Balancing the toughness and strength in polypropylene composites

Fracture toughness, a parameter representing the resistance to fracture and capacity of a material to absorb impact force or energy, is one of the key performance indicators that need to be considered when selecting plastics to fabricate the parts for critical structural applications. Most plastics exhibit brittle type of fracture with low fracture toughness which can greatly limit their performance especially for long-term and special applications. A relatively simple and straightforward strategy to enhance the fracture toughness is incorporating elastomers into plastics via direct melt compounding processing. However, in the case of polypropylene composites, the existence of a second phase including filler or fiber and the importance of interfacial bonding between the polymer matrix and filler, requires the mechanism and the effectiveness of toughening strategy to be studied carefully. This paper presents an overview of the toughening mechanism in Polypropylene and provides the details of different techniques for achieving the right balance between strength and toughness in thermoplastic composites. The concept of toughness in this work covers both macro and micro-level toughness that refers to structural toughness and toughness as impact behavior of composites. The factors influencing the efficiency of toughened polymer composites are discussed in detail. Current challenges and future direction in toughening mechanism in thermoplastics composites are proposed for promoting the application of different strategy or combining a couple of strategies for enhancing the fracture toughness of thermoplastic composites.