Post industrial wood raw material as natural fiber base for wood plastic composites (WPC) based on PVC and PP matrix material Dipl.-Ing. S. Wolf, Dipl. Ing. S. Wolf, Ing. Mag. Dr. P. Hausberger, Ing. M. Szakacs, BSc
Overview Introduction Why WPC Theoretical background Why post industrial wooden raw materials Design of experiments Selected Results Conclusion / Outlook 2
Why WPC Wood is a prefect material, however. Wood for outside use has to be Treated and/or maintained to withstand weather and biological forces Chemical or heat treatments Use of hard (rain-forest) wood Logging under certain conditions 3
Why WPC Real wood will be advertised d Nice color Long lasting Natural product 4
Why WPC Reality on wooden decks Fading / graying 5
Why WPC Reality on wooden decks splintering warping 6
Why WPC Reality on wooden decks Less dimension stability 7
Why WPC Reality in use of natural ressources Ecologically critical (esp. tropical wood) 8
Therefore WPC Technical Ecological Higher resistance against Use of local resources weathering / fading Long lasting and Lasting / different colors sustainable products Lower water absorption Less maintenance Growth rates: US: 22% EU: 51% Sources: Wood k plus 2009 9
Theoretical background WPC (Wood-Polymer-Compound): Natural fiber hybrid composite Plastic processing is used (extrusion & injection molding) Mainly 50% to 70% wood (> 70% for interior use, < 50% for injection molding) Main matrix materials: PE, PP or PVC Complex profiles in one step Density is higher than added density of individual components (close to matrix material) Standard processing tools as usually used for wood 10
Theoretical background WPC (Wood-Polymer-Compound): Polymer structure Wood = biological Polymer (Polysaccharide) Plastic = artificial Polymer (PP, PVC, PE) Binding forces between Polymers determine technical characteristics ti of WPC Non-polar plastics (Polyolefins) coupling agents like maleated polyolefins Polar materials (PVC) reduced / skipped coupling agents Consistency of raw material is critical for production Matrix material: mostly industrial produced Fiber material: mostly mixed wood fiber waste different source / kind of wood moisture content, fiber length and so on 11
Why post industrial wooden raw material Tendency for biomass/energy use price will increase less natural fiber available Industrial production process well documented raw-material stable quantity available Uniform quality homogenous particle size consistent t & reduced d moisture well-known kind of wood Less pre-treatment necessary MDF / HDF fiber waste FSC/PEFC certified raw material Local available Well controlled end-product (Formaldehyde content) Till now mainly used for thermorecycling in conjunction with intensive filtering technologies (e.g. cement plants) 12
Design of experiments Test / Production Lines (direct extrusion): Cincinnati Konos 38 (up to 40kg/h) Cincinnati FIBEREX 58 (up to 80kg/h) MAS new conical co-rotating twin-screw extruder for real production (up to 250kg/h) Fiber raw material: industrial-wooden production 35,00 30,00 waste (silo-stored at supplier site) 25,00 20,00 resin content up to 12% Polymer matrix material: PVC (Solvay, pre-mixed Dry-blend) PP (Borealis) Massena anteil der Kornklasse en in % 15,00 10,00 5,00 0,00 28,42 Fiber sieving analysis 12,02 8,63 8,04 6,10 4,02 2,43 1,22 0,22 0,19 1,24 0,00 0,00 0 250 500 1000 2000 4000 8000 Sample 70 % < 710 µm Kornklassen in µm Big dust (< 180µm) amount Production cut > 2000µm 13
Design of experiments General conditions: Melt quality in extrusion sufficiently plasticized in venting zone Minor smell due to resin content Uncolored sample medium/dark brown Melt temperature Main trail plan: Trial Plan PVC Wood fiber content PP 50% 50% 50% 45% 55% 40% 60% 40% 35% 65% 70% 30% 75% 25% 80% 20% Other trail parameters: Coupling agent (0 to 3%) UV-stabilizer (0 to 2%) Color (0 to 4%) Different MFI for PP (1 to 8) 14
Design of experiments Performance Indicators tested: Strength th (material + end-product testing's) Coloring Weathering (color change, retained strength after weathering) Fungal decay Creeping Water absorption (change of mass, retained strength) Extension (water absorption, storage at constant climate, therm. extension coefficient) Performance optimization: Strength 15
Selected results: Bending strength th (DIN EN 178) Bending strength PVC based WPC 50% fiber ratio 55% 60% 65% 000% 0,00% 0,50% 1,00% 1,50% 2,00% 10 80 70 60 50 40 30 20 UV-stabilizer ratio 0 bending stren ngth [MPa] 60% 70% 75% fiber - ratio PVC-based WPC 80% Less influence on fiber ratio and UV-stabilizer ratio Bending strength PP based WPC 0,00% PP-based WPC Strong dependency on coupling agents 1,00% 3,00% 2,00% 0 80 70 60 50 40 30 20 10 coupling agent ratio bending strength [M MPa] Initial samples have reached very high bending strength values compared to literature 16
Selected results: Water absorption (DIN EN 317) Significantly better binding forces of polar matrix materials Coupling agents compensate binding forces off-set on short term water ab bsorption [% %] 30 25 20 15 10 5 PVC based WPC 2hours 24 hours 168 hours 336 hours 672 hours off-set binding forces PP based WPC water ab bsorption [% %] 30 25 20 15 10 5 PP based WPC 70% fiber content 0 50% 55% 60% 65% 70% 75% 80% fiber content 0 0% 1% 2% 3% coupling agent ratio 17
Selected results: artificial i weathering Existing UV-stabilizers (HALS) are insufficient for WPC Sufficient stabilized color masterbatch will guarantee long lasting color (minimum 4%) Slight color changes will happen after 100h 55% fiber / 45% PVC 1,5% UV-stabilizer (HALS) 0,5% UV-Stabilizer 1,0% UV-Stabilizer 1,5% UV-Stabilizer 2,0% UV-Stabilizer 55% fiber / 45% PVC, 1,5% UVstabilizer (HALS), 2% color 18
Selected results: creep behavior (ÖNORM ENV 1156) WPC will face creeping (plastic deformation under load) WPC with PVC matrix materials will have significant advantages PP based WPC with 60% Wood fiber content PVC based WPC with 50% to 65% Wood fiber content 19
Selected results: change of properties after aging Like wood, WPC will also loose mechanically strength after artificial weathering (aging) UV-stabilizers doesn t improve mechanical aging so far flexural modulus after artificial weathering bending strength after artificial weathering impact strength after artificial weathering ulus lexural mod [GPa] f l 8 6 4 2 0 0 h 1000 h 71% 66% 0,0% 1,5% UV-Stabilizer [%] b e nding stre ngth [M p a] 80 60 40 20 0 0 h 1000 h 89% 82% 0,0% 1,5% UV-Stabilizer [%] ngth ²] m pact stre [K J/m m im 6 5 4 3 2 1 0 0 h 1000 h 100% 98% 0,0% 1,5% UV-Stabilizer [%] 20
Selected results: Thermal coefficient i of expansion Thermal coefficient of expansion based on polymer matrix material 3t to 6times higher h than wood WPC is nearly an isotropic material material thermal coefficient of expansion α Practical result ΔL @ 40K, L o =4m wood 5-8 x 10-6 0,8-1,3 mm WPC - PVC based 18-21 x 10-6 2,9-3,3 mm WPC - PP based 35-38 x 10-6 5,6-6,1 mm WPC - PE based 38-42 x 10-6 6,1-6,7 mm 21
Selected results: Performance optimization i of WPC Optimization has been done mainly on processing level Pre-homogenizing i Adjusted venting Fine adjustment of recipe Better particle dispersion strength [Mpa] bending 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 PP based WPC 70% fibers 30% PP PVC based WPC 55% fibers 45% PVC optimized PVC based WPC 55% fibers 45% PVC felxural modulus [Gpa] 10 9 8 7 6 5 4 3 2 1 0 PP based WPC 70% fibers 30% PP PVC based WPC 55% fibers 45% PVC optimized PVC based WPC 55% fibers 45% PVC impact strength [KJ/m²] 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 PP based WPC 70% fibers 30% PP PVC based WPC 55% fibers 45% PVC optimized PVC based WPC 55% fibers 45% PVC 22
Conclusion Post industrial wooden waste will be an economical as well as ecological raw material source for WPC Material as well as process know-how is needed for up-cycling of this raw material source PVC as a matrix material has technical advantages - especially due to its polarity therefore e e PVC based WPC is superior to PP based WPC in most technical values 23
Conclusion / Outlook Process as well as recipe optimized PVC-based WPC will come close to mechanical characteristics of natural wood Especially due to high strength and reduced creep behavior, applications close to constructive wood engineering might be possible 200 200 bend ding strength [MP Pa] 180 160 140 120 100 80 60 40 1 [9] 2 [10] spruce 1 pine 1 maple 1 k 1 larch 1 oak teak 1 opt. WPC beech 2 thermo beech 2 ash 2 t thermo ash 2 bend ding strength [MP Pa] 180 160 140 120 100 80 60 40 Standard WPC opt. WPC ash spruce beech teak oak maple pine larch thermo ash thermo beech 20 0 20 flexural modulus [GPa] 0 4 6 8 10 12 14 16 24
Conclusion / Outlook Special applications (reality and possible future) Landing stage at Danube river (lower Austria) Swimming platform (Carinthia) WPC-cap (to replace aluminum) for wood windows to improve thermal insulation (Austria) Decking with privacy fence Possibilities of use of WPC at play-grounds oriented by nature for (upper Austria) sustainable toys with reduced maintenance and improved child safety 25
Acknowledgment Special gratitude to Wood-K Plus, Upper Austria extruwood GmbH My colleagues from FH Technikum Wien 26