TPU has been widely used in: shoe materials, ready-made clothing, inflatable toys, aquatic and underwater sports equipment, medical equipment, fitness equipment, car seat materials, umbrellas, suitcases, leather bags, etc.
TPU films are widely used in sports shoes: trademark decoration on soles and uppers, air bags, air cushions, oil bags, etc. Nowadays, there are two trends in the application of TPU films on sports shoes:
The first is the popular trend caused by Nike sports shoes, which is to screen-print and color the TPU film first, and then use high frequency to Shaped and bonded to the upper for decoration to achieve special decorative effects.
The second is to use a waterproof and moisture-permeable TPU film to fit the shoe material cloth to achieve a waterproof and moisture-permeable effect.
Attention when injection molding TPU plastic raw materials: The main reasons for various adverse phenomena in injection molding are as follows: 1. The differences in properties of the plastic raw materials themselves; 2. Molding conditions such as temperature and pressure , caused by improper settings such as the injection rate, 3 caused by defects in the design or production of the molding mold, 4 caused by poor design of the shape, thickness, etc. of the molded product, 5 caused by improper selection of the injection molding machine and insufficient capacity. In fact, The cause of injection molding failure is not simple. It is usually caused by a combination of the above factors. The determination of the cause of failure depends on the experience and technology of the operator. The mold cavity filling process. It is recommended to consult relevant professionals before processing to reduce loss costs. Market application of TPU DuPont plastic raw materials in the United States: From the shoes we wear to daily necessities, to electrical appliances, automobiles, aviation fields, satellites, etc., plastics are inseparable. With the development of urban construction and agricultural production factoryization, my country's single For PC, the annual demand reaches about 260,000 tons. With the increasing demand for plastic raw materials for industrial and daily life, multinational companies have invested in the construction of polycarbonate industry in my country. Currently, the three major multinational companies investing in PC production in China include Germany's Bayer, Japan's Teijin, and the United States' GE. The project, invested and constructed by German Bayer Company and Shanghai Chlor-Alkali Co., Ltd., is expected to expand to 200,000 t/a.
Characteristics
The main characteristics of TPU are:
Wide range of hardness: By changing the ratio of each reaction component of TPU, products with different hardness can be obtained. And as the hardness increases, its products still maintain good elasticity and wear resistance.
High mechanical strength: TPU products have outstanding load-bearing capacity, impact resistance and shock absorption properties.
Outstanding cold resistance: TPU has a relatively low glass transition temperature and maintains good elasticity, flexibility and other physical properties at minus 35 degrees.
Good processing performance: TPU can be processed using common thermoplastic material processing methods, such as injection molding, extrusion, calendering, etc. At the same time, TPU and certain polymer materials can be processed together to obtain polymer alloys with complementary properties.
Oil, water and mold resistant.
Good recyclability.
As an elastomer, TPU [1] is a material between rubber and plastic. This can be seen from its rigidity. The rigidity of TPU can be measured by the elastic modulus. The elastic modulus of rubber is usually 1~10Mpa, TPU is 10~1000Mpa, and plastic (nylon, ABS, PC, POM) is 1000~10000Mpa. The hardness range of TPU is quite wide, from Shore A 60 to Shore D 80 and has high elasticity throughout the hardness range; TPU is flexible in a wide temperature range of -40~120℃ without the need for plasticizers; TPU It has good resistance to oils (mineral oil, animal and vegetable oils and lubricating oils) and many solvents; TPU also has good weather resistance and excellent resistance to high-energy rays. The well-known wear resistance, tear resistance, and yield strength are all excellent; high tensile strength, large elongation, and low long-term compression permanent deformation rate are all significant advantages of TPU.
The TPU performance introduced here includes three aspects: mechanical properties, physical properties and environmental properties.
1. Mechanical properties: The mechanical properties of TPU elastomer mainly include: hardness, tensile strength, compression performance, tear strength, resilience and wear resistance, flex resistance, etc., and TPU elasticity In addition to these properties, the mechanical properties of plastics also include high shear strength and impact energy.
(a) Hardness: Hardness is an indicator of a material's ability to resist deformation, nicks and scratches. TPU hardness is usually measured with Shore A (Shore A) and Shore D (shore D) hardness testers. Shore A is used for softer TPU, and Shore D is used for harder TPU. The hardness is mainly determined by the hard segment content in the TPU structure. The higher the hard segment content, the hardness of TPU will increase accordingly. After the hardness increases, other properties of TPU will also change. Tensile modulus and tear strength increase, rigidity and compressive stress (load capacity) increase, elongation decreases, density and dynamic heat generation increase, and environmental resistance increases. There is a certain relationship between the hardness of TPU and temperature. When cooling from room temperature to the mutation temperature (-4~-12℃), the hardness does not change significantly; at the mutation temperature, the hardness of TPU suddenly increases and becomes very hard and loses elasticity. This is due to the crystallization of the soft segment.
(b) The relationship between hardness and modulus stress and elongation and the relationship between hardness and tear strength. As the hardness of TPU increases, the 100 elongation stress and 300 elongation stress increase rapidly, and the elongation decreases. This is due to the fact that the increase in hardness is mainly due to the increase in hard segment content. The higher the hard segment content, the easier it is for the hard segment phase to form sub-crystalline or crystalline structures, which increases the number of physical cross-links and limits material deformation. If the material is deformed, the stress must be increased, thereby increasing the elongation stress and decreasing the elongation. The relationship between TPU hardness and tear strength. As the hardness increases, the tear strength increases rapidly. The reason is the same as the explanation of modulus.
The formula and performance of TPU can be arranged in many kinds of combinations. However, in the actual design of formulas and industrial production, due to the mutual limitations of raw materials (polyols, polyisocyanates and chain extenders), it is still very difficult to develop products that can be used for very high-end applications.