Introduction: Origins of Thermoplastic Elastomers
Thermoplastic Elastomers (TPEs) are a polymer blend which is used in a variety of different applications like automotive, construction and the medical industry. Thermoplastic polymers are soft, rubber-like materials with elasticity while heat-setting elastomers are rubbery and hard.
What properties of TPEs make it so unique?
Even though Thermoplastic Elastomers are, well, thermoplastic, they exhibit elasticity similar to rubber. They are relatively soft, break, tear and tear easily. TPEs are also resistant to most chemicals and mechanical damages.
TPEs can be made to meet the requirements needed in any given application in many different grades of tensile strength, modulus, elongation at break (E-Modulus) and specific gravity. While these differences do not make them different materials, they may seem like it since they all put out the same result.
Grades Available in the TPE Industry
There are 7 different grades of TPEs and it is important to know what each one is used for and what properties each grade offers. These grades differ by the chemical composition of the polymer and in some cases the molding temperature of the polymer.
1) Styrenic Block Copolymers (TPE-S) – Styrenic block copolymers are made up of three different components. First, there is a styrene block and then the middle part of the TPE consists of ethylene or butyl rubber. The end block is made from TPE-S, which can have a tensile strength range from 30,000 to 60,000 psi and elongation at break between 550 and 1000%. TPE-S grade is used in many applications such as medical products, surgical equipment and automotive/transportation. The chemical composition of this grade makes it resistant to low temperature as well as extreme temperatures making it one of the most commonly used grades of Thermoplastic Elastomers in automotive and construction industries.
2) Thermoplastic Polyolefins (TPE-O or TPO) – Polyolefins are made of polymers that are hydrocarbons. The main difference between polyolefins and polystyrene is the presence of double bonds in polyolefins which make them more flexible than polystyrenes. TPE-O is synthetic, tough, strong and wear resistant with a tensile strength between 50,000 and 60,000 psi. The chemical structure of this grade makes it fairly difficult for it to get dirty since it does not absorb as many pollutants. These are qualities that make TPE-O grade popular in medical equipment, automotive/transportation and building/construction applications.
3) Thermoplastic vulcanisates (TPE-V or TPV) – These Vulcanisates are the most common grade of TPEs seen in the market today. They are made up of four components including styrene polymer, diene rubber, zinc oxide and calcium carbonate that can make up to 5% of the polymer. TPE-V is an elastomeric polymer with a tensile strength between 55,000 psi and 75,000 psi along with an elongation at break of 600-1100%. Its chemical composition makes it resistant to most chemicals and also gives it a high heat resistance range. These qualities ensure that TPE-V grade is used for many purposes such as automotive/transportation, building/construction, medical equipment and general industry.
4) Thermoplastic polyurethanes (TPE-U or TPU) – When a polymer has a chemical structure of both TPE and TPU, it is classified as TPU. The three main components of Thermoplastic polyurethanes are TPE-U, diene rubber and zinc oxide but the ratio in which they are included can vary depending on what grade is being used. TPE Polyurethanes also have varying tensile strengths. They range from 30,000 psi to 70,000 psi with an elongation at break from 700 to 2000%. If a soft and tough surface is needed then TPE-U grade will be chosen but the highest strength that a polymer can reach is with TPV grade. This makes TPV grade a popular choice for harnesses, belts and hose applications.
5) Thermoplastic copolyesters (TPE-E or COPE or TEEE) – The main components of a Thermoplastic copolyester is polyester, diene rubber and zinc oxide. The copolyester plays an important role in determining the grade’s flexibility, tensile strength and elongation at break. Even though TPE-E has varying strengths based on what grade it is (i.e.: 30,000 psi to 40,000 psi) it offers a high versatility for many types of applications such as building/construction or automotive/transportation. TPE-E also has properties that make it resistant to chemicals and heat making it optimal for medical equipment or harnesses or hose applications.
6) Melt processable rubber (MPR) – When the chemicals in a TPE are altered and the polymer is heated, it changes into an MPR. The Thermoplastic Polyurethane grade would then be used to that point and then the MPR is added to make the final product. TPE-MPR grades offer a range of tensile strengths from 60,000 psi to 80,000 psi as well as elongation at break from 700 to 2000%. These factors make this grade popular for medical equipment, harnesses and hose applications. With a chemical composition that makes it resistant to most chemicals, heat and many other things, this grade also makes it optimal for uses in the automotive/transportation industry where it can be used for bumpers, belts or hose applications.
7) Thermoplastic polyether block amides (TPE-A) – The main components of this grade are ethylene-propylene copolymer and hexamethylene diamine. This grade is known for its unique high strength, low temperature resistance and good chemical resistance. TPE-A is also very resistant to hydrolysis which allows it to be resistant to many types of chemicals. TPE-A is a flexible, tough, wear resistant polymer that has a strength range from 40,000 psi to 70,000 psi with an elongation at break between 700 and 1000%. TPE-A is a popular choice in medical equipment and automotive/transportation industries.