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When it comes to injection Molding demanding parts for high-performance applications, material choice is absolutely critical. There are plastics formulated to offer exceptional hardness, stiffness, wear resistance and dimensional stability — ideal when toughness and durability are essential. This article explores which plastics are regarded as the “hardest” in injection molding and what to consider when using them. It also briefly highlights how a reliable equipment supplier such as BOHANG can support production of parts in these challenging materials.
Hardness in plastics for injection molding typically refers to high modulus (rigidity), high hardness on the Rockwell or Shore scale, excellent abrasion and wear resistance, high dimensional stability (low creep, low shrinkage) and suitability for demanding environments (high temperature, chemical exposure, fatigue). These properties allow the molded parts to perform under load, in sliding or bearing duty, or where surface wear and precision are critical.
In practice, the “hardest” plastics are often engineering thermoplastics (rather than commodity grades) and often contain reinforcement (glass fibre, mineral filler) or special crystalline structure. They also require stricter processing conditions (drying, temperature control, mold design) compared to standard plastics.
POM stands out for hardness, strength and dimensional stability. It is characterised by high modulus and excellent wear resistance — properties rarely matched in injection moulding thermoplastics. According to a review: “POM … is characterised by its high strength, hardness and rigidity to −40 °C.” Applications include precision gears, bearings, lock systems, and sliding parts — use cases where metal replacement is common. Because of its crystalline structure and low shrinkage, POM demands good mold temperature control, uniform wall thickness, and drying may be required. In short: when you need one of the hardest plastics for injection moulding, POM is often the first material to evaluate.
Polycarbonate is another top-tier engineering thermoplastic. It offers high impact resistance, good temperature resistance and rigidity. According to material selection guides: “If you need something a little tougher than ABS or able to withstand a little higher temperature, try polycarbonate (PC).” It is used for safety helmets, bullet‐proof applications, enclosures and components where transparent or tinted housing is required. While PC is superb in many ways, it is less hard (in the sense of wear resistance) than some fillers or specialised materials, and may require coatings or surface treatments for scratch and abrasion resistance. But for applications where both toughness and hardness are required, PC is often chosen.
Beyond pure base resins, hardness can be significantly enhanced by reinforcement. For example, nylon (PA66) or PPS (polyphenylene sulphide) filled with glass or carbon fibre, or POM filled with lubricant/mineral, yield parts that are extremely stiff and hard. Material guides show that glass-fill dramatically increases mechanical and dimensional performance. One must remember that reinforced compounds require more aggressive processing: higher mould temperatures, slower cooling, more aggressive screw/machine wear (especially when glass fibre is used) and good equipment maintenance.
Application environment: Evaluate temperature, load, sliding or wear surfaces, chemical exposure, dimensional tolerance and life-cycle.
Hardness vs toughness trade-off: Often very hard plastics can become brittle; you must balance hardness with impact resistance.
Mold and processing limitations: Hard plastics may have higher melt temperatures, greater shrinkage or require more careful drying. For example, drying of nylons or reinforced materials is essential.
Wear on tooling: Reinforced compounds, especially with glass or mineral fillers, are abrasive on moulds and screws. Maintenance and tooling material selection are important.
Cost and cycle time: Some high‐hardness materials are more expensive and require longer cycles due to slower cooling or temperature control.
Dimensional stability and post-processing: In high precision parts, low creep and low shrinkage are important. POM is excellent in this regard.
Using truly hard plastics enables smaller, lighter parts that replace metal, achieve longer wear life, tighter tolerances and less maintenance. For industries such as automotive, aerospace, medical devices, consumer electronics and industrial machinery, hard plastics unlock design freedom and cost savings. Moulding these materials effectively requires the right equipment, precise control and partner expertise.
Working with hard plastics places extra demands on the injection moulding machine, tooling, mould temperature control, drying systems and process stability. This is where choosing a capable equipment supplier matters. For example, BOHANG shows a strong commitment to high-precision moulding equipment including bottle-blowing machines, Packing Machines, Manipulators and moulds. While their primary focus is on bottle-blowing, the underlying theme of precision, repeatability and automation carries over to injection moulding of engineering plastics. Partnering with a supplier like BOHANG ensures you can handle the challenges of hard plastics — from maintaining consistent shot quality to handling tougher moulding materials.
When asking what is the hardest plastic for injection moulding, materials like POM and reinforced PC stand out. POM delivers exceptional hardness, wear resistance and dimensional stability. PC adds toughness and temperature resistance with good rigidity. For even tougher applications, reinforced thermoplastics with fillers push the boundaries further. The choice ultimately depends on the part’s application, required durability, tooling and process capabilities. And as the material becomes more demanding, having robust moulding equipment and an experienced supplier such as BOHANG becomes vital for production success. If you are preparing a project that requires one of these hardest plastics and reliable moulding output, it may be wise to contact BOHANG to discuss how their equipment and support can align with your material and production goals.
