Influence of Organic-Filler on Phenol-Formaldehyde Adhesion to Wood

Transcription

1 Influence of Organic-Filler on Phenol-Formaldehyde Adhesion to Wood Xing Yang, Audrey Zink-Sharp, Charles E. Frazier Macromolecular Science and Engineering Sustainable Biomaterials Virginia Tech

2 Outline Project introduction Adhesive viscometric analysis Adhesive fracture testing Bondline thickness measurement Adhesive penetration measurement Filler surface analysis Conclusions Future work Xing Yang 2

3 Research Problem The most common adhesive in veneer bonding applications is phenol/formaldehyde (PF) formulated with an organic filler Objective how fillers (particle size, types) impact adhesive performance how this relates to adhesive flow behavior bondline thickness adhesive penetration understand filler surface chemistry & surface area Xing Yang 3

4 Organic filler Research Problem corn cob residue (CCR) by-products of furfural industry hemicellulose removed alder bark (Modal) red alder bark in western North America high % lignin walnut shell one type of nutshells High % lignin Xing Yang 4

5 Frequency (%) Filler particle size distribution Corn Cob Residue (CCR) C-C, C-1, C-2, C-3 Alder Bark (Modal) Walnut shell M-C, M-1, M-2, M-3 W-C, W-1, W-2, W C-C M-C W-C 1 3 small to large particles Xing Yang Particle size ( m) 5

6 Frequency (%) Frequency (%) Frequency (%) C-1 M-1 W C-2 M-2 W Particle size ( m) C-3 M-3 W Particle size ( m) Particle size ( m) 6

7 C-C M-C W-C C-1 M-1 W-1 Obvious particle-size difference C-2 M-2 W-2 C-3 M-3 W-3 7

8 Viscometric analysis Steady state flow (T=25 o C): Conditioning: 2 min; no pre-shearing Shear rate increasing: 0.05 to 4000 s -1 Concentric cylinder geometry No conditioning; no pre-shearing Shear rate decreasing: 4000 to 0.05 s -1 Xing Yang 8

9 Viscosity (mpa s) 10 4 M-1 M-2 M Shear rate increasing Shear rate (1/s) Viscosity (mpa s) 10 4 W-1 W-2 W Shear rate increasing Shear rate (1/s) Viscosity (mpa s) 10 4 C-1 C-2 C Shear rate increasing Shear rate (1/s) 9

10 Viscosity (mpa s) 10 4 M-1 M-2 M Shear rate decreasing Shear 10 1 rate 10 2 (1/s) Viscosity (mpa s) 10 4 W-1 W-2 W Shear rate decreasing Shear rate (1/s) Viscosity (mpa s) 10 4 C-1 C-2 C Shear rate decreasing Shear rate (1/s) 10

11 ph Alkaline extraction C- unfractionated W- unfractionated M- unfractionated Initial ph of buffer: 12 Solid content: 4.0% Alkaline Extract (%) W: 6.33 M: 9.69 C: Stirring time (h) CCR stands out w/ large quantity of alkaline extract Xing Yang 11

12 Adhesion testing Matched substrates Two premium boards selected for top & bottom of each bondline Xing Yang 12

13 Adhesion testing adhesive: g (55lbs/1000ft 2 ) temperature: 160 C pressure: 190 ± 3.4 psi Time to reach a bondline temp of 104 C plus 2 mins Rip into fracture specimens 50 mm 10 Grain angle = 3-5 o 20 mm 10 mm mm Xing Yang 13

14 Mode-I fracture testing Adhesion testing G 2 P ( a x) b( EI ) eff 2 G P b a x (EI) eff = mode-i fracture energy = critical load = beam width = crack length = crack length correction = effective flexural rigidity Xing Yang 14

15 Non-parametric Statistical Analysis Kruskal-Wallis test (KW test) check if at least one mean differs Steel-Dwass method (SD method) pairwise comparisons Confidence level 95% (α=0.05) Software JMP 9 Xing Yang 15

16 Critical Fracture Energy (J/m 2 ) A A B # data points: # specimens: C Corn Cob Residue Modal (Alder Bark) Walnut Shell C1 C2 C3 M1 M2 M3 W1 W2 W3 D E F F G Filler Statistical analysis report C-1 A C-2 A C-3 B M-1 C M-2 D M-3 E W-1 F W-2 F W-3 G Modal stands out Xing Yang 16

17 Bondline thickness measurements 60 mm 10 mm Reflected light microscopy 860 um Filler Measurements C C C M M M W W W Xing Yang 17

18 Bondline Thickness ( m) # data 10points: # specimens: A A A B Corn Cob Residue Modal (Alder Bark) Walnut Shell C1 C2 C3 M1 M2 M3 W1 W2 W3 Size effects of modal & walnut shell No size effects with CCR C D E F G Filler Statistical analysis report C-1 A C-2 A C-3 A M-1 B M-2 C M-3 D W-1 E W-2 F W-3 G Xing Yang 18

19 Specimens Adhesive penetration measurements Objective To measure adhesive penetration at different crack points 55 mm Crack locations 10 mm Extra locations > 3 locations in 10 mm interval 125 mm Crack initiation loci for a selected fracture specimen Crack length (mm) M-3-A-1 M-3-A-2 M-3-A-3 M-3-A-4 M-3-A-5 M-3-B-1 M-3-B-2 M-3-B-3 M-3-B-4 M-3-B-5 Crack locations are not evenly distributed along bondline Xing Yang 19

20 40 mm 140 mm 50 mm U L Completely water saturated Water aspiration (3 h, 17 mmhg) Water soaked (>24 h, atmosphere) ~30 μm thick, ~20 mm long Sledge microtome No. of sections > 2 at each location Upper & lower Xing Yang 20

21 Nikon Eclipse LV100 POL 100X magnification Field of view: 870 micron per image # of images stitched: 24*3 5% overlap on the horizontal direction when stitched Transmitted light microscopy Grain angle = 3-5 o 20 mm 10 mm mm Xing Yang 21

22 U L Maximum penetration (MP) 400 μm MP = n 1 y i n Set bondline as section baseline in every 400 μm interval, y i measured along the ray Interval skipped when section baseline is absent n is the total No. of measurements Xing Yang 22

23 Adhesive penetration ( m) C-1-1-U C-1-1-L C-1-2-U C-1-2-L M-1-1-U M-1-1-L M-1-2-U M-1-2-L 1438 M-3-1-U M-3-1-L M-3-2-U M-3-2-L Penetration in two bonded wood subtracts are different 23

24 Adhesive penetration ( m) C C M M M M-3-2 Critical Fracture Energy (J/m 2 ) # data 50points: # data points: Bondline thickness ( m) C # data points: C-1-1 C-1-2 C-1-2 M-1-1 M-1-1 M-1-2 M-1-2 M-3-1 M-3-1 M-3-2 M

25 Filler particle surface analysis Contact angle of well defined liquids in contact with specimen Washburn equation Column wicking h: distance traveled by the liquid in time t R e : effective interstitial pore radius θ: contact angle γ L : liquid surface tension η: liquid viscosity Xing Yang 25

26 Filler Unfractionated size Control moisture Vacuum oven dry (45 o C; 5.4 mmhg) Control unit column weight (UCW) UCW = weight of fillers in column (mg) height of filler in column (mm) Filler UCW (mg/mm) Observations CCR 4.90± Walnut Shell 5.65± Modal 4.55± h 2 = R eγ L cos θ 2η R e : effective interstitial pore radius t Xing Yang 26

27 Washburn Equation h 2 = R eγ L cos θ 2η R e = 2η γ L K SP cosθ = 2ηK L R e γ L t = Kt Square of height (mm 2 ) C-control dry (Hexane) -1 Y=13.48X R 2 = Time (s) Xing Yang 27

28 2 h 2 /t(mpa.mm 2 ) 2 h 2 /t(mpa.mm 2 ) 2 h 2 /t(mpa.mm 2 ) Perfluorohexane Hexane Octane Dodecane CCR Perfluorohexane Hexane Octane Dodecane Walnut shell Perfluorohexane Pentane Hexane Heptane Octane Dodecane Modal Y=0.174X R 2 = Y=0.515X R 2 = Y=0.346X R 2 = L (mn/m) L (mn/m) L (mn/m) Filler R e (μm) CCR Walnut shell Modal Xing Yang 28

29 Contact angle (degree) Water Formamide Ethyl acetate 1-bromonaphthalene cis-decalin Liquid Water Filler Successful tests/total tests CCR 4/4 Walnut shell 4/5 Modal 4/4 80 CCR 4/4 70 Formamide Walnut shell 4/4 60 Modal 4/4 50 CCR 4/4 40 Ethyl acetate Walnut shell 4/4 30 Modal 4/ CCR Walnut shell Modal 1-bromonaphthalene CCR 4/4 Walnut shell 4/4 Modal 4/8 CCR 4/4 cis-decalin Walnut shell 4/4 Modal 4/7 Xing Yang 29

30 Surface energy component (mn/m) Surface energy components 35 Acid-base Harmonic mean Geometric mean γ S LW : Nonpolar component Type Non-polar Polar C W M C W M Non-spreading liquid cis-decalin 1-bromonaphthalene Ethyl acetate Formamide Water C W M LW S - S + S AB S S γ S : Lewis basic parameter γ S + : Lewis acid parameter γ S AB : Polar component γ S : Surface energy Nonpolar components γ S AB = 2 γ S γ S + γ S = γ S LW + γ S AB dominate surface chemistry of all fillers Xing Yang 30

31 Surface area measurements From wicking method A s = 2(1 Φ) ΦρR e A s : specific surface area Φ: volume fraction ρ: specific density R e : effective interstitial pore radius Filler R e (μm) CCR Walnut shell Modal Density, g/cm 3 (STDEV) (0.064) (0.026) (0.022) Φ: volume fraction Xing Yang 31

32 Frequency (%) 8 6 C-C M-C W-C 4 2 Modal stands out in surface area Particle size ( m) Specific Surface Area Filler Average (m 2 /g) STDEV (m 2 /g) COV (%) Observations CCR Walnut shell Modal Xing Yang 32

33 Conclusions Viscometry revealed that adhesive flow is affected by filler type (CCR stands out) filler particle size Statistical analysis revealed that filler particle size impacts adhesive performance, particularly for modal bondline thickness for modal and walnut shell; no effect for CCR Modified MP measurements showed great statistical variation, as expected- but no clear differences between fracture specimens no clear correlations between adhesive critical energy, penetration and bondline thickness Filler surface analysis via column wicking revealed different interstitial pore radius among all filler types filler-dependent surface effects Xing Yang 33

34 Future work Seek correlations between adhesive performance, penetration, bondline thickness via statistical analysis Investigate more about filler chemistry Xing Yang 34

35 Acknowledgements Wood-Based Composites Center National Science Foundation Technical Sponsors: GP Chemicals Momentive Willamette Valley USDA FS Forest Products Lab Xing Yang 35

36 Thank you for attention! Xing Yang 36