Here is a comparison of PP (Polypropylene) and ABS (Acrylonitrile Butadiene Styrene) for safety protective cases, focusing on strength, temperature resistance, and cost.

1. Strength and Structural Properties

ABS is the clear winner in terms of rigidity and surface hardness. It is a very strong, stiff, and impact-resistant engineering plastic. It has excellent dimensional stability and resists deformation under load, making it ideal for cases with integrated mounting points or complex, rigid structures that must maintain precise shapes.

PP is more flexible and ductile. It has good impact resistance but tends to be less rigid and can deform more easily under heavy weight or stress. PP is known for its excellent "living hinge" property, but for a standard case, ABS provides a more solid and robust feel. For pure drop protection against cracking, PP's flexibility can be an advantage.

2. Temperature Resistance

PP has a significant advantage in heat resistance. Its melting point is higher (~130-171°C), and it retains its properties better at elevated temperatures. It is more suitable for applications where cases might be left in vehicles, near machinery, or in direct sun.

ABS has a lower heat deflection temperature and softens at a lower point (~90-105°C). It can warp when exposed to sustained high heat, limiting its use in very hot environments.

3. Cost

PP is generally the lower-cost material. It is a commodity polymer with lower raw material costs and is often easier and faster to process (e.g., injection mold), contributing to a more economical final product.

ABS is typically more expensive. It is a higher-performance engineering plastic with a higher raw material cost. Its processing can also be slightly more demanding.

Summary of Trade-offs:

Choose ABS when you need a stronger, stiffer, and more precisely dimensioned case and where high heat exposure is not a primary concern. It offers a premium feel and structural integrity.

Choose PP when cost, chemical resistance, and higher temperature tolerance are priorities, and where some case body flexibility is acceptable. It provides excellent value and durability for general-purpose and thermally challenging use cases.