerated weathering of polystyrene and high-impact poly- styrene were carried out in the present investigation. The structural changes in the polymer samples were characterized by using FTIR spectroscopy, tensile strength testing, and SEM spectroscopy. The natural exposure was conducted throughout the year. Rates of photooxidation were determined by measuring the evaluation in hydroxyl and carbonyl regions. The surface deterioration was revealed from SEM micrographs. The drop in tensile strength was also monitored. A correlation between natural and artificial weathering was considered for lifetime prediction in a short exposure time. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1676 –1682, 2002 Key words: HIPS; oxidative degradation; natural weathering; accelerated weather- ing; photooxidation; degradation; radiation; FTIR INTRODUCTION Natural weathering of plastics refers to the ad- verse response of plastics to climate. Upon expo- sure of polymers to environmental conditions, the physical or chemical attack leads to their degra- dation. The UV light and heating effects of solar radiation play major roles and the polymer leads to chain scissions. The solar UV light (295– 400 nm) generally contains  5% of solar energy but it is sufficient to break the bonds of polymers. As a consequence of degradative reactions, the poly- mer loses properties such as mechanical, rheo- logical, thermal, electrical, and changes in color, and finally leads to embrittlement. Thus, the ser- vice life becomes limited, due to weathering 1 of polymers. The deterioration of a material depends on how and to what extent it interacts with its surroundings. Weathering implies the action of an individual or a combination of various environ- mental factors on polymers (i.e., heat, light, ion- izing radiation, oxygen, ozone, humidity, rain, wind, dust, bacteria, and chemical pollutants). Apart from structural and morphological changes, the natural aging also depends on geo- graphic locations (latitude, longitude, mountain, sea, desert, etc.), seasons, and environmental and atmospheric conditions. In India, Pakistan, or Saudi Arabia, where the radiation from the sun reaching to the earth is greater (250 kW cm -2 ), the weathering life is only 2–5 years. Accelerated (artificial) weathering usually involves controlled conditions where exposure to various factors can be standardized and compared. In addition, it permits the isolation and control of particular environmental factors for detailed evaluation. The most important feature of artificial weather- ing is that it can accelerate degradation of the materials under known conditions. The service life of a polymer can be predicted with the forma- tion of carbonyl and hydroxyl group absorption. The natural and artificial weathering of poly- mers such as low-density polyethylene (LDPE), 2 polypropylene (PP), 3 LDPE-linear low-density poly- ethylene (LLDPE) blends, 4 and E-P copolymers 5 was discussed earlier, but the terrestrial (global) Correspondence to: R. P. Singh (singh@poly.ncl.res.in). Journal of Applied Polymer Science, Vol. 85, 1676 –1682 (2002) © 2002 Wiley Periodicals, Inc. 1676