Hydroxyl-terminated Linear Polyurethane

Updated: 2026-07-19

Overview

Hydroxyl-terminated linear polyurethane (HTPU) is a specialized polymer featuring reactive -OH groups at both ends of its molecular chain. These terminal hydroxyls enable crosslinking with isocyanates, making HTPU a key building block for polyurethane systems. The linear structure provides flexibility while maintaining strength, distinguishing it from branched alternatives. Developed in the mid-20th century alongside polyurethane chemistry advancements, HTPU bridges the gap between simple diols and complex polyurethane networks. Manufacturers tailor its properties by adjusting the polyol/diisocyanate ratio and chain extenders, allowing precise control over final product characteristics.

Physical and Chemical Properties

HTPU exhibits a unique combination of mechanical and chemical properties. The hydroxyl value (typically 20-120 mg KOH/g) determines reactivity, while molecular weight influences viscosity and flexibility. Most formulations show excellent resistance to oils, abrasion, and ozone degradation. Thermal stability generally ranges from -40°C to 120°C, with decomposition occurring around 200°C. The polymer's solubility parameters make it compatible with common polyurethane processing methods, including solvent casting and reactive injection molding. Hydrogen bonding between chains contributes to its notable tensile strength despite the linear architecture.

Main Applications

In adhesives, HTPU serves as the backbone for high-performance structural bonds in automotive and aerospace assemblies, offering superior flexibility compared to epoxy alternatives. Coatings formulations leverage its weatherability for protective layers on industrial equipment and flooring systems. The elastomers sector utilizes HTPU in medical devices (catheters, seals) and industrial components (gaskets, rollers) where fatigue resistance is critical. Emerging applications include 3D printing resins and thermoplastic polyurethane (TPU) modifiers, where its linear structure improves layer adhesion and post-processing properties.

Safety and Storage

While HTPU poses minimal acute toxicity, proper handling precautions are essential. Use nitrile gloves and eye protection when handling liquid forms, and ensure adequate ventilation to avoid vapor accumulation during heating processes. Solid forms may generate dust requiring particulate respirators during machining. Storage requires moisture-proof containers with nitrogen blankets for sensitive formulations. Shelf life typically exceeds 12 months when stored below 30°C. Monitor for viscosity changes or hydroxyl value drift in aged material, which may indicate moisture absorption or partial polymerization.

B2B Procurement Guide

Industrial buyers should prioritize suppliers with batch-to-batch consistency testing, particularly for hydroxyl value and molecular weight distribution. Request technical datasheets specifying: 1) Hydroxyl value tolerance (±5%), 2) Acid value (<1 mg KOH/g), and 3) Water content (<0.1%). For large-volume purchases (>1 ton), consider toll manufacturing agreements allowing customized formulations. Verify ISO 9001 certification and request samples for compatibility testing with your existing systems. Bulk pricing tiers typically apply at 500kg+ quantities, with drum (200kg) and tote (1000kg) being common packaging options.