Quality assurance of a recycled product is currently one of the biggest issues that the plastic recycling industry faces. The purity of the input plastic waste stream has significant influence over the quality of the recycled product. This research evaluated the impact of polylactic acid (PLA) contamination within the input waste stream of high-density polyethylene (HDPE) recycling. The ultimate tensile strength was noted to reduce by 50% when PLA contamination was at 10%. An investigation into the effect that UVA radiation (simulating solar radiation) has on HDPE contaminated with PLA was also performed to determine the long-term effect of the bioplastic contamination. After UVA treatment, the ultimate tensile strength was reported to reduce by 51% when PLA contamination was only at 2.5%. A water contact angle analysis indicated the PLA contamination increased the hydrophilic nature of the HDPE sheets, potentially creating issues if the intended use of the recycled product was to store liquids. Microscopic analysis of the HDPE sheets contaminated with PLA showed deformations, ridges, cracks, and holes appear on the surface due to the immiscibility of the two polymers that was confirmed by FTIR analysis. Colour changes were visibly noted, with UVA exposure increasing the rate of colour change. Based on the findings in this study, PLA contamination of even 1% in a HDPE waste stream would significantly reduce the quality of the recycled product.

This study examined the accuracy of design equations specified in the North American, European, and Australian/New Zealand standards for determining the shear-out capacity of bolted connections in cold-reduced steel sheets. The tested variables were end distance, bolt (hole) diameter, sheet thickness, edge distance, and material properties. The paper showed that the catenary action in a narrow strip downstream of the bolt has a significant effect on the shear-out capacity, and is not accounted for in the design codes. The contribution of catenary action was corroborated with finite-element analysis results. The paper also showed that the edge distance of a bolted connection has insignificant effects on the shear-out capacity, although it affects the failure mode. An additional finding is that shearing (rather than sawing) the end of a cold-reduced steel sheet sometimes can change the failure mode into end splitting, but not to the same extent as in hot-rolled steel plates. Based on the test results of 60 single-bolted specimens with end distances ranging from 1.25 to 3.0 times the bolt diameter, this paper derived a shear-out equation that is dimensionally consistent, continuous, and transparent, and that is much more accurate than the code equations. The proposed equation, which includes the bolt diameter as a parameter, was verified against independent test specimens with end distances as small as 1.0 times the bolt diameter. A resistance factor of 0.70 is recommended for use with the proposed equation for determining the shear-out capacity of bolted connections in cold-reduced steel sheets.