Distinguish TPE, TPEE, TPU in one article! Speed Collection!

TPE, TPE, TPU are all elastomer materials, each with its own advantages and application range, which material to choose mainly depends on the use environment and use requirements. Let's take a closer look at these three materials today.

Thermoplastic elastomers are environmentally friendly composites that combine rubber properties with the advantages of plastic processing. It not only has the high elasticity of rubber and excellent compression set performance, but also has the characteristics of easy processing of plastics, and can achieve efficient production through injection molding, extrusion and other processes, in line with the development trend of low-carbon and environmental protection. Affected by historical evolution and usage habits, there is no unified naming system for thermoplastic elastomers at home and abroad. In most regions, it is customary to refer to these materials collectively by the English abbreviation TPE, which is regarded as a general term for thermoplastic elastomers.

TPE

TPE (thermoplastic elastomer) has the characteristics of environmental protection, non-toxicity, safety and reliability, and has excellent coloring properties, soft and comfortable touch, and excellent properties such as weather resistance, fatigue resistance and temperature resistance. It has excellent processability, not only can it be recycled to reduce costs, but it can also be coated and bonded with PP, PE, PC, PS, ABS and other substrate materials through the overmolding process, and can also be molded separately.
At present, there are a wide variety of TPEs that have been industrially produced worldwide, covering almost all fields of synthetic rubber and synthetic resins, mainly including the following categories:
Styrene: such as SBS, SIS, SEBS, SEPS, etc.; 
Olefins: including TPO, TPV, etc.; 
Dienes: TPB, TPI, etc.; 
Vinyl chloride: such as TPVC, TCPE, etc.; 
Urethanes: represented by TPU; 
Esters: Typical varieties are TPEE; 
Amides: e.g. TPAE; 
Special categories: including organic fluorine (TPF), organosilicon, ethylene, etc.

Advantages: It has the high elasticity of rubber and the characteristics of injection molding; Environmentally friendly, non-toxic and safe, with excellent colorability, soft touch, weather resistance, fatigue resistance and temperature resistance, superior processing performance, no vulcanization, can be recycled to reduce costs, can be double injection molding, can also be molded separately.
Disadvantages: The biggest problem of SBS and SIS is poor heat resistance, and the use temperature generally cannot exceed 80°C. At the same time, its tenemolinity, weather resistance, oil resistance, and wear resistance cannot be compared with rubber.

TPEE
Thermoplastic polyester elastomers (TPEEs) are a class of linear block copolymers containing PBT (polybutylene terephthalate) polyester hard (crystalline phase) and aliphatic polyester or polyether (amorphous phase) soft segments. 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 resistance and solvent erosion, etc., has good processability, and can be filled, strengthened and alloyed and modified, and has been widely used in auto parts, hydraulic hoses, cables and wires, electronic appliances, industrial products, stationery and sports supplies, biomaterials and other fields.

Physicochemical properties of TPEE
(1) Mechanical properties
By adjusting the ratio of hard and soft segments, the hardness range of TPEE can be flexibly varied from Shore D32 to D80, and its elastic and strength properties are intermediate between those of rubber and plastic. Compared to other thermoplastic elastomers (TPEs) of the same hardness, TPEEs exhibit higher modulus at low strain. This feature enables the use of TPEE to reduce the cross-sectional area of the product and effectively reduce the amount of material used in scenarios where modulus is the key design metric.

(2) Tensile strength and load performance 
Compared to polyurethane elastomers (TPUs), TPEEs have significantly higher compression and tensile modulus and can withstand greater loads at the same hardness. In the environment above room temperature, its flexural modulus is prominent, especially suitable for the production of cantilever beams, torque-type components and high-temperature parts. In addition, TPEE combines low-temperature and gentle compliance with excellent low-temperature notched impact strength, and its abrasion resistance is comparable to that of TPU. Its excellent fatigue resistance combined with high elasticity makes it an ideal material for cyclic load scenarios such as gears, rubber rollers, flexible couplings, transmission belts, etc.

(3) Wide-range temperature adaptability 
The heat resistance of TPEE is enhanced with the increase of hardness, the maximum service temperature can reach 200°C, it can withstand the baking process of 150~160°C in the automobile production line, and the mechanical properties are maintained at high temperatures, and the tensile strength above 120°C far exceeds that of TPU. The low temperature resistance is also excellent, the embrittlement temperature is below -70°C, most grades can be used for a long time at -40°C, and the operating temperature range covers -70~200°C.

(4) Resistance to chemical media 
TPEE has excellent oil resistance, strong resistance to polar liquid media such as acids, alkalis, amines, and glycols at room temperature, and the higher the hardness, the better the chemical resistance. The anti-swelling and permeability resistance of organic solvents, fuels and gases are outstanding, and the permeability of fuel is only 1/300~1/3 of that of oil-resistant rubber such as neoprene and nitrile rubber.

(5) Weather resistance and anti-aging characteristics
Under natural conditions such as water mist, ozone, and atmosphere, TPEE has good chemical stability. However, similar to most TPEs, UV exposure can trigger degradation, so UV protection additives are required for outdoor applications or products exposed to direct sunlight. Typical formulations can use shielding materials such as carbon black and pigments, combined with phenolic antioxidants and benzotriazole ultraviolet absorbers to synergistically improve anti-aging ability.

(6) High resilience and long-term reliability
When applied to spring scenarios, TPEE can give the spring a long service life to ensure the smooth start-stop and speed change of mechanical systems (such as trains). Compared with metal springs, it has no rust risk, strong resistance to environmental deterioration, and no hidden danger of elastic rupture; Compared to rubber materials, it has better reusability and high elastic retention.

(7) Advantages of multiple processing and molding
TPEE has excellent melt stability and thermoplasticity, and supports a variety of thermoplastic processing processes such as extrusion, injection, blow molding, rotational molding, and melt casting. The melt viscosity is insensitive to shear at low shear rate, and decreases with the increase of shear rate at high shear rate. Since the melt is highly sensitive to temperature (a temperature difference of 10°C can lead to a change in viscosity by several times to tens of times), the temperature parameters need to be strictly controlled during the molding process.

TPU
Polyurethane thermoplastic elastomer (TPU), also known as polyurethane rubber, is a class of elastic polymer materials rich in urethane groups (NHCOO) in the molecular chain. The preparation process is based on the chemical reaction of low-polyester diisocyanate, polyether/polyester polyols with hydroxyl terminal groups and low-molecular-weight diol chain growers.
TPU is a block polymer, and its molecular structure is composed of two parts: soft segment: composed of flexible long chains of polyols, which are arranged in an amorphous curl arrangement, giving the material flexibility, elasticity, hygroscopicity and low temperature resistance; Hard section: formed by diisocyanate and chain extender, it forms a repeating crystallization unit through orderly arrangement, providing high strength, rigidity and high melting point for the material.
A large number of urethane groups and ether/ester/urea groups in the TPU molecular chain are combined by strong hydrogen bonding, and TPU varieties with differentiated properties can be derived based on different formulations of ether or ester polyols. This structural property gives it excellent abrasion resistance, toughness, high elasticity and compatibility with other polymers.

Performance characteristics of TPU:

(1) Structural diversity

TPU is divided into compounding, casting and thermoplastic according to the processing technology, with complex chemical structure and diverse properties: polyester TPU: high mechanical strength, excellent oil resistance, but weak water resistance; Polyether TPU: Low temperature resistance and water resistance are outstanding, and mechanical properties and oil resistance are slightly inferior to polyester type. Overall, the physical properties of TPU are between those of conventional rubber and thermoplastics, and have comprehensive performance advantages.

(2) Performance control of the ratio of hard segment to soft segment

As a block copolymer, the composition ratio of hard segment and soft segment in TPU directly determines the performance performance: hard segment: dominant modulus, hardness and tear strength; Soft section: mainly affects elasticity and low temperature performance. TPU has a wide range of hardness (Shore A10-D75), in which it retains high elasticity and has better load-bearing capacity than other elastomers at the same hardness.

(3) Wear resistance and tensile performance

The abrasion resistance of TPU is 2~10 times that of natural rubber, and the elongation at break is as high as 600%~800% (300% higher than that of natural rubber), showing excellent deformation resistance.

(4) Mechanics and thermal properties

Parametric mechanical indexes: density 1.14~1.22g/cm³, tensile strength 30~65MPa (esters are slightly higher than ethers); Thermal performance: long-term use temperature range - 50~90°C, maintain good flexibility in this range.

(5) Environmental tolerance

TPU has excellent performance in chemical corrosion resistance, oil resistance, radiation resistance, oxygen resistance, ozone resistance, fatigue resistance and vibration resistance, and has good heat resistance, low molding and processing costs.

(6) Comparative advantages of materials

vs metal: light weight, low noise, wear resistance, low processing cost, corrosion resistance; 

vs plastic: non-brittle, elastic memory, wear-resistant;

vs Rubber: Abrasion resistant, cut resistant, tear resistant, high load-bearing, potting/pourable, wide range of hardness.

(7) Limitations and improvements in weather resistance

TPU has weak weather resistance and is prone to aging and degradation under sunlight, so antioxidants and light stabilizers need to be added during processing to improve environmental adaptability.