Improvement of ash wood bonding quality with 1C-Polyurethane adhesive and hydrophilic primer for load bearing application P eter Niemz 1) , Gaspard Clerc 1) Joseph Gabriel 2) Dario Salzgeber 2), Thomas Strahm 3) 1) Bern University of Applied Science, Biel/CH 2 ) Henkel & Cie., Sempach/CH, 3) neue Holzbau AG, Lungern /CH peter.niemz@bfh.ch Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
1. Introduction volume change of softwoods and hardwoods from NFI 2 to NFI 3 in Switzerland (U. B. Brändli 2010) softwoods volume change swiss stone spruce fir pine larch others total pine [Mio. m³] -7.55 2.96 -0.55 2.13 0.20 0.42 -2.40 [%] -4.1 5.2 -4.1 11.0 9.2 41.5 -0.9 hardwoods volume change beech maple ash oak chestnut others total [Mio. m³] 4.28 2.06 2.87 0.59 0.18 1.98 11.96 [%] 6.2 21.8 24.4 7.1 3.8 18.0 10.4 Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
Problems softwood-hardwood for glulam softwood hardwood pine, spruce beech, ash Costs ( forest, roundwood): 80-100CHF/fm 45-75CHF/fm 1700 (ash)-2000CHF/m 3 (beech) Costs glulam : 600CHF /m 3 « Baubuche » Pollmeier 650 -780CHF/m 3 Material using: Germany 2005: 61,1%, 2010: 49,5% (Mantau), rest for energy Objective: More using of hardwood for glulam, CLT, LVL from beech, « Baubuche », other wood based materials Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
2. Properties of hardwood and softwood ➢ hardwood higher swelling ratio in property spruce beech ash Denisty , ϖ 12 % 300- 430 -640 540- 700 -900 450- 690 -860 relation to softwood (kg/m 3) ➢ higher MOE, higher strength (also MOE (bending) (MPa) 7.300- 11.000 -21.400 12.300-16.400 4.400- 13.400 -18.100 shear strength – delamination) Compression strength 33- 50- 79 41- 62- 99 23… 52 …80 (MPa) Problems: delamination test according EN 302-2 Tensile strength 21… 90 …245 70… 165 …293 57- 135 -180 (MPa) why: Bending strength 49- 78- 136 74- 123 -210 58.. 105 …210 ▪ higher stress during delamination (MPa) ▪ different extractives Max. swelling (%) R=3,5-3,7 R=5,8 R=4,5-5,0 T=7,8-8,0 T=11,8 T=8,0-8,4 pH-Wert 4,0-5,3 5,8 Hot water extract (%) 2,0 1,9 5,8 2,9-6,8 Variant Acidic acid Formic acid ∑ [mg/kg] Ø pH [mg/kg] [mg/kg] Sample Sample Sample Sample Sample Sample 1 2 1 2 1 2 Quelle: Wagenführ Holzatlas, 2000 Beech 113.9 114.5 9.58 9.58 123.5 124.1 123.8 5.39 Ash 225.6 227.5 50.72 50.72 276.3 278.2 277.3 5.18 Spruce 421.3 423.8 13.17 13.21 434.7 437.0 435.9 4.74 Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
3. Selected examples for using of hardwood in the timber construction Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
Timber construction with beech and ash (Holzbau Beer/Switzerland) for the crane (« BauBuche ») ash and beech Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences 6
House of Natural Resources ETH Zurich (glulam from ash wood) Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
Reinforcement from spruce with ash (timber conections) Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
used adhesives in the timber construction Used adhesives in European Countries (Euwid 2005): Certification in Germany necessary, not in Switzerland MUF/MF 49%, PUR 15%, UF 12%, PRF 20%, sonstige 2% (EPI) Selected producers: ➢ MUF/MF: z.B. Dynea; BASF; AkzoNobel (GripPro=MF) ➢ PRF: Dynea/Norge, Oxiquim/Chile ➢ 1C-PUR; 2C-PUR (glued – in rods), elastic system for windows, parquet: Henkel; Jowat; Collano; Nolax (new 1 C PUR) ➢ EPI (Dynea) ❖ High difference beween the systems and in a system Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
4. Gluing of hardwood (glued laminated timber) Parameters for testing gluing properties: • EN302-1: tensile shear strength A1≥10N/mm 2 , A4 ≥ 6N/mm 2 , wood failure (mean values) • EN302-2: delamination, length of delaminated bondlines ≤5% Material: • Ash wood for glulam, different 1C-PUR, Primer (based on tenisides from Henkel), gluing under industrial conditions) Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
Factors influencing bonding quality Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
Why we have this problems? hardwood: higher MOE, higher strength, higher swelling in • relation to softwood, different extractivs different strain distribution from bondline into wood • (depending on the adhesive stiffness) stiffness UF>MUF>PRF>PUR penetration from adhesive into cell wall (only PRF), no • penetration PUR, different strain distribution?, swelling from wood by using water based adhesives adhesion properties in wet conditions different ? • (problems with 1C- PUR and MUF under wet conditions melamine and ash wood) low wood failure, priming needed for 1C-PUR Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences 12
Experimental tests step1: tests in the Lab, shear strength (A1-A5) • step 2: test different adhesives (EPI, MUF, 1C- PUR producer • 1), industrial glulam production, delamination test step 3: test 1C-PUR producer 2 and priming, Areodux A185 • as reference (Loctite 1C-PUR systems and Loctite PR 3105) (delamination)) step 4: test 1C- PUR with priming (adhesives with low • reactivity, gluing direct after primer aplication) and technological optimization, industrial aplication from adhesive: 180g/m 2 step 5: small technological optimizations (EMC, lamella • thickness, pressure, waiting time after primer application, primer application in g/m 2 ) Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
Gluing under industrial conditions Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
step 1: different adhesives (MUF, EPI, 1-PUR (producer 1) Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
step 2: 1C- PUR, producer 2 and priming PUR with low reactivity (pressing time 12h), 20g/m 2 primer (10% concentration), manuell adhesive application 16 Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
step 3: producer 2, primer concentration and waiting time Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
step 4: delamination EN 302-2 of ash wood (primer concentration) Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
step 5: delamination EN 302-2 of ash wood (PC+ wating time), reduced lamella thickness 25mm and EMC Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
delamination from ash wood 1C PUR with primer, HB 181, 20g/m 2 Primer (10%), 10 min. open time + reduced lamella thickness (25mm) without priming HBS 707 with priming Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences 20
5. Conclusions ▪ Problems with delamination test (EN 302-2 for hardwood, only few adhesives fullfill norms (PRF Aerodux A185, special 1C -PUR (low reactivity and with priming, strong difference between adhesives)) ▪ Also optimization from technology (EMC, grading from lamellas, lamella thickness, pressure) important Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
Thank you very much BFH Biel, 2018 Berner Fachhochschule | Haute école spécialisée bernoise | Bern University of Applied Sciences
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