In search of metal-free technology for PLA production

Injection Moulding Machine

AIMPLAS, the Plastics Technology Center in Spain, has launched the InnoREX project together with 11 other enterprises and institutes to develop a new technology for polylactic acid (PLA) production that will improve its homogeneity and exclude the use of metallic catalysts.

Although bioplastics is a more sustainable solution compared with conventional petroleum-based polymers, metal-containing catalysts are needed to improve the polymerization rate of lactones, posing a hazard to health and the environment.

In addition to seeking a metal-free manufacturing method, the project aims to obtain energy savings and a single monolayer packaging that may be processed by both injection and extrusion molding.

To ensure short market entry times commercially well-established co-rotating twin screw extruders will be used as reaction vessels.

The reason commercial polymerizations are not yet carried out in twin screw extruders is the short residence time and the static energy input of the extruder, which allows no dynamic control of the reaction, explained AIMPLAS, adding that this is an area that InnoREX would like to address.

The project will try to utilize the rapid response time of microwaves, ultrasound and laser light to achieve a precisely-controlled and efficient continuous polymerization of high molecular weight PLA in a twin screw extruder. Energy savings will be achieved by combining polymerization, compounding and shaping in one production step.

Parallel to all this, the project includes a detailed analysis of the packaging life cycle. The prototype obtained as a result will be a single thin walled monolayer packaging (of a thickness possibly not exceeding a millimeter) intended for the food sector, processed through injection or extrusion to obtain a thermoforming and film packaging to be used when there are demands of lower thickness.

AIMPLAS role within the project is mainly related to the study of processability (injection and extrusion) of developed PLA grades, including mechanical, physical and thermal characterization of prepared packages by injection molding, and extrusion cast-sheet and thermoforming. It will also include an extensive development of additivation strategies.

The project will run till May 2016. A workshop will be organized on October 20 at AIMPLAS’ premises to report on its objectives and developments.