Man-made Cellulose Fibres as Reinforcement for Poly(lactic acid) (PLA) Composites International Congress Innovative Natural Fibre Composites for Industrial Applications April 15th-18th 2009 Nina Graupner & Jörg Müssig Hochschule Bremen / University of Applied Sciences Faculty 5 / BIOMIMETICS Biological Materials

Content Use of natural fibres for industrial applications Impact characteristics Production of composites Results Fibre characteristics Composite characteristics Influence of processing parameters Summary, conclusions & outlook

Bio-based materials for industrial applications Biological materials, procedure & application Amount (region) Biodegradable plastics (packaging industry) 60,000-70,000 t (Western Europe, 2007) (permantent use) 30,000-40,000 t (Germany, 2007) Compression moulding with natural fibres, without cotton (automobile industry) 29,000 t (Germany, 2005) Compression moulding with cotton fibres (truck manufacturer) 79,000 t (Germany, 2003) Natural fibre injection moulding and extrusion 3,000-4,000 t (Europe, 2006) (Gahle, 2008.-changed)

PLA/Kenaf – mobile phone + (Nviroplast) (NEC) (anonym, 2006)

Flax / PLA urn by Jakob Winter (Satzung, Germany) (Grashorn, 2007)

PLA/Kenaf spare tire cover made by Toyota Spare tire cover in Toyota RAUM (2003) made from kenaf fibre reinforced PLA (based on sugar beet) LCA on the spare tire cover showed reduced CO2 emissions volume by as much as 90 % compared to conventional petroleum-based plastics Index 100 Carbon neutral effect 50 Petroleum based plastics Bioplastics (Anonym, 2007 )

Problem: Impact Bast fibre reinforced composites mostly display high stiffness and tensile characteristics But: impact characteristics are often the limiting factors for a use as construction materials due to the force elongation characteristics of the bast fibres

Load-strain curves of different cellulose fibres Tensile strength, N/mm² Hemp Cotton Lyocell 800 700 600 500 Lyocell fibres combine high elongation and high tensile strength 400 300 200 100 1 2 3 4 5 6 7 8 9 10 Elongation, %

Impact strength of different composites Kind of fibre Charpy impact strength of composites in kJ/m² Charpy impact strength of neat PLA in kJ/m² Reference 40 % hemp 10 24 (Graupner, 2009) 40 % flax 11 15 (Oksman et al., 2003) 40 % kenaf 9 (Graupner, 2008) 40 % cotton 29 40 % Lyocell 40 30 % Cordenka 70 16 (Bax & Müssig, 2008)

Lyocell as additive for impact improvement Unnotched Charpy impact strength Mixing 50 % hemp and 50 % Lyocell fibres increased the impact strength clearly (Graupner, 2009)

Production of Lyocell/PLA composites Reinforcement: 3 kinds of Lyocell fibres (industrially gained fibres based on 100 % cellulose, density: 1.5 g/cm3) produced by Lenzing AG (Lenzing, Austria) in different fineness (15.0, 6.7, 1.3 dtex) Matrix: Nature Works™ PLA polymer 6202D, density: 1.24 g/cm3, melting temperature 160-170°C, glass transition temperature: 60-65°C (Topkapi) (Packaging International)

Production of semi-finished parts Production of multilayer webs and needle felts with fibre loads of 20 and 40 mass-% and a mass per unit area of 2000 g/m² Single layer web Fibres Positioned multilayer web Needle felt Carding machine Cross layer Needle felt machine (Müssig, 2001)

Compression moulding Pre-cut parts of 300 x 250 mm2 were compression moulded (Rucks, Glauchau, Germany) Pre-heating at 180°C for 10 min Compression moulding with 3.2 MPa at 180°C for 10 min Aluminium slats as spacer (thickness: 2 mm) Demoulding at approx. 60°C

Results: Characteristics of 3 kinds of Lyocell fibres for composite production Fibre width, µm Tensile strength, N/mm² Young´s modulus, N/mm² Elongation at break, % Lyocell 1.3 10.5 46.7 5260 15.3 Lyocell 6.7 23.3 30.9 3744 13.0 Lyocell 15.0 32.5 23.0 3013 11.9 Clear influence of fibre fineness on mechanical fibre characteristics

Results: Tensile strength of composites made from multilayer webs vs Results: Tensile strength of composites made from multilayer webs vs. needle felts Influence of fibre fineness can be seen Composites made from the needle felts show significant higher tensile strength compared to composites made from the multilayer webs

Results: Reduction of fibre mass content of the multilayer webs Tensile strength Reduction of fibre mass content of the multilayer webs lead to increased tensile strength of the composites

Results: Impact strength of composites made from the multilayer webs Unnotched Charpy impact strength Increasing impact strength with raising fibre mass content Composites with a low degree of compaction No significant influences whether multilayer webs or needle felts were used

Results: SEM micrographs of tensile fractured surfaces 40 % Lyocell 1.3 multilayer web/PLA composite 40 % Lyocell 1.3 needle felt/PLA composite 20 % Lyocell 1.3 multilayer web/PLA composite

Results: Influence of process parameters of 40 % Lyocell multilayer web / PLA Tensile strength: 42 N/mm² Young´s modulus: 4142 N/mm² Impact strength: 33 kJ/m² Tensile strength: 82 N/mm² Young´s modulus: 6784 N/mm² Impact strength: 40 kJ/m² - 10 min pre-heating, 180 °C - 10 min compression moulding 180 °C - 10 min pre-heating, 180 °C - 10 min compression moulding 180 °C 3 h pre-drying, 105 °C - 20 min compression moulding 180 °C (Graupner, 2009) Clear inluence on: compaction Process parameters coating of fibres with matrix interfacial interactions between fibres and matrix

Summary, conclusions & outlook Lyocell fibres have great potential as reinforcement (high tensile strength and high elongation at break) Lyocell and PLA fibre are processable with conventional textile and formpressing techniques Semi-finished textile products and process parameters have a clear influence on the composite characteristics Compression moulding times and temperatures as well as the influence of pre-drying and pre-heating are important factors Full potential of Lyocell fibres could not be achieved due to suboptimal process parameters using multilayer webs Needle felts lead to better composite characteristics than multilayer webs An optimised production leads to Lyocell/PLA composites which show high impact properties combined with good tensile characteristics

Nina Graupner & Jörg Müssig Thank you very much for your attention! Nina Graupner & Jörg Müssig University of Applied Sciences Faculty 5 / BIOMIMETICS Biological Materials email: nina.graupner@hs-bremen.de

Acknowledgements We thank … Dr. Sames (Lenzing AG, Lenzing, Austria) for supplying Lyocell fibres Dipl.-Ing. C. Grashorn (IST Ficotex, Bremen, Germany) for supplying PLA Prof. Dr. A. S. Herrmann (Faserinstitut Bremen e.V., Bremen Germany) and G. Gödecke (NAFGO GmbH, Neerstedt, Germany) for support in semi-finished product and composite production the students of the course Materials Research at University of Applied Sciences Bremen – Biomimetics for measuring tensile and impact strength of needle felt reinforced composites

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