PET (Polyethylene Terephthalate) Chips Introduction

Definition and Production Process
PET chips refer to polymerized raw materials generally processed into flake-like granules of approximately 4×5×2 mm. Production routes include:

  • Direct Esterification (PTA Process): Dominant since the 1980s due to 20-30% lower raw material consumption and 40% shorter reaction time versus alternative methods. In China, nearly all manufacturers now use the PTA process.

  • Transesterification (DMT Process).
    Large-scale production employs continuous processes, while semi-continuous and batch processes suit small-to-medium diversified production facilities. Applications now span fibers, containers, packaging materials, films, photographic films, and engineering plastics.
    Because the production process of DMT is not environmentally friendly, it is gradually being phased out now.

Classification by Composition and Structure

  1. Blended Chips
    A method of physically mixing two or more polymers to enhance material properties.

  2. Copolymerized Chips
    Involves the simultaneous polymerization of two or more monomers to form polymers with specific performance characteristics.

  3. Crystalline Chips
    Features high crystallinity in molecular structure, enhancing mechanical strength and heat resistance.

  4. Liquid Crystal Polyester (LCP) Chips
    Exhibit liquid-crystalline phase under specific conditions, delivering superior optical and electrical properties.

  5. Cyclic Polyester Chips
    Contain ring-structured molecules, typically possessing high molecular weight and exceptional physical properties.

Classification by Application

  1. Fiber-Grade Polyester Chips

    • Primarily for spinning polyester staple and filament fibers

    • Used in apparel fabrics, tire cords, and woven papermaking filter nets

    • Subclassified by delusterant content: ultra-bright, bright, semi-dull, full-dull

  2. Bottle-Grade Polyester Chips

    • Widely applied in packaging for beverages, particularly carbonated drinks

  3. Film-Grade Polyester Chips

    • Mainly for producing polyester films with specific process indicators

Classification by Functional Properties

Specialty PET

1. Colored Polyester Chips

  • Principle: Dope dyeing technology – Solvent dyes are dried, melted, filtered, metered, then uniformly blended with polyester melt via high-efficiency static mixers before spinning.

  • Advantages:

    • Eliminates dyeing defects (shade variation, staining, uneven dyeing)

    • Forms a homogeneous solid solution with dye (excellent light/wash/rubbing fastness)

    • 100% dye utilization, zero wastewater/gas emissions

    • Reduces dyeing costs by 30-40% versus conventional processes

  • Applications: Home textiles, industrial textiles, apparel textiles

2. Flame-Retardant (FR) Polyester Chips

  • Development Purpose: Resolve flammability issues in textile products

  • Mechanism: FR additives function through endothermic reactions and surface shielding to:

    • Reduce combustible surface temperature

    • Inhibit flammable gas generation

    • Prevent flame propagation

3. Antistatic Polyester Chips

  • Principle: Achieved by:

    • Adding antistatic agents

    • Introducing hygroscopic antistatic groups

  • Methods:

    • Copolymerization: Incorporating antistatic monomers during polymerization

    • Blending: Adding conductive additives (carbon nanotubes, polypyrrole, nano-silver) to form conductive networks

  • Effect: Enhances surface polarity and moisture absorption

4. Moisture-Wicking Polyester Chips

  • Principle: Utilizes capillary action from micro-grooves on fiber surfaces to:

    • Transport sweat via wicking, diffusion, and transmission

    • Rapidly migrate moisture to the fabric surface for evaporation

  • Function: Regulates body temperature and maintains skin dryness

5. Anti-Pilling Polyester Chips

  • Principle: Synthesized using polyethylene glycol (PEG) with hydrophilic groups through transesterification and polycondensation

  • Process Innovation: Special spinning technology enhances capillary action

  • Performance:

    • Combining the moisture management of natural fibers

    • Eliminates wet-cling effect during heavy perspiration

  • Applications: Sportswear, underwear, socks, towels (pure or blended with cotton/wool/silk)

  • Research Milestone: Breakthrough by Prof. Ronggen Ling (Zhejiang Sci-Tech University) solving pilling resistance challenges

6. Antibacterial Polyester Chips

  • Principle: Incorporation of antibacterial agents during manufacturing to inhibit bacterial growth

  • Methods:

    • In-situ polymerization: Uniform dispersion in polymer matrix

    • Masterbatch blending: Adding inorganic biocides before spinning

  • Applications: Antibacterial clothing, underwear, bedding

7. Optical Brightener Polyester Chips

  • Principle: Fluorescent whitening agents absorb UV light and emit blue-violet wavelengths to neutralize yellowness

  • Impact: Enhances visual whiteness and market competitiveness in textiles

8. Low-Melt Polyester Chips

  • Principle: Melt point reduction via:

    • Copolymerization: Introducing melt-lowering monomers

    • Additive blending: Incorporating eutectic agents (e.g., benzoates)

  • Key Applications:

    • Binder fibers in nonwovens (apparel interlinings, electrical insulation)

    • Fiberfill provides superior softness and bulkiness versus PP/PE

    • Thermal bonding processes in nonwoven production

Industrial Significance

Polyester chips play critical roles across industries due to their versatile properties. Different types are utilized in fields ranging from textiles and packaging to construction materials and automotive components, with global production exceeding 80 million tons annually.