Polypropylene/polystyrene blend: An example of the processing-structure- property relationship in the education of polymers [Mistura polipropileno/poliestireno: Um exemplo da relação processamento-estrutura-propriedade no ensino de polímeros]

Abstract

Polymer blends remain an important research topic in different areas, in spite of innumerous studies over the years. In particular, mixtures of polypropylene and polystyrene are among the most studied, mainly owing to their low cost and technological relevance. In this work, the students enrolled in the discipline Polymer Processing I (PG24) in the Materials Science Graduate Program (PGCIMAT-UFRGS) produced blends of polypropylene and polystyrene, where all polymer processing steps were performed during lab classes. Then, each student undertook a characterization procedure with a specific technique, which included samples preparation, the analysis itself and discussion of the results. Subsequently, the results were confronted in the classroom, where we sought the correlations. Finally, all students reviewed this article, including suggestions and criticisms. As expected, the mixture of polystyrene and polypropylene formed an immiscible blend. Furthermore, the processing affected the characteristics of the polymers, leading to a reduction in molecular weight, and as a result a drop in its physical properties. In the PP/PS mixtures, phase separation produced PS domains with micrometers in size, and low adhesion to the PP matrix, which explains the loss of mechanical properties.