Orientation-Induced Structure-Property Relationships in Recycled PET-Based Blends Containing Amorphous Copolyesters...

Area of Science:

• Polymer Science
• Materials Science
• Recycling Technology

Background:

• Recycled polyethylene terephthalate (PET) often contains amorphous copolyester impurities (PETG, PCTG) and polycarbonate (PC).
• These impurities pose challenges for high-performance applications requiring orientation drawing, impacting mechanical properties and processability.
• Understanding the influence of these contaminants is crucial for effective PET recycling and product development.

Purpose of the Study:

• To systematically investigate the impact of amorphous copolyester (PETG, PCTG) and polycarbonate (PC) impurities on the orientation behavior of PET-based blends.
• To analyze the resulting mechanical properties (tensile strength, modulus, elongation at break) and physical characteristics (density, thermal shrinkage) as a function of draw ratio.
• To establish structure-property relationships linking molecular orientation, crystallization, and macroscopic performance in recycled PET systems.

Main Methods:

• Preparation of model PET-based blends using virgin materials.
• Inline melt spinning of monofilaments followed by controlled orientation drawing up to a draw ratio of 6.5.
• Comprehensive analysis of mechanical properties, density, and thermal shrinkage at varying draw ratios.

Main Results:

• PET-rich blends demonstrated superior mechanical performance, enhanced by strain-induced crystallization, leading to increased density and reduced thermal shrinkage.
• Amorphous copolyesters (PETG, PCTG) suppressed crystallization, resulting in lower modulus and significantly higher thermal shrinkage.
• Polycarbonate (PC) reduced maximum draw ratios and tensile strength but showed low shrinkage at moderate draw levels.

Conclusions:

• Even small amounts (~10 wt%) of amorphous polyester impurities significantly alter orientation efficiency and end-use properties of PET blends.
• Feedstock control is critical in recycling processes to ensure the quality of recycled PET for high-performance oriented products.
• Clear structure-property relationships were established, highlighting the detrimental effects of specific impurities on the performance of oriented PET materials.