چكيده به لاتين
Polyvinyl chloride is the third commonly used polymers in the world and its properties have been studied for many years. This material is used in applications such as water and sewage pipes and various extruded profiles and sheets. They are inherently hard and should be plasticized usually. They are divided in to two categories; plasticized and unplasticized PVC (PPVC andUPVC).the durability of these materials especially in construction is too important. The durability of these polymers exposed to solvents, heat, light, chemicals and moisture may be affected, and the increase/decrease in the properties reduction is important. The durability of UPVC can be evaluated by weathering, UV irradation and thermal degradation. In this paper the changes in the thermal, physical and mechanical properties of UPVC profiles with Different titanium dioxide contents (i.e. 2, 5, 7 phr) under the artificial accelerated weathering in Xenon chamber and thermal degradation (contineous and discontineous) were studied. To investigate degradation of the material, the mechanical and colorimetric propertiy were evaluated. The accelerated artificial weathering was conducted by exposing samples for 1200 hr and 3600 hr to Xenon light. Thermogravimetric Analysis (TGA), Dynamic Mechanical Analysis (DMTA), Diffuse Reflection Spectroscopy (DRS), Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR) and scanning electron microscopey (SEM) were used to investigate the morphological properties of the samples. The mechanical test results showed a decreasing trend with increasing in TiO2 content up to 5 phr. The excessive amount of pigment from 5 to 7 phr had a negative effect on the properties. The results showed that the tensile and flexural strength and the tensile and flexural modulus under weathering and thermal degradation were increased slightly. The analysis revealed the formation of new functional groups. They showed that accelerated weathering caused degradation of pigment (i.e. fading) which probably could cause polymer degradation in linger exposure times. In contraste, thermal treatment caused polymer degradation. Thermal stability of the samples after the degradation methods was decreased . The loss of the storage modulus and increase in Tg due to the weathering and thermal degradation was demonstrated by DMTA analysis. SEM analysis showed the formation of voids through degradation on the surface of the samples. Color variations and yellowing in both degradation methods were observed.
Keywords: UPVC; TiO2; artificial weathering; Thermal degradation; TGA; DMTA
