Thermoplastic copolyesters (TPEE)

Thermoplastic elastomers: elastic behavior without vulcanization Thermoplastic elastomers are materials that combine the resilience and flexibility of elastomers with the processability of thermoplastics. They can be processed by injection molding, extrusion, coextrusion, blow molding or multi-component molding without classical vulcanization, which shortens the production cycle and provides greater freedom in part design. In practical use, a thermoplastic elastomer is evaluated not only by its softness. For a finished product, the critical factors are Shore hardness, elastic recovery, compression set, flex resistance, abrasion behavior, contact with lubricants or cleaning agents, adhesion to rigid polymer, color stability, surface feel and repeatability of properties in series production. How thermoplastic elastomers differ from rubber Classical rubber obtains its properties after vulcanization, that is, chemical cross-linking of the polymer structure. Thermoplastic elastomers develop their elastic behavior through the physical structure of the material: soft elastomeric segments and harder thermoplastic domains. This allows TPE to be melted, formed and reprocessed, which is not possible for most vulcanized rubbers. For the manufacturer, this means the ability to produce flexible parts on standard thermoplastic equipment, combine a soft layer with a hard body, reduce the number of processing operations and control part geometry more precisely. At the same time, TPE is not always a direct replacement for rubber: for high temperatures, aggressive environments, extreme compression deformation or long service life, the material family must be selected correctly. Main families of thermoplastic elastomers Thermoplastic elastomers are not a single material but a whole group of polymer systems. This group includes TPE-S based on SBS or SEBS, polyurethane TPU, polyester TPEE, dynamically vulcanized TPV, TPO, PEBA and other special elastomeric compounds. Each family has its own mechanics, temperature range, chemical resistance and processing behavior. SEBS and SBS compounds are often used for soft overlays, grips, sealing elements, consumer products and parts with a pleasant tactile feel. TPU is chosen where high wear resistance, tensile strength, abrasion resistance and operation under mechanical load are required. TPEE is used in dynamically loaded parts that must retain resilience, shape and service life under cyclic deformation. TPV and TPO can be suitable for parts requiring elasticity, weather resistance, better heat resistance or behavior close to rubber systems, but with the possibility of thermoplastic processing. Therefore, the selection of a thermoplastic elastomer always starts not with the name TPE, but with the operating conditions of the part. Shore hardness and the real performance of an elastic part Shore A or Shore D hardness is an important parameter, but it does not describe the full behavior of a thermoplastic elastomer. Two grades with the same hardness can recover their shape differently after compression, have a different modulus at small deformations, different surface tackiness, different abrasion resistance and different service life under repeated flexing. For seals, compression set and the material's ability to retain sealing force over a long time are important. For grips — tactile feel, coefficient of friction, resistance to sweat, contamination and surface aging. For flexible technical elements — fatigue endurance, shape stability, service temperature and behavior after thousands or millions of deformation cycles. Adhesion to rigid polymers and multi-component molding Thermoplastic elastomers are often used in 2K molding or overmolding, where a soft layer is formed on a rigid substrate of PP, PE, ABS, PC, PA, PBT or another polymer. In such parts, not only the softness of the TPE matters, but also stable adhesion to the base material after cooling, flexing, friction and service load. Insufficient adhesion can lead to delamination of the soft layer, loss of tightness, edge tearing or unstable part performance. Therefore, for soft overlays, sealing zones, buttons, grips and combined housing parts, the TPE must be selected to match the specific rigid polymer, molding temperature, contact geometry and molding conditions. Sealing, compression set and long-term shape recovery For sealing parts, a thermoplastic elastomer must not only compress but also retain the ability to recover its shape after prolonged load. If the material has a high compression set, the seal gradually loses its sealing force, which can lead to loss of tightness, play or unstable operation of the assembly. In such tasks it is important to account for temperature, compression duration, thickness of the sealing element, contact with water, lubricants, cleaning agents or other environments. A material that works well as a soft overlay on a grip will not necessarily be a good seal in a technical assembly. Wear resistance, friction and surface behavior In many products TPE acts as a contact surface: with the hand, another part, the floor, a cable, metal or an abrasive environment. Therefore, the coefficient of friction, resistance to abrasion, contamination, dust, scratches, marks and surface aging become important. For wheels, rollers, dampers, overlays and support elements, these parameters can be more important than the nominal hardness. TPU usually has significantly better wear resistance and strength than many soft SEBS compounds, but it can have a different tactile feel, different processing and higher drying requirements. SEBS can be better for a soft touch, flexibility and economical parts, but it does not always withstand abrasive load or intensive mechanical work. Temperature, chemical environment and aging The temperature range and chemical resistance of thermoplastic elastomers strongly depend on their family. Some materials work better in soft consumer parts, others in contact with lubricants, others in dynamic assemblies or at elevated temperatures. Contact with fuels, oils, cleaning agents, sweat, cosmetics, water, salts or UV radiation can affect different TPE grades differently. For outdoor products, UV stability and weather resistance are important. For technical seals — environmental resistance and compression set. For cable jackets — flexibility, abrasion, temperature and regulatory requirements. For medical or consumer products, odor, additive migration, food contact, sanitary requirements or surface feel may be important. Processing of thermoplastic elastomers TPE can be processed by injection molding, extrusion, coextrusion, blow molding, calendering or multi-component molding. However, the processing window depends on the specific material: TPU and TPEE often require careful drying, SEBS compounds can be simpler to process, and TPV has its own requirements for temperature, shear and melt stability. In injection molding, flow, absence of flash, surface, shrinkage, demolding and dimensional stability are important. In extrusion, the critical factors are profile uniformity, surface, absence of blocking, thickness stability, and behavior during winding and cooling. In 2K molding, the bond strength between the soft elastomer and the rigid base is additionally evaluated. Typical applications of thermoplastic elastomers Thermoplastic elastomers are used in parts requiring flexibility, elasticity, a soft surface, sealing or damping: seals, gaskets, cuffs, flexible inserts and sealing elements; grips, soft overlays, buttons, anti-slip surfaces and soft-touch elements; hoses, tubes, profiles, cable jackets and coextrusion products; wheels, rollers, shock absorbers, dampers and support elements; soft components of consumer, sports, medical and technical products; parts for 2K molding with adhesion to PP, ABS, PC, PA, PBT or other polymers; elastic elements for automotive, electrical and industrial applications; products where rubber needs to be replaced with a thermoplastically processable material. Critical parameters for selecting a thermoplastic elastomer For the correct selection of a TPE, it is necessary to evaluate not only Shore hardness but the full technical task of the product: material family: SEBS, SBS, TPU, TPEE, TPV, TPO, PEBA or another system; Shore A or Shore D hardness and the actual elastic behavior; compression set and shape recovery after prolonged compression; fatigue endurance under flexing, tension or cyclic deformation; resistance to abrasion, friction, contamination and surface aging; service temperature range and behavior in cold conditions; contact with lubricants, fuels, water, salts, sweat, cosmetics or cleaning agents; the need for UV stabilization, weather resistance or color stability; adhesion to the rigid polymer in overmolding or 2K molding; processing method: molding, extrusion, coextrusion, blow molding or a special technology; sanitary, food, medical or regulatory requirements, if they are important for the product; batch stability, repeatability of color, surface and mechanical behavior. Selection of thermoplastic elastomers from Material Wizard Material Wizard selects thermoplastic elastomers according to the real function of the part: hardness, elastic recovery, compression set, contact environment, temperature, wear, surface tactility, adhesion to rigid polymers, processing method, product geometry and the economics of series production. This approach makes it possible to choose not simply a soft polymer, but a technically justified elastomeric system for a specific product: a seal, grip, jacket, profile, damper, overlay, 2K part or a technical element with service-life requirements. For the manufacturer, this means predictable material behavior in processing, assembly and operation.