materials development | Optimising formulations
kind of polymers and additives we want to use,” says Maier. “Then we can set up a DoE that will identify key component interactions. If everything works out, you will be able to enter a range of properties that you want, and the software will suggest how you can achieve them.”
Flame retardants and synergists
As an example, Maier cites experiments to optimize fl ame retardant polyamide compounds. “This can get rather complicated,” he says, in what is something of an understatement. Polymaterials worked with three fl ame retardants, six synergists, and fi ve different additives. It calculated around 270 different compositions for the DoE, which it ran in around two weeks.
An example for combinatorial screening – the stars represent traditional petrochemical polymers, while the black circles represent commercial bioplastic blends and compounds. The coloured circles show bioplastic blends from Polymaterials’ screening programme with bioplastics contents of 50-90%. The size of the symbol equates to the impact toughness (Charpy, kJ/m2
) and dosable fi llers and fi bres is also possible.
Polymaterials is bound by confi dentiality agreements in all its development projects, but Maier says that the company has worked with every large raw material manufacturer in Germany and most in Europe, and it is now also beginning to work with independent com- pounding companies.
“We typically suggest to our customers that we start
with a screening process in which we use a few quick tests to identify components worth looking at, based on previous experience and also on price and availability, and then we run a combinatorial plan to fi gure out what
The accompanying graphs show just how compli- cated things can get, even without taking mechanicals into consideration. With one fl ame retardant/synergist combination, for example, adding more fl ame retardant signifi cantly improves fl ame resistance, while changing the level of the synergist has little effect. But then in glass-reinforced compounds, everything changes. Flame retardance improves if you use more synergist, but the FR addition rate makes little difference. So it may pay to optimize the amount of glass before you optimize the FR system, Maier says.
Why does this happen? Glass fi bres do not burn, so they might be expected to add to the fl ame retardance of a compound; but they may also act like tiny wicks in a candle. Nobody is yet sure.
“We can play around with the property profi le you
want to have,” says Maier. For example, the system will fi nd which compounds achieve V-0, and then they can be optimized for mechanicals. Or the model can be used to target costs of compounds that perform within a set property window. “We can make predictions such as, ‘if you want to base the compound on this matrix material, then V-0 will never be cheaper than X euros/ kilo,’” says Maier. But how much does it all cost? “Pricing is not always
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