회사 소식 Plastic Recycling Granulator Knife Selection Guide: Blade Recommendations for PP/PE/PET Materials

Plastic recycling granulation is a core link in resource recycling, where PP (polypropylene), PE (polyethylene), and PET (polyethylene terephthalate) are the most common recycled materials, accounting for over 70% of total plastic recycling. These three materials have significant differences in physical properties (hardness, toughness, adhesion, abrasiveness)—PP has medium toughness and is prone to containing impurities, PE is soft and highly adhesive, and PET is hard, brittle, and highly abrasive. These differences directly lead to distinct granulator knife selection logics. Ignoring material differences and making blind selections can result in frequent blade wear, material adhesion and blockage, uneven pellets, and other issues. Focusing on tungsten carbide cemented carbide (suitable for the high wear resistance requirements of recycling granulation), this article uses clear tables and plain expressions to break down the granulation pain points, blade selection parameters, and adaptation schemes for the three materials, helping industry practitioners make precise matches and improve the stability and economy of recycling granulation.

Before selection, let’s sort out the key characteristics and granulation difficulties of the three materials to understand "why differentiated knife selection is needed":

The "impurity content" of recycled plastic is a key variable for selection—the more impurities (sediment, metal, fibers), the higher the requirements for blade impact resistance and wear resistance. Tungsten carbide materials (HRA≥90) can balance hardness and toughness by adjusting cobalt content and grain size, perfectly adapting to the complex working conditions of recycled materials.

Below are exclusive blade configurations for PP, PE, and PET recycling granulation, covering key parameters such as tungsten carbide grade, cutting edge structure, and blade body design, which can be directly referenced for selection:

Recycled PP materials often contain sediment and metal debris, making blades prone to chipping from impact. Therefore, high-cobalt tungsten carbide grades (YG10/YG12) are preferred—higher cobalt content enhances blade toughness to resist impurity impact. The serrated edge design reduces material stretching and winding, while the chamfered edge avoids chipping caused by excessive sharpness.

PE materials are soft with a low melting point, and are prone to adhering to the cutting edge due to frictional heating during cutting, leading to blockage and pellet drawing. Therefore, low-cobalt, high-hardness tungsten carbide (YG6/YG8) is selected, with a mirror-polished surface and PTFE anti-adhesion coating to reduce material adhesion. The arc edge design reduces cutting resistance, and heat dissipation grooves help cool down, further inhibiting adhesion.

PET is hard, highly abrasive, and brittle, prone to burrs, resulting in rapid blunting of the blade edge. Therefore, fine-grain, high-hardness tungsten carbide (YG6/YG6X) is used—ultra-fine grains improve cutting edge hardness and wear resistance, extending service life. The thickened edge and reinforced blade back design avoid chipping when processing hard materials, and the straight edge structure ensures cutting sharpness, reducing pellet burrs.

• High impurity content (>5%): For PP, upgrade to YG12X (higher cobalt content); for PET, select YG8 (appropriately improve toughness) to avoid chipping;
• Low impurity content (<2%): For PE, select ordinary YG8 without coating; for PP, downgrade to YG8 to reduce costs.

• High output (daily output >10 tons): Choose wide cutting edges (edge length 150-200mm) + thickened blade bodies (thickness 10-15mm) to improve cutting efficiency and durability;
• Low output (daily output <5 tons): Choose conventional cutting edges (length 80-120mm) to balance cost and efficiency.

• Installation Gap: Control the gap between the moving blade and fixed blade at 0.1-0.3mm; excessive gap easily causes pellet drawing, while insufficient gap exacerbates wear;
• Daily Maintenance: For PE granulation, regularly clean material accumulation on the cutting edge (a small amount of mold release agent can be applied); for PET granulation, promptly clean residual impurities on the edge after use to avoid abrasion;
• Edge Grinding: When the blade is slightly dull, perform precision grinding (maintaining the original edge angle) to extend service life.

• Mistake 1: Blindly selecting high-hardness grades (e.g., YG6) for PP granulation → Ignoring toughness, leading to edge chipping from impurities;
• Mistake 2: Using serrated edge blades for PE granulation → Aggravating material winding and causing blockage;
• Mistake 3: Selecting high-cobalt grades (e.g., YG12) for PET granulation → Insufficient hardness, resulting in rapid edge blunting.

The selection of granulator knives for PP, PE, and PET recycling essentially involves matching the "toughness, adhesion, and abrasiveness" of the material with the "cobalt content, grain size" and "cutting edge structure" of tungsten carbide:

• Recycled PP: High-cobalt tungsten carbide + serrated edge (impact resistance + anti-winding);
• Recycled PE: Low-cobalt tungsten carbide + arc edge + anti-adhesion treatment (anti-adhesion + low resistance);
• Recycled PET: Fine-grain, high-hardness tungsten carbide + thickened straight edge (high wear resistance + anti-chipping).

As a tungsten carbide industry practitioner, we can provide customized blade solutions based on your specific material impurity content, granulator parameters, and output requirements—from tungsten carbide grade adjustment to cutting edge structure design, fully adapting to recycling granulation working conditions. If you need precise configuration recommendations for special scenarios (e.g., high-impurity PP granulation, thick PE film granulation), please contact us for customized advice to help improve plastic recycling efficiency and reduce knife replacement costs!