PEE, TPU, and TPV are all elastomer materials, each with its own advantages and application scope. The choice of which material mainly depends on the use environment and use requirements. Today, we will introduce these three materials in detail.
Thermoplastic polyester elastomer (TPEE) is a kind of linear segmented copolymer containing PBT (polybutylene terephthalate) polyester hard segment (crystalline phase) and aliphatic polyester or polyether (amorphous phase) soft segment. TPEE is a high-performance engineering-grade elastomer with the advantages of high mechanical strength, good elasticity, impact resistance, creep resistance, cold resistance, bending fatigue resistance, oil resistance, chemical resistance and solvent erosion, and good processability, which can be processed by filling, strengthening and alloying modification and has been widely used in auto parts, hydraulic hoses, cables and wires, electronic appliances, industrial products, stationery, biological materials and other fields.
2. Physicochemical properties of TPEE
(1) Mechanical properties
By adjusting the ratio of soft and hard segments, the hardness of TPEE can be changed from Shore D32 to D80, and its elasticity and strength are between rubber and plastic. Compared to other thermoplastic elastomers (TPEs), TPEE has a higher modulus than other TPEs of the same hardness at low strain. When modulus is an important design condition, using TPEE can reduce the cross-sectional area of the product and reduce the amount of material in the extrusion line machine production process.
(2) Tensile strength
Compared with polyurethane elastomers (TPU), the compressive and tensile modulus of TPEE are much higher, and if the same part is made by TPEE and TPU of the same hardness, the former can withstand larger loads. Above room temperature, TPEE has a high flexural modulus and is suitable for making cantilever beams or torsion-type parts, especially for high-temperature parts. TPEE has good low-temperature flexibility, and its low-temperature notch impact strength is better than that of other TPEs, and its wear resistance is comparable to TPU. TPEE has excellent fatigue resistance, combined with high elasticity characteristics, making this material an ideal material under multiple cyclic load conditions. It is suitable for making gears, rubber rollers, flexible couplings, belts, etc.
(3) Heat resistance
TPEE has excellent heat resistance, the higher the hardness, the better the heat resistance. The use temperature of TPEE is very high, so it can adapt to the baking temperature of the automobile production line (150 to 160 ℃), and it has little loss of mechanical properties at high temperature. When it is used above 120°C, the tensile strength of TPEE is much higher than that of TPU. In addition, TPEE also has excellent low temperature resistance. The brittle point of TPEE is lower than -70°C, and the lower the hardness, the better the cold resistance, and most TPEE can be used for a long time at -40°C. Due to its balanced performance at high and low temperatures, TPEE has a very wide operating temperature range and can be used at -70 to 200°C.
(4) Chemical resistance
TPEE has excellent oil resistance and is resistant to most polar liquid chemical media (such as acids, alkalis, amines and glycol compounds) at room temperature, and its chemical resistance increases with its hardness. TPEE has good anti-swelling performance and anti-penetration performance to most organic solvents, fuels and gases, and its permeability to fuel is only 1/3 to 1/300 of that of oil-resistant rubber such as neoprene, chlorosulfonated polyethylene, and nitrile rubber.
(5) Weather resistance and aging resistance
TPEE has excellent chemical stability under various external conditions such as water mist, ozone, and outdoor atmosphere. Like most TPEs, they will degrade under the action of UV light, so in terms of outdoor applications or where the product is exposed to sunlight, UV light protection additives, including carbon black and various pigments or other shielding materials, should be added to the formulation. The combined use of phenolic antioxidant and benzotriazole type UV shielding agent can effectively prevent UV aging.
(6) High resilience
The application of TPEE material to the spring can make the spring have a long service life, which can help the train start, accelerate, decelerate and stop smoothly. Unlike metal springs, it will not rust, deteriorate under natural conditions, or cause elastic cracks and losses. Compared with rubber materials, it has greater reusability and maintains good elasticity.
TPEE has excellent melt stability and sufficient thermoplasticity, so it has good processability and can be processed by various thermoplastic processing technologies, such as extrusion, injection, blow molding, rotational molding and melt casting. At low shear rates, TPEE melt viscosity is insensitive to shear rate, while at high shear rates, its melt viscosity decreases with increasing shear rate. Since TPEE melt is very sensitive to temperature, its melt viscosity changes several times to dozens of times within the range of 10 °C, so the temperature should be strictly controlled during molding.
Polyurethane thermoplastic elastomer (TPU), also known as polyurethane rubber, belongs to a class of elastic polymer materials containing more urethane groups (-NHCOO-) in the molecular chain. It is prepared by the interaction of oligoester diisocyanates with polyether or polyester polyols with terminal hydroxyl groups and diol chain extenders of low molecular weight.
TPU is a block polymer. Generally, the soft segment is formed by the flexible long chain of polyol, and the hard segment is formed by diisocyanate and chain extender. The hard segments are alternately arranged in an orderly manner, forming a crystalline unit with a repeating structure, which endows the elastomer with properties such as high strength, rigidity, and high melting point; the soft segments are arranged in a disordered curling arrangement to form an amorphous region, which endows the elastomer with properties such as flexibility, elasticity, hygroscopicity and low temperature resistance.
The TPU molecular chain contains a large number of urethane groups and ether, ester and urea groups, which are combined with strong hydrogen bonds. Formulations from numerous ethers and esters can give rise to TPU varieties with very different properties. These structural characteristics give TPU excellent wear resistance, toughness and high elasticity, and it is also easily compatible with other polymers.
4. Performance of TPU
(1) The formation and combination of TPU are diverse and various, including mixing type, casting type and thermoplastic type. The chemical structure is also relatively complex, and the properties are different. For example, polyester TPU has high mechanical properties and good oil resistance. But the water resistance is poor; the low temperature resistance and water resistance of polyether TPU are better than polyester type, but oil resistance and mechanical properties are worse than polyester type. In general, they all have good physical comprehensive properties, and their properties are between those of general rubber and thermoplastics. TPU is generally divided into mixing type, casting type and thermoplastic type.
(2) TPU is a block copolymer, and the composition ratio of hard segment and soft segment determines the performance of TPU. The hard segment has a special effect on the modulus, hardness and tear strength, while the soft segment mainly affects the elasticity and low temperature properties of the product. TPU has excellent softness and resiliency, ranging from very soft to very hard, from very flexible to very rigid, or from a hydrophilic type that absorbs water to a hydrophobic type that repels water. It can maintain high elasticity within a relatively wide hardness range (Shore A10 to D75), and has higher bearing capacity than other elastomers under the same hardness.
(3) TPU has excellent wear resistance, and its wear resistance is 2 to 10 times that of natural rubber; the elongation at break is as high as 600% to 800%, which is 300% higher than that of natural rubber.
(4) The impact strength of TPU is relatively high, the density is 1.14 to 1.22g/cm3, and the tensile strength is 30 to 65MPa in tpu film extrusion line. The polyester TPU is slightly higher than the polyester type in terms of these properties; the thermal performance is also high, and it can also show its good soft elasticity at the long-term use temperature of -50 to 90℃.
(5) TPU has good chemical resistance, oil resistance, radiation resistance, oxygen resistance, ozone resistance, fatigue resistance and vibration resistance, high heat resistance, and low molding and processing costs.
(6) Compared with metal materials, TPU products have the advantages of light weight, low noise, wear resistance, low processing cost and corrosion resistance; compared with plastics, TPU has the advantages of no brittleness, elastic memory, wear resistance, etc.; Compared with rubber, TPU has the advantages of wear resistance, cutting resistance, tear resistance, high bearing capacity, potting, pouring, and a wide range of hardness.
(7) TPU has poor weather resistance and is prone to aging and degradation under sunlight, so antioxidants and light stabilizers should be added during processing.
Thermoplastic vulcanizate (referred to as TPV), also referred to as thermoplastic rubber (TPR), but this abbreviation is easy to be confused with other types of TPE, because usually thermoplastic elastomers are also known by everyone as thermoplastic rubber, especially styrene elastomer. At least in China, it seems that "TPR" has become its exclusive name. When TPR is mentioned, it refers to thermoplastic elastomers based on styrene elastomers such as SBS and SEBS, which are inseparable from the large consumption of styrene elastomers in the field of civil and final consumer goods.
If the name of thermoplastic vulcanizate is more detailed, it should be thermoplastic dynamic vulcanizate. The word "dynamic" is added to more specifically describe the process of producing this thermoplastic vulcanizate - dynamic vulcanization. The technology refers to the vulcanization of the rubber during the melt blending of the rubber and the thermoplastic. Of course, the rubber is continuously mixed with the thermoplastic while the rubber is vulcanized. Therefore, the vulcanized rubber is distributed as a dispersed phase in the thermoplastic continuous phase.
2. Composition of TPV
TPV is mainly composed of two parts: one is plastic, as the continuous phase; the other is rubber, as the dispersed phase. Usually rubber needs to be combined with softening oil or plasticizer. Vulcanizing agent and some auxiliary additives are also essential. In addition, some inorganic filling materials will be added in order to reduce costs or improve performance in certain aspects.
3. Performance of TPV
(1) Good elasticity and compression deformation resistance. Its environmental resistance and aging resistance are equivalent to those of EPDM rubber, and its oil resistance and solvent resistance are comparable to those of general-purpose neoprene rubber.
(2) Wide application temperature range (-60 to 150℃), wide application range of softness and hardness (25A to 54D), and the advantage of easy dyeing greatly improves the freedom of product design and multilayer extruder machine production.
(3) Excellent processing performance: It can be processed by thermoplastic processing methods such as injection and extrusion. It is efficient, simple and easy to operate, without adding equipment, with high fluidity and low shrinkage.
(4) It is green and environmentally friendly, can be recycled, and the performance is not significantly reduced after repeated use for six times, which meets the EU environmental protection requirements.
(5) The specific gravity is light (0.90 to 0.97), the appearance quality is uniform, it is high-end, and the hand feel is good.
4. Application of TPV
Based on the above performance characteristics, compared with traditional rubber materials, other TPE elastomer materials or PVC and other plastic materials in a wide range of applications, TPV has certain alternative advantages in terms of comprehensive performance and comprehensive cost. Thus, it provides a new choice for product enterprises in product innovation, enhancing product added value and competitiveness.
A. Extended door of automobile safety airbag.
B, hydraulic hose.
C. Industrial wheels. Wear-resistant and lightweight.
D. Flexible coupling: wear resistance, low heat generation under high load and high torque.
E. The inner layer of fire hose: effects of hydrolysis resistance, mildew resistance and fatigue resistance are excellent.
F. Sole of cross-country skiing boots: good flexibility at low temperature and good fatigue resistance.
G. Automobile dust cover.