The State of TPEs Part Two
TPEs further edge into soft PVC’s market share
Thermoplastic elastomers are a popular material of choice due to their beneficial properties – soft touch, flexibility, recyclability, temperature resistance, and the ability to over-mold onto hard substrates, among other attributes. Often, thermoset rubbers or silicon are the incumbent material being replaced.
And while TPEs have long replaced soft PVC in automobile interiors, a conflux of consumer tastes, environmental concerns and regulation are opening new markets for TPEs to take foot.
Health concerns regarding the use of phthalate plasticizers in some soft PVC remain a hot topic – the European Union is currently reviewing restrictions on four phthalate categories, and many U.S. retailers and manufacturers have already limited or banned their use in items like toys or baby products. Consumers are also becoming more aware of the possible health risks associated with phthalate plasticizers used to soften PVCs – the smell emanating from a new shower curtain could signify more than just an unpleasant odor.
Star Thermoplastics Tom Dieschbourg says that in many ways soft PVCs and TPEs are not natural competitors, but “when the government or when society determines they want a different or better product, then you have to address that. Five or 10 years ago, Walmart decided they weren’t going to have any more plasticized PVC baby bottle nipples. Whatever their decision making process was, they made that decision, and so they had to convert everything over to TPEs. When the Europeans decided that hydrochloric acid from the incineration of PVC had an adverse effect on their incinerators and (contributes to) acid rain, then they drove that.
“I definitely expect to see more regulation, I would just hope that as the regulatory bodies get involved that they try and add common sense into it also. PVC has been used in the medical industry in the U.S. for many, many applications, and they have done that for 40 or 50 years and they have no data to report any adverse effects. So I’m not pro-PVC, but I’m pro-rational thinking.”
Use in Consumer Products
Whether or not phthalates do cause real-world health problems, TPE’s properties themselves are often making the material a suitable replacement for soft PVCs, especially with consumer products. And even though many soft PVCs do not use any phthalates as a plasticizer, the health concerns have cast a shadow over the entire category.
The choice to use TPEs is made both for “the environmental issue, and the performance,” says Guenter Scholz, senior manager in TPU product development, BASF. Take, for example, a smart phone’s power cord. “You bend it often, and PVC cables start to break very early, and that’s not an issue with a TPU.”
The mechanical durability of TPEs is also highlighted in low temperatures. Soft PVCs begin to fail around the freezing point.
“If you were buying jumper cables for your car and you bought the cheap PVC-based ones, over the winter your cables are going to crack and bend, because the PVC does not have the low-temperature flexibility,” Dieschbourg says.
TPE’s temperature resistance extends in the other direction as well, operating up to 150 degrees Celsius, depending on the formula, according to KRAIBURG TPE Corporation Distribution & Marketing Manager Katherine Olano. “PVC cannot be used in high temperature applications because it will generally start to degrade at 135 degrees Celsius.”
PVC does have its strong suits as well, which is why it’s still one of the most-used plastics in the world. It’s fire retardant, and cheaper than TPEs, in general. It’s ideal for cable jacketing installed behind a wall or other stationary location where it will not crack nor require abrasion resistance. But for items that humans regularly interact with, TPE’s benefits are clear.
“I would say that, no doubt about it, PVC is a lower cost item and it’s a trade off on your value,” Dieschbourg says. “If you don’t need that grip, if you don’t care about it, if it just needs to look like a grip and you don’t want that better feel, then (soft PVCs) are going to be a little bit less expensive, and it will still look the same.”
That can make a big difference for a consumer doing laundry, trying to grip a dryer’s knob after transferring the clothes from a washer.
“Your hands are wet, the knob doesn’t have a good grip on it,” Dieschbourg continues. “They used to be PVC and they used to look like it was soft. But they’re no longer slippery, they’re TPE.”
For high-volume applications like electrical boots that were historically molded from PVC for its low cost, manufacturers are seeing the benefit of using TPEs, says Elastocon TPE Technologies President David Barkus. “Our materials are less destructive to your processing equipment and tooling. You don’t have the chlorine or the ingredients in the formula that attack your metal surfaces.
“So again, processors look beyond the low cost of (PVC) and evaluate faster processing, higher flow, faster cycle times and less abrasion to the equipment, too.”
Barkus adds that processors who work with several different materials might avoid PVC due to concerns that machinery is not properly cleaned before they run a different material through the line.
“Whether it’s a phthalate or non-phthalate PVC, I think certain molders and processors assume they’ll eliminate PVC from their raw material list completely,” he continues. “They don’t even allow it in the door, that way they don’t have to carry the potential burden. Largely because the end customer has a concern about it, so they’re the ones who are kind of dictating they don’t want it, they don’t want to be around it.”
Among other applications, Scholz sees opportunity for TPEs to replace PVCs in the market of printed films used for logos and text on the side of police cars, taxi cabs, billboards, buses and other objects that require abrasion resistance.
“In that case, TPU has big potential, but only when there is a high mechanical impact on these surfaces where PVC is not good enough,” he explains. “PVC is not really stable against sunlight and longtime aging. When you look at the car body, where you need resistance again stone hits or these things, and when you have a long-term relation of sunlight and high temperature, PVC is not the best in that case. TPU is coming up slowly, but it’s coming up more and more.”