Selecting between thermoplastic polyurethane and thermoplastic elastomer for a polycarbonate application is a decision that the substrate’s specific chemistry and service requirements make more consequential than it would be for ABS. PC’s susceptibility to chemical stress cracking means that an incompatible compound degrades the housing rather than simply failing to adhere — a failure mode with different consequences and a different validation approach than simple delamination. Matching the elastomer to PC requires understanding which material family minimizes this risk while delivering the required performance properties.

Starting Point: What PC Needs From an Elastomeric Layer

Before comparing TPU and TPE, the application’s requirements on PC should be clear. The elastomeric layer on a PC housing must:
– Bond reliably to the substrate without primers in most applications
– Not trigger chemical stress cracking in the PC under mechanical load
– Maintain bond integrity through the service temperature range
– Survive whatever cleaning agents, UV loading, and mechanical demands the application imposes

Both TPU and the right TPE sub-class can meet these requirements. The question is which does so most reliably for a given application.

TPU on PC: Where It Leads

TPU’s polar chemistry produces consistent adhesion on PC across a wider range of process conditions than SEBS or other common TPE sub-classes. The urethane-to-carbonate ester interaction is robust, grade documentation for PC compatibility is available from major suppliers, and the material’s mechanical property range covers the full spectrum from ultra-soft grip surfaces to structural protective layers.

Ether-based TPU leads for applications involving moisture, perspiration, or aqueous cleaning agents. Hydrolysis resistance from the ether linkage ensures that bond strength and elastomer properties are maintained over a multi-year service life — critical for consumer electronics, medical devices, and wearables that see repeated cleaning cycles.

Where moisture is not a primary concern, ester-based TPU provides higher initial bond strength and is appropriate for dry interior applications in automotive and industrial instrumentation.

COPE on PC: Where It Leads

COPE is the TPE sub-class with natural affinity for PC through ester-to-ester chemistry. It matches TPU’s adhesion performance on PC under optimized conditions and provides a higher service temperature capability than equivalent-hardness TPU in certain formulations — relevant for automotive interior components that reach 90–100°C during peak solar loading.

COPE is appropriate when elevated service temperature performance is the primary requirement, when ester-chemistry adhesion to PC is specifically advantageous for the application, and when processing conditions can be controlled to meet COPE’s mold temperature requirements.

The trade-off: COPE’s ester backbone is susceptible to hydrolysis in the same way as ester-based TPU. Moisture-exposed applications require special consideration of COPE’s long-term durability. Ether-based COPE grades address this but are less widely available than ether-based TPU.

SEBS on PC: When to Use and When to Avoid

SEBS can be made to work on PC with adhesion promotion, but it is not the natural pairing. SEBS’s styrenic end-blocks have chemical affinity for ABS’s styrene phase but limited affinity for PC’s ester-dominated surface. Without coupling agents or tie-layers, SEBS on PC produces inconsistent bond strength — adequate in some conditions, insufficient in others, with wide scatter that makes production qualification difficult.

For applications where SEBS is specified for cost reasons and COPE is considered overspecified, the adhesion promotion process steps (silane coupling agent application, COPE tie-layer molding, or plasma treatment) must be incorporated and validated. When those steps are factored into total process cost, the material cost advantage of SEBS over COPE or TPU frequently narrows or disappears.

SEBS is appropriate on PC where: (1) adhesion promotion is already in the process plan, (2) the specific UV stability of SEBS’s hydrogenated mid-block is the primary material requirement, and (3) bond strength requirements are lower than structural overmolding demands.

Chemical Stress Cracking: How TPU and TPE Compare

Both TPU and COPE can trigger CSC on PC if the compound formulation contains incompatible additives. The risk is not inherent to the material type — it is a function of specific compound formulations and the PC grade’s stress state.

Managing CSC risk for TPU: request PC-specific grade documentation from the TPU supplier, confirm low solvent and aromatic content, and validate under sustained load before production approval.

Managing CSC risk for COPE: fewer pre-screened PC-compatible grades are commercially available, requiring more compound-level investigation. SEBS compounds with processing oils may pose higher CSC risk than either TPU or COPE — evaluate additive packages carefully.

For CSC risk evaluation and compound screening support for your specific PC application, Email Us.

Application-by-Application Recommendation

Portable electronics and consumer devices: Ether-based TPU on PC or PC/ABS. Wide grade availability, documented CSC screening, strong moisture resistance, adequate UV stability with stabilizer packages.

Wearables and skin-contact applications: Medical-grade ether-based TPU on PC with biocompatibility documentation (ISO 10993, USP Class VI).

Automotive interior components on PC/ABS substrates: TPU with UV-stabilizer package and automotive-grade fogging/VOC documentation. COPE for high-temperature zones exceeding 85°C sustained.

Industrial handheld equipment on PC housings: Ether-based TPU for chemical resistance and mechanical durability. COPE where elevated temperature is the primary constraint.

Protective covers and cases on PC substrates: SEBS with adhesion promoter is viable at lower bond strength requirements; TPU or COPE for structural overmolds where peel loading is applied to the bond.

Summary Decision Framework

Use TPU when:
– Bond reliability across process variation is the priority
– Moisture or cleaning agent exposure is present
– PC-specific grade documentation is needed for design qualification
– Broad supplier availability is a supply chain requirement

Use COPE when:
– Sustained service temperatures above 80°C are expected
– Ester-chemistry PC adhesion is specifically required
– Process conditions can be controlled to COPE’s temperature requirements

Use SEBS only when:
– Adhesion promotion is in the process plan
– UV stability without UV stabilizer additives is required
– Bond strength requirements are within SEBS’s achievable range on PC with promotion

Incure’s adhesive and coating formulations are developed for demanding PC applications including elastomer bonding systems for electronics, medical, and automotive programs. For technical support on material selection, Contact Our Team.

Visit www.incurelab.com for more information.