Design Your Next Product with Soft-Touch TPEs

TPEs are a class of materials that behave a lot like rubber, but process like a thermoplastic.  TPEs consist of “hard” (crystalline) and “soft” (amorphous) phase systems in the form of blends, alloys, or block copolymers.  The “hard” phase is responsible for the TPE’s thermoplastic properties, like service temperature, tensile strength, and chemical resistance, while the “soft” phase gives the TPE its rubber-like properties, including flexibility and compression set.  Together, these hard/soft phase systems combine to offer unique performance and processing benefits. 

There are several families of TPEs, classified by their composition or technology.  Teknor Apex manufactures three types:  Styrenic Block Copolymer Blends (TPE-S or SBC), Polyolefinic Rubber Blends (TPE-O or TPO), and Thermoplastic Vulcanizates (TPE-V or TPV).

Compounding is the process of blending or melt-mixing polymers with additives resulting in a final “compound” or composite plastic with the characteristics, physical and thermal properties specific to that formula or recipe.   As a custom compounder, Teknor Apex develops specialty formulations that satisfy the unique demands of individual applications.

TPEs provide rubber-like elasticity without the design and processing limitations of rubber, and offer performance advantages over conventional thermoplastics like flexible PVC.

Especially in medical applications where silicone can be over-engineered for the application – styrenic TPEs (TPE-S) offer:

• Reduced raw material costs – TPE costs only a fraction of what silicone costs.  Also, TPE scrap can be reground, reused and recycled, for additional savings and precessing efficiencies.
• Improved design flexibility – Unlike silicone, TPEs can be injection molded efficiently into precise parts with intricate designs.  Further, TPEs can be 2-shot molded or overmolded onto stiffer materials like polypropylene (PP) or polycarbonate (PC). 
• No curing agents – TPEs do not require a curing process like rubber does, therefore eliminating the possibility of extractables or leachables due to residual curing agents.
• Improved permeability/barrier properties – silicone exhibits absorption issues with certain proteins and anti-oxidants and is extremely permeable to gases.  These concerns are eliminated with specialty TPEs.  

Thermoplastic vulcanizates (TPVs) offer several advantages, especially in seals and gaskets for the automotive and building and construction industries:

• More Design Freedom – TPVs can be co-extruded into a seal, or over-molded on to PP for an air-tight gasket; using a more cost-effective process (part consolidation, less assembly) resulting in better functionality
• Reduced Environmental Impact – TPVs are lighter weight (reduced shipping costs) and recyclable.  TPV processing is less energy-intensive than EPDM and results in less overall scrap.
• Improved long-term Sealing Performance – TPVs have better aging properties than EPDM and maintain their physical properties better over the life of the part

Styrenic-based TPEs offer several advantages in performance and design flexibility:

• Superior elastic properties
• Better weather resistance and UV resistance
• Greater flexibility at low temperatures, and less susceptible to deformation or cracking.  TPEs have a wider service temperature range versus PVC in general.
• Over-molding and co-extruding over polyolefins (PP, PE) or engineering resins like PC, ABS, and Nylon with excellent adhesion
  
• Lower density, yielding lighter-weight parts. (Specific Gravity = 0.89 versus 1.2)
• Better compression set or higher resistance to deformation due to rubber-like characteristics
• More options for surface feel and finish; TPEs can be formulated for high gloss or a matte, rubber-like finish
• Naturally free of plasticizers, phthalates or halogens

The Shore hardness scales were created to give a common reference point when comparing different rubber and plastics materials.  Shore hardness is measured using a durometer gauge, which uses a needle on a spring to penetrate the sample and provide a reading.  Various scales are used, depending on the hardness of the material:

• Shore OO scale measures extremely soft gel materials
• Shore A scale measures a range of materials from very soft and flexible rubber to semi-rigid plastics
• Shore D scale measures hard rubbers, semi-rigid and rigid plastics

TPEs are unique materials, because depending on the formulation, they can take the form of a super-soft gel or a hard plastic like polypropylene.  With this vast hardness range, all three scales are used to measure the hardness of TPEs, the most common however, is the Shore A scale. 

This comparison table of the Shore hardness scales provides helpful context:

TPE compounds can be used for applications that will come into contact with food.  In order to recommend the right formulation and identify the appropriate regulatory compliance needs for the application, one must consider the following:

1. What type of food will the TPE contact? (I.e: acqueous, dry, fatty, drinking water, alcoholic beverage, acidic, etc.)
2. Is the application intended for single or repeated use?
3. In what countries will the product be made and sold?
4. What temperature will the TPE be exposed to?

Teknor Apex understands that with consumer products like housewares, speed to market is paramount. Therefore, we have an entire range of TPE products that already comply with US FDA and European Union directives for food contact. 

Check out the Monprene® RG Series for Regulated Markets. 

Regulatory changes and cost pressures have paved the way for breakthrough innovations in TPEs for medical applications, replacing materials like flexible PVC, silicone, and latex. 

TPEs are the premier choice for medical applications requiring flexibility or rubber-like elasticity due to their high degree of purity (low level of extractables) and excellent balance of price and performance.

Medalist® TPEs were developed specifically for medical applications. These materials are made with FDA food-grade compliant ingredients, are biocompatible (or ISO 10993-5 compliant) and are manufactured in an ISO-13485 certified facility.  Standard Medalist grades are free of animal derived materials (ADM-free), and are formulated to be free of PVC, phthalates, BPA, and latex proteins.