Microwave Devulcanized Crumb Rubbers in Polypropylene Based Thermoplastic Dynamic Vulcanizates

Area of Science:

• Materials Science
• Polymer Chemistry
• Sustainable Engineering

Background:

• Recycling chemically crosslinked rubbers is challenging due to their 3D molecular structure and cost-efficiency demands.
• Devulcanization of discarded rubber, followed by grinding, offers a viable recycling pathway.
• Thermoplastic dynamic vulcanizates (TDVs) blend thermoplastics and rubbers, offering processability and elasticity.

Purpose of the Study:

• To develop polypropylene (PP)-based TDVs using microwave devulcanized crumb rubber (dCR).
• To investigate the partial substitution of fresh model rubber (MR) with dCR in PP-based TDVs.
• To analyze the impact of composition and processing parameters on TDV properties.

Main Methods:

• TDVs were produced via continuous extrusion using PP, a tire model rubber (NR/SBR blend), and varying amounts of dCR.
• Compositions ranged from 40/60/0 to 50/35/15 (PP/MR/dCR).
• Processing parameters including screw configuration, temperature profiles, and PP feeding methods were optimized.

Main Results:

• Partial substitution of fresh MR with dCR was achieved up to 10 wt % in the TDV formulation.
• Mechanical properties of the TDVs were maintained even with the inclusion of dCR.
• The study identified optimal processing conditions for PP-based TDVs incorporating recycled rubber.

Conclusions:

• Microwave devulcanized crumb rubber (dCR) can be effectively incorporated into polypropylene-based TDVs.
• Up to 10 wt % substitution of fresh rubber with dCR is feasible without compromising mechanical integrity.
• This research contributes to sustainable rubber recycling by enabling the use of devulcanized rubber in high-performance TDVs.