Materials Bacteriostatic
Materials Bacteriostatic PLA compound for 3D printing Material innovation at Benvic takes the fight directly to Covid 19 All around the world today, resources are being mobilized to fight the novel Corona virus (SARS- CoV-2) and the related disease Covid 19; from sanitary systems to industries and citizen actions. All nations are committed to find solutions that can reinforce and support medical procedures, hospitals and health structures. At Benvic (Chevigny Saint Sauveur, France) the spirit of innovation was mobilised immediately - in order to help manufacturers meet the worldwide crisis with fast-track products and healthcare solutions. The company’s range of PLA compounds, for example, has seen high demand, particularly from the additive manufacturing sector who are supplying to the medical frontline. Additive manufacturing, one process of which is 3D printing, has been proven to be an excellent way to make products instantly, and in a decentralized manner. Many kinds of machines in different laboratories, companies, universities and healthcare professionals can reproduce the same part in order to meet unexpected demands. These additive-made parts can also be easy modified on the CAD software and adapted to circumstances without constraints. Additive manufacturing can be undertaken using various polymer grades. However, the biopolymer PLA is most used in common practice and is very well adapted to manufacturing from smaller machines. Benvic, with its biopolymer range Plantura ® , has already developed an extensive range of PLA compounds for compostable and durable use. Benvic is already supplying many filament producers in their additive manufacturing and has boosted its support to these companies during this Covid 19 crisis. In addition, Benvic has developed technology that allows these polymer compounds to benefit from bacteriostatic properties. The inbuilt feature of the new Benvic additive prevents bacteria proliferation on any kind of plastic surface, particularly for those who are expected to be in contact with body skin. Benvic’s bacteriostatic polymer has been tested according to the international quality standards, ISO22196 and ISO 846. “We have developed this new material, with our filament partner, and within quite a short time for an end-customer in Italy who is print protecting masks,” says Camilla Bortolon, account manager for Plantura product range. “Such masks are customized in line with the user morphology which is only made possible via the 3D printing process. Our new materials can make these masks reusable simply by changing the filter. In this way we can optimize resources in order to fight the virus,” she adds. The Benvic Plantura range covers rigid and soft materials that can be used by any filament maker or by any extruder. The bacteriostatic additive - a technology that is exclusive to Benvic - can also be provided as masterbatch or compound for thermoplastic polymers. The speedy development of the Plantura range illustrates Benvic’s ability to quickly create and supply high-grade polymers with just the right characteristics to areas of urgent manufacturing need, and thereby help save lives. Benvic is an independent group and a leader in European polymer compounding for various markets. Benvic has production facilities in France, Italy, Spain, Poland and UK. MT www.benvic.com Magnetic for Plastics www.plasticker.com • International Trade in Raw Materials, Machinery & Products Free of Charge. • Daily News from the Industrial Sector and the Plastics Markets. • Current Market Prices for Plastics. • Buyer’s Guide for Plastics & Additives, Machinery & Equipment, Subcontractors and Services. • Job Market for Specialists and Executive Staff in the Plastics Industry. Up-to-date • Fast • Professional 32 bioplastics MAGAZINE [04/20] Vol. 15
Materials Gluten makes PLA tougher Joint project GLUPLAST successfully completed at KUZ The biobased and biodegradable plastic PLA has a very high strength of up to 70 MPa and an extremely high stiffness of up to 6 GPa. However, it is brittle without the addition of suitable additives, which greatly limits its potential applications. Current measures to increase plastic deformability and thus toughness mainly concern the blending of PLA with elastic degradation-resistant polymers based on petrochemical raw materials, such as thermoplastic polyurethanes or ethylene copolymers. Within the framework of the joint project GLUPLAST, funded by the German Federal Ministry of Economic Affairs and energy (BMWi), the Kunststoffzentrum Leipzig, Germany (KUZ) and its industrial partner CompraXX (Brehna, Germany) have succeeded in modifying the impact resistance of PLA by means of the natural material wheat gluten. In the project, the cross-linking tendency of the gluten during heat treatment was to be used for the production of a crosslinked elastomer phase, which is finely distributed within the PLA matrix as a result of the blending process using a twin-screw extruder. This leads to a significant increase in the toughness of the base material PLA with given adhesion. Influencing the gluten crosslinking The cross-linking of gluten starts already at a temperature of approx. 80 °C. PLA blends containing gluten, which were prepared at 160 °C, initially showed an insufficient degree of fragmentation of the gluten phase. Therefore, the intensive and rapid temperature-related cross-linking was opposed to a significant reduction of the phase diameter and thus to fine fragmentation. Hence, the elongation at break (approx. 1.4 %) and notched impact strength (approx. 1.5 kJ/m²) were observed to be clearly below the PLA level. In order to achieve a finer distribution of the gluten phase in the PLA matrix, two approaches were pursued at the KUZ: 1. temporary suppression of the cross-linking by adding chemical additives, 2. weakening of the cross-linking by diluting the wheat gluten with flour. Materials for the generation of gluten-containing polymer blends 1. bioplastics: PLA Ingeo 6202D, PLA Ingeo 3001D, PLA Blend Bioflex 6514 (reference), 2. natural product containing gluten (GN): Wheat gluten (protein content of approx. 85 wt.%, GN_85), wheat flour (GN_10), gluten flour mixture (GN_40), 3. plasticizer: Glycerol (GL), 4. compatibilizer (and viscosity reducers): oxalic acid (OA), 5. reducing agent, antioxidant, trapping reagent (RAT): Sodium hydrogen sulfite (SHS), acetylsalicylic acid (ASA), L-cysteine (LC). Positive influence on the mechanical properties The aim of the GLUPLAST project to enhance the impact strength of polylactide (PLA) by means of gluten-containing natural substances (GN) was achieved. PLA with an elongation at break of approx. 3.5 % and a notched impact strength of approx. 2 kJ/m² was selected as reference. By adding the GN to the PLA, the elongation (here up to 30 %) and notched impact strength (4 kJ/m²) was be positively influenced. The values here were clearly above the PLA level. The blend mechanics also shows a strong dependence on the protein content of the GN phase (Figure 1). Fig. 1: Stress-strain diagrams for PLA_6202 blends with 40 wt.% GN_10, GN_40 and GN_85; a): with 4.5 wt.% RAT, b): with 4.5 wt.% RAT and OA A finer distribution of the GN in the PLA matrix was achieved on the one hand by lowering the protein content of the GN and on the other hand by adding chemical additives (RAT), such as sodium hydrogen sulphite, L-cysteine and acetylsalicylic acid. A significant improvement in phase adhesion and thus PLA blending could be achieved by the addition of oxalic acid to the GN. The gluten content in the blend was preferably 40 wt.%. The material mechanics achieved in the project is positively evaluated by the partners. Successful material testing in the injection moulding process The gluten blends can easily be processed by injection moulding, see Figure 2. The browning of the material caused by the Maillard reaction, which increases with increasing protein content of the natural product phase, can be concealed by the addition of colour batch. The industrial partner CompraXX aims to market the research results. Compraxx was able to successfully transfer the results from laboratory to pilot plant scale. The combination of PLA with wheat gluten results in interesting material properties, which enable exciting applications in the field of household and office products, for example. MT www.kuz-leipzig.de Fig.2: Injection moulded yarn spools (dyed yellow) made of PLA_6202/GN_40 (60/40 w/w) bioplastics MAGAZINE [04/20] Vol. 15 33
