RECYCLED WASTE PLASTICS AS BUILDING MATERIAL FOR LOW-COST SHELTERS

Abstract

Executive Summary: This project aims to divert plastic waste and recycle it into building materials. The end product is lightweight, cost effective, and durable while still being an effective thermal insulator. The process designed in this report can create building materials from waste plastics that can be utilized to build homes for low-income communities and victims of natural disasters. During the duration of this project, creating a prototype and finalizing an end product preceded the design of the process. The prototyping phase consisted of collecting three types of plastics, type 1 (PETE), type 2 (HDPE), and type 5 (PP). The plastics were then agitated with soap and water to get a clean material, air dried, and tested using two different heat sources, an iron and convection toaster oven. Four different experimental setups utilizing these two different heat sources were conducted. Inside these two sources, temperature and pressure were tracked and noted per experiment. Using the experimental results, a process was designed. Many conclusions were drawn from the results of this design. Based on the prototyping done by the team, it was determined that a mass ratio of 1:2:1 of PETE, HDPE, and PP plastics was ideal for forming a brick. It was also concluded that the ideal size for these bricks was 6” x 12” x 3.75”. This allows for a large enough volume to reduce the amount of bricks required to construct a strong structure but is not so large that it is extremely heavy. There are square protrusions of 3.85” x 3.85” x 1.07” on the top and indentations on the bottom of the brick of the same dimensions. These protrusions and indentations allow for bricks to interlock and easily snap together to form walls and corners. A semi-batch process proved to be the best way to operate a plant for this process, which sorts, cleans, and shreds the plastic before forming the end product. The process proved to be economically feasible with an annual profit of over $600,000. There is still some uncertainty in the end product design. This is due mostly to a halt in prototyping due to the COVID-19 pandemic. Therefore, the process design is based off of what the team was able to accomplish prior to the pandemic. There are three major assumptions in the design of this process. First, it is assumed that there is a market for our product stemming from an ​increased​ frequency of natural disasters. The second assumption is that the plant is able to obtain the used plastics for the process for free which would likely come from a local recycling center. Finally, an assumption that there is enough plastic and market to warrant running the plant continuously as a semi-batch process. Another major uncertainty lies with how much of each compound is released in the vapor fumes and further testing for this parameter is highly recommended. However, this project can be economically feasible given the current run conditions and assumptions. It is recommended that this process move forward after further prototyping is done and more is understood about the compounds present in fumes.