Multifunctional Block Copolymers, Acting as Recycling Aids, by Atom Transfer Radical Polymerization

Area of Science:

• Polymer Chemistry
• Materials Science
• Sustainable Plastics

Background:

• Developing effective recycling additives is crucial for enhancing the properties and processability of recycled polymers like polylactide (PLA).
• Existing modifiers often face limitations in improving multiple material characteristics simultaneously or maintaining stability during processing.

Purpose of the Study:

• To synthesize novel block copolymers as multifunctional recycling additives for polylactide (PLA).
• To evaluate the impact of these additives on PLA's melt viscosity, material stability, impact strength, and UV degradation resistance.
• To investigate the structure-property relationships of two generations of synthesized additives.

Main Methods:

• Synthesis of first-generation block copolymers using poly(pentylene-co-hexylene carbonate)diol, 2,4-diisocyanatotoluene, and a novel macroinitiator.
• Modification of the first-generation additives with 3,5-ditertbutyl-4-hydroxybenzoic acid (DHBA) to create second-generation reactive additives.
• Characterization of copolymer properties, including epoxy group content and degree of epoxide opening.
• Incorporation of additives into PLA via extrusion melting and evaluation of blend properties (melt viscosity, mechanical strength, UV stability).

Main Results:

• First-generation additives increased PLA's relative melt viscosity, stabilized properties, and enhanced impact strength.
• Second-generation additives with over 8% epoxide ring opening showed diminished performance in mechanical properties.
• Second-generation additives effectively suppressed UV degradation in PLA blend plates.

Conclusions:

• The synthesized block copolymers demonstrate potential as effective recycling additives for PLA, offering tailored improvements in processability and durability.
• The degree of modification (epoxide opening) significantly influences the additive's performance, with optimal levels required for mechanical enhancement.
• These novel additives show promise for improving the UV resistance of recycled PLA materials.