Considerations, benefits and unintended consequences of banning plastic shopping bags for environmental sustainability: A systematic literature review

Although the ban on plastic bags is gaining in prominence as a policy option to manage plastic bag litter, there are mixed views on its rationale and effectiveness. This study employs a systematic literature review to understand considerations, benefits and unintended consequences of banning plastic bags. The review’s results pointed to the limited success of a plastic bag ban owing to lack of suitable alternatives, limited state capacity to monitor and enforce the ban, thriving black market, structural and instrumental power of the plastic industry. The power of the industry was manifested by the covert practice of deflecting accountability to consumers by focusing on business-oriented solutions, including an inclination towards self-regulation. The findings of this study underscored the need for a global treaty to address the transient nature of plastic bag litter and moving away from the symbolic gesture of targeting only plastic shopping bags but considering the environmental impact of all forms of plastic such as straws, foamed plastics, plastic bottles and caps. There is a general consensus in literature that the end of plastic shopping bags is not nigh due to their utilitarian benefits. This study therefore recommends the promotion of a circular economy focusing on ecological modernisation, sustainable plastic bag manufacturing and recovery strategies such as recycling as a long-term strategy. A significant strand of literature reviewed also recommends the adoption of community-driven approaches such as voluntary initiatives as opposed to a plastic bag ban as they proved to be effective in promoting environmental citizenship behaviours in countries such as Finland.

Evaluation of Compressive and Energy Absorption Characteristic of a Closed-cell Polymeric Foam subject to Dynamic Loading

Foamed plastics have been used in many engineering fields because of their superiority in low density, energy absorption, thermal insulation, and acoustic damping capacities. With foams, it is known that the microstructure of cells directly relates to macroscopic deformation behaviour. However, mechanical properties based on microstructures composed of non-uniform cells have not been fully understood. This study aims to clarify the mechanical properties grounded on microstructures of foamed plastics subjected to dynamic loading. The quasi-static and dynamic compression test was carried out using foamed plastic with anisotropy in the cell structure, then the strain rate dependence of deformation and energy absorption characteristics was investigated. It was confirmed that the local buckling of the cells was the dominant deformation mode in the plastic collapse of the test piece. It was also confirmed that cell buckling was initiated around the middle in the height after the plastic collapse, then propagated to the whole specimen in both the quasi-static and dynamic tests by using digital image correlation. The stress-strain relationships and the amount of absorbed energy showed strain rate dependence owing to the deformation mode in which the local buckling of the cells is dominant.

Arctic Climate Insulation Systems

The article describes the features of the implementation of insulation systems in extreme climatic conditions, including in conditions of significant negative and alternating temperatures, high wind speeds and more. It is noted that the adaptation of building systems to similar operating conditions places special demands on heat-insulating materials, as well as resistance to mechanical and climatic influences, vapor permeability, and stability of properties for the entire period of operation. Taking into account the temperature regime of the polar territories, it becomes necessary to develop special solutions for the creation of insulating shells that have high heat engineering uniformity and durability, as well as those that are resistant to very negative and alternating temperatures. Also important is the heat, moisture, and vapor barrier properties of these systems. Taking into account the operational features of the polar territories, three main groups of objects requiring complex isolation and protection can be distinguished: residential buildings, roads on permafrost, modular buildings and residential capsules of mobile equipment. The article considers the feasibility of implementing such heat-efficient systems using foamed plastics, namely products based on extruded polystyrene foam and foamed polyethylene. Solutions are proposed for the implementation of overlaps over ventilated cellars, insulation of walls, roads and mobile structures.

The Applied Study Based on the Injection Molding Mechanism of Microcellular Foamed Plastics (MCFP)

Injection molding is one of several molding technology of microcellular foamed plastics. This paper mainly discusses the injection molding mechanism and applications of microcellular foamed plastics here, and analyzes the influence of microcellular foamed plastics injection molding process parameters, including injection pressure, melt temperature, injection time, etc.; At the same time, this paper makes a more systematic discussions for the injection molding technology of microcellular foamed plastics, and the typical cases of microcellular foamed plastics in engineering application are introduced in detail.

Effect of shear factor on bubble nucleation of polystyrene using supercritical fluid as a foaming agent

The effect of shear factor on bubble nucleation during the foaming extrusion process with polystyrene (PS) using the supercritical fluid (SCF) carbon dioxide (CO2) as a foaming agent was studied based on the energy transformation in this article. The influence of shear factor (which is caused by the velocity gradient in a conical die) on the dynamics of bubble nucleation was investigated and determined. The critical radius for bubble nucleation is presented through the Taylor deformation theory by using a nuclear embryo to represent the state in the bud of the appearance of the nuclear bubble. Theoretical analysis shows that a spherical nuclear bubble can split into two new nuclear bubbles after the deformation in the shear flow field; the radius of the new nuclear bubble is greater than the critical radius, so it can finally grow into a larger nuclear bubble. The shear factor increased the number of the nuclear bubbles in the polymer melt and so increased the density of the bubbles and decreased the diameters of the bubbles. This article proposes a qualitative judgment which indicates that the shear factor in a conical die has a beneficial effect on bubble nucleation, and helps to produce foamed plastics with fine bubbles.