Preparation and properties of PP/SEBS foam materials

Abstract

In this study, styrene-ethylene-butene-styrene block copolymer (SEBS) is blended with polypropylene (PP) to improve the melt strength of PP. Azodicarbonamide (AC) is used as a chemical foaming agent to prepare PP foaming materials with good mechanical properties by moulding foaming. The melt strength of the material, the content of the nucleating agent and the concentration of the foaming agent will affect the foaming effect of the material. Orthogonal optimization experiments are designed for these three factors to explore the best ratio of foaming materials. The results show that when PP:SEBS = 85:15, the addition amount of nano-SiO₂ is 3%, and the content of AC foaming agent is 5%, the cell structure of the foaming material is the best. The cell structure is observed by SEM,the average cell diameter is reduced to 45.73 μm, and the cell density is increased to 4.12 × 10⁶ cells cm⁻³. The apparent density of the material is measured to be 0.62 g cm⁻³, which is 32% lower than that of pure PP (0.91 g·cm⁻³). The tensile strength of PP/SEBS foamed composites is lower than that of pure PP and pure PP foamed materials, but its elongation at break is 124.3% higher than that of pure PP, and 238.8% higher than that of pure PP foamed materials. The bending strength of PP/SEBS foamed material is lower than that of pure PP and pure PP foamed material. The impact strength of PP/SEBS is only 8.4 % lower than that of pure PP, and 60.8 % higher than that of pure PP foamed material.