Linear Thermoplastic Elastomer
Thermoplastic polyester elastomer (TPEE), also known as polyester rubber, is a type of block linear copolymer containing PBT polyester hard segment (crystalline phase, providing strength) and polyether soft segment (continuous segment).
The rigidity, polarity and crystallinity of the TPEE hard segment give it outstanding strength and good high temperature resistance, creep resistance, solvent resistance and impact resistance; the low glass transition temperature and saturation of the soft segment polyether give it excellent low temperature resistance and aging resistance. It combines the excellent elasticity of rubber and the easy processing of thermoplastics.
Production Technology
Raw materials
The hard segment in TPEE generally selects high-hardness crystalline PBT, and the soft segment selects non-crystalline polyether (such as polyethylene glycol ether PEG, polypropylene glycol ether PPG, polytetramethylene glycol ether PTMG, etc.) or aliphatic polyester (such as polylactide PLLA, polyglycolide PGA, polycaprolactone PCL, etc.).
Synthesis process
TPEE can be synthesized by DMT route or PTA route. Generally, DMT or PTA and butanediol are first esterified, and then polyether or aliphatic polyester is added for polycondensation reaction.
Production status
Polyester-polyether type TPEE is a general-purpose TPEE with relatively balanced heat resistance, low temperature resistance, chemical resistance and processing performance. By adjusting the ratio of hard and soft segments, the Shore hardness can vary between 28. and 80.
Product Applications
A. Automotive Industry
Initially, the automotive industry, especially under-the-hood parts, was considered the main application area for polyester elastomers. Drive shaft dust covers made of polyester elastomers have been mass-produced to replace traditional drive shaft dust covers made of neoprene.
B. Industrial Applications
Polyester elastomers are also widely used in various industrial parts, such as hydraulic pipes that are heat-resistant, oil-resistant, and have a long service life. Due to the inherent stability of TPEE, it can be used for hydraulic pipes with copper or metal braids. At the same time, due to its excellent wear resistance and creep resistance, it can also be used to make various conveyor belts and conveyor belts.
C. Sports and Leisure Industry
Another application area of TPEE is sporting goods. In sports shoes, polyester elastomers are mainly used to make the air lining of the soles, and can also be used in winter sports goods. Polyester elastomers are also used in golf balls. The inner layer just below the surface of the golf ball is often made of this material, making full use of the excellent energy absorption properties of polyester elastomers. Other applications in this field include putters and club handles.
D. Film application
The chemical properties of the soft segment in polyester elastomers determine that it is an excellent material for producing breathable films. The first large-scale commercial application example is Sympatex polyester breathable film, which is mainly used for clothing linings with elasticity and breathability. In addition, the excellent wear resistance and load bearing capacity of polyester elastomers make it a shock-absorbing material for rails.
E. Mobile phones
In the field of mobile phones, compared with the current silicone rubber materials, TPEE has a short production cycle and a small weight, and can be used in mobile phone keyboards, mobile phone antenna housings and seals. The effect of changing the remote control buttons from traditional silicone rubber to TPEE is quite ideal. If this technology is promoted, the use of TPEE will increase greatly.
TPEE’s Physical and Chemical Properties
A. 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.
B. Tensile strength
Compared with polyurethane elastomer (TPU), TPEE has much higher compression and tensile moduli. If the same parts are made of TPEE and TPU with the same hardness, TPEE can withstand greater loads.
C. Heat resistance
TPEE has excellent heat resistance, and the higher the hardness, the better the heat resistance. TPEE has a high operating temperature and can adapt to the baking temperature of the automobile production line (150 to 160°C), and the loss of mechanical properties at high temperatures is very small. When used above 120°C, TPEE’s tensile strength is much higher than TPU.
D. Chemical resistance
TPEE has excellent oil resistance and can withstand most polar liquid chemical media (such as acids, alkalis, amines and diol compounds) at room temperature, and its chemical resistance increases with the increase of its hardness.
E. 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 ultraviolet light, so when used outdoors or the product is exposed to sunlight, ultraviolet protection additives, including carbon black and various pigments or other shielding materials, should be added to the formula.
F. High resilience
TPEE materials are applied to springs, which can make the springs have a longer service life and help trains start, accelerate, decelerate and stop smoothly. Unlike metal springs, it will not rust, will not deteriorate under natural conditions, and will not produce elastic cracks and losses.
G. Processability
TPEE has excellent melt stability and sufficient thermoplasticity, so it has good processing performance 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.
The Significance of Recycling Thermoplastic Elastomers
As the use of thermoplastic elastomers increases year by year, the amount of waste generated also increases. Recycling thermoplastic elastomers can not only reduce environmental pollution, but also effectively save resources. Through recycling, discarded thermoplastic elastomers can be reprocessed and made into new products, thereby realizing the recycling of resources.
The recycling process of thermoplastic elastomers
The recycling process of thermoplastic elastomers mainly includes the following steps:
The second step is classification. The collected thermoplastic elastomers need to be classified. Different types of thermoplastic elastomers have different properties and processing characteristics, and classification can improve the efficiency of subsequent recycling.
The third step is cleaning. The classified thermoplastic elastomers need to be cleaned to remove impurities and contaminants attached to the surface to ensure the purity of the recycled materials.
The fourth step is crushing. The cleaned materials need to be crushed and processed into small particles. This process helps with subsequent reprocessing and improves the utilization rate of materials.
The fifth step is reprocessing. The crushed thermoplastic elastomer particles can be reprocessed by injection molding, extrusion, etc. to make new products. These new products can be widely used in various fields, extending the life cycle of materials.
