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Purpose: The pervasive use of plastics, coupled with inadequate waste management systems in many countries, has led to widespread leakage of plastics into the environment. In South Africa, the predominant type of shopping bags are single-use plastic bags; but paper, biodegradable plastic and re-usable bags have emerged as alternatives. To compare these alternatives in terms of environmental impacts across the whole product life cycle, we carried out a cradle-to-grave life cycle assessment (LCA) of 16 shopping bag types available in South Africa. Methods: The comparison includes single-use plastic, bioplastic and paper bags, as well as re-usable bags (typically made from plastic in South Africa). The functional unit was based on the estimated annual volume of groceries purchased per capita. An attributional LCA was carried out using the ReCiPe 2016 Midpoint(H) method, with 18 mid-point impact categories. In addition, given the lack of an impact category for plastic pollution in existing methods, we developed a mid-point indicator based on the persistence of plastics (and other materials) leaked to the environment (Persistence of leaked material, PersistenceLM). Specific attention was placed on modelling end-of-life and waste management in the South African context. Economic-based allocation at the point of substitution was used to apportion environmental impacts to virgin and recyclate material, and the production of recyclate was modelled using system expansion. Results and discussion: Re-usable bag types, specifically the 70 µm High Density Polyethylene (HDPE) and non-woven Polyester bags, had the lowest environmental impacts for all indicators, except PersistenceLM. Paper and biodegradable plastic bags had a lower PersistenceLM impact as compared to the petro-based plastic bags, and therefore may be preferable in terms of avoiding plastics accumulating in the environment. The re-usable bags need to be used at least 3 to 10 times to offer lower environmental impacts than single-use ones. Among the single-use bags, biodegradable bags made from imported Polybutylene Adipate Terepthalate (PBAT) plus starch showed the lowest environmental impacts across all impact categories, including PersistenceLM, followed by the Paper bag. The single-use 24 µm HDPE bag (HDPE_24) with no recycled content had the highest overall environmental impacts, while increasing the recycled content reduced overall environmental impacts by up to 52%. Compared to other countries, the high environmental impacts of plastic bags in South Africa can largely be attributed to the coal-to-liquids process used for polymer production, which is intensive in terms of both energy and raw materials. [ABSTRACT FROM AUTHOR]

High-density polyethylene (HDPE), bagasse fibers treated by four pulping processes (AS-AQ (alkaline sulfite anthraquinone), SODA-AQ (soda anthraquinone), MEA (monoethanolamine) and chemical–mechanical pulping (CMP)), three levels of nano-SiO2(0, 2, and 5 wt%), and maleic anhydride polyethylene as coupling agent were used to produce pulp–plastic composites (PPCs) by injection molding. The physical and mechanical properties of corresponding composites were evaluated according to ASTM standards. The results showed that compared to untreated bagasse/HDPE composite, the addition of bagasse pulp fibers increased significantly the mechanical properties such as tensile strength and modulus, flexural strength and modulus, and hardness. The chemical pulps-reinforced composites showed better mechanical strengths than that of CMP-reinforced composites, but in some properties, CMP pulp composites have comparable results to the chemical pulp-reinforced composites. Natural fibers (untreated and treated) increased water absorption and thickness swelling of composites compared to pure HDPE. The addition of nano-SiO2particles showed both increasing and decreasing trends on physical and mechanical properties ofPPCs. [ABSTRACT FROM PUBLISHER]

Radiographic images of paper are used to study the watermarks and the pattern of chain and laid lines originating from the sieve used in the production of the paper. X-rays with low penetrative power are used to obtain images with sufficient contrast as a result of differences in thickness/density of the paper. This article explains the improvement in contrast which can he obtained by lowering the X-ray tube potential, which reduces the penetrative power of the beam. Lowering the tube potential is limited by the attenuation of the radiation in air, which ultimately becomes so strong that exposure times become Unacceptably long. By replacing the air with helium, this attenuation of the X-ray beam can be reduced. A container for helium was developed which had an airtight fit to the exit window of the X-ray tube and has an exit window of a very thin layer of polyethylene. The effect of the technique was investigated by measuring the first and second half value layer (HVL) the beam expressed in millimetres of high density polyethylene (HDPE). [ABSTRACT FROM AUTHOR]