Thermoplastic and Thermosetting Plastic: Properties, Examples and Recycling

Thermoplastic and thermosetting plastic are distinguished by their behaviour following shaping. The majority of thermoplastics can, for instance, soften by means of heat and be reshaped multiple times. Standard thermoset plastics cure into a stable network, which cannot be remelted by usual means.

The difference there’s that clean polyethylene offcuts and a cured fiberglass panel have different recycling paths. Even PTFE, a thermoplastic, needs processes beyond ordinary melt extrusion.

Thermoplastic and thermosetting plastic: the key differences

The difference between thermoset and thermoplastic materials concerns network formation during processing. Ordinary thermoplastics soften when heated and return to solid form on cooling. Ordinary thermosets form a nonreversible crosslinked structure during cure.

A conventional cured epoxy can’t return to its liquid state by reheating.

The Open University explanation of polymers connects reversible softening with thermoplastic behavior. It also notes that thermal and oxidative degradation can change the properties of reprocessed material. Compatible feed can be remolded and recycled after its quality is assessed.

Thermoplastic examples and thermosetting plastic examples

Familiar products provide useful starting points, but classify the resin rather than the whole object. A reinforced panel contains both a polymer matrix and reinforcement; a cable can contain several plastic materials. Physical properties such as rigidity alone do not differentiate thermosetting plastics and thermoplastics.

What are 10 examples of thermoplastics?

10 typical thermoplastic families: polyethylene, polypropylene, PVC, polystyrene, PET, ABS, polycarbonate, polyamide, acrylic and polyoxymethylene. These names include many grades with different properties. Both HDPE and LDPE are polyethylene so they’re summed up as one family here.

These thermoplastic materials belong to various families; this list is not a guide to mixing scrap.

These types of thermoplastics differ in moisture sensitivity, additives, processing windows and end uses. Kitech’s guide to plastic examples and applications follows the connection between product and polymer in more detail.

What are 5 examples of thermosetting plastics?

Five well-known thermosetting plastic families are cured epoxy, phenolic, melamine formaldehyde, urea formaldehyde, and unsaturated polyester resin. Their finished networks are the relevant property. An uncured liquid or molding compound is a processing material; the final cured product behaves differently.

The use of fillers and reinforcement also changes the properties of each mixture.

• Cured epoxy: adhesives, coatings and fiber-reinforced components.
• Phenolic: molded electrical and heat-resistant components.
• Melamine-formaldehyde: decorative laminates and molded household items.
• Urea-formaldehyde: adhesives used in wood-based panels.
• Unsaturated polyester: fiberglass panels, tanks and molded composite parts.

Is PVC a thermoset or thermoplastic?

PVC is a thermoplastic. It can be rigid or pliable as the properties of the end product vary by formulation. Flexible PVC hasn’t become a thermoset just because plasticizers have been incorporated – for scrap it’s a good idea to identify the PVC and its additives and the polymer – whilst offcuts can be rigid-profile or mixed cables.

The Syracuse University Plastics Collection provides information on these families of materials and their uses, the thermosetting amino resins and thermoplastic acetal.

Two other names require attention. PET is a thermoplastic polyester; cured unsaturated polyester is a thermoset. Polyurethane also spans different structures: thermoplastic polyurethane, or TPU, differs from permanently crosslinked polyurethane systems.

Polymer chains, cross-links and the curing process

A polymer chain is one where the units along the chain are linked through polymerization from the monomers. In ordinary thermoplastic polymers, heating makes the material soften and become able to be shaped, but cooling makes it less formable.

Breaking the polymer backbone is degradation, not the intended shaping process.

Thermosetting polymers (also called thermoset polymers) complete a curing process in which chemical bonding takes place across molecules. It can form an irreversible network during standard processing. That process is powered by heat, a hardener or another trigger, and it varies based on the composition. “Thermosetting” does not mean that every system requires the same application of heat and pressure.

Crosslinking also accounts for why some elastic materials act like thermosets. Vulcanized rubber can bend and stretch while its network prevents ordinary remelting. See the Open University explanation of crosslinking in molded rubber. On the other hand, a solid thermoplastic may soften as it heats up.

Hardness, flexibility and network structure are separate characteristics.

Heat resistance, strength and chemical resistance

No one type is universally stronger or more heat resistant. As a comparison, look at the real grade mechanical properties: tensile strength, impact resistance, resistance to deformation and chemical resistance under the target time and temperature, especially at high temperature. Reinforcement, geometry, loading time and temperature may be more important than the thermoplastic vs thermoset designation.

The following published values illustrate different thermal measurements.

Sources: INEOS polypropylene reference and Ultimaker ABS data sheet, April 2022. Each value is attributed to that document and material condition.

Semi-crystalline thermoplastics have crystalline regions that melt; amorphous ABS has a glass transition rather than a crystalline melting point. Heat deflection measures deformation under a specified load. Vicat measures a specified penetration response.

ASTM D648-18 results must not be compared directly with results from ISO 75-1 and ISO 75-2.

For a corrosion-resistant tank liner, assess the specific chemical, concentration and exposure temperature. For an electrical insulator, determine the necessary electrical insulation performance and dimensional stability. Heat and chemical resistance are application requirements, not automatic benefits of every type of thermoset.

How thermoplastic and thermoset materials are molded

Thermoplastic forming typically requires heating to achieve flow and cooling to lock the shape. Thermoset molding introduces a reactive material and controls its cure. Suitable grades of thermoset or thermoplastic polymers can be injection molded, but material preparation, tools and temperature control differ.

An injection molding machine needs to be matched to the material and process.

Continuous thermoplastic profiles or sheet are manufactured by extrusion. Thermoforming reshapes suitable heated sheet. Compression molding, resin transfer molding and thermoset injection molding process different reactive compounds and reinforced plastics.

Composite materials may be reinforced with glass or carbon fibers, and the position of the fibers in the mold impacts the strength of the finished product and also the mold process.

PTFE is an important exception to simple melt-line thinking. A study of PTFE paste extrusion describes powder blended with lubricant, preforming, paste extrusion and sintering. Its high molecular weight and flow behavior prevent ordinary melt extrusion. Identifying a thermoplastic is therefore only the first step in choosing equipment.

Molding temperature and pressure can limit viable processes before resin price matters for heat-sensitive structures. Handling reinforcement and occupying tools for large reinforced parts can account for much of the manufacturing time.

Thermoplastic recycling and thermoset recovery routes

Appropriate thermoplastic scrap can be sorted and cleaned, reduced in size and reused to produce another product. Recovery routes detailed below identify recyclable resin, filler, fibres and chemical products.

The European EURECOMP project report discusses grinding thermoset composites for filler and separate solvolysis trials to separate reinforcement from resin. In that historical project, researchers could not efficiently separate all liquid-phase molecules for reuse. Recovering a fibre and recovering a reusable resin are two different things.

Thermoplastics can also degrade during reprocessing. A 2024 HDPE recycling study found chain scission initially, with increased oxygen exposure shifting the dominant mechanism toward long-chain branching. This affects how recyclate quality should be assessed; a fixed promise of unlimited unchanged cycles is misleading.

The U.S. Environmental Protection Agency overview distinguishes conversion, depolymerization and purification. Conversion can produce oils, gases and char, while direct combustion recovers energy. These routes aren’t interchangeable with turning sorted scrap into pellets.

What changes manufacturing and recycling costs?

Total cost is affected by tooling, processing time, handling of the reinforcement, material preparation and the value of the accepted output. Choosing thermoplastics or thermosets does not guarantee the cheapest route. A cheap resin price may be overcome by a long cycle; cheap scrap can be expensive if its separation leaves very little usable material.

A 2023 study by Uekert and colleagues compared closed-loop recycling routes for common plastics and identified electricity, steam and organic solvents as major process contributors. A separate 2006 automotive floor-pan study found that tool thermal cycling and fabric scrap affected its epoxy versus reactive-polyamide comparison.

Build these cost categories into the comparison of proposals: feed prep, utilities, consumables, cycle or throughput, reject handling, and finally the customer’s output specification. Historical research explains the drivers; current quotations need the proposed feedstock and production conditions.

How to choose a route for plastic scrap

Select a scrap route by identifying the material, defining its state and agreeing on the product that will leave the process. Then match the equipment to those requirements. A material name alone leaves unanswered whether the batch contains cured resin, incompatible polymers, reinforcement, moisture or contamination.

Clean PE production offcuts may be a candidate for size reduction and melt reprocessing after their grade and output needs are established. Cured glass-fiber epoxy offcuts can also be shredded, but the resulting fragments do not become PE-like melt feed. Instead they could potentially be accepted as fillers or used for a composite-recovery protocol.

For a Kitech equipment discussion, provide the resin or product identity, cured state, reinforcement, contamination, incoming form and intended output. The plastic shredder range addresses size reduction; a plastic pelletizing line serves a different processing stage.

Where recyclable thermosets fit today

Recyclable thermoset studies involve designed cleavable networks, dynamic bond exchange and alteration of some existing cured materials. These approaches change the chemistry or network behavior that makes conventional thermosets difficult to recycle.

MIT’s 2020 work introduced cleavable units into pDCPD precursors. A 2022 unsaturated-polyester study used catalyst-assisted mechanochemical treatment to convert an already cured network into a reprocessable one. The authors described the latter as exploratory work without process optimization.

In October 2026, Aditya Birla executive Amit Dixit described the company’s dynamic epoxy system in CompositesWorld. Its reported capabilities include thermoforming and a specific solvolysis route. These are material-specific developments from the named organizations. They don’t establish a universal process for mixed thermoset waste or a Kitech-owned resin technology.

Frequently asked questions

The comparisons are a mixture of polymer teaching resources, published research and supplier data. The two scrap batches are illustrative scenarios, not documented customer trials by Kitech.