Low molecular weight polyisobutylene (LMPIB) is a class of polymers with specific molecular weights and structural characteristics, synthesized from isobutylene as the main monomer via cationic polymerization. Its number average molecular weight typically ranges from several hundred to tens of thousands. Compared to ordinary high molecular weight polyisobutylene, it exhibits lower melt viscosity, better flowability, and certain adhesion properties while maintaining the inherent chemical inertness and hydrophobicity of polyisobutylene, thus finding wide application in various industrial fields.
Structurally, LMPIB consists of repeating isobutylene units. The main chain is saturated and lacks polar functional groups, giving it excellent chemical resistance and antioxidant capacity, allowing it to exist stably in acidic, alkaline, saline, and most organic solvent environments. Its low molecular weight weakens intermolecular forces and reduces chain entanglement, thus it is mostly a viscous liquid or semi-solid at room temperature, making it easy to process and mix. It can be used directly as an additive or as a standalone film.
In terms of performance, low molecular weight polyisobutylene possesses excellent electrical insulation and water resistance, low dielectric loss, and high volume resistivity, making it suitable for cable filling and insulation material modification. Its low volatility and wide temperature range stability allow it to function as a thickener, pour point depressant, and friction reducer in greases, sealants, and damping materials. Furthermore, this material exhibits good compatibility with mineral and synthetic oils, improving the viscosity-temperature characteristics and mechanical stability of lubrication systems. In the adhesives and sealants field, it can adjust initial tack and holding power, enhancing wetting and adhesion to difficult-to-bond substrates.
Its applications are wide-ranging. In the petroleum industry, low molecular weight polyisobutylene (PHB) is commonly used as a viscosity index improver for lubricating oils and a component of fuel detergents. In cosmetics and personal care products, it serves as a skin feel improver and a waterproof film-forming agent, imparting a silky feel and sweat resistance. In the pharmaceutical field, its low toxicity and chemical inertness make it suitable for use as a base material in pharmaceutical ointments and as an auxiliary material for sustained-release carriers. In food packaging and contact materials, compliant HPB can also be used as a component of sealing and moisture-proof coatings.
With the increasing demand for refined and high-performance downstream products, HPB is developing towards narrow molecular weight distribution control, functional modification, and green and environmentally friendly production. By optimizing polymerization processes and raw material systems, energy consumption and emissions can be reduced while maintaining excellent properties, further broadening its application prospects in new energy, electronics, and high-end manufacturing fields.
