While most articles or references to thermoplastic elastomers credit Kraton with the introduction of TPEs (for footwear), the real credit (in this author’s opinion) for the founding and ongoing success of TPEs goes out to several people, governments, and firms, such as:
- Charles Goodyear, who, back in the 1840s, was determined to overcome the two major flaws of natural rubber: It became solid and cracked in the cold of winter, and it melted into a “goo” in the heat. Whether on purpose or serendipitously, when Goodyear uniformly heated sulfur-fortified rubber at a relatively high temperature, he created melt-proof, reliable, “vulcanized” rubber.
- Germany’s discovery prior to World War II of SBR (styrene-butadiene rubber, first dubbed “Buna S”), and the USA’s manufacturing of SBR during the war to replace Southeast Asian supplies of natural rubber.
- Monsanto, with its highly aggressive introduction and marketing of Santoprene (technically a thermoplastic vulcanizate) in the 1980s (Santoprene is now offered by AES). Why the credit to Monsanto? Within the material’s first year, the firm and its marketing people published 26 actual customer testimonial stories, produced myriads of literature, created and published 15 or so ads, and put highly trained sales personnel in the field. The company even convinced the industry’s leading media and their directories to add a new plastics category: thermoplastic elastomers.
- GLS Corporation, in the late 1980s, for taking TPEs a step further by encouraging companies to challenge GLS to develop specialized formulations for new and unique applications—dozens to hundreds of them. As the company’s customers grew, so did the sales of TPEs.
- And a host of smaller firms, including spinoff firms (like Star Thermoplastics) started by people who once worked for Shell’s Kraton, GLS, and Monsanto. Many of these firms, starting in the early 1990s, have carried the torch into numerous other industries by continuing to develop specialized formulations for new applications. Why have they been successful? As the older, larger TPE firms chose to concentrate selling off-the-shelf formulations in larger quantities with minimum buys, the startups, with their variety of labs and R&D resources, filled the void with customization services.
Yesterday & Today
As referred to above, the actual founding of what was to evolve into the family of TPEs goes back nearly two centuries ago when Charles Goodyear first crosslinked rubber by vulcanization. Yet even his early efforts were preceded just slightly by Thomas Hancock who was able to reduce the molecular weight of rubber by milling.1
In more recent times, during World War II, Germany was able to polymerize dimethyl butadiene to produce a substitute for natural rubber from Asia. And more recently, around 1975, ethylene propylene diene monomer (EPDM) in the elastomer phase was cross-linked during the mixing process (called dynamic vulcanization), resulting in the development of thermoplastic elastomers that were soft and had all the beneficial and required properties, features, and benefits of both plastic and rubber.
Today, there are six distinct types of TPEs, many of which require vulcanization (as does rubber) to be manufactured: styrenic block copolymers (SBCs) and blends, copolyesters (COPEs), polyether block amides (PEBAs), thermoplastic polyurethanes (TPUs), thermoplastic vulcanizates (TPVs), and thermoplastic olefins (TPOs). And, as new alloys come on the market, the potential for new types or families of TPEs and applications are boundless. Each type or family of TPE has similar characteristics but offers different features and benefits such as recyclability (in most cases), heat resistance, durability, elongation, abrasion resistance, clarity, etc.—and they all can be produced using standard molding or extrusion processes.
During the 1990s and into the first 13 years of this century, things literally exploded for TPEs and TPE sales, given the needs of the automotive industry to reduce weight and for consumer products to be differentiated—plus a call for better-performing and better-looking products (power-drill handles, for example). Given these needs to substitute better materials for old ones, and for lower-cost ways to produce them, TPEs grew at the rate of 6% a year through 2013.
Now, with up to 4 million tons of TPE formulations being sold and consumed worldwide annually, and with better compounds and more applications coming out almost daily, it’s expected that TPEs will continue to grow through 2018 at an expected rate of 6.0 to 6.3%—becoming a $23.9 billion industry, with the U.S. market expected to reach $15.3 billion. Much of this growth will come as a result of increased automotive/transportation and healthcare demands.
As noted at the beginning of this article, much of the growth of modern TPEs in the 1980s and beyond can be attributed to many firms offering extensive laboratory services. They’ve helped designers, manufacturers, and marketers with specialized (and sometimes proprietary) formulations for new and often unique products or applications.
Then something strange and foreboding happened: larger plastics firms and compounders, as well as investment groups, saw TPEs as a “cash cow.” With their purchase of medium-to-large TPE compounders, the creation of specialized compounds for new applications—and the staffs and willingness to do this—were reduced, with emphasis placed on selling “off-the-shelf “ formulations.
As the North American economy has begun to strongly bounce back, and manufacturing is returning to N.A.’s shores, there most certainly will be a rebound by companies and entrepreneurs to resume the “American Way” by innovating and creating new products with new material needs. At least three new companies (two new to the USA, plus a large PVC manufacturer that’s expanding its product range to include TPEs) are expected to become the latest contenders in the marketplace.
Challenges and demands will be met by smaller-to-medium-size firms, and maybe by the several larger firms coming from Europe and China which most likely don’t or won’t consider R&D as overhead, but rather as a profit center. They are focused not only on meeting customer needs on a one-to-one basis but also, through research, on offering materials and ways that actually reduce the cost of end-product production costs and material usage costs.
The future of TPEs continues to look bright as a major revenue-generator for all parties concerned in the proverbial “art to part” process, from designer to the manufacturer and to the marketer. The markets are primarily driven by demands for higher performance and lighter weights in automotive and other industries, and by the replacement of other materials such as latex and rubber in numerous other products. Calls for TPEs to bond better to more substrates are a constant challenge. Also, there are increasing demands for materials such as TPEs to replace PVC in a variety of applications. And lastly, calls for more TPEs with even better features and benefits, and more eco-friendly formulations and acceptable pricing levels, will offer compounders greater challenges—and opportunities—than ever before.
- G. Holden, Understanding of Thermoplastic Elastomers, Hanser Gardner, 1999.