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bioplasticsMAGAZINE_1405

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bioplasticsMAGAZINE_1405

Hopper Extruder Spinning

Hopper Extruder Spinning head Temp [°C] Rear Front Spinning pump [U/min] Extruder Speed [U/min] Zone 1 Zone 2 Temp (°C) Zone 3 Temp (°C) Zone 4 Temp (°C) Zone 5 Temp (°C) Die plate [°C] Speed m/min Godet 4 Speed m/min Godet 3 Potentiometer Potentiometer Temp(°C) Texturing Speed m/min Godet 2 Potentiometer Cooling air speed Cooling duct Cooling-air Temp (°C) Potentiometer Potentiometer Temp(°C) Temp(°C) Spinningoil Speed m/min Winder Chill roll Cooling-air Temp (°C) Godet 1 Potentiometer Potentiometer Potentiometer Programming Stand by button Temp Temp ok Extruder Spinnp. Spinning pump on off Extruder on off Speed Spinning pump Potentiometer Spinning pressure control (bar) Fig. 2: Flow diagram of spinning machine (Source: Grafe) The first three curves (from top to bottom) show the thermal absorption behaviour of the carbon-black coloured PA6 yarn. The varying absorption behaviour is due to the varying concentrations of carbon black. The carbon-black coloured yarns heat up faster than the IRT coloured yarns within the same time period. A uniform end temperature (approx. 40-55°C) is attained after approximately 100 seconds. www.grafe.com By: Carlos Caro Project leader GRAFE Advanced Polymers GmbH Blankenhain, Germany PA6 heats up faster than PA66. The degree of (IRT) thermal transmission (lower curves) depends on whether there is enough colourant and whether the UV and VIS ranges are completely or partially absorbed. The heat-up speed in the same time period is much lower, the uniform end temperature of maximum 40°C is attained only after 4 minutes (in comparison to 100 seconds for the carbon-black coloured yarn). The results show that the temperature differences between IRT yarns and carbon-black coloured yarns are between 10 and 15°K. One must, of course, consider the concentrations of carbon black and of IRT active colourants in the yarn. Further work is needed, e.g. formulations as compounds (dosing 100%) or as masterbatch (dosing 7-10%), optimization of measuring methods to determine thermal absorption under conditions of use and finally using the formulation for PLA applications. Generally speaking, the cooling down effect is good. However, this new process places very special technical demands on the formulation, fiber spinnability and measuring methods. • 60 50 40 30 20 10 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Time in sec (*10) Fig. 4: Increase in temperature as a function of time (Data source: Nylstar Spain) PA6 PA6 PA6.6 Cool-1 Cool-2 18 bioplastics MAGAZINE [05/14] Vol. 9

Fibres & Textiles New biobased monofilaments Technical textile market is very traditional and very high demanding, in terms of performances, quality level, prices and compliances. The traditionally used polymers, at least for what is related to the monofilament extrusion and spinning, are all coming from oil (Polypropylene, Polyesters, Polyamides are the main ones). In 2009 Sider Arc (Cornaredo, Italy) research and development team started working on new polymeric materials for monofilament spinning, looking towards the direction of bio or green. The aim of this activity was to select new materials (coming from renewable resources) and try to get monofilaments with the same performances of the standard oil derived materials. The first polymer Sider Arc started working with was PLA or polylactic acid. The reason for this choice can be found in its chemical nature: the material is coming from renewable resources but it’s a thermoplastic biopolymer (therefore available on the market and amendable by additives). The hydrolytic degradation leads to products that can be easily assimilated by fungi or bacteria, making the difference in specific end-uses. PLLA polymer (coming from the L-lactide isomer) is the one that Sider Arc started to process, due to the higher cristallinity (about 37%) and to the slow degradation process. In terms of polymer processing, the critical point for PLA extrusion is directly related to the materials sensitivity to hydrolysis: drying must be accurate and water content has to go down to ppm level, otherwise the molecular weight will be too low, and the melt viscosity won’t be enough for the spinning. Rheological behaviour can be considered comparable with polyolefins, with a little bit lower melt elasticity. Crystallization rate, temperature control in the stretching phase and thermo fixation are, together with the selection of the right monofilament spin finish, are the most important issues for extrusion and polymer processing into yarns. Biolene monofilaments, made with 100% PLA polymer, are part of Sider Arc’s range of products since end of 2009, the actual diameter range is from 50 to 200 µm, mainly developed for the medical market, for applications such as tissue engineering /recovering of healing tissues, where the advantage of a material which is radio transparent and not toxic is required. Further applications for these monofilaments are in the spacer fabrics market (3D fabrics), due to the properties of stiffness and elastic recovery, or in hot liquid filtration and tea bags (finest counts) and in the 3D printers technology (coarser counts). In the last two years Sider Arc started evaluating also new sources for the polymeric materials. Green HDPE (made from sugar cane based bio-ethanol): The idea behind is to have monofilaments with the same performances of the yarns coming from oil-based polyethylene, but obtained with ecological processes. The development work done by Sider Arc R&D staff in this case is with the suppliers (polymer producers) to have the right grade for monofilament extrusion, and on the spinning – stretching process to get the same mechanical parameters and dimensional stability that can be achieved with the standard grades. Applications for these monofilaments can be found in shading and protective nets, coated nets for pipes (protection against corrosion), ropes, clothes labelling. The described developments (as well as other developments with e.g. recycled PET) are starting from tradition, but they’re running in the direction of green, with the aim to grant to the technical textile market the highest possible quality and the best possible performances, but with sustainable monofilaments. MT www.siderarc.com tensile stress [cN] 2.500,00 Fossil based HDPE chips 2.000,00 1.500,00 1.000,00 Green HDPE chips 500,00 0,00 0 10 20 30 40 50 60 70 80 Elongation [%] Comparison between HDPE monofilaments coming from oil derived grades and from green sources. Tensile test on 0.25mm diameter monofilaments. bioplastics MAGAZINE [05/14] Vol. 9 19

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