Experimental and statistical study of the effect of temperature and waste ratio on the mechanical properties and cost of polystyrene polypropylene plastic blends
Document Type
Article
Publication Date
2020
Abstract
Since most plastics are not biodegradable, plastic recycling is the main part of global efforts to reduce plastic in the waste stream. Sorting of plastics imposes lots of difficulties which can be avoided by introducing plastic blends. This paper starts by reviewing the recent attempts to study plastic blends. Accordingly, the purpose of this study is to analyze experimental results and apply statistical measures using ANOVA to study the effect of increasing the waste ratio that contains both waste polystyrene and polypropylene on the mechanical properties of pure polystyrene when injected at different temperatures. Cost is taken as a response factor to analyze whether the degradation of mechanical properties is justified by a decrease in cost. As expected, cost dramatically decreases with increasing the waste ratio at any temperature. Increasing the waste ratio resulted in better mechanical properties with a maximum at a 30% waste ratio at 200 °C and 220 °C. This paper ends with a multi-objective optimization analysis that helps decision-makers optimize the properties needed of the studied plastic blend by controlling both the temperature and waste ratio.
Recommended Citation
Saeed Sameer Ibrahim Almishal, Tamer A. Mohamed, Mostafa Shazly, Experimental and statistical study of the effect of temperature and waste ratio on the mechanical properties and cost of polystyrene polypropylene plastic blends, Heliyon, Volume 6, Issue 6, 2020, e04166, ISSN 2405-8440, https://doi.org/10.1016/j.heliyon.2020.e04166.
Comments
Conclusion Plastic blends offer an easier and more effective solution for plastic recycling than of sorting. The study of polystyrene-polypropylene waste plastic blends revealed that pure polystyrene is highly favored only when both optimization of strength and stiffness are of high importance. However, when cost and toughness are brought to the equation; waste plastic blends showed better results. The ideal injection temperature and waste ratio that guarantee certain optimization criteria cannot be found easily. For instance, a waste ratio of 40.34% injected at 193C provided an optimization with equal importance for all of the response factors. This is mainly due to the fact that the four response factors behave differently when changing temperature and waste ratio. All the mechanical properties dramatically decreases with increasing injection temperature of the pure PS. For the 20 percent waste ratio mixture, while strength keeps decreasing with temperature, toughness reached a minimum at 200C and stiffness reached a maximum at roughly 195C. For the 50% waste ratio, each of strength and toughness had a maximum value at 200C injection temperature. This maximum point slightly shifted to 195C for stiffness. At the same ratio, there was a small increase in cost due to energy requirements.
Increasing the waste ratio at a constant injection temperature of 180C did not significantly affect stiffness but it led to a significant decrease in the strength and a maximum was observed at a 20% waste ratio for toughness. For increasing the waste ratio at 200C and 220C led generally to better mechanical properties that were optimized at a 30% waste ratio mixture. Cost dramatically decreased with increasing the waste ratio at any temperature. Despite the new and rising efforts to understand and characterize plastic blends, more research is needed to develop models that cover all range of plastics and properties that can consequently provide ultimate optimization tools for non-sorting plastic recycling.