PET (Polyethylene Terephthalate) is widely used in packaging, automotive parts, and electronic appliances due to its excellent heat resistance, chemical corrosion resistance, and processability. Tensile properties, as core mechanical indicators, directly determine product durability and service life—for example, PET packaging films require sufficient tensile strength to resist deformation during transportation, while automotive PET components need structural stability under dynamic stress. With rising performance demands in high-end applications, scientifically enhancing PET’s tensile properties has become a key industry focus. Below are technical approaches from material modification, molding process optimization, and post-treatment reinforcement.
Material modification optimizes internal force transfer by adjusting PET’s molecular structure or adding functional components, including blending, filling, and copolymerization.
Blending PET with compatible polymers (e.g., PBT) improves crystallinity and reduces internal defects, significantly boosting tensile strength. Industry data confirms that proper PBT blending increases elongation at break while maintaining processability, suitable for automotive interiors. Blending with elastomers enhances tensile toughness, preventing brittle fracture for flexible parts.
Filling with inorganic/organic agents (e.g., glass fiber) is mainstream—glass fiber-reinforced PET doubles tensile strength and rigidity, ideal for electronic housings and automotive structural parts. Coupling agents improve fiber-matrix adhesion to avoid interface delamination. Carbon fiber or nano-calcium carbonate also enhance tensile properties for high-end applications.
Introducing third monomers (e.g., glycol ethers, adipic acid) adjusts molecular chains: flexible monomers increase elongation at break, while rigid monomers improve tensile strength. Copolymerized PET meets scenario-specific needs (e.g., high-toughness grades for films, high-strength grades for engineering parts), aligning with high-performance PET trends.
Molding parameters influence crystallinity and defects; precise control enhances tensile properties without formula changes.
Key parameters: melt temperature (avoid degradation or poor flow), injection pressure (improve density by full cavity filling), and cooling rate (prevent insufficient crystallization or oversized crystals via optimized cooling channels).
For films/sheets, proper stretch ratio aligns molecular chains to boost tensile strength and modulus; stretch temperature matches PET’s glass transition temperature to avoid chain breakage or insufficient orientation. Synchronize extrusion and traction speeds to reduce internal stress.
For blow molding, optimize parison uniformity and blow-up ratio to ensure even molecular orientation; control blow pressure and cooling for stable quality.
Post-treatment eliminates internal stress and optimizes crystallinity for high-end products.
Annealing releases stress, promotes regular crystallization, and improves interchain bonding. Precise temperature and time control avoids deformation or ineffective stress relief, with parameters tailored to product thickness and structure.
Plasma treatment enhances surface density and reduces defects, preventing crack propagation to maintain tensile performance. Control treatment intensity to avoid surface damage.
Heat setting after stretching fixes molecular orientation for stable tensile properties, suitable for long-term stress scenarios (temperature below PET’s melting point).
In summary, enhancing PET’s tensile properties requires synergistic optimization of material modification, process control, and post-treatment. Current trends (green modifiers, intelligent molding) drive efficient, eco-friendly, and precise technologies, expanding PET’s high-end applications.
