Plastics materials are widely used in manufacturing various industrial and home appliances, due to their lightweight and durability. The increased production and use of plastics have led to environmental challenges, particularly plastic pollution contributing to climate change through increased carbon emissions. To address this, recycling and reusing procedures have been implemented to reduce plastic accumulation in landfills. However, despite over 500 billion plastic bags entering the consumption value chain annually, only about 1% of them are recycled.[1]
Flow Chart of Composite Formation
Considering the environmental pollution caused by plastic usage and the low rate of plastic recycling, Dr Jimmy Li, Assistant Professor in the School of Science and Technology at Hong Kong Metropolitan University, initiated a research project which aimed at addressing these issues. The project focused on exploring alternative solutions by utilising plastic waste to manufacture construction bricks, thereby mitigating the aforementioned problems. This research project was supported by the Faculty Development Scheme of the Hong Kong Research Grants Council.[2]
Single Screw Extruder vs. Twin Screw Extruder. (Source: Martin, C. (2015). Processing thermoplastic urethanes via twin screw extrusion. Szycher's handbook of polyurethanes. 3ed. Boca Raton: CRC, 865-88.)
The research team proposed a mixture for making bricks that includes common building materials like gypsum, quick lime, sand, and fly ash, along with at least one type of plastic. The plastic used can be chosen from various types of thermoplastic (a type of plastic that can be melted and moulded) such as ABS, nylon, PLA, etc. The method of forming the bricks involves mixing the aforementioned materials to create a composite, followed by compression moulding to shape the bricks.
The effectiveness of the bricks proposed in this study was compared to that of traditional bricks made from sand through compressive strength and water absorption tests. The results demonstrated that the bricks with plastic waste can withstand more pressure without breaking, and they are better at preventing water from seeping into buildings because they have fewer tiny holes for the water to pass through.
The use of plastic waste in the brick composition provides a means of recycling and reusing plastic materials, reducing their accumulation in landfills and their impact on the environment. Furthermore, since plastic materials are often available at lower prices compared to the cost of acquiring sand and soil through traditional means, incorporating plastic waste into the construction industry can reduce the overall cost of construction.
Chemical structure of talc. (Source: T. Vulcan, “Talc molecule [Image],” Aug.18, 2010. https://seekingalpha.com/article/221208-so-much-more-than-just-an-innocent-white-powder-talc-market-is-one-to-watch (accessed Jan. 14, 2021).)
MFI Measurement Method (Source: Plastics — Determination of the Melt Mass-Flow Rate ( MFR ) and Melt Volume-Flow Rate ( MVR ) of Thermoplastics (BN EN ISO 1133-1:2011). 2011. BSI Standards Limited.)
The invention resulting from the research project, which involves the formation of bricks comprising one or more types of plastic materials, was granted a Hong Kong short-term patent (no. HK30091805) in December 2023.
For more details, please refer to the following publications generated from the research project:
'A Review on Melt Flow Index Characteristics of Polylactide (PLA) for Recycle Use in 3-D Printing', Journal of Testing and Evaluation.
'Recycling Polyethylene Terephthalate to Make 3D Printing Filaments', Chapter 8, 3D Printing Revolution and Sustainable Product Development.
'A Review on Utilization of Plastic Wastes in Making Construction Bricks', IOP Conference Series: Earth and Environmental Science (EES).
'A Review on Mechanical Properties Modification of Polymer with Talc Powder', 2021 IEEE International Symposium on Product Compliance Engineering – Asia (ISPCE-ASIA).
[1] Guzman, A., & Munno, M. (2015). Design of a Brick With Sound Absorption Properties Based on Plastic Waste & Sawdust. IEEE Access, 3, 1260-1271. https://doi.org/10.1109/access.2015.2461536
[2] Reference: RGC FDS project UGC/FDS16/E05/19
