Ultraviolet aging behavior of polypropylene sacks by outdoor weathering

Abstract

Polypropylene (PP) sacks are widely used in outdoor commodities, resulting in wear and tear due to weathering. This work studied the mechanical and chemical performance of typical polypropylene woven sack samples outdoor-weathered for 21 days. Rather than using the general regional information posted by the meteorology authority, two custom-designed, location-specific devices have been developed to measure the exact atmospheric temperature, humidity, and ultraviolet (UV) intensity at the experimentation site. The effects of outdoor weathering on unit weight, mean thickness, tensile strength, elongation-at-break in warp and weft directions, bursting strength and height were investigated by fourier transform infrared (FTIR) spectrometry analysis, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) imaging. The mechanical and chemical performances of original and weathered polypropylene samples were compared. The performance differences were evaluated and compared statistically by analysis of variance (ANOVA). Although the samples were weathered for only 21 days, a dramatic drop was observed in their mechanical performances. As a result of photo-oxidation, both the tensile strength along the warp and weft directions and the bursting strength of the weathered samples declined severely (88.3%, 95.6% and 97.8%, respectively). Furthermore, the elongation-at-break in warp and weft directions and height of weathered samples increased sharply (91.5%, 90.4% and 71.5%, respectively). The FTIR, DSC results and SEM images substantiated the observed performance deteriorations.

Graphical abstract