Wood & Natural Fibers. Lecture 3 CE Vikram Yadama

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1 Wood & Natural Fibers Lecture 3 CE Vikram Yadama

2 Gross Wood Structure Principal Directions Longitudinal Radial Tangential Stem Components Cambium Sapwood Heartwood V. Yadama,

3 Softwood Anatomy Softwood Tracheids Rays Earlywood Transition V. Yadama,

4 Southern Pine Most Common Species in So. US Abrupt Transition High Mechanical Properties V. Yadama,

5 Hardwood Anatomy Hardwood Tracheids Rays Vessels Vessel Patterns V. Yadama,

6 Aspen Common in Northern Regions of US and Canada Diffuse Porous Low Mechanical Properties V. Yadama,

7 Wood Fibers Long Softwood Tracheids Short Hardwood Tracheids Shortest Hardwood Vessel Elements V. Yadama,

8 Wood Properties Species MOE 10 6 psi MOR 10 3 psi SG Doug Fir So. Pine Yellow Poplar Aspen V. Yadama,

9 Factors influencing wood quality structure microfibril angle chemical composition anatomical features density uniformity of density knots slope of grain amount of sapwood mature wood vs. juvenile wood V. Yadama,

10 Structure microfibril angle effects properties dimensional stability chemical composition Cellulose (40-55%) Hemicellulose (20-25%) Lignin (20-35%) Extractives (2-9%) V. Yadama,

11 Source: Sjostrom 1981 V. Yadama,

12 Source: Sjostrom 1981 O HO O Cellulose HO O OH OH O O OH HO O HO OH O O HO OH O OH HO Crystallinity of wood cellulose ~67-90% (Salmén L., de Ruvo A., 1985, Wood and Fibre Science 17(3): ) Cellulose Homopolysaccharide; Glucose repeating unit; Linear molecules DP can vary between Insoluble in most solvents High tensile strength Aggregate together in bundles to form microfibrils alternate of highly ordered crystalline and less ordered amorphous regions V. Yadama,

13 Source: Sjostrom 1981 Hemicelluloses Repeat Unit- Glucose and other sugars (mannose, xylose, arabinose) Heteropolysaccharide DP ~200 Branched structures Readily soluble in water Composition & structure differ between SW & HW V. Yadama,

14 Source: Sjostrom 1981 CH 2 OH Lignin Phenolic structures Amorphous Highly x-linked (believed to be) Acts as matrix material to cellulose fibers CH 3 O Lignin CH 2 OH CH CH 2 OH CHOH CH CHOH CH 2 OH HO O CH H CH O 3 CO CH CHOH OCH 3 O CH 2 OH CH CHOH CH 2 CH CH OH O CH CH CH 2 O OCH 3 OCH 3 HOCH 2 CH 2 OH O HC OCH 3 CH O CH O CHOH CH 3 O CH 2 OH CH 2 OH OCH 3 O CH CH O CHOH CHOH CH 3 O OCH 3 V. Yadama, 2007 OH OH 14

15 Extractives Termed by method of extraction Water soluble, Ether soluble, etc. Proteins Amino acids Enzymes Toxins (defense proteins) Fats, fatty acids, fatty alcohols Phenols, terpenes, steroids Resin acids, rosin, waxes V. Yadama,

16 Inorganics Silica Crystalline Uptake Exterior exposure (dust, sand, etc) Amorphous Ash Deposited in cell wall Between polymer layers Remaining after combustion at 575 F (301 C) Mixture of different mineral salts V. Yadama,

17 Structure Anatomical features type of pits number of pits types of rays Pit Opening size 0.1 to 2 μm Aspirated or not Lumen size (>10 μm) Cell wall thk: 2-5 μm Piceoid Pits: Aperture is smaller than pit border Pinoid Pits: large window like openings S. J. EICHHORN, J. SIRICHAISIT, R. J. YOUNG, 2001 V. Yadama,

Density Influences properties Influences

18 Density Influences properties Influences processibility Greatly varies within a tree within a stand within species Douglas-fir: Yellow-poplar: between species Uniformity of density Marra, 1992 Southern pine Aspen V. Yadama,

19 Knots Reduces strength properties grade of lumber, veneer Degree of influence depends on size location shape soundness V. Yadama,

20 Slope of grain Grain orientation effects stiffness strength dimensional stability warping Spiral Grain Max. slope of grain 1 in 25 (2.3 deg.) 1 in 10 (5.6 deg.) 1 in 5 (11.4 deg.) MOR Impact bending 96% 95% 81% 62% 55% 36% V. Yadama, 2007 Wood Handbook,

21 Percent Sapwood Juvenile wood vs. mature wood Juvenile wood higher microfibril angle lower density shorter fibers thinner cell walls less dimensional stability warping lower strength properties higher lignin and hemicellulose content; lower cellulose content V. Yadama,

22 Desirable Attributes for Specific Products Product Dimension Lumber Veneer Glulam Wood-strand Composites WPC Property of Importance Stiffness & Strength; Dimensional Stability; Warp; Treatability Stiffness & Strength; Number & Size of Knots; Appearance; Gluability; Peelability Stiffness & strength; Warp; Gluability Compressibility; Gluability Chemical composition; Density & Uniformity; Fiber Properties; Processibility; Permeability V. Yadama,

23 Wood Characteristics Needed for Desired Properties Wood Property Density Stiffness & Strength Dimensional Stability Warp Biological/Chemical Characteristics Sapwood%; Fertilizer; Fiber Properties Density; Microfibril angle; Knots; Slope of Grain Slope of grain; Microfibril angle; Sapwood%; Extractive content Microfibril angle; Slope of grain Gartner, 2005 V. Yadama,

24 Wood Characteristics Needed for Desired Properties Treatability Gluability Peelability Compressibility Chemical Composition Processibility/Permeability Sapwood% Porosity; Extractive Content; Density uniformity; ph & buffering capacity Density uniformity; Slope of grain; knots; Microfibril angle; Growth ring width Density; Cell wall thickness Juvenile vs. Mature wood Extractive Content; Pits; Density & Uniformity; fiber compliance & quality Gartner, 2005 V. Yadama,

25 Natural Fibers Derived from Animal, vegetable, or mineral Usually refers to wood fiber, agro-based bast, leaf, seed, and stem fibers; cereal straws (rice, wheat) Bast fiber (fiber bundles between nodes) Just below the bark also referred to as skin fiber Phloem vs. Xylem Accounts for less than 30% of the stem (Kenaf & Flax) Shive woody inner core (shorter fibers) V. Yadama,

26 Some Attributes Low density (max density of ~93pcf or 1.5 SG) Source for environmentally friendly composite materials High tensile strength Long several meters Low bulk density 2010 expected usage 100,000 tonnes/annum V. Yadama,

27 Types of Natural Fibers Flax V. Yadama,

28 Hemp V. Yadama,

29 Jute V. Yadama,

30 Sisal from leaves V. Yadama,

31 Kenaf V. Yadama,

32 Coir from seeds V. Yadama,

33 Processing Retting - Process to separate bast fiber from woody core - bacterial/enzymatic -- rotting away of inner stalk - chemical sodium hydroxide (uniform quality) - mechanical Breaking Scutching Hackling Combing V. Yadama,

34 Issues Storage & variability in the growing season Can contain fiber nodes weak points Aging Low bulk density Feeding Metering Fiber bridging Higher ash content (silica in rice hull & wheat) Highly variable properties Hydrophilic V. Yadama,

35 Chemical Constituents Similar to wood Cellulose, HC, Lignin Also contain pectins (complex polysaccharides) Source: Clemons & Caulfield, In: Functional fillers for plastics. V. Yadama,

36 Source: Rowell, RM, RA Young, and JK Rowell Paper and Composites from Agro- V. Yadama, 2007 Based Resources. CRC Lewis Publishers, NY, NY. 446pp. 36

37 Summary of Chemical Composition Differs by species, growing, etc. Cellulose Highest- Cotton, Bast, Leaf, and Wood Fiber Lowest- Cereal Straw, Grasses Hemicelloses Highest- Cereal Straw, Grasses Lowest- Cotton, Bast, Leaf, and Wood Fiber Lignin Highest- Wood, Bast Lowest- Cotton, Leaf Ash Highest- Cereal Straw, Grasses Lowest- Wood, Cotton Silica Highest- Cereal Straw, Grasses V. Yadama,

38 Fiber Dimensions Source: Rowell, RM, RA Young, and JK Rowell Paper and Composites from Agro-Based Resources. CRC Lewis Publishers, NY, NY. 446pp. V. Yadama,

39 Source: Rowell, RM, RA Young, and JK Rowell Paper and Composites from Agro-Based Resources. V. Yadama, 2007 CRC Lewis Publishers, NY, NY. 446pp. 39

40 Summary of Physical Dimensions Bast Fibers Bast Length- >1 to 4 m Ultimate Fiber Length- 1 to 70 mm Leaf Fibers Bast Length- >1 to 3 m Ultimate Fiber Length- 1 to 11 mm Seed Hair Seed Hair Length- <1 to 50 mm Cereal Straw Length- 0.6 to 3 mm Grass Straw Length- 2 to 5 mm V. Yadama,

41 Physical & Mechanical Properties Source: Rowell, RM, RA Young, and JK Rowell Paper and Composites from Agro- V. Yadama, 2007 Based Resources. CRC Lewis Publishers, NY, NY. 446pp. 41

42 Source: Rowell, RM, RA Young, and JK Rowell Paper and Composites from Agro- V. Yadama, 2007 Based Resources. CRC Lewis Publishers, NY, NY. 446pp. 42

43 Tensile Strength Rowell, RM, RA Young, and JK Rowell Paper and Composites from Agro-Based Resources. CRC Lewis Publishers, NY, NY. 446pp. V. Yadama,

44 More on Properties -- Kenaf Source: Rowell et. al, In: Kenaf Properties, Processing, and Products, edited by Sellers & Reichert V. Yadama,

45 Summary of Mechanical and Physical Properties Density Glass g/cm3 Polymers and Natural Fibers 1 to 1.5 g/cm3 Stiffness Carbon, Kevlar, Glass- 33, 18, 10.5 (10 6 psi) Bast, Leaf, Seed Hair- 4, 2.5, 1.2 (10 6 psi) Polyester, Rayon- 0.5, 0.3, 0.1 (10 6 psi) Strength Carbon, Kevlar, Glass- 520, 405, 400 (10 3 psi) Bast, Leaf, Seed Hair- 30 to 250 (10 3 psi) Polyester, Rayon- 25 to 150 (10 3 psi) Elongation Carbon, Kevlar, Glass- 1.5 to 3 % Bast, Leaf, Seed Hair- 1 to >5 % Polyester, Rayon- 20 to 35 % Conclusions Synthetic have good Stiffness to weight ratio Natural fibers have good Strength to weight ratio with improved ductility Polymeric have excellent ductility and good strength with poor stiffness V. Yadama,

46 Moisture & Durability Chemical constituents similar to wood are hydroxyl and other oxygen containing groups Attract moisture though hydrogen bonding Moisture effects properties & processing To reduce moisture, we ca Disperse better and encapsulate Adjust fiber content or reduce particle size Achieve better bonding between fiber & matrix Chemically modify fiber Protect composite product from moisture -- capping V. Yadama,

47 Other issues UV degradation Biological degradation Low thermal stability (<200 deg. C) Aging effects Odor volatile gases Burns easily Dust Hydrophilic V. Yadama,

Kenaf-PP Extruded Composite Source: Losure and Dunn, 1999.

48 Kenaf-PP Extruded Composite Source: Losure and Dunn, In: Kenaf Properties, Processing, and Products, edited by Sellers & Reichert High porosity due to moisture Show adherence to PP Good particle alignment V. Yadama,

49 Wheat Straw Residues for Thermoplastic Composites Karl Englund Anke Shirp Michael Wolcott V. Yadama,

50 Objectives Biological Removal Removal of amorphous constituents Hemicelluloses, lignin Reduce bulk density Particle Size Influence of particle size distribution (PSD) on properties of WPC V. Yadama,

51 Wheat Straw Composition *Westbred 936 Cellulose 32% Lignin 19% Wood (5-10% higher) Hemicelluloses 28% Primarily Xylans Ash 10% Others 6% * Houghton et al Fungal Upgrading of wheat straw for straw-thermoplastics production. V. Yadama, Applied 2007Biotechnology and Biochemistry. 113:

6-week inoculation period Large batch Non-sterilized

52 Biological Treatment Fungal Degradation Hemicelluloses, Lignin White Rot (Pleurotus ostreatus) 6-week inoculation period Large batch Non-sterilized straw Composite Formulation DOE Wheat, HDPE, CA,Lub V. Yadama,

53 Mechanical Properties Flexure Tests (ASTM D790) Similar to wood/thermoplastic composites Formulation (Fiber/HDPE/CA/Lub) Run #1-75/18/4/3 Run #2-55/38/4/3 Run #3-55/41/4/0 Properties Fiber Type Density MOE MOR (lb/ft 3 ) (Mpsi) (psi) Pine Wheat- Neat Wheat-Deg Pine Wheat- Neat Wheat-Deg Pine Wheat- Neat Wheat-Deg V. Yadama,

54 Water Sorption Compared to wood/thermoplastic composites Much greater WA and TS than pine At lower filler levels Degraded wheat lowest performance 75/18/4/3 (Wheat/HDPE/CA/Lub) 55/38/4/3 (Wheat/HDPE/CA/Lub) Thickness Swell (%) Wheat -Neat Wheat - Degrade Pine Thickness Swell (%) Wheat - Neat Wheat - Degrade Pine Time (hrs) V. Yadama, 2007 Time (hrs) 54

55 SEM Pine/HDPE Wheat/HDPE V. Yadama,

56 Particle Size Distribution Ro-Tap Procedure Wheat Finer Particles Increases w/degradation treatment Weighted % Neat Wheat Degraded Wheat 60-mesh Pine pan Mesh Size (Tyler) V. Yadama, Larger Particles

57 PSD Ro-Tap Analysis Wheat Higher level of fines Wood Commercial American Wood Fibers (AWF) Prior to Drying Weighted % " Screen 0.046" Screen 0.027" Screen 60-mesh Pine 10 0 pan Mesh Size (Tyler) Larger Particles V. Yadama,

58 Wheat vs. Wood Water Sorption PSD Influences Thickness Swell(%) mesh Pine 60-mesh Pine 5/64 Wheat 3/64 Wheat 0.027" Wheat Time (hours) V. Yadama,

59 Commercial Processing 86mm Extruder (WMEL and Strandex) Hollow deckboard Thermal Degradation Primarily Undegraded Straw Storage Issues? V. Yadama,

60 Thermal Degradation Gravimetric Analysis (TGA) 10C/min scan 100 Weight Loss (%) Temperature (C) V. Yadama,

61 Storage of Wheat Aged 8+ months in non-environmentally controlled facility Showed more susceptibility to thermal degradation Untreated Bio-deterioration Treatment % Weight Loss Un-aged Aged % Weight Loss Un-aged Aged V. Yadama, 2007 Temperature (C) Temperature (C) 61

62 Summary Mechanical results of wheat/thermoplastic composite are similar to wood filler Water sorption is increased with wheat Enhanced by larger particles and bio-deterioration treatment Less polymer integration within cellular structure Thermal degradation is a concern for non-treated wheat straw Stored material V. Yadama,

63 Permeability of Wood Low & highly variable 3 mechanisms for fluid penetration Diffusion Diffusion 1/(wood density) 2 Very slow; extremely slow to impossible with non-polar or non-swelling liquids Pits play a role for non-polar liquids if openings are big enough Capillary flow pressure differential produced by surface tension forces at the gas-liquid interface Secondary mechanism V. Yadama,

64 Permeability of Wood Pressure flow Hydrodynamic flow mass flow due to pressure differential Through large openings lumens, pits Rapid and can control penetration and retention More variation among woods in pressure flow than diffusion rates Directional (long./tangential ratio of ) Generally requires lot of pressure to impregnate wood need to displace air; easier to penetrate green wood Diminishing rate of flow over time Refractory wood Douglas fir Pre-treat wood to make it more permeable moisture removal, presteaming, removal of extractives, chemical & biological pretreatments V. Yadama,

Opportunities for Lignocellulosic Materials and Composites

Opportunities for Lignocellulosic Materials and Composites In: Emerging technologies for materials and chemicals from biomass: Proceedings of symposium; 1990 August 26-31; Washington, DC. Washington, DC: American Chemical Society; 1992. Chap. 2. ACS symposium