1. TPEE
Thermoplastic polyester elastomer, abbreviated as TPEE or COPE, is a kind of linear block polymer containing PBT (polybutylene terephthalate) polyester hard segment (crystalline phase) and aliphatic polyester or polyether soft segment (amorphous phase). TPEE is a high-performance engineering-grade elastomer, which has the advantages of high mechanical strength, good elasticity, impact resistance, creep resistance, cold resistance, bending fatigue resistance, oil resistance, chemical and solvent corrosion resistance, good processability, and can be filled, reinforced and alloyed. It has been widely used in automobile parts, hydraulic hoses, cables and wires, electronic appliances, industrial products, stationery, biomaterials and other fields.
Physical and chemical properties of TPEE
● Mechanical properties By adjusting the proportion of soft and hard segments, the hardness of TPEE can be changed from Shore D32 to D8, and its elasticity and strength are between rubber and plastic. Compared with other thermoplastic elastomers (TPEs), the modulus of TPEE is higher than that of other TPEs with the same hardness under low strain conditions. When modulus is an important design condition, TPEE can reduce the cross-sectional area of products and reduce the amount of materials.
● tensile strength compared with polyurethane elastomer (TPU), the compressive modulus and tensile modulus of TPEE are much higher, and the TPEE and TPU with the same hardness can bear more load when making the same part. Above room temperature, TPEE has a high bending modulus, which is suitable for making cantilever beams or torque components, especially for making high-temperature components. TPEE has good flexibility at low temperature, notch impact strength at low temperature is better than other TPEs, and wear resistance is equivalent to TPU. TPEE has excellent fatigue resistance, which, combined with high elasticity, makes it an ideal material under repeated cyclic loading, and is suitable for making gears, cots, flexible couplings, belts, etc.
● heat resistance TPEE has excellent heat resistance, and the higher the hardness, the better the heat resistance. The use temperature of TPEE is very high, which can adapt to the baking temperature of automobile production line (15-16℃), and it has little loss of mechanical properties at high temperature. The tensile strength of TPEE is much higher than that of TPU when used above 12℃. In addition, TPEE has excellent low temperature resistance. The brittle point of TPEE is below -7℃, and the lower the hardness, the better the cold resistance. Most TPEE can be used at -4℃ for a long time. Because of its balanced performance at high and low temperatures, TPEE has a very wide working temperature range and can be used at -7-2℃.
● Chemical-resistant TPEE has excellent oil resistance, and can resist most polar liquid chemical media (such as acids, alkalis, amines and glycol compounds) at room temperature, and its chemical resistance increases with the increase of its hardness. TPEE has good swelling resistance and permeability resistance to most organic solvents, fuels and gases, and its permeability to fuel is only 1/3-1/3 of that of oil-resistant rubber such as chloroprene rubber, chlorosulfonated polyethylene and nitrile rubber.
● weather resistance and aging resistance TPEE has excellent chemical stability under various external conditions such as water mist, ozone and outdoor atmosphere. Like most thermoplastic elastomers (TPE), it will degrade under the action of ultraviolet light (ultraviolet light below 31nm is a major factor of degradation). Therefore, for outdoor applications or products exposed to sunlight, ultraviolet protection AIDS should be added to the formula, including carbon black, various pigments or other shielding materials, phenolic antioxidant and benzotriazole ultraviolet shielding agent, which can effectively prevent ultraviolet aging.
● High resilience The application of TPEE material to the spring can make the spring have a long service life and help the train to start, accelerate, decelerate and stop smoothly. Different from metal spring, it will not rust, deteriorate in natural environment, or cause elastic fracture and loss. Compared with rubber material, it has greater reusability and good elasticity.
● processability 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, rotary molding and melt casting. At low shear rate, TPEE melt viscosity is insensitive to shear rate, while at high shear rate, melt viscosity decreases with the increase of shear rate. Because TPEE melt is very sensitive to temperature, its melt viscosity changes several times to dozens of times within the range of 1℃, so the temperature should be strictly controlled during molding.
2. TPU
Polyurethane thermoplastic elastomer (TPU), also known as polyurethane rubber, belongs to a kind of elastic polymer material with more carbamate groups (—NHCOO—) in its molecular chain. It is prepared by reacting oligomeric diisocyanate with polyether or polyester polyol with terminal hydroxyl group and low molecular weight diol chain extender. Polyurethane elastomer is a kind of block polymer, which generally consists of flexible long chain of polyol as soft segment and diisocyanate and chain extender as hard segment. Hard segments and hard segments are arranged alternately and orderly to form crystalline units with repeated structure, which endows the elastomer with high strength, rigidity and melting point. The soft segments are arranged in disorder to form an amorphous region, which gives the elastomer flexibility, elasticity, hygroscopicity and low temperature resistance. The molecular chain of polyurethane elastomer contains a large number of urethane groups and ether, ester and urea groups, which are combined by strong hydrogen bonds. Polyurethane elastomers with very different properties can be obtained from the formulations generated by many ethers and esters. These structural characteristics make polyurethane elastomer have excellent wear resistance, toughness and high elasticity, and it is also easy to be compatible with other polymers. (1) The properties of polyurethane thermoplastic elastomer < P > (1) The formation and combination of TPU are diverse and varied, including mixing type, casting type and thermoplastic type. The chemical structure is also complicated and the properties are different. For example, polyester TPU has high mechanical properties and good oil resistance, but poor water resistance; The low temperature resistance and water resistance of polyether TPU are better than polyester TPU, but the oil resistance and mechanical properties are worse than polyester TPU. Generally speaking, they all have good physical comprehensive properties, which are between ordinary rubber and thermoplastic. TPU is generally divided into mixing type, casting type and thermoplastic type.
(2)TPU is a block copolymer, and the ratio of hard segment to soft segment determines the performance of TPU. Hard segment has a special effect on modulus, hardness and tear strength, while soft segment mainly affects the elasticity and low temperature performance of products. TPU has excellent flexibility and resilience, ranging from very soft to very hard, from very good flexibility to very rigid, or from hydrophilic type that can absorb water to hydrophobic type that can repel water, and maintains high elasticity in a wide hardness range (Shore A1-D75), and has higher bearing capacity than other elastomers at the same hardness.
(3)TPU has excellent wear resistance, which is 2-1 times that of natural rubber; The elongation at break is as high as 6%~8%, which is 3% higher than that of natural rubber.
(4) The impact strength of TPU is relatively high, the density is 1.14-1.22g/cm3, and the tensile strength is 3-65MPa, and the ester TPU is slightly higher than the ether TPU; The thermal performance is also high, and it shows good softness and elasticity at the temperature of -5-9℃ for a long time.
(5) TPU has good chemical resistance, oil resistance, radiation resistance, oxygen resistance, ozone resistance, fatigue resistance and vibration resistance, and high heat resistance, while the molding and processing costs are low.
(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 non-brittleness, elastic memory and wear resistance. Compared with rubber, TPU has the advantages of wear resistance, cutting resistance, tear resistance, high bearing capacity, potting, pouring and wide hardness range.
(7)TPU has poor weather resistance and is prone to aging and degradation in sunlight, so antioxidants and light stabilizers should be added in the processing.
3.TPV
Thermoplastic Vulcanizate, abbreviated as TPV, is abbreviated as Thermoplastic Rubber, abbreviated as TPR in Chinese, but this name is easily confused with other types of TPE. Because thermoplastic elastomers are usually called thermoplastic rubber, especially styrene elastomers, it seems that "TPR" has become its proper name at least in China. When TPR is mentioned, it refers to thermoplastic elastomers based on styrene elastomers such as SBS and SEBS, which is inseparable from the large consumption of styrene elastomers in civil and end consumer goods.
if the name of thermoplastic vulcanized rubber is more detailed, it should be thermoplastic dynamically vulcanized rubber (in English), and the word funny dynamically is added to more specifically explain the process of producing this thermoplastic vulcanized rubber-dynamic vulcanization, which means that rubber is vulcanized during the melting and mixing of rubber and thermoplastic, and of course, rubber is constantly mixed with thermoplastic while being vulcanized. Corresponding thermoplastic static vulcanized rubber means that the rubber is vulcanized according to the traditional method, and then the vulcanized rubber is ground into powder by the grinding equipment, and finally mixed with molten thermoplastic. Theoretically, TPV with excellent performance can also be prepared by this method, but so far, it is only in the laboratory stage.
composition
TPV is mainly composed of two parts, one is plastic as continuous phase, and the other is rubber as dispersed phase. Usually rubber needs to be matched with softening oil or plasticizer. Vulcanizing agents and some auxiliary agents are also essential. In addition, in order to reduce the cost or improve some performance, some inorganic fillers will be added.
Specific properties
1. Good elasticity and compression deformation resistance, environmental resistance and aging resistance are equivalent to those of EPDM, and its oil resistance and solvent resistance are comparable to those of general chloroprene rubber.
2. The application temperature range is wide (-6-15℃), the application range of hardness and softness is wide (25A—54D), and the advantages of easy dyeing greatly improve the freedom of product design.
3. Excellent processability: it can be processed by injection, extrusion and other thermoplastic processing methods, which is efficient, simple and easy to operate, without adding equipment, with high fluidity and small shrinkage.
4. It is green and environmentally friendly, can be recycled, and its performance has not obviously decreased after repeated use for six times, which meets the environmental protection requirements of the European Union.
5. Light specific gravity (.9-.97), uniform appearance quality, high surface grade and good hand feeling.
based on the above performance characteristics, compared with traditional rubber materials, other TPE elastomer materials (including TPR\SBS, SEBS, TPU, etc.) or plastic materials such as PVC, TPV has certain substitution advantages in comprehensive performance and comprehensive cost, thus providing new choices for product enterprises in product innovation, product added value enhancement and competitiveness improvement.
A, automobile airbag deployment door. The best materials in Hytrel have been confirmed at home and abroad.
B. hydraulic hose. Hytrel is used for both inner and outer layers, and the extruder screw is a Gradual transition screw with equal pitch and high compression ratio (2.7/1 ~ 4/1).
C. industrial wheels. Wear resistance and light weight.
D, flexible coupling: wear-resistant, low heat generation under high load and high torque.
E, inner rubber of fire hose: excellent hydrolysis resistance, mold resistance and fatigue resistance.
F, cross-country ski boot soles: good flexibility at low temperature and good fatigue resistance.
G, automobile dust cover
EPDM TPV (such as Santoprene) is used for mid-range dust covers (such as rack dust covers), and TPEE (such as Hytrel) is used for middle and high-grade dust covers (such as CVJ). Tianjin Huanyu Company has mass-produced imported production equipment.
only TPEE with hardness of 47D can meet the mechanical performance requirements of Volkswagen and Delph. Production technology: injection-blow molding, the equipment is the same as TPV dust cover. Water content must be strictly controlled before TPEE injection molding (<: .1%), the temperature sensitivity of TPEE is higher than that of TPV, so more attention should be paid to it.
At present, the most used TPEE product in china rubber industry is automobile dust cover, but the relative consumption is still small. According to DuPont, Shuehiro Company in Japan changed from traditional silicone rubber to Hytrel to make buttons for remote control, thus shortening the production cycle and enhancing the flexibility of design, which is quite amusing. If this technology is popularized, the consumption of TPEE will increase greatly.