TPU vs TPE vs TPV vs Silicone (LSR) Injection Molding: Elastomer Selection Guide

When a product requires a flexible seal, soft-touch grip, protective bumper, or bellows boot, engineering and sourcing teams face four competing elastomer families: Thermoplastic Polyurethane (TPU), Styrenic Thermoplastic Elastomer (TPE-S / SEBS), Thermoplastic Vulcanizate (TPV, such as Santoprene), and Liquid Silicone Rubber (LSR).

The first three (TPU, TPE-S, and TPV) are thermoplastic elastomers—they melt in a standard heated injection barrel (180–230 °C), solidify in a cooled steel mold (20–60 °C) in 15–35 seconds, and allow runner regrind recycling. The fourth (LSR) is a thermoset elastomer—pumped as a chilled two-part liquid (15–25 °C) into a scorching-hot mold (170–210 °C) where it crosslinks irreversibly. Choosing the wrong elastomer family causes seals to take a permanent flat set after 30 days, soft-touch grips to peel off rigid housings, or tooling budgets to double unnecessarily.

1. Master Comparison Matrix: TPU vs TPE-S (SEBS) vs TPV vs Silicone (LSR)

Engineering / Commercial Metric	TPU (Thermoplastic Polyurethane)	TPE-S / SEBS (Styrenic Block Copolymer)	TPV (Vulcanized EPDM + PP, e.g., Santoprene)	LSR (Liquid Silicone Rubber — Thermoset)
Polymer Architecture	Thermoplastic (Urethane hard + Polyether/Polyester soft segments)	Thermoplastic (SEBS/SBS rubber compounded with PP & oil)	Thermoplastic (Crosslinked EPDM rubber particles inside a PP matrix)	Thermoset (Platinum-cured vinyl-methyl polysiloxane)
Shore Hardness Range	60 Shore A – 75 Shore D (soft rubber to hard structural shell)	5 Shore A – 60 Shore D (ultra-soft gel to semi-rigid)	35 Shore A – 50 Shore D	5 Shore A – 80 Shore A
Continuous Service Temp Range	-40 °C to +85 °C (peak +110 °C)	-40 °C to +80 °C (softens rapidly above 85 °C)	-50 °C to +135 °C (excellent under-hood heat aging)	-55 °C to +200 °C (up to +250 °C in heat-stabilized grades)
Abrasion, Cut & Tear Resistance	Best-in-class (15–35 kN/m tear; 3×–5× TPE/TPV/LSR)	Fair to Low (scuffs and tears under sharp mechanical load)	Moderate (good flex fatigue, moderate cut resistance)	Moderate (high elongation >400%, but low tear propagation strength once nicked)
Compression Set (22–70 h @ 70–100 °C, ASTM D395)	Fair (30% – 50%; improves to ~25% if post-annealed)	Poor to Fair (35% – 65% — loses seal pressure under heat)	Very Good (20% – 30%) — closest thermoplastic to EPDM rubber	Best-in-class (10% – 20% even at 150–175 °C)
Oil, Fuel & Hydrocarbon Resistance	Excellent (Polyester TPU) / Fair (Polyether TPU)	Poor (mineral oils and fuels swell and dissolve the SEBS matrix)	Good to Very Good (resists automotive fluids, coolants, acids/bases)	Fair (standard LSR swells in fuels; requires Fluorosilicone FVMQ for fuel)
Natural Overmolding Bond (No Primer)	PC, ABS, PC/ABS, PMMA, ASA (polar resins)	PP & PE (standard grades); PC/ABS/PA (modified polar grades)	Polypropylene (PP) (outstanding weld bond)	Requires chemical primer or specialized self-bonding LSR + heat-resistant substrate (PA66, PBT, PC)
Feel & Cosmetics	Smooth, slightly glossy, tough/leathery feel; can be water-clear	Velvety, dry, soft-touch matte feel; easily colored	Matte, rubbery industrial finish (slightly grainy); opaque	Silky, non-tacky skin-safe feel; optically clear or pigmented
Biocompatibility & Sterilization	Medical polyether grades (ISO 10993, EtO/Gamma)	Medical tubing/grip grades (EtO/Gamma; limited steam)	Food/water grades (NSF / FDA); limited implant use	Gold standard (USP Class VI, ISO 10993, repeated 134 °C steam autoclave)
Relative Mold & Piece Cost	Tool: 1.0x Part: 1.3x – 1.8x	Tool: 1.0x Part: 1.0x (Lowest)	Tool: 1.0x Part: 1.2x – 1.5x	Tool: 1.6x – 2.5x (cold-runner + vacuum) Part: 2.2x – 4.0x

2. Head-to-Head Decision Guides for Buyers

A. TPU vs TPE (SEBS): When Does TPU Justify Its Higher Cost?

• Choose TPU whenever the part experiences sliding abrasion, high tensile load, sharp impacts, or oil/grease contact—such as protective ruggedized phone/tablet cases, industrial caster wheels, cable strain-relief boots, hydraulic seals, and footwear outsoles. Standard TPU also bonds directly to PC and ABS without expensive specialty compounding.
• Choose TPE-S (SEBS) when the primary goal is ergonomic soft-touch grip feel (30–65 Shore A), lowest piece cost, fast cycle times, or overmolding onto a polypropylene (PP) substrate (such as toothbrush handles, power-tool grips, razor handles, and indoor consumer electronics feet).

B. TPE-S vs TPV (Santoprene): The Under-Hood Seal & Bellows Divide

Both TPE-S and TPV use a polypropylene thermoplastic phase, meaning both bond effortlessly to rigid PP substrates. The difference lies inside the rubber phase:

• In TPE-S, the styrenic rubber phase is un-crosslinked; above 80–85 °C, the rubber softens and creeps under compression, causing gaskets to leak.
• In TPV, microscopic EPDM rubber particles are dynamically vulcanized (chemically crosslinked) during compounding. That crosslinked EPDM phase gives TPV a 135 °C continuous thermal ceiling, 20%–30% compression set, and long-term flex-fatigue survival for automotive rack-and-pinion boots, weatherstripping, dishwasher seals, and under-hood air ducts.

C. TPU / TPV vs Liquid Silicone Rubber (LSR): When Must You Cross Over to Thermoset LSR?

Avoid jumping to LSR if a thermoplastic elastomer (TPU or TPV) meets your thermal and compression-set spec, because LSR requires dedicated two-component metering pumps, a heated mold with a chilled cold-runner deck, and ultra-tight 0.002–0.005 mm parting-line tolerances to prevent silicone flash.

• Cross over to LSR only when your application requires at least one of four non-negotiable silicone properties:
  1. Extreme Thermal Range (< -50 °C or > +135 °C up to +200 °C) where all thermoplastic elastomers melt or turn glass-brittle;
  2. True Long-Term Compression Set (10%–20%) for high-reliability waterproof IP68 radial/axial O-rings and automotive connector seals that must maintain contact pressure for 10 years;
  3. Medical Autoclave Sterilization (121–134 °C steam) & Skin/Infant Safety (respirator masks, infant bottle nipples, implantable/wearable medical sensors);
  4. Zero-Draft Undercut Demolding: Cured 30–50 Shore A LSR stretches 300%–600% and snaps back with zero permanent deformation, allowing parts with deep internal undercuts to be stripped directly off solid cores without complex mechanical slides.

3. Tooling & Processing Differences Across the Four Elastomers

Tooling / Process Factor	TPU	TPE-S (SEBS)	TPV (Santoprene)	LSR (Liquid Silicone)
Pre-Drying Requirement	Mandatory (≤ 0.02% moisture, 80–110 °C for 3–4 h in desiccant dryer)	None (for PP-based TPE); 70–80 °C for 2–3 h (for polar PC/ABS-bonding TPE)	Recommended (75–85 °C for 2–3 h) to prevent surface porosity	None (2-part liquid pumped from sealed 20 L / 200 L drums)
Barrel / Melt Temperature	185 – 230 °C	180 – 220 °C	190 – 225 °C	Chilled barrel & cold runner (15 – 25 °C)
Mold Cavity Temperature	20 – 60 °C (water cooled)	20 – 45 °C (water cooled)	30 – 60 °C (water cooled)	Heated mold (170 – 210 °C electric cartridges)
Maximum Safe Vent Depth	0.015 – 0.025 mm	0.015 – 0.030 mm	0.015 – 0.025 mm (flashes easily at high shear)	0.002 – 0.005 mm (2–5 µm + vacuum evacuation)
Recommended Part Ejection	Matte core (VDI 24–27), 2°–5° draft, stripper plate or air poppets	Standard ejector pins (Ø4–8 mm) or air poppet; releases easily	Standard ejector pins or stripper plate	Pneumatic air-blow off, roller brushes, or robotic peel

Buyer FAQs

What is the main difference between TPU and TPE in injection molding?

TPU (Thermoplastic Polyurethane) is a harder-wearing, higher-strength elastomer (60 Shore A to 75 Shore D) with 3× to 5× higher abrasion resistance, superior tear strength, and strong resistance to oils and grease, plus natural melt adhesion to polar PC and ABS. TPE (specifically styrenic TPE-S / SEBS) is softer (5 Shore A to 60 Shore D), 25%–45% lower in cost, requires no pre-drying in standard grades, and bonds naturally to polypropylene (PP), making it ideal for soft-touch consumer grips that do not face heavy mechanical wear.

When should I choose TPV (Santoprene) instead of standard TPE?

Specify TPV (Thermoplastic Vulcanizate) instead of standard styrenic TPE whenever a seal, bellows, or grommet must operate continuously between 85 °C and 135 °C, resist automotive under-hood oils and coolants, or maintain a tight long-term compression seal (20%–30% compression set vs 40%–60% for TPE-S). Because TPV contains crosslinked EPDM rubber particles inside a polypropylene matrix, it delivers near-thermoset rubber recovery while running on a standard thermoplastic injection press.

Is TPU or Silicone (LSR) better for waterproof seals and wearable devices?

For room-temperature rugged enclosures, protective cases, and abrasion-exposed cable boots, polyether TPU is more economical (40%–60% lower tooling and part cost) and far more resistant to cuts and tearing. For high-temperature gaskets (> 90–200 °C), long-term low-compression-set IP68 O-rings, medical autoclavable components, and prolonged skin-contact wearables, Liquid Silicone Rubber (LSR) is superior because it never takes a permanent compression flat-spot and is completely inert and hypoallergenic.

Can TPU, TPE, and LSR run in the same injection mold?

TPU, TPE-S, and TPV can often be sampled in the same thermoplastic injection mold (since all three melt at 185–230 °C, solidify in a 20–60 °C water-cooled mold, and shrink 0.8%–1.8%), provided the core is matte-textured so soft TPU does not vacuum-stick. Liquid Silicone Rubber (LSR) cannot run in a thermoplastic mold—LSR requires a dedicated thermoset press with liquid metering pumps, electric cartridge heaters holding the mold at 170–210 °C, vacuum cavity seals, and 0.002–0.005 mm flashless shut-offs.

Disclaimer

PlasticsTechnologyAlliance.com is an independent buyer resource. It does not manufacture parts, sell materials, or certify suppliers. Elastomer compression set, chemical swell, and overmolding peel strength are grade-specific; verify material selection against supplier datasheets and T1 functional seal testing.