Natural Materials for Low Cost Plastic Development

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1 Natural Materials for Low Cost Plastic Development Alan K.T. Lau FIMechE FHKIE FIMMM FIoM FIEAust Professor and Director Product Testing and Analysis Centre Department of Mechanical Engineering The Hong Kong Polytechnic University Kowloon Hong Kong

2 Natural Materials and their Composites Product Development Biomedical Applications

3 Focus Type of Natural Fibre Mechanical Properties Preprocessing Treatment Recycled Fibre Composites Industrial Applications

4 Fibres Natural fibres Man made fibres Plant based fibres (Cellulose or lignocellulose fibres) Animal based fibres (Protein) Mineral Wood Cane, grass & reed Stalk Leaf Bast (Stem) Seed Fruit Wool &Hair Silk Asbestos Fibrous brucite Hard Wood (Oak) Soft Wood (Pine) Bagasse Esparto Canary grass Wheat Maize Barley Sisal leaf Abaca leaf Henequen Flax Jute Hemp Cotton Kapok Rice husk Coir Lambswool Goat hair Angora wool Mulberry silk Tussah silk Spider silk Wollastonite Inorganic whiskers Phragmites Communis Rye Oat Pineapple leaf Ramie Kenaf Milkweed seed Cashmere Yak hair Elephant grass Rice Palm leaf Horse hair Bamboo Human hair Flight feather Down feather

5 Mechanical Properties Strength Elongation at Break E (GPa) Natural Fibers (Mpa) (%) Kenaf Coir Bamboo (*) Sisal Palm (*) Banana Hemp Pineapple Spider silk Cocoon silk (*) Wool Human Hair (Nikifordis et al 1992) (elderly) 4.46 (Young)

6 P. Wambua et al. Comp. Sci. Tech. 2003; 63: Vf = 30%, E-glass/PP (Vf=30%) = 32 MPa Plant-based fibre E-glass Hemp Jute Coir (Coconut) Sisal Banana Bamboo Density (g/cm 3 ) Tensile Strength (MPa) E-Modulus (GPa) Elongation at Failure (%) Moisture Absorption (%) Banana Jute Sisial Bamboo Hemp Coir

7 Ultimate Tensile Strength of PP = 19 MPa

8 PALF bundle in 100 m (with compatibilizer (PEA-g-GMA) Pineapple leaf fibre (PALF) in soy-based biothermoplastic. Liu et al. Green composites form soy based plastic and pineapple leaf fiber: fabrication and properties evaluation. Polymer. 2005;46:

9 Low water absorption Low cost High strength Biodegradable 6-8 months to grow up Bamboo fibre

10 Pre-treatment Polar surface of the natural fibre Hydrophilic fibre Water absorption and diffusion Hydrophobic plastic Incompatible Poor interfacial adhesion 1. Expansion of wet fibre (grey region indicating stress in the matrix 2. Wet composite after stress has been released by molecular relaxation processes 3. Contraction of the fibre during drying Results Decrease the mechanical properties Accelerate the degradation

11 Biopolymer Starch type Cellulose Chitin and Chitosan Bacterial polymer Biodegradation Modes Microorganism Fungi Bacteria (aerobic activity) Enzymes Catalytic activities

12 Polymer Melting Point ( C) Glass-Transition Temp, Tg ( C) Modulus (GPa) a PGA to 12 LPLA >24 DLPLA Amorphous to 16 PCL ( 65) ( 60) 0.4 >24 PDO N/A ( 10) to 12 PGA-TMC N/A N/A to 12 85/15 DLPLG Amorphous to 6 75/25 DLPLG Amorphous to 5 65/35 DLPLG Amorphous to 4 50/50 DLPLG Amorphous to 2 Degradation Time (months) b Polyester to 4.5 Recyclable Epoxy to Reusebale # LDPE 98 to to MPa Recyclable PP to to 1.4 Recyclable a Tensile or flexural modulus. b Time to complete mass loss. Rate also depends on part geometry.

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14 Silk Fiber Animal based Biocomposites Silks (from cocoons and spiders) are kinds of animal based nature fibres which are high strength, bio degradable, commercially available and low cost. This outer layer, silk sericin is a natural macromolecular protein derived from cocoon Bombyx mori, and used to ensure the cohesion of the cocoon by gluing silk threads together. The protein resists oxidation, is antibacterial, ultra violet (UV) resistant, and absorbs and releases moisture easily. The cocoon shells subjected to increasing heat treatments. (starting from left to right): untreated; at 190 C; 250 C; 350 C; 450 C and 550 C for over 0.5 hr. (Zhang et al. J. Appl. Poly. Sci. 2002; 86: )

15 Mechanical properties of silks (silkworm and spider dragline), biomaterial fibers and tissues Materials UTS (MPa) Young s Modulus (GPa) % Strain at break B. mori silk Spider dragline silk Collagen Collagen X-linked PLA Tendon (compose mainly of collagen) Bone Kevlar (49 fibers) Synthetic Rubber

16 Mechanical Property Tests for Silk/PLA Composites Pure PLA PLA (5mm 5% w t.% silk) Young's Modulus (GPa) Hardness (Hv) Flexural Modulus (GPa) Tensile strength and modulus of PBS and five silk/pbs biocomposites (Lee et al. Comp. Sci. Tech. 2005; 65: )

17 Samples Pure PLA 3819 Modulus of Elasticity (MPa) Chicken Feather Fiber CFF/PLA (fiber from upper (flight) portion of feather) CFF/PLA (fiber from lower (down) portion of feather)

18 Samples Failure Extension (mm) Flexural Modulus E (Gpa) Percentage Increase (%) PLA HEMP CFF Silk Bamboo

19 Interfacial Bonding Properties Basically, the mechanical and thermal properties of natural fibre composites are governed by their interfacial bonding properties. Up to date, many studies have been conducted going along this direction to determine or improve their bonding strength. Nanoindentation?? Microdroplet test Single fibre pullout test Microbond test Silane treatment (chemical coupling) Oxidization Surface cleaned by methanol and benzene Natural fibre surface layer (enhancement of the bonding strength with PE coconut (waxy layer))

20 Manufacturing Processes Injection moulding (pellets) Compression moulding (mat and fabrics) Resin transfer moulding (mat and fabrics) Hand lay up (chops, mat and fabrics) Spray lay up (mat and fabrics) Infusion and vacuum bagging (mat and fabrics)

21 Interfacial Bonding Properties Duigou et al. Comp. sci. tech. 2010; 70: Tradition shear lag models Surface Configuration Chemical bonding Mechanical interlocking Polar Hydroxyl (OH) groups Hydrophilic Natural Fibre Hydrophobic Polymer Matrix Wettability Natural Fibre (from filaments to a fibre) Degradation at adjacent region of the fibre Manufacturing processes Surface of coconut fibre with and without removing waxy layer (Brahmakumar et al. 2005; 65: ) Li et al. Comp. Pt A. 2008; 39:

22 Advantages # F.d.A. Silva et al. / Composites Science and Technology 68 (2008) Low cost and light weight (reduction of the cost of products) Non abrasive nature (less impact to the environment) High specific properties and biodegradability Limitations Moisture absorption Poor wettability Large scattering in mechanical properties Not sufficient understanding of mechanisms controlling their mechanical behaviour and failure modes Difficulties in modelling (FEM and theoretical analysis) Damage detectability Acoustic emission Embedded sensor technologies Thermo graphical technologies Sisal fibre (#)

23 Industrial Collaboration The use of recycled plastics for product development Design competition with University s students; Design competition Factory Visit Seminars Consultation Establishment of Standard for quality control of materials; Collaboration Investigation on the basic properties of natural filler reinforced recyclable plastics Research Projects

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28 Recyclable Plastics and their Composites Provide Lightweight and Eco Solutions for Product, Building, Construction, Transportation on and Automobile Engineering Industries