A new concept for efficient production of thermoformed PLA goods from Brückner Formtec incorporates cast technology with pinning, twin screw extrusion and in-ine thermoforming. Production prices competitive with trays made of PET or PS are promised.
Thermoforming substrates commonly do not require a double side polished surface due to the surface modification during the thermoforming process, the company states. So production by chill roll and electrostatic pinning with only one polished side is possible. In addition, the high heat exchanging capacity of the chill roll is perfectly suitable for PLA, which has a low heat transfer coefficient making it more cost effective than a calendering process.
As PLA is highly hygroscopic, in a regular, off-line production process the sheets often have to be predried before thermoforming. This energy and time consuming procedure can be omitted by the implementation of an in-line system, says Brückner. ”Fully automated, not only the cost of predrying can be eliminated - even higher savings in labour cost for handling and storage can be realized.” Another benefit claimed is very high utilization of the film surface - as no edge trim has to be removed prior to thermoforming, “up to 85 per cent of the surface is used effectively”.
According to Brückner, the low waste percentage from the in-line thermoforming process makes it possible to grind the complete scrap in-line. “Due to the possibility to process up to 30 per cent regrind with twin screw extrusion,” the company states, “direct feed-back into the extrusion process is possible. This means that in the overall process no waste is generated.”
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