Detailed explanation of the characteristics and application fields of TPU film and PU materials

TPU (thermoplastic polyurethane elastomer) film and PU (polyurethane) materials, as two important branches in the field of polymer materials, have become indispensable functional materials in modern industry and daily life with their unique physical and chemical properties and a wide range of application scenarios. In this paper, we will systematically analyze the differences in the characteristics of these two materials and the direction of technological evolution from the dimensions of molecular structure, mechanical properties, processing technology and industrial applications.
### First, the molecular structure and basic characteristics are compared
The molecular chain of TPU film is composed of alternating hard segments (diisocyanate and chain extender) and soft segments (polyester or polyether polyols), and this "rigid-flexible" microstructure gives it excellent elastic recovery ability. Laboratory data shows that the elongation at break of high-quality TPU films can reach 500%-800%, and the tensile strength is maintained in the range of 30-50MPa, while maintaining an operating temperature range of -40°C to 120°C. Conventional PU materials, on the other hand, form a three-dimensional network structure through cross-linking reactions, which have a wider hardness range (Shore A60-D80), but are less thermoplastic and usually require molding or pouring molding.
In terms of weather resistance, the latest research by BASF in Germany shows that the retention rate of mechanical properties of TPU films with nano-titanium dioxide is still more than 85% after 2000 hours of QUV aging test. In contrast, aromatic PU is prone to yellowing under ultraviolet irradiation, which needs to be improved by adding light stabilizers. The difference in hydrolytic stability between the two is more significant: the strength loss of polyether TPU after 30 days of immersion in 85°C/95%RH environment is no more than 10%, while the strength of polyester PU can be reduced by 30%-40% under the same conditions.
### Second, the industrialization breakthrough of key performance indicators
In recent years, breakthroughs in material modification technology have greatly improved the performance of TPU films. A conductive TPU film developed by a Japanese company has been used in the manufacture of wearable medical sensors by embedding a network of silver nanowires with a surface resistance as low as 5Ω/sq while maintaining an elongation of more than 200%. In the field of flame retardant, TPU films modified with intumescent flame retardants can meet the UL94 V-0 standard, and their limiting oxygen index (LOI) exceeds 32%, which is successfully applied to aircraft interior materials.
The innovation of PU foam materials is equally remarkable. The bio-based PU developed by Covestro uses castor oil derivatives as raw materials, and its compression set coefficient is 15% lower than that of petroleum-based products, and carbon emissions are reduced by 40%. In terms of acoustic applications, the sound absorption coefficient of open-cell PU foam can reach more than 0.9 in the frequency range of 500-4000Hz, making it the core material of high-end automotive NVH solutions.
### Third, the technical division of processing technology
TPU films are mainly produced using blow molding, casting, or calendering processes. The newly developed multi-layer co-extrusion technology can achieve 5-7 layers of functional superposition, such as the "respiratory membrane" used in a brand of sneakers, which contains a composite structure of antibacterial layer, breathable layer and support layer, and the water vapor transmission rate (WVTR) exceeds 5000g/m²·24h. In contrast to the PU process, which relies on reaction injection molding (RIM) or spraying processes, the thickness of the microporous PU integral skin foam used in BMW's instrument panels can be precisely controlled between 0.3 and 0.8 mm by the mold temperature.
In terms of environmentally friendly production, the water-based TPU film production line has achieved zero solvent emissions, and the VOC content is less than 50μg/m³. The global warming potential (GWP) of HFO blowing agent technology being promoted by the PU industry is 99.9% lower than that of traditional HCFC blowing agents, but the cost of equipment modification is increased by about 20%.
### Fourth, the differentiated expansion of application fields
**Medical field**: TPU film is the first choice for prosthetic heart valve coating materials due to its biocompatibility (ISO 10993 tested), and its anticoagulant coating technology can reduce the thrombosis rate by up to 70%. The application of PU in the load-bearing part of the prosthesis takes advantage of its high damping characteristics, and the energy absorption efficiency is 40% higher than that of traditional silicone.
**Sports Equipment**: The midsole of the Adidas 4DFWD running shoe adopts a 3D printed TPU grid structure, with a rebound rate of up to 65% and an energy loss of only 12%. PU material shows unique value in professional sports protective gear, and its slow rebound characteristics can extend the cushioning time to 50-80 milliseconds in the event of impact, significantly reducing the risk of sports injuries.
**Smart wearable**: South Korea's LG's latest flexible display adopts a TPU substrate, which can be bent and folded with a radius of 3mm, and the number of bending times is more than 200,000 times. The application of PU in VR haptic feedback gloves realizes tactile simulation of different forces by adjusting the Shore hardness.
**Industrial Protection**: TPU/PU composite protective clothing has become a new trend in the industry, the outer TPU film provides chemical resistance (98% resistance to sulfuric acid attack), and the inner layer of PU foam provides thermal insulation performance in the environment of -30°C. In the field of anti-corrosion of oil pipelines, the adhesion of polyurea (PU derivative) spray coating is more than 15MPa, and the cathodic peeling radius is less than 5mm.
### 5. Sustainable development and technological foresight
Biodegradable TPU has become a research hotspot, and the TPU film based on polycaprolactone developed by a German company has a degradation rate of more than 90% in 6 months under industrial composting conditions. The PU recycling technology has made a breakthrough, and the chemical depolymerization process can reduce more than 90% of the mattress foam to the original polyol.
In the next five years, smart responsive materials will be the way forward. The temperature-sensitive TPU film has achieved a 300% performance mutation at 35°C, while the shape memory PU can complete the preset deformation under the irradiation of a specific frequency electromagnetic wave. These breakthroughs will promote the continuous expansion of the application boundaries of the two types of materials in emerging fields such as robot skin and adaptive construction.
Through continuous material innovation and process optimization, TPU film and PU materials are redefining the performance limits of flexible functional materials, and their coordinated development will provide key material support for strategic industries such as medical health, green energy, and intelligent equipment. According to industry data, the global TPU film market is expected to reach US$5.8 billion in 2025, while the overall PU market will exceed US$78 billion, with a compound annual growth rate of 8.7% and 5.3% respectively.