Thermoplastic elastomers (TPEs) have the elastic behaviour of rubber and the processability of thermoplastics. The Freedonia Group has forecast that demand will expand by 6.4% per year to around 2.15 million tons in 2006. There is potential for these new, exciting materials to expand into the much larger thermoset rubber markets. This review includes comparisons between the two material types.
There are three major types of TPE: block copolymers, rubber/plastic blends and dynamically vulcanised rubber/plastic alloys known as thermoplastic vulcanisates. The chemistry of these materials and how their unique properties are achieved are discussed in this review. For example, some of the early types of TPEs were made by blending plastics and rubbers to combine the properties. As these materials are incompatible, separate phases are formed, each conferring different properties on the blend.
There are many developments taking place in this field. Specialist grades are being introduced for specific applications and with unique properties, such as softness or processability. New types of styrene block copolymers have improved high temperature ageing, fluid resistance, elastic recovery and set. New block copolyester TPEs have better blow moulding processability, softness and high dynamic flexing fatigue performance.
One of the advantages of TPEs over thermoset rubbers is that they can be processed by standard plastics processing methods. This review considers rheology, injection moulding, extrusion, blow moulding, thermoforming and other secondary processes.
There are a variety of factors to consider when designing with TPEs, which are discussed here. One particular advantage is in combining components of a product as TPEs can be co-injected or used in overmoulding, reducing assembly steps.
This review is accompanied by around 400 abstracts from papers and books in the Rapra Polymer Library database, to facilitate further reading on this subject. A subject index and a company index are included.
2. Structure of Thermoplastic Elastomers
2.1 Block Copolymers
2.2 Rubber/Plastic Blend
2.3 Thermoplastic Vulcanisates
3. Chemistry of Thermoplastic Elastomers
3.1 Block Copolymer Chemistry
3.2 Rubber/Plastic Blend Chemistry
3.3 Thermoplastic Vulcanisate Chemistry
4. Properties of Thermoplastic Elastomers
4.1 Service Temperature, Ageing and Resistance to Oils
4.3 Abrasion Resistance
4.5 Tensile Strength and Tear Resistance
4.6 Barrier Properties
4.7 Adhesion and Bondability
4.9 Flex Fatigue Resistance
5. Designing with Thermoplastic Elastomers
5.1 Design Concepts
5.1.2 Fabrication Considerations
5.1.3 Component Deformation
5.2 Key Design Parameters
5.3 Comparison with Thermoset Rubbers
5.4 Set and Elastic Recovery
5.5 Stress Relaxation
5.6 FEA Analysis and Hyperelasticity
6. Fabrication of Thermoplastic Elastomers
6.1 Processing and Rheology Overview
6.2 Comparison with Thermoset Rubber Processing
6.3 TPE Fabrication Processes
6.3.1 Injection Moulding
6.3.3 Blow Moulding
6.3.5 Secondary Processes
7. Thermoplastic Elastomers Markets and Applications
7.1 TPE Markets
7.2 TPE Applications
Abbreviations and Acronyms
Abstracts from the Polymer Library Database
Ken Kear has worked as a Senior Applications Specialist with Advanced Elastomer Systems.. He has over 20 years of extensive experience in developing and working with thermoplastic elastomers. He is a member of the Society of Plastic Engineers (SPE). He has written and presented papers on this topic since the 1980s including the 2003 TPE TOPCO.