Thermal and Rheological Response to Ultraviolet Stabilizers Additive in Linear Low Density Polyethylene under Sever Environmental Conditions

摘要

Background and Objective: There are different plastic materials for outdoor usage and depending on several factors related to their weatherability selection is made. Polyethylene (PE) is the simplest polymer chemically used for such purposes, it is one of the most common plastics due to their low cost and simplicity of manufacture. Thermal stability and ultraviolet (UV) resistivity are main properties to be considered when any of PE grades are used for outdoor applications. In this paper Ultraviolet stabilizer has been added in different concentrations to leaner low density polyethylene (LLDPE) to measure the deterioration of the thermal and rheological properties when subjected to sever conditions such as the gulf desert conditions. Materials and Methods: The LLDPE resins mixed with different weight percentages of ultraviolet absorbing additives were compounded in a twin-screw extruder. The prepared films were exposed to severe outdoor weathering conditions, involving high temperature , dust, humidity and intense solar energy, for various periods over 9 months period (Kuwait is one the hottest spots on earth during summer). Results: Results were obtained after exposure to outdoor weathering, the films were tested for thermal stability using thermo gravimetric analysis (TGA). It was found that the overall thermal stability has improved with the incorporation of Ultraviolet (UV) additives, however, increasing exposure time beyond 4 months showed lower thermal stability of the samples those contains 0.6% additives as reflected by the temperature at which decomposition is initiated. Moreover, scanning electron microscopy (SEM) results showed a clear surface and morphological change which consequently can affect product rheology. Processability of the samples was also investigated using a discovery hybrid rheometer, the results indicated a predominance of the viscous behavior over the elastic one for samples with 0.3% UV concentration. Conclusion: Generally, the study results concluded that the LLDPE containing UV absorbers at a 0.3% concentration have shown better improvement in comparison with other concentrations in terms of thermal degradability and processability.