Wear, oil, transparent, good elasticity
TPU (Thermoplastic polyurethanes) name is thermoplastic polyurethane elastomer rubber. (60HA-85HD), wear-resistant, oil-resistant, transparent, good elasticity, in the daily necessities, sporting goods, toys, decorative materials and other fields have been widely used in the field of polyester and polyester, Halogen-free flame retardant TPU can also replace the soft PVC to meet more and more areas of environmental requirements.
The so-called elastomer refers to the glass transition temperature is lower than the room temperature, elongation at break> 50%, external recovery after recovery is better polymer materials. Polyurethane elastomers are a special category of elastomers. The polyurethane elastomers have a wide range of hardness and a wide range of properties. Therefore, polyurethane elastomers are a kind of polymer material between rubber and plastic.
Can be heated plasticized, chemical structure is not or rarely cross-linked, the molecules are basically linear, but there is a certain physical cross-linking. This type of polyurethane is called TPU.
The main features of TPU are:
Hardness range: by changing the TPU reaction components of the ratio, you can get different hardness of the product, and with the increase in hardness, the product still maintain good flexibility and wear resistance.
High mechanical strength: TPU products carrying capacity, impact resistance and shock absorption performance.
Cold resistance highlights: TPU glass transition temperature is relatively low, at minus 35 degrees still maintain good flexibility, flexibility and other physical properties.
Good processing performance: TPU can be used to process the common thermoplastic materials processing, such as injection molding, extrusion, rolling and so on. At the same time, TPU and some polymer materials can be co-processing performance of complementary polymer alloy.
Resistant to oil, water resistant, resistant to mold.
Good recycling efficiency.
TPU as an elastomer is a material between the rubber and plastic, which from its rigid view, TPU rigidity can be measured by the elastic modulus. Rubber elastic modulus is usually 1 ~ 10Mpa, TPU in 10 ~ 1000Mpa, plastic (nylon, ABS, PC, POM) in the 1000 ~ 10000Mpa. TPU has a wide range of hardness, from Shore A 60 to Shore D 80 and has high elasticity over the entire hardness range; TPU is -40 to 120 ° C over a wide temperature range with flexibility without plasticizer; TPU The oil (mineral oil, animal and vegetable oils and lubricants) and many solvents have good resistance; TPU also has good weather resistance, excellent resistance to high-energy ray performance. Well-known abrasion resistance, tear resistance, and creep strength are excellent; high tensile strength, elongation, long-term compression and low permanent deformation rate are the significant advantages of TPU.
The TPU performance described here includes three aspects: mechanical properties, physical properties and environmental performance.
1. Mechanical properties: TPU elastomer mechanical properties include: hardness, tensile strength, compression properties, tear strength, resilience and wear resistance, resistance to interference, etc., and TPU elastic plastic mechanical properties, in addition to these Performance, there are higher shear strength and impact power and so on.
(a) Hardness: Hardness is an indicator of the ability of materials to resist deformation, nicks and scratches. TPU hardness is usually measured by Shore A and Shore D hardness tests. Shore A is used for relatively soft TPU and Shore D for harder TPU. Hardness is mainly determined by the hard segment content of the TPU structure. The higher the hard content, the higher the hardness of the TPU. After the hardness increases, the other properties of the TPU will change, the tensile modulus and tear strength increase, the rigidity and compressive stress (load capacity) increase, the elongation decreases, the density and dynamic heat increase, resistance to environmental performance increases. TPU hardness and temperature there is a certain relationship. From the room temperature cooling to the sudden temperature (-4 ~ -12 ℃), the hardness did not change significantly; at the mutation temperature, TPU hardness suddenly increased and become very hard and lose elasticity, which is due to the effect of soft segment crystallization.
(b) the relationship between hardness and modulus and elongation and the relationship between hardness and tear strength. With the increase of TPU hardness, 100% modulus and 300% tensile stress increased rapidly, elongation decreased. This is mainly due to the increase in hard content: the hard segment content is high, the formation of the hard segment is easier to form secondary crystal or crystalline structure increases the number of physical cross-linking and limit the material deformation. If the material deformation must be increased stress, thereby increasing the tensile stress, while elongation decreased. TPU hardness and tear strength of the relationship, with the increase in hardness, tear strength increased rapidly, the reason is the same with the interpretation of the modulus.
TPU formulations and performance can be a very wide variety of permutations and combinations. However, in the actual design of the formula and industrial production, but because of raw materials (polyols and polyisocyanates and chain extenders) mutual restrictions, so that really can be used for high-end applications R & D is still very difficult.
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