Overview of Thermoplastic Elastomer Recycling Methods

1. Introduction

In general, the recycling of thermoplastic materials—whether collected from manufacturing processes or post-consumer products—can be categorized into four main resource recovery routes:

• Reuse as general-purpose plastics

• Use in plastic blending (polymer blends)

• Raw material regeneration (chemical recycling)

• Energy recovery

Conventional plastic recycling is typically a form of secondary (mechanical) recycling. Used products (such as bottles) are collected, cleaned, shredded into flakes or powder, or reprocessed through melting, melt filtration, and pelletizing to form plastic granules. These powders or pellets are often blended with virgin resin at defined ratios.

It should be noted that most thermoplastics cannot be remelted indefinitely. Repeated processing can negatively affect polymer properties, leading to mechanical strength loss, discoloration, and potential partial crosslinking. As a result, 100% recycled material is rarely used in high-performance applications.

Mixed plastic recycling involves combining incompatible plastics into polymer blends, which are mainly used in low-end applications such as plastic lumber.

Raw material regeneration generally refers to depolymerization. Condensation polymers, such as polyethylene terephthalate (PET) and polyamides, can be chemically broken down into their original monomers—diacids, diols, or diamines—through reversible reactions such as alcoholysis, hydrolysis, and glycolysis. For example, PET methanolysis regenerates dimethyl terephthalate and ethylene glycol. These recovered monomers are primarily used to produce new virgin polymers.

Energy recovery includes incineration, where waste plastics are burned to generate heat or electricity, as well as advanced processes such as pyrolysis, gasification, hydrogenation, and liquefaction. The resulting products can be used as fuels or refinery feedstocks.

Recycling Methods for Thermoplastic Elastomers (TPEs)

Because thermoplastic elastomers (TPEs) behave similarly to conventional thermoplastics, they can be recycled using the same methods. Many TPEs are suitable for multiple recycling cycles. For recycling purposes, the Society of Automotive Engineers (SAE) classifies commercial TPEs into compatible groups, allowing them to be separated and recycled efficiently. In this system, TPEs are categorized in the same manner as rigid thermoplastics such as polypropylene (PP) and polystyrene (PS).

Recycling of Thermoplastic Vulcanizates (TPVs)

Thermoplastic vulcanizates (TPVs) are widely used in automotive applications—such as weather seals, steering system bellows, constant-velocity joint boots, airbag door covers, body plugs, interior skins, and clutch seals—as well as in household appliances like dishwasher sumps, door seals, and compressor mounts.

Post-consumer products and production scrap can be simply ground in pelletizers, and the regrind pellets can be added back into virgin material at relatively high ratios. TPV regrind is compatible with pellets made from thermoplastic polyolefins (TPOs). In fact, adding TPV recyclate can improve certain performance characteristics of TPO compounds.

Many automotive manufacturers have implemented large-scale vehicle dismantling programs in cooperation with polymer producers. These initiatives often operate within closed-loop recycling systems, allowing materials to be recovered and reused in the same or similar products.

Other Recycling Routes for TPE Components

Other recycling pathways for TPE components are similar to those used for conventional elastomers, including energy recovery through incineration. A key advantage of TPEs in this context is their relatively low sulfur content, which has a positive impact on incinerator flue gas composition.

However, a major challenge in recycling TPE components is that they are often not pure TPE materials. Many parts contain inserts, are part of overmolded structures, or consist of composites or polymer blends. For the largest TPE family—styrenic block copolymers (SBCs)—approximately one-third of total production is used in inherently non-recyclable applications such as oil modifiers, adhesives, and asphalt modifiers.

Magnetic Separation Technology for TPE Recycling

A recent development in the recycling of overmolded and co-extruded TPE components is the use of magnetic separation technology. Magnetic separation is a mature technique widely used in mining, aggregates, and bulk material processing, and it is already common for removing metal contaminants from plastics and rubber.

To enable polymer separation from blends (for example, TPEs combined with polypropylene or other rigid plastics), a small amount of magnetic additive—typically about 1% by weight—is incorporated into the TPE material.

Studies have shown that these additives do not adversely affect the physical properties of the material or the adhesion performance in overmolding applications. During recycling, granulated waste is conveyed on a belt system, where resin pellets containing magnetic additives are separated using rollers equipped with embedded high-strength rare-earth magnets. The attracted pellets are collected in hoppers after detaching from the roller, while mechanical diverters help separate the two material streams efficiently.

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