When shopping for lubricants today, advises John Murphy, look for materials that offer a performance 'package' - and don't be put off by the price.
For a long time, compounders have known that the addition of a lubricant can improve the viscosity and flow of the compound. But there has usually been a downside: it also tends to leach out of the compound, with results that may be difficult to predict, but often requiring a cleaning stage before the moulded parts can be printed or painted.
But there has been considerable fundamental work recently on how a lubricant works in a thermoplastic mix. Lubricants usually act by modifying the viscosity of the melt, by introducing different surface energies at the interface between the phases. But simple sticking between the melt and the processing machinery (screws, barrels and dies) can also be a significant brake on throughput (not to mention requiring frequent stoppages for cleaning down), and there has been some development and selection of lubricants directed towards improving this.