Thermoplastic expandable microspheres (TEMS), launched in the early 1980s, are spherical particles that consist of a polymer shell that encapsulates gas. They are, in a sense, micro “balloons,” and upon heating, a tremendous volume and density change takes place.
Expancel microspheres expand when heated and have dual functionality as both lightweight fillers and blowing agents. Image courtesy Nouryon.This feature is a consequence of the tailor-made combination of:A thermoplastic shell softening at the glass transition temperature, anda blowing agent with a suitable boiling point (normally a hydrocarbon) simultaneously expanding when heated that, in turn, puts pressure on the shell walls. When inflated, this dramatic increase in volume of the microsphere makes it a great blowing agent, a filler providing surface effects, performance flexibility, and weight reduction.
TEMS are used in food packaging, elastomeric cool roof coatings, shoe soles, fiber and paper board, various applications in the automotive industry, and in products such as sealants, putties, and artificial marble. By combining monomers into various copolymers and the right blowing agent(s), expansion windows from 50° to 300°C can be achieved. Most commercially applicable products, however, expand around 100° to 200°C.
Utilization of TEMS brings several specific benefits, including:
- Controlled foaming for plastics processing;
- weight reduction for automotive parts to improve fuel efficiency;
- improved sound insulation and stone-chip resistance in car underbody coatings;
- better shock absorption/dampening in shoe soles;
- reflective properties in exterior coatings that reduce the need for power-consuming air conditioners;
- displacement of expensive resins, thus reducing material cost;
- Improved feel, filling, and application of cosmetics; and
- protection and insulation of potential bio-based compostable packaging solutions.
Generally, TEMS are employed in design and performance to modify surfaces, provide better insulation, and to add volume without simultaneously adding weight.
While an effective ingredient in the aforementioned products, the possibility of introducing bio-based TEMS will accelerate the development of more sustainable products. In particular, the synthesis of polymers from renewable resources is receiving increasing attention due to the future depletion of fossil fuels and concerns about environmental sustainability. Sustainable solutions are also sought by the younger generations of today, and the industry has the responsibility to look for and bring these solutions to market.
The development of a new bio-platform is seen as a natural step in extending the applicable use of TEMS and to address the future needs of the market. To that end, Nouryon is seeking input and potentially looking to partner with other industry stakeholders to develop concepts for bio-based (and possibly biodegradable) Expancel-branded TEMs, and introducing bio-based raw materials (monomers and blowing agents) into formulations to develop a product that is at least partially bio-derived.
Thanks to the versatility in the formulation of microspheres, where different monomers (building blocks) are combined into co-polymers, it is now possible to introduce numerous bio-based monomers in advanced formulations, gradually increasing bio-derived content without giving up product performance. There is already existing proof of concepts for expandable microspheres comprising bio-derived monomers such as dimethyl itaconate, diethyl itaconate, and ?-methylene-?-valerolactone, as well as a number of acrylate-type monomers.
Together, these monomers give the opportunity to formulate products in the whole temperature range mentioned above. With support from industry around the world, the next, more environmentally-friendly, evolution in TEMS technology is achievable.
Nouryon believes that it is important for our industry to step up to the massive challenge of switching from a fossil-based economy to a circular one. Companies that join forces to develop sustainable solutions can help meet this challenge and make a difference for future generations. About the author
Anna Larsson Kron is Strategic Research & Innovation Manager at Nouryon. For more information, email [email protected]