Methods for Modifying PET

1. Filler Modification of PET
   Filler modification is one of the most direct and effective methods to comprehensively improve material properties by incorporating inorganic components with entirely different characteristics from the polymer matrix.

2. Nanoparticle-Modified PET
   Research on PET nanocomposites modified with nanoparticles has become well-established. Ke et al. used layered clay to modify PET via intercalation polymerization, producing PET/clay nanocomposites. Results showed that when the clay content was 5 wt%, the heat distortion temperature of the composite increased by approximately 20–50°C compared to pure PET, while the modulus improved by about 2-fold.

3. Glass Fiber-Modified PET
   Compared to nanoparticles, micron-sized glass fibers (GF) offer significant advantages in cost and controllability, making them widely used for filler modification of polymer materials.

4. Blending Modification of PET
   Blending modification involves combining two or more polymers, including PET, in appropriate proportions under specific temperature and shear stress conditions through melt blending to form polymer alloys or blends with new properties. The key factor in this process is the compatibility between the polymers.

5. Polyolefin-Modified PET
   PET and PE exhibit significant differences in chemical structure and are inherently incompatible. Studies on simple binary blends of the two have shown that improving PET's impact performance through polymer blending requires enhancing their compatibility via compatibilization. In HDPE/PET blends, the addition of EVA and EAA improved impact strength.

When PET is blended with PP, the resulting alloy combines the advantages of both, enhancing overall performance. For example, PET improves PP's heat resistance, while PP reduces PET's moisture sensitivity. However, without a compatibilizer, PET/PP blends exhibit weak interfacial adhesion and poor mechanical properties.

PET/PS is an incompatible system, requiring compatibilizers to achieve miscibility. Research has found that adding styrene-glycidyl methacrylate copolymer P(S-GMA) as a reactive compatibilizer to PET/PS blends resulted in a well-bonded PET/PS/P(S-GMA) system with improved mechanical properties.

6. Polyester-Modified PET
   PBT, a rapidly developing engineering plastic since the 1970s, exhibits superior mechanical properties and toughness compared to PET, along with good moldability. However, its heat resistance and flowability are inferior to PET, and it is more expensive. According to Teijin, adding 0.5% talc as a nucleating agent to PET/PBT blends yields composites with excellent impact resistance and low molding shrinkage.

PC possesses outstanding mechanical properties, high toughness, and a high glass transition temperature but suffers from poor flowability and aging resistance. Blending PET with PC enhances impact strength, and such blends have been industrialized abroad for automotive components.

7. Elastomer Toughening Modification of PET
   ABS, one of the most widely used polymers, combines excellent toughness with superior overall performance compared to HIPS. Blending PET with ABS improves PET's impact strength.

Studies have found that the molecular weight of PET in blends is highly sensitive to processing temperature. PET chain hydrolysis is associated with heat and residual catalyst impurities in ABS. A decrease in PET's molecular weight leads to significant losses in impact performance and elongation at break, though modulus and flexural strength remain unaffected.