PBT masterbatch is a concentrated mixture where pigments and/or additives are embedded in a carrier resin made from polybutylene terephthalate (PBT). It is used to impart color or special functional properties (such as flame retardancy, toughness, or weather resistance) to PBT-based plastics simply by mixing it with the base resin during processing.
Key Features and Composition:
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Carrier resin: Primarily PBT, chosen for compatibility with PBT end-use applications.
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Additives: These can include pigments (for coloration), flame retardants, toughening agents, antioxidants, lubricants, and other functional agents.
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Typical composition ratios (by mass):
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PBT resin: 60–95%
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Pigments (e.g., titanium dioxide): up to 70% for color masterbatch
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Additives such as flame retardants: 0–30%.
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Common formulations might look like:
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Universal type: PBT resin 90–95%, additives ~1–2%.
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Enhanced (e.g., glass fiber reinforced): PBT 60–70%, glass fiber 30–40%.
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Color masterbatch example: PBT 10–30%, titanium dioxide 30–70%, dispersant, flame retardant, antistatic, photostabilizer in smaller percentages.
Production Process:
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Raw material preparation: Accurate weighing and selection of PBT resin and additives to meet target properties. Moisture control is critical to avoid hydrolysis of PBT.
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Mixing: Components are premixed in a high-speed mixer, ensuring initial uniformity (typically 5–15 minutes of mixing).
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Extrusion and compounding: The mixture is processed through a twin-screw extruder, where thorough melting, mixing, and dispersion of additives is achieved. Temperature control and screw design are important for quality and uniformity.
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Pelletizing: The compounded material is cut into masterbatch pellets for ease of use in further processing.
Applications:
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Electronics and electrical: Connectors, switches, coil bobbins—chosen for insulation, dimensional stability, flame retardance.
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Automotive: Engine components, interior parts—heat and chemical resistance, mechanical strength.
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Fibers: Toothbrush bristles, wigs, technical fibers.
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Optical cables: Buffer tubes with color masterbatch for identification and protection.
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Household appliances and modified plastics: Color, durability, special functionalities.
Advantages:
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Highly uniform dispersion of color or functional additives
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Stable performance and color fastness
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Easy handling compared to direct pigment or additive addition
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Improved production efficiency and less dust/pollution compared to powder additives.
Types of PBT Masterbatch
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Color Masterbatch – Adds color to PBT resin for aesthetic or branding purposes.
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Functional Masterbatch – Includes additives for UV protection, flame retardancy, anti-static properties, or lubrication.
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Reinforced Masterbatch – Incorporates fillers like glass fibers to improve mechanical strength.