Recycling of poly(methyl methacrylate) scrap in the styrene–methyl methacrylate copolymer cast sheet process

Poly(methyl methacrylate), PMMA, scrap generated during the casting process for PMMA cast sheet is an industrial waste stream, which has a high impact on the PMMA production cost and environment. This paper presents an alternative way to reduce the processing cost of PMMA cast sheet and decrease industrial waste by using styrene (S) as a co-monomer with methyl methacrylate (MMA) monomer, in conjunction with recycling of PMMA scrap in the S–MMA copolymer cast sheet process. The influence of factors, such as the concentrations of S and PMMA scrap, on the preparation of S–MMA copolymer cast sheet mixed with PMMA scrap was investigated. The characterization of basic copolymer composition, the physical, and the mechanical properties of the final products were examined. The results show that it is possible to recycle PMMA scrap into the S–MMA copolymer cast sheet process, and it does not affect the desired properties of final copolymer products. Finally, the environmental impact of recycling the PMMA scrap was evaluated by using the life cycle inventory (LCI) data for material grouping according to environmental and material properties. The results show the decrease of natural resource consumption and pollutions (65 tons/year of coal, 147.5 tons/year of crude oil, 180 tons/year of natural gas, 825 tons/year of CO2, 4 tons/year of NOx, 4.5 tons/year of SOx, 3.25 tons/year of CH4, 0.8 tons/year of dust, 88 × 106 mg/year of BOD, 10,000 m2 of land conversion) with respect to the recycling of 5% acrylic waste scrap in the S–PMMA cast sheet production process. Moreover, 5% of recyclable PMMA scrap can reduce the costs of raw material, waste disposal, processing, and transportation, which are approximately 6–7% saving of the total cost.