A new polyamidedeveloped specifically by BASF for water-assisted injection molding (WAIM) is being actively used by Teklas, a Turkish automotive supplier. The complex-shaped tubes that Teklas is currently developing for almost all large European automobile
manufacturers are used in the engine compartment for cooling water, air and oil.
WAIM is a good fit because the inner channel must be extremely smooth so fluids can move easily. Other critical requirements are low pressure drop and good chemical resistance. With WAIM, the walls thicknesses are consistently uniform and as thin as possible to hold down resin costs.
Water-assisted injection molding uses a fluid under pressure to core out a hollow plastic part in the mold. Sounds like gas-assisted injection molding? Yes, but with a big difference. The thermal conductivity of water is 40 times greater than gas; its heat capacity is four times greater. That translates into a 50% faster cooling cycle time than with gas-assist molding. Water has higher viscosity than gas and is incompressible. That means that plastic is compressed uniformly into thinner walls – approximately 25% thinner than in typical gas-assist molding. One specific—and important benefit for the automotive tubes—is the uniformity of wall thickness around bends and other geometric shapes.
That’s a big advantage because as the number of car models increases, so do the constraints within the engine compartment. design engineers are developing very specific, integrated solutions. Use of plastic tubes in place of the heavier metal tubes results not only in weight savings, but also eliminates the need for expensive metalworking equipment.
To date BASF has had success using WAIM with polyamide 6 polyamide 6/6, polybutylene terephthalate (PBT) and polyethylene terephthalate (PET).