Industrial sealing applications demand more of an elastomeric material than most product categories. A seal that fails at 70°C instead of the specified 90°C, or one that swells in hydraulic fluid and loses compression set performance, produces equipment failure with downstream costs that dwarf the original material savings. Selecting between TPU and TPE for seals and gaskets requires understanding not just which material bonds to the housing substrate, but which material’s physical properties hold up through the service conditions the seal must survive.
What Industrial Seals Require
Seals and gaskets perform through compression. Compressed between mating surfaces, they deform to fill microscopic irregularities in the mating faces and prevent fluid or gas passage. Performance depends on:
Compression set resistance. Under sustained compression, elastomers creep and lose some of their recovery capability — the percentage of permanent deformation after compression and recovery is the compression set value. Low compression set (20% or below) means the seal maintains most of its original height after sustained loading, preserving sealing force. High compression set (above 40%) means the seal has flattened substantially and sealing force has declined.
Temperature range. The elastomer must remain flexible and maintain compression set performance at both the minimum and maximum operating temperatures. Seals that stiffen and crack at low temperatures or soften and extrude at high temperatures fail through the same mechanism: inadequate compression force at the sealing interface.
Chemical resistance. The fluid being sealed must not attack the elastomer. Swelling, extraction of plasticizers, surface softening, or degradation of the elastomer’s physical properties all lead to seal failure over time.
Substrate compatibility (for bonded seals). When the seal is bonded to a housing component — a metal flange, a plastic mounting plate, or a composite housing — the bond between the seal and the substrate must withstand the mechanical forces on the assembly.
TPU for Industrial Seals
TPU offers characteristics that make it suitable for specific sealing applications:
High tensile and tear strength. TPU’s mechanical durability exceeds most TPE sub-classes at equivalent Shore hardness. For seals that experience mechanical abrasion, extrusion under high differential pressure, or cut-through risk from sharp edges in the sealing groove, TPU’s mechanical properties provide a margin that softer elastomers cannot.
Shore hardness range for hard seals. TPU is available in Shore 70A to 65D — the upper range overlaps with semi-rigid seal applications (dynamic shaft seals, high-pressure lip seals) where SEBS or soft COPE would be too soft to resist extrusion under pressure.
Substrate compatibility for bonded seal assemblies. TPU bonds to PA, PC, ABS, and PET housings through polar chemistry. This is relevant for integrated seal-and-housing designs where the seal is overmolded directly onto the housing component.
TPU limitations for sealing: Standard ester-based TPU is susceptible to hydrolysis — not appropriate for sustained water, steam, or aqueous fluid sealing. Ether-based TPU improves hydrolysis resistance. TPU is not recommended for fuel or aromatic hydrocarbon sealing without formulation-specific verification. Compression set performance of TPU is generally adequate but inferior to EPDM-based TPV in sustained-compression applications.
TPE Sub-Classes for Industrial Seals
Each TPE sub-class serves distinct sealing environments:
SEBS-based TPV and SEBS compounds. SEBS is used in low-to-medium duty environmental seals, gaskets for enclosure water resistance, and dust seals. Low compression set performance is modest; SEBS is appropriate for seals under light sustained compression. Not recommended for high-pressure or high-temperature sealing.
EPDM-based TPV. TPV with an EPDM rubber phase provides near-vulcanized-rubber compression set performance — the key advantage of TPV over standard SEBS or COPE in sealing applications. EPDM-phase TPV provides:
– Compression set values approaching solid EPDM rubber
– Weather and UV resistance (EPDM’s inherent property)
– Ozone resistance
– Compatible with steam, water, and aqueous fluids
EPDM-based TPV is used in automotive door seals, window seals, pipe joint gaskets, and industrial enclosure seals. It bonds to EPDM rubber substrates through shared rubber chemistry — relevant for assemblies that integrate TPV and extruded EPDM profiles.
COPE (Copolyester elastomers). COPE provides higher service temperatures than SEBS or standard TPU, with usable properties to 120–140°C depending on grade. For seals in high-temperature environments — engine bay, industrial process equipment — COPE’s temperature capability is an advantage. COPE is not recommended for fuel or oil contact; ester-based chemistry has limited hydrocarbon resistance.
PEBA. PEBA is used in sealing applications where flexibility at low temperatures (-40°C and below) and chemical resistance to hydraulic fluids are required. Relevant in hydraulic system seals for construction equipment and aerospace applications.
Chemical Resistance as the Primary Filter
For fluid-sealing applications, chemical resistance to the specific fluid eliminates candidates before substrate compatibility or mechanical properties are evaluated:
Water and steam: Ether-based TPU, EPDM-based TPV, SEBS (limited temperature). Not ester-based TPU or COPE.
Petroleum fuels (gasoline, diesel): NBR-phase TPV, specialized TPU. Confirm with supplier. Not standard SEBS, COPE, or PEBA.
Hydraulic fluids: PEBA, specialized ether-TPU, NBR-phase TPV depending on fluid formulation. Not COPE.
Acids and bases (chemical process sealing): Verify specific chemical compatibility by grade. EPDM-based TPV performs in many dilute acid/base environments.
Food and pharmaceutical fluids: FDA-compliant grades required. Medical-grade SEBS, FDA-compliant TPU, food-grade silicone alternatives.
For chemical resistance data and seal material qualification support, Email Us.
Bonded Seal Applications: Substrate Compatibility
When seals are bonded to metal, plastic, or composite housings, the bond must withstand the pressure differential across the seal, thermal cycling that expands and contracts both materials at different rates, and the mechanical forces from assembly compression.
Metal housings (aluminum, steel): Standard polyurethane adhesives bond TPU and COPE to metal surfaces. Surface preparation — degreasing, light abrasion, primer application — is required for structural metal bonds. Isocyanate-based primers create reactive sites on metal surfaces for PU adhesive bonding.
PA housing components: TPU bonds to PA through overmolding or PU adhesive bonding. PEBA bonds to PA through overmolding. Both approaches are used in bonded seal-and-housing assemblies for medical and automotive applications.
PP and polyolefin housings: CPO primer plus PU adhesive is the most reliable bonding approach for TPU-to-PP seal assemblies. TPO compounds bond to PP through polyolefin chemistry without primers — relevant when a compatible TPO compound meets the sealing requirement.
Process Summary
For environmental seals on ABS and PC housings: SEBS for light-duty; TPU for durability. Both bond without primers.
For automotive weather and door seals: EPDM-based TPV for compression set performance and EPDM substrate compatibility.
For high-temperature industrial seals: COPE for temperature capability on PET and PA substrates.
For high-pressure and abrasion-exposed seals: TPU (ether-based for moisture resistance) for mechanical durability.
For fuel and hydrocarbon fluid seals: NBR-phase TPV. Verify specific compound compatibility.
Incure’s adhesive and coating formulations include isocyanate-based adhesion promoters for rubber-to-metal bonding, CPO primer systems for polyolefin seal housings, and PU adhesive formulations for elastomer-to-substrate bonded seal assemblies. For technical support on your sealing application, Contact Our Team.
Visit www.incurelab.com for more information.