HTV vs LSR Silicone Rubber

HTV vs LSR Silicone Rubber: A Practical Comparison Guide

HTV (High-Temperature Vulcanization) and LSR (Liquid Silicone Rubber) are two processing forms of the same base silicone chemistry, but they differ fundamentally in how they are processed, what applications they suit, and what economics apply at different production volumes. Choosing between HTV and LSR is one of the most important material and process decisions in silicone product design.

The Core Difference: Physical State Before Cure

HTV (also called HCR — High-Consistency Rubber) is a solid, putty-like compound that is processed by compression molding, transfer molding, or extrusion. It must be cut to weight and placed in a heated mold. Cycle times are 3–10 minutes for compression molding.

LSR is a pumpable two-part liquid (parts A and B, mixed 1:1) that is processed by Liquid Injection Molding (LIM). It flows into any cavity geometry through a cold runner and cures in 30–90 seconds in a heated mold. The liquid state enables part geometries that solid HTV cannot produce.

Property Comparison

When HTV Is the Right Choice

Extrusion applications: HTV is the only option for continuously extruded silicone profiles, tubing (other than fine medical tubing), cable jackets, and extruded cord stock. LSR cannot be extruded continuously.

High Shore hardness (>70A): LSR is practically limited to Shore 70A maximum. Shore 75A or 80A HTV is used for cable jackets and structural seals where LSR cannot reach the required firmness.

Simple geometry at low-to-medium volume: Compression-molded HTV has very low tooling cost (a simple two-part steel mold costs a fraction of an LSR injection tool). For production volumes below ~50,000 pieces/year, HTV compression molding typically has better total cost.

Custom compound formulations: HTV mill compounds allow more flexibility in filler loading, reinforcement, and specialty additive incorporation than standard LSR grades. Conductive compounds, ultra-high-tear grades, and extreme-temperature HTV formulations are more readily available than equivalent LSR grades.

When LSR Is the Right Choice

High-volume medical and baby products: At volumes above 100,000 pieces/year, LSR LIM with multi-cavity tools (8, 16, 32, or 64 cavities) produces a cost per part lower than comparable HTV compression molding. Flash-free production eliminates post-mold trimming — critical for medical and baby product safety (no sharp flash edges).

Complex geometries with undercuts: LSR's liquid state fills undercuts, fine features, and thin-walled sections that compression-molded HTV cannot reproduce. Baby nipple teat geometries, medical device valve membranes, and wearable device seals with complex sealing lips are standard LSR applications.

Overmolding onto thermoplastics: Self-adhesive LSR grades bond directly to PC, PA, PBT, and ABS in two-shot molds or insert molding — an assembly that is impossible or difficult to achieve with HTV. Applications: medical device grips, smartwatch cases, consumer device seals.

Clean-room production: LIM processing is a closed, automated system compatible with ISO Class 7/8 clean rooms. HTV compression molding involves manual compound handling that limits clean-room compatibility.

Cost-Volume Decision Framework

Below ~50,000 pieces/year: HTV compression molding typically preferred (low tooling cost). 50,000–200,000 pieces/year: Evaluate both — depends on geometry complexity and post-processing cost. Above 200,000 pieces/year: LSR LIM typically preferred (lower per-part cost, automated production).

Contact us to discuss your specific application requirements and connect with qualified HTV and LSR suppliers.