Evolution of carbonyl index with time and its effects on polymer film performance

Abstract

Degradation in plastics is of upmost importance as it has a drastic effect on end-use properties. The study conducted consists of studying different techniques that can be used to follow and quantify the evolution of degradation in plastic Polyethylene (PE) agricultural films, designed for a three years lifetime. This evolution was tested using several techniques, including TGA, DSC, FTIR, spectrophotometry, tensile, and shear rheology. A correlation is made that relates the degradation behavior between these different techniques. Among this research, two machines were designed in order to make the project feasible, including a QUV weatherometer machine manufactured to meet ASTM standards. Also, a natural weathering Greenhouse prototype with a heating unit was designed. Correlation factors were set between these devices and an approved ASTM QUV lab machine. Four different blends were processed using a Formac Polifilm single screw blown film line, with 200 microns thickness and 2 blow up ratio (BUR). The sample obtained from blend 1 contains UV Master Batch (MB) that consists of UV absorber, antioxidant and Hindered Amine Light Stabilizer (HALS), sample 2 contains only UV absorber and Antioxidant for thermal stabilization, sample 3 contains Antioxidant with lower loading of UV MB and sample 4 is our benchmark pure polyethylene having no additives. Sample 1 currently used in industry showed similar behavior as sample 3, noting that sample 3 is more cost efficient and hence can now be adopted from the results of this study. Sample 4 displayed the quickest degradation response. What is key to note is that all tests showed similar trends.