Types and choices of powder

1. Selection of Dispersant A high-quality dispersant should possess several key characteristics: it must effectively disperse filler particles and prevent their agglomeration, ensure good compatibility with both the resin and the filler, maintain thermal stability during processing, and provide sufficient fluidity during molding. It should not cause color fading, impact the final product’s performance, or be toxic. Additionally, cost-effectiveness is a major consideration in its selection. Typically, the dispersant is used at around 5% by weight of the masterbatch. 2. Types of Dispersant (1) Fatty acids, aliphatic amides, and esters such as stearic acid amide can be combined with higher alcohols to enhance lubrication and thermal stability. The typical dosage ranges from 0.3% to 0.8%. These compounds can also serve as lubricants for polyolefins. Another option is hexenyl bis stearamide, commonly known as ethylene bis stearamide (EBS), which acts as a high-melting-point lubricant, typically added at 0.5% to 2%. Stearic acid monoglyceride (GMS) and glyceryl tristearate (HTG) are also used. Oleic acid derivatives are usually applied at 0.2% to 0.5%. Paraffinic hydrocarbons, such as solid paraffin wax with a melting point between 57°C and 70°C, are poorly compatible with resins and have limited dispersibility, so they are generally used at less than 0.5%. (2) Paraffin Wax Paraffin wax functions mainly as an external lubricant. However, being a non-polar linear hydrocarbon, it does not wet metal surfaces and cannot prevent PVC resins from sticking to metal walls. It works best when combined with stearic acid and calcium stearate. Liquid paraffin has a freezing point between -15°C and -35°C, and while it has poor compatibility with resins, it is often used at 0.3% to 0.5%. Excessive amounts may negatively affect processing. Microcrystalline paraffin, derived from petroleum refining, has a higher molecular weight and more isomers, with a melting point between 65°C and 90°C. It offers good lubricity and thermal stability but poor dispersion. It is typically used at 0.1% to 0.2%, ideally in combination with butyl stearate and higher fatty acids. (3) Metal Soaps Metal soaps are salts of higher fatty acids, such as barium stearate (BaSt), which is suitable for various plastics and is typically used at about 0.5%. Zinc stearate (ZnSt) is ideal for polyolefins and ABS, with a dosage of around 0.3%. Calcium stearate (CaSt) is commonly used for general-purpose plastics as an external lubricant, with a dosage range of 0.2% to 1.5%. Other examples include cadmium stearate (CdSt), magnesium stearate (MgSt), and copper stearate (CuSt). (4) Low Molecular Waxes Low molecular waxes are derived from cracked and oxidized polymers like polyethylene, polypropylene, polystyrene, or modified materials. They include oligomers with different functional properties. Common types include homopolymer, oxidized homopolymer, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, and low molecular ionomer. Among these, polyethylene wax is the most widely used. Typical polyethylene wax has a molecular weight of 1500–4000 and a softening point of 102°C. Higher molecular weight variants have a softening point of 106°C. Oxidized polyethylene wax, with ester or soap groups, provides balanced internal and external lubrication for PVC, PE, PP, and ABS, improving transparency and overall performance.

Butt Welding Crosses

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