Waterproof membranes are made from a variety of materials, including traditional hydrophobic materials represented by fluorides, high-performance polymers such as thermoplastic polyurethane (TPU), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF), as well as emerging bio-based materials, fluorine-free materials, and various nanocomposite materials.
Thermoplastic polyurethane (TPU) is a block copolymer composed of polyols, diisocyanates, and chain extenders. Based on the type of soft segments, TPU is mainly divided into three categories: Polyester-type TPU has good oil and solvent resistance but poor hydrolysis resistance; polyether-type TPU has excellent hydrolysis resistance and is suitable for humid and hot environments; and polycarbonate-type TPU has excellent comprehensive performance and is particularly suitable for medical and high-end electronic packaging fields.
With green transformation and technological development, new materials are constantly emerging, mainly including bio-based polymers and fluorine-free waterproof materials . For example, research has developed high-performance, fluorine-free, waterproof and breathable materials through industry-academia-research collaboration. These materials boast a hydrostatic pressure of up to 18000 mmH₂O and a moisture permeability of 7000 g/m²·24h. Some products achieve high levels in core indicators and utilize bio-based polymers to replace some petroleum-based materials.
To enhance the barrier properties, mechanical strength, or impart special functions to waterproof membranes, base materials are often combined with functional materials. For instance, combining TPU with nanomaterials such as SiO₂, graphene, and zinc oxide nanowires can significantly reduce water vapor transmission rate (WVTR) while maintaining good transparency and flexibility. Numerous related studies and commercialized products exist both domestically and internationally, such as DuPont's "HydroShield" composite TPU waterproof membrane and BASF's TPU/nano-silica composite membrane.
