Developing Insulating Polymeric Foams: Strategies and Research Needs from a Circular Economy Perspective

Recent Developments in Synthesis, Properties, Applications and Recycling of Bio-Based Elastomers

In 2021, global plastics production was 390.7 Mt; in 2022, it was 400.3 Mt, showing an increase of 2.4%, and this rising tendency will increase yearly. Of this data, less than 2% correspond to bio-based plastics. Currently, polymers, including elastomers, are non-recyclable and come from non-renewable sources. Additionally, most elastomers are thermosets, making them complex to recycle and reuse. It takes hundreds to thousands of years to decompose or biodegrade, contributing to plastic waste accumulation, nano and microplastic formation, and environmental pollution. Due to this, the synthesis of elastomers from natural and renewable resources has attracted the attention of researchers and industries. In this review paper, new methods and strategies are proposed for the preparation of bio-based elastomers. The main goals are the advances and improvements in the synthesis, properties, and applications of bio-based elastomers from natural and industrial rubbers, polyurethanes, polyesters, and polyethers, and an approach to their circular economy and sustainability. Olefin metathesis is proposed as a novel and sustainable method for the synthesis of bio-based elastomers, which allows for the depolymerization or degradation of rubbers with the use of essential oils, terpenes, fatty acids, and fatty alcohols from natural resources such as chain transfer agents (CTA) or donors of the terminal groups in the main chain, which allow for control of the molecular weights and functional groups, obtaining new compounds, oligomers, and bio-based elastomers with an added value for the application of new polymers and materials. This tendency contributes to the development of bio-based elastomers that can reduce carbon emissions, avoid cross-contamination from fossil fuels, and obtain a greener material with biodegradable and/or compostable behavior.

One More Step towards a Circular Economy for Thermal Insulation Materials-Development of Composites Highly Filled with Waste Polyurethane (PU) Foam for Potential Use in the Building Industry

The rapid development of the building sector has created increased demand for novel materials and technologies, while on the other hand resulting in the generation of a severe amount of waste materials. Among these are polyurethane (PU) foams, which are commonly applied as thermal insulation materials. Their management is a serious industrial problem, due to, for example, their complex chemical composition. Although some chemical and thermochemical methods of PU foam recycling are known, their broader use is limited due to requirements related to the complexity and safety of their installation, thus implicating high costs. Therefore, material recycling poses a promising alternative. The incorporation of waste PU foams as fillers for polymer composites could make it possible to take advantage of their structure and performance. Herein, polypropylene-based composites that were highly filled with waste PU foam and modified using foaming agents were prepared and analyzed. Depending on the foam loading and the foaming agent applied, the apparent density of material was reduced by as much as 68%. The efficient development of a porous structure, confirmed by scanning electron microscopy and high-resolution computed micro-tomography, enabled a 64% decrease in the thermal conductivity coefficient. The foaming of the structure affected the mechanical performance of composites, resulting in a deterioration of their tensile and compressive performance. Therefore, developing samples of the analyzed composites with the desired performance would require identifying the proper balance between mechanical strength and economic, as well as ecological (share of waste material in composite, apparent density of material), considerations.

Innovative Applications of Polymeric Foams

The new open Special Issue of Materials, entitled "Innovative Applications of Polymeric Foams", aims to highlight original and review papers on new scientific and applied research and provide outstanding contributions to inform the community's understanding of innovative applications of polymeric foams [...].

Environmental Impacts of Photovoltaic Energy Storage in a Nearly Zero Energy Building Life Cycle

Climate change, the economic crisis and the current geopolitical situation are the biggest challenges of today. They participate to a fundamental extent in the creation of international policies. Renewable energy sources are thus gaining worldwide popularity. The paper deals with the assessment of the impact of four selected stages of the life cycle of a NZEB building on the environment in 13 impact categories. The analysis is performed in accordance with the LCA method using the attributional modeling approach. The results show the partial and total shift of impacts on the environment of photovoltaic energy storage in comparison with photovoltaic energy export across the building life cycle. Along the climate change impact reduction as a positive effect on the environment, a substantial impact increase is observed on the depletion of abiotic resources. Results also show the total environmental impact of the building life cycle, considering the use of stored energy in a lithium-based battery as being beneficial in most categories despite the relatively high impact increment in the stage of replacement.