Dec 13 2005
BASF has introduced applications for its Elastollan Lo-Tac thermoplastic polyurethane (TPU) technology in cured-in-place piping used to rehabilitate aging pipes.
“Small towns and big cities alike are concerned about their water infrastructure due to years of neglect to pipes installed many decades ago,” said Luc Lupien, Senior Market Development Specialist for BASF’s Elastollan TPU business in North America. “Many sewer pipes are cracked and severely leaking, allowing groundwater to infiltrate sewer systems, have joints out of place, or are clogged by tree roots. The costs to dig up old pipes and replace them can be astronomical.”
Cured-in-place pipes were first developed in the 1970s to repair sewer systems without having to replace old piping. In early applications, a tube made from TPU was laminated with a polyester-based felt, with the felt facing the inner side. The felt was then impregnated with an epoxy resin or a polyester thermoset resin, and the saturated pipe would be inverted into the old pipe. Heat was then introduced to cure the resin to affix the replacement tube to the original pipe wall, resulting in a rehabilitated pipe that can last for several decades.
However, air pressure is becoming the preferred method to invert the replacement tube to the original pipe because it is more efficient and eliminates the need to handle large quantities of water to invert the tube. Water has a lubricating effect on TPU to offset its inherent property of tackiness. The absence of this lubricant in the air pressure process resulted in the TPU liner reverting to its tacky nature, which made it difficult to invert, especially in smaller diameter pipes. This diminished the attractiveness of TPU for cured-in-place piping.
“BASF developed a solution with our Lo-Tac technology this year at our operations in Wyandotte, Mich., that will make Elastollan TPU more attractive for cured-in-place piping projects,” said Lupien. “Our Elastollan Lo-Tac TPU features low tackiness, good adhesion, contact transparency, good aesthetics and process efficiency. The technology also offers the performance properties of standard TPUs, such as resistance to abrasion and heat.”
According to Lupien, typical techniques used to lower the inherent tackiness and coefficient of friction in TPU, such as adding lubricants, waxes or inorganic fillers, negatively impact performance and aesthetic properties of finished products. For example, lubricants and waxes tend to bloom to the surface over time, which could be detrimental to the product’s adhesion characteristics. Adding inorganic fillers can diminish or eliminate transparency.
“Through BASF’s patent-pending, proprietary technology, Elastollan Lo-Tac TPU products are manufactured with a very low coefficient of friction and contact clarity without incorporating any lubricants, waxes or inorganic fillers that cause blooming or affect transparency in end products,” said Lupien.
“With its low tackiness and low coefficient of friction accompanying the performance properties of conventional TPU, Elastollan Lo-Tac TPU is emerging as a material of choice for cured-in-place pipes,” he said.