Understanding Toughness and Rigidity in Modified Plastics

 In material science, toughness and rigidity are often opposing concepts. Rigidity (or stiffness) is a measure of a material's resistance to deformation, quantified by its tensile or flexural modulus. A material with high rigidity, like one filled with glass fiber, will have high hardness and strength but may be brittle. Toughness, on the other hand, is a material's ability to absorb energy and deform plastically before fracturing, indicated by high impact strength and elongation at break. Tough materials are more flexible and softer. As engineering plastics, an ideal material possesses both high rigidity and toughness, but enhancing one often compromises the other. A common practice is to use a combination of elastomers and fillers; elastomers improve impact strength (toughness), while inorganic fillers like minerals or fibers increase stiffness and strength. For many plastics like PVC, PS, and PP, impact modifiers such as ACR, MBS, CPE, or ABS are essential to overcome low-temperature brittleness. However, these modifiers often reduce other properties like tensile strength, hardness, and heat resistance. Therefore, formulating a modified plastic requires a careful balance to achieve the optimal combination of properties for the specific application.