Performance of pyrolysis oil-based wood adhesives in OSB. (Composites and Manufactured Products).
Phenol-formaldehyde (PF) resins are widely used as thermosetting adhesives for exterior-grade wood composites. They develop durable, rigid, and strong bonds in wood strands like oriented strandboards (OSB). In 1997, 1.6 million metric tons of adhesive resin solids were consumed in North America and 94 percent of this volume was formaldehyde-based (urea, melamine, and resorcinol). Around 86 percent (275 kilotons resin solids) of the resins consumed by the strandboard industry are PF resins and 14 percent are polymeric diphenyl methylene diisocyanate (PMDI) (20). With the growing market share of OSB (1), the demand for these adhesives will likewise increase. Phenol, a petroleum-based chemical, is sensitive to the price of petroleum, which is dictated in large part by the Organization of Petroleum Exporting Countries (OPEC). This scenario, coupled with the growing concern for environmental protection, led to the present study. One approach in reducing the cost of PF resin is to replace the petroleum-based pheno ls with chemicals derived from renewable materials such as softwood barks that are abundantly available as a by-product of the forest-based industry. Although these residues are also used to produce energy, the bulk of these are incinerated or discharged in landfills or dumps, which creates potential air, water, and soil pollution problems. An alternate solution is fast pyrolysis, which enables the conversion of various biomass materials into pyrolysis oil and wood charcoal. The reactivity of the phenolic-rich fraction of pyrolysis oil has been investigated by Kelley et al. (10). They found that this fraction had more phenolic hydroxyl groups and fewer methoxyl groups than lignins. Lignins have been commercially utilized to replace 15 to 35 percent of the phenol in PF resin formulations and have been used in selected wood-composite mills in North America (20). Chemical characterization of biomass pyrolysis oil has also been conducted using sequential elution chromatography on silica gel followed by analysis u sing GC/MS (14). A process of extracting the phenol/neutral fraction from pyrolysis oil using a solvent extraction technique was developed by Chum et al. (5). The fraction was mixed with pure phenol (50:50) and polymerized with formaldehyde. The final resin compared very well with a commercial PF resin for plywood. However, the lengthy solvent extraction method, associated with a relatively low phenol/neutral fraction yield, negatively influences the process economics. Himmelblau (7) has also formulated an adhesive made of raw pyrolysis oil derived from mixed hardwoods and reported successful substitution of 50 percent in PFresin formulation.
PF-bonded boards need high temperature curing or need long pressing time to obtain acceptable bond strength. They may sometimes be partly cured after hot-pressing, and in order to continue the curing process, boards are hot-stacked (13). The effect of hot-stacking on urea-formaldehyde- (UF) and PF-bonded boards was investigated and it has been found that temperature and exposure time had a great impact in the reduction of thickness swelling. Storing the panels in stacks at a high temperature also improved the internal bond (IB) of PF-bonded panels, but adversely affected the UF-bonded boards (13). For the modern, lower formaldehyde UF adhesives, however, a short period (15 to 30 min.) post-curing significantly improved the mechanical and thickness swelling properties of the boards (12). Post-treatment at 240[degrees]C was also found to be effective in producing dimensionally stable wood composites (8) The use of high temperature was based on the concept that above the softening temperature of lignin and carb ohydrates components, plastic flow occurs, which relieves the internal stresses built up during hot-pressing (8).
In previous studies, using dynamic mechanical analysis of fiber-reinforced phenolics, it was found that stiffness and glass transition temperature (Tg) of the adhesives could be increased by post-curing (11). Likewise, studies of PF-bonded boards showed marked improvement in IB with post-heat treatment (8,13). A 10 percent improvement in IB was also observed in UF-bonded particleboards stored below 100[degrees]C for up to 30 minutes after hot-pressing (12).
Many developments have also been made in the addition of reactive compounds to improve rheology and bonding of lignocellulosics. Some accelerating additives have been added to increase the rate of cure of PF resins (15,16,20).
Wood adhesives based on pyrolysis oil derived from softwood bark residues are being developed for OSB. The main goal of the study was to develop a high-performance oil-derived PF resin for OSB. The whole oil was used to replace part of the phenol in PF resin formulations. The effect of hot-stacking (simulated by putting the boards in the oven at 150[degrees]C for 2 hr. after hot-pressing) on the mechanical properties and thickness swelling of the boards bonded with the new type of wood adhesive was evaluated. Likewise, the effect of addition of accelerator in resin formulations on the final properties of the boards was also investigated.
The pyrolytic oil known as Biophen[TM] (18) was produced using a proprietary process (Pyrocyling[TM]) leading to an overall phenolic-rich oil yield of 37 percent (anhydrous basis) (17). The feedstock originated from processed softwood barks and was composed of fir (70% vfv) and black spruce (30% v/v). The oil (411-H1007) is composed mostly (~65%) of phenolic compounds, including lignins, tannins, and labile compounds (Table 1) (19). It has a pH of 3.0 and a low molecular weight carboxylic acids content of around 1.5 percent. Its moisture content is about 18 percent.
A series of oil-based PF resins with 25 and 35 percent by weight replacement of phenol by pyrolysis oil were prepared. The molecular weight of pyrolysis oil was assumed and calculated to be the same as that of phenol. Phenol, pyrolysis oil, formaldehyde, and sodium hydroxide (NaOH) were reacted in a resin kettle equipped with a condenser, mechanical stirrer, and cooling coils.
F/P 'molar' ratios (F) were: Fl = 1.75; F2 = 2.0; F3 = 2.25; while NaOH/P 'molar' ratios (C) were: C1 = 0.25; C2 = 0.35; and C3 = 0.45. An accelerator was added (2.5% based on resin solids) in some resin formulations. Dynea (formerly Neste Resins Canada) commercial core (N1) and surface (N2) resins were used as controls.
The viscosity of the resins during synthesis was measured by Gardner-Holt viscosity tubes. Some of the resin properties evaluated included percent nonvolatile matters, pH, gel time, and viscosity. Gel time was determined at 120[degrees]C using a Sunshine[TM] gel tester, while the viscosity of the resin after synthesis was measured by a Brookfield RVT at 25[degrees]C.
BOARD MANUFACTURING CONDITIONS
Currently used commercial OSB manufacturing conditions (Table 2) were employed in the manufacture of homogeneous and 3-layer (50:50 core:face) boards made of trembling aspen wood strands. Post-treatment of panels was done by placing the boards in an oven for 2 hours at 150[degrees]C immediately after hot-pressing. A study showed that the temperature after 48 hours for hot-stacked 19-mm nominal thickness PF boards (200 boards, overall height of 3.8 m) was about 100[degrees]C, and that even after 8 days, the temperature was still around 60[degrees]C (13). Hence, the choice of 150[degrees]C post-curing temperature for 2 hours in the oven employed in the present study approximates stacking conditions employed on PF-bonded boards prior to delivery to the customers.
EVALUATION OF PROPERTIES OF BOARDS
The thickness swelling and mechanical properties such as modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond (IB) in both the dry and wet (2-hr. boil) conditions were evaluated according to the test methods and requirements of the Canadian Standards CSA (0437.1-93) for OSB products (4). The boards were conditioned for at least 3 weeks at 20 [+ or -] 2[degrees]C and 65 [+ or -] 2 percent relative humidity prior to test. For the thickness swelling of the boards, the test specimens were submerged in water maintained at a temperature of 20[degrees]C for 24 hours. Two panels were made for each adhesive formulation. The properties of untreated and post-heat-treated boards were compared by t-test.
RESULTS AND DISCUSSION
As shown in Table 3, the pH of the experimental resins (10.1 to 10.3) was close to the pH of the commercial surface resin (~10.2) except for 25F2C2 and 35F2C3, which are slightly higher (~10.7). These two experimental resins have a higher NaOH/P molar ratio at the same level of phenol replacement. They have higher viscosity than the commercial surface resin (90 to 150 cP), but within the acceptable limits of what is being used in the industry (< 250 cP). Gel time measured by the Sunshine gel tester at 120[degrees]C showed that the experimental resins had slightly longer gel time (~ 450 to 610 sec.) than commercial resins (~ 400 to 420 sec.). Resin 35F3C2 had a shorter gel time than the rest of the experimental resins, which could be due to its higher F/P molar ratio, and higher percent replacement of phenol.
Table 4 and Figures 1 through 3 show the results of the mechanical tests and thickness swelling of the boards bonded with the control and experimental panels. The requirements of the standard for each test are indicated in the table and in the graphs. The mechanical properties of experimental boards relative to the control panels (Table 5) was determined by dividing the values obtained in experimental boards with those obtained in control panels. This procedure was done to directly compare the results of the tests obtained with different batches.
Internal bond. -- As shown in Table 4 and Figure 1, all the homogeneous and 3-layer experimental panels with or without post-treatment, exceeded the requirement for dry IB (0.345 MPa) set by GSA 0437. Even without post-treatment, high dry IB values (0.412 to 0.575 MPa) were obtained in experimental resins. In wet IB, experimental homogeneous panels bonded with 25 percent phenol replacement passed the standard with marked improvement after posttreatment. Generally higher IB values were obtained with 25 percent replacement than with 35 percent replacement (Tables 4 to 6). The highest IB value (dry and wet) among homogeneous panels was obtained in 25F1C1A and could be due to the high cross-linking promoted by the accelerator (15). The wet IB (Fig. 2) of untreated homogeneous boards bonded with 35 percent phenol replacement did not meet the standard. Postheat treatment, however, gave satisfactory wet IB in 35F2C2. The experimental resins with higher NaOH/P seemed to have lower IB values than those with lower NaO H/P molar ratio at the same phenol replacement. Homogeneous boards bonded with higher F/P at 35 percent phenol replacement (35F3C2) gave higher wet LB than the lower F/P molar ratio (35F2C2). This result could be due to higher methylolation occurring at the higher F/P molar ratio than at the lower F/P molar ratio (6). Such formulations would emit more formaldehyde for further cross-linking during hot-pressing.
It is interesting to note that 3-layer boards with experimental surface resin passed the wet LB test even without post-treatment (Fig. 2). Post-treated 3-layer experimental boards (N1/35F2C2) gave the same wet IB value with the control, while N1/35F3C2 gave slightly higher wet IB than the control (Table 4, Fig. 2). The 3-layer boards with experimental resins (25F2C2A/35F3C2) in both the core and surface layers also gave acceptable wet IB values even without post-treatment.
The dry IB strength of the boards increased by 3 to 19 percent (Table 6) with post-treatment in homogeneous panels, while in 3-layer boards up to 22 percent improvement was obtained. Post-treatment had a strong effect in wet IB with up to 245 percent increase in experimental homogeneous panels bonded with 35F3C2. The 3-layer control panel (control 4, Table 4) had an increase in IB of about 2 percent while control 5 and the rest of the experimental boards had an average increase of 47 percent. Post-treatment thus allowed further polymerization of the resin making the boards more water resistant and eventually giving higher wet IB strength. This increased degree of polymerization was shown by Differential Scanning Calorimetry with isoconversional kinetics where the oil-based resins achieve a good degree of crosslinking, but more slowly than neat PF resins (2).
The relative IB values of the experimental resins (Table 5) showed that 25F1ClA obtained the highest value (0.89) among the homogeneous panels in dry tests while panels bonded with 35F2C3 gave the lowest both in dry and wet tests. The 3-layer panels gave higher average relative IB than the homogeneous panels. Panels bonded with N1/35F3C2 gave the highest relative dry and wet IB values among the 3-layer panels (Table 5).
The percent change with wet IB was much higher than in the dry IB. Percent improvement of wet IB of experimental panels ranged from around 20 to 245 percent as compared to dry IB, which ranged from 3 to 22 percent. The t-test (Table 7) further shows that post-treatment was highly significant in the wet IB of the majority of the panels compared to the dry IB. This higher result could be due to the internal methylene ether bridges rearrangement to a tighter methylene bridges network (9), occurring during post-curing, thus making the boards more heat- and water-resistant.
Bending properties. -- As shown in Table 4, all the homogeneous and 3-layer panels, treated and untreated, exceeded the requirements for MOR (dry and wet) and MOE set by CSA 0437. Some experimental boards gave higher bending strength and MOE than the control. There is no clear indication on the effect of post-treatment on the MOR (dry and wet) and MOE on the boards. Although post-treatment had improved the bending properties of the majority of the panels, it gave a negative effect in some panels. It was observed that negative values were found more in homogeneous panels than in the 3-layer boards. The percent improvement (or reduction) of bending properties in most of the panels was also minimal (Table 6). Further analysis by t-test has shown that post-treatment did not have any significant effect on the dry MOR of all the panels (Table 7). The wet MOR and MOE of the majority of the boards were also not affected by post-treatment. Similar results were obtained as in a previous study (13) where other researchers found that on UF- and PF-bonded boards, hot-stacking had no significant effect on their bending strength and MOE. Another study (12), however, showed that post-curing of particleboard bonded with lower formaldehyde content UF resin gave a 15 and 20 percent improvement of MOR and MOE, respectively.
Thickness swelling. -- As shown in Figure 3, all the untreated homogeneous panels except for Control 1 did not meet the requirement of the standard. In 3-layer boards, however, three sets of panels passed the standard even without post-heat treatment. Two of these boards were bonded with control resins (core and surface) and the other one had experimental resin as the surface resin (N1/35F2C2). Of all the properties evaluated, the effect of the postheat treatment (2 hr. at 150[degrees]C) was most evident in thickness swelling (Table 7). All post-heat-treated panels had lower thickness swelling compared to the untreated ones. Likewise, all post-treated boards passed the standard. Post-treatment reduced thickness swell between 20 and 40 percent or an average of 32 percent. A study on UF- and PF-bonded boards showed that hot-stacking reduced thickness swelling (12,13). The higher the temperature and the longer the panels are exposed while stacking, the greater is the reduction in thickness swelling (13).
The formulated resin with the highest NaOH/P molar ratio (35F2C3) gave the highest thickness swelling in post-treated homogeneous boards, which could be due to the increased hydrophilicity of the resin caused by its higher caustic content. Homogeneous boards bonded with 25C1F1A gave the lowest thickness swell among the experimental boards (Tables 4 and 5).
Softwood barks, which are abundantly available as by-products in the forest-based industry, are used in the generation of energy, although a large portion of these are incinerated or discharged in landfills, which creates potential air, water, and soil pollution problems. However, the conversion of bark residues to pyrolysis oil and charcoal is environmentally friendly.
A previous study (3) showed that the total emitted volatile organic compounds (VOCs) obtained by expressing all individual detected VOCs as alpha-pinene, was lower for both the experimental (bonded with pyrolysis-oil based adhesive) and the commercial samples, than the mean value obtained with 10 commercial OSB panels after a 6-hour exposure in the environmental chamber. However, a study on the type and amount of VOCs liberated during the hot-pressing of the boards should be conducted to fully evaluate the environmental impact of the newly developed wood adhesives.
CONCLUSIONS AND RECOMMENDATIONS
These preliminary results indicate that 3-layer panels (50:50, core:surface) could be produced with a 35 percent phenol replacement as surface resin. The IB values obtained from these panels (N1/35F2C2; N1/35F3C2) were comparable to the control. The results obtained in 3-layer panels indicated the strong potential of pyrolysis oil for surface resin. Acceptable properties obtained in 3-layer boards with experimental resins in core and surface layers also indicated that 25 percent replacement of phenol with some accelerator added could be used as core resin with 35 percent replacement of phenol as surface resin, giving an overall phenol replacement of 30 percent in each panel of 50:50, core:surface ratio.
Post-treatment (2 hr. at 150[degrees]C) significantly improved the IB and thickness swelling properties of the boards, but not the bending properties. The resin formulations evaluated so far can be further modified to take full advantage of the vacuum pyrolysis oil. Higher phenol replacement in PF resin formulations should be worked on.
[Figure 1 omitted]
[Figure 2 omitted]
[Figure 3 omitted]
TABLE 1 Typical chemical composition of pyrolysis oil (19). Compound/family Concentration in total oil (%wt of oil, water-free basis) Hydrocarbons 3 Sugars 9 Low-molecular-weight 1.5 acids High-molecular-weight 10 acids Alcohols 2.5 Esters and ketones 4 Phenols 10 Steroids and triterpenoids 4 Lignin/tannin-based 48 compounds Labile compounds 8 Total 100 TABLE 2 General parameters used in board manufacture. Parameter Value Replicate 2 boards Wood strands 3-in.-trembling aspen Resin content 2.5 wt% (on ovendry wood basis) Resin type Control resin (homogeneous boards) - liquid commercial surface resin Control resin (3-layer boards) - liquid commercial core and surface resins Experimental resins - 25 and 35 percent phenol replacement Panel dimension 11.1 by 610 by 610 mm (7/16 by 24 by 24 in.) Panel construction Random orientation/ homogeneous and three layers Mass distribution For 3-layer - 25 wt% (top): 50 wt% (core): 25 wt% (bottom) Target density 640 kg/[m.sup.3] (40 pcf) Mat MC 6 [+ or -] 1% Support Screen caul at the bottom Total press cycle 180 sec., including 30 sec. closing; 30 sec. degas Press temperature 215[degrees]C Wax 1.5 wt.% (on ovendry wood basis) Post-treatment (a) With and without post-heat treatment (a) Boards were placed in an oven at 150 [degrees]C for 2 hours immediately after pressing. Table 3 Some properties of the commercial and experimental resins. (a) Resin Phenol F/P NaOH/P code replacement molar ratio molar ratio pH (%) (F) (C) 25F1C1 25 1.75 0.25 10.1 25F1C1A 25 1.75 0.25 10.2 25F2C1 25 2.0 0.25 10.0 25F2C2 25 2.0 0.35 10.6 35F2C2 35 2.0 0.35 10.3 35F3C2 35 2.25 0.35 10.2 35F2C3 35 2.0 0.45 10.7 Commercial core resin 0 -- -- 12.2 (N1) Commercial surface resin 0 -- -- 10.2 (N2) Resin Viscosity Gel time code at 25[degrees]C at 120[degrees]C (cP) (sec.) 25F1C1 168 560 25F1C1A 145 537 25F2C1 148 613 25F2C2 248 549 35F2C2 215 566 35F3C2 175 447 35F2C3 232 559 Commercial core resin 150 402 (N1) Commercial surface resin 93 424 (N2) Resin Non-volatile code solids (%) 25F1C1 52.6 25F1C1A 51.2 25F2C1 50.3 25F2C2 51.7 35F2C2 51.8 35F3C2 49.8 35F2C3 51.9 Commercial core resin 50.2 (N1) Commercial surface resin 57.2 (N2) (a) F = F/P ratio; F1 = 1.75; F2 = 2.0; F3 = 2.25; C = NaOH/P ratio; C1 = 0.25; C2 = 0.35; C3 = 0.45; A = accelerator; N1 = Dynea's liquid core resin; N2 = Dynea's liquid surface resin. TABLE 4 Mechanical and thickness swelling properties of OSB panels bonded with commercial and experimental resins. Resin % phenol F/P Batch Code (a) replacement molar ratio 1 Control 1 (N2) -- - - Homogeneous 25F1C1 25 1.75 panels 25F1C1A 25 1.75 25F2C1 25 2.0 2 Control 2 (N2) -- -- Homogeneous 35F2C2 35 2.0 panels 35F2C3 35 2.0 3 Control 3 (N2) -- -- Homogeneous 25F2C2 25 2.0 panels 35F3C2 35 2.25 4 Control 4 (N1&N2) -- -- 3-layer panels Core - N1 -- -- (50:50 core:face) Face-35F2C2 35 2.0 5 Control 5 (N1&N2) -- -- 3-layer panels Core - N1 -- -- Face - 35F3C2 35 2.25 Core - 25F2C1A 25 2.0 Face - 35F3C2 35 2.25 Dry IB CSA 043-93 0.345 MPa Standards: (minimum) NaOH/P Batch molar ratio Density (kg/[m.sup.3]) (MPa) 1 - - 690 0.634/0.709 (b) Homogeneous 0.25 690 0.542/0.572 panels 0.25 690 0.565/0.655 0.25 680 0.518/0.591 2 -- 670 0.545/0.618 Homogeneous 0.35 680 0.458/0.514 panels 0.45 670 0.412/0.459 3 -- 720 0.543/0.648 Homogeneous 0.35 730 0.468/0.480 panels 0.35 710 0.485/0.514 4 -- 730 0.578/0.605 3-layer panels -- 710 0.575/0.539 (50:50 core:face) 0.35 5 -- 720 0.503/0.586 3-layer panels -- 710 0.482/0.580 0.35 0.25 705 0.433/0.489 0.35 Wet IB Dry MOR Wet MOR 0.104 MPa 17.2 MPa 8.6 MPa (minimum) (minimum) (minimum) Batch (MPa) 1 0.364/0.522 40.9/33.7 19.7/17.9 Homogeneous 0.222/0.343 33.1/37.7 18.3/17.2 panels 0.256/0.407 42.2/41.0 18.1/22.4 0.251/0.384 33.9/39.0 20.3/21.2 2 0.134/0.327 33.4/37.7 15.4/20.6 Homogeneous 0.061/0.143 30.9/28.8 13.9/17.3 panels 0.041/0.070 32.7/26.8 14.2/13.1 3 0.192/0.303 37.6/39.7 17.9/19.4 Homogeneous 0.088/0.200 31.2/32.6 15.7/15.9 panels 0.068/0.235 34.2/34.2 18.1/16.4 4 0.292/0.297 31.7/35.9 16.9/19.7 3-layer panels 0.279/0.297 32.4/32.7 16.5/16.7 (50:50 core:face) 5 0.207/0.252 33.8/36.1 15.7/17.7 3-layer panels 0.254/0.356 28.6/30.7 17.3/14.8 0.122/0.213 30.0/30.9 15.9/16.7 MOE TS 3.1 x [10.sup.3] MPa 15% (minimum) (maximum) Batch MPa x [10.sup.3] (%) 1 4.4/4.3 15/9 Homogeneous 4.2/4.6 17/11 panels 4.9/5.0 16/10 4.8/5.2 17/11 2 3.8/4.3 16/11 Homogeneous 3.9/3.8 20/12 panels 4.2/3.7 19/15 3 4.8/4.6 17/12 Homogeneous 4.0/4.2 18/14 panels 4.2/4.3 20/14 4 4.3/4.5 12/9 3-layer panels 4.1/4.3 14/11 (50:50 core:face) 5 3.8/4.4 15/10 3-layer panels 3.5/3.6 17/12 4.2/3.9 18/13 (a)F = F/P ratio; F1 = 1.75; F2 = 2.0; F3 = 2.25; C = NaOH/P ratio; C1 = 0.25; C2 = 0.35; C3 = 0.45; A = accelerator; N1 = Dynea's liquid core resin; N2 = Dynea's liquid surface resin. (b)Bold numbers are values from post-treated panels. TABLE 5 Relative mechanical and thickness swelling properties of OSB panels bonded with commercial and experimental resins. (a) Rasin % phenol F/P NaOH/P code (b) replacement molar ratio molar ratio Density kg/[m.sup.3] 2SF1C1 25 1.75 0.25 690 25FlClA 25 1.75 0.25 690 25F2C1 25 2.0 0.25 680 25F2C2 25 2.0 0.35 730 35F2C2 35 2.0 0.35 680 35F3C2 35 2.25 0.35 710 35F2C3 35 2.0 0.45 670 Core - N1 -- -- -- 710 Face - 35F2C2 35 2.0 0.35 Core - N1 -- -- -- 710 Face - 35F3C2 35 2.25 0.35 Core - 25F2C1A 25 2.0 0.25 705 Face - 35F3C2 35 2.25 0.35 Rasin Dry Wet Dry Wet code (b) IB IB MOR MOR 2SF1C1 0.85/0.81 (d) 0.61/0.66 0.81/1.12 0.93/0.96 25FlClA 0.89/0.92 0.70/0.78 1.03/1.22 0.92/1.25 25F2C1 0.82/0.83 0.69/0.74 0.83/1.16 1.03/1.18 25F2C2 0.86/0.75 0.46/0.66 0.83/0.82 0.88/0.82 35F2C2 0.84/0.83 0.46/0.44 0.92/0.76 0.90/0.84 35F3C2 0.89/0.70 0.66/0.78 0.91/0.86 1.01/0.85 35F2C3 0.76/0.74 0.31/0.21 0.98/0.71 0.92/0.64 Core - N1 0.99/0.89 0.96/1.00 1.02/0.91 0.98/0.85 Face - 35F2C2 Core - N1 0.96/1.0 1.16/1.41 0.85/0.85 1.1/0.84 Face - 35F3C2 Core - 25F2C1A 0.86/0.83 0.59/0.84 0.89/0.86 1.0/0.94 Face - 35F3C2 Rasin code (b) MOE TS (c) 2SF1C1 0.95/1.07 1.13/1.22 25FlClA 1.11/1.16 1.07/1.11 25F2C1 1.10/1.21 1.13/1.22 25F2C2 0.83/0.91 1.06/1.20 35F2C2 1.03/0.88 1.25/1.09 35F3C2 0.88/0.93 1.18/1.17 35F2C3 1.11/0.86 1.19/1.36 Core - N1 0.95/0.96 1.17/1.22 Face - 35F2C2 Core - N1 0.92/0.82 1.14/1.20 Face - 35F3C2 Core - 25F2C1A 1.10/0.89 1.21/1.30 Face - 35F3C2 (a)Relative values were calculated by dividing the values obtained in experimental boards with those from the control boards. (b)F = F/P ratio; F1 = 1.75; F2 = 2.0; F3 = 2.25; C = NaOH/P ratio; C1 = 0.25; C2 = 0.35; C3 = 0.45; A = accelerator. (c)Lower values are desired. (d)Bold numbers are values from posi-treated panels. TABLE 6 Percentage differences for the mechanical properties and thickness swelling of OSB with and without post-heat treatment. (a) Resin % phenol F/P NaOH/P Batch code replacement molar ratio molar ratio 1 Control 1 (N2) Homogeneous 25F1C1 25 1.75 0.25 panels 25F1C1A 25 1.75 0.25 25F2C1 25 2.0 0.25 2 Control 2 (N2) Homogeneous 35F2C2 35 2.0 0.35 panels 35F2C3 35 2.0 0.45 3 Control 3 (N2) Homogeneous 25F2C2 25 2.0 0.35 panels 35F3C2 35 2.25 0.35 4 Control 4 (N1&N2) -- -- -- 3-layer panels Core - N1 -- -- -- Surface - 35F2C2 35 2.0 0.35 5 Control 5 (N1&N2) -- -- -- 3-layer panels Core - N1 -- -- -- Surface - 35F3C2 35 2.25 0.35 Core - 25F2C1A 25 2.0 0.25 Surface - 35F3C2 35 2.25 0.35 Dry Wet Dry Wet Batch IB IB MOR MOR MOE TS 1 11.8 43.4 (-17.6) (-9.1) (-2.3) -40.0 Homogeneous 5.5 54.5 13.9 (-6.0) 9.5 -35.3 panels 15.9 52.9 (-2.8) 23.8 2.0 -37.5 14.1 58.9 15.0 4.4 8.3 -35.3 2 13.4 144.0 13.0 34.1 13.2 -31.2 Homogeneous 12.2 134.4 (-6.9) 24.9 (-2.6) -40.0 panels 11.4 70.7 (-17.9) (-7.7) (-11.9) -21.0 3 19.3 57.8 5.7 8.8 (-4.2) -29.4 Homogeneous 2.6 127.3 4.5 1.3 5.0 -22.2 panels 6.0 245.6 0.1 (-9.1) 2.4 -30.0 4 4.7 1.7 13.3 16.4 4.6 -25.0 3-layer panels (-6.3) 6.4 1.0 1.3 4.9 -21.4 5 16.5 21.7 6.7 12.7 15.8 -33.3 3-layer panels 22.2 40.2 7.6 (-14.9) 0 -29.4 12.9 74.6 3.1 5.3 (-7.1) -27.8 (a)Values in parentheses show reduction of properties. Negative values are desired in thickness swelling. TABLE 7 T-test comparison of the mechanical and thickness swelling properties between untreated and post-heat treated OSB panels. (a) Resin % phenol F/P NaOH/P Batch code (**) replacement molar ratio molar ratio 1 Control 1 (N2) -- -- -- Homogeneous 25F1C1 25 1.75 0.25 panels 25F2C1A 25 1.75 0.25 25F2C1 25 2.0 0.25 2 Control 2 (N2) -- -- -- Homogeneous 35F2C2 35 2.0 0.35 panels 35F2C3 35 2.0 0.45 3 Control 3 (N2) -- -- -- Homogeneous 25F2C2 25 2.0 0.35 panels 35F3C2 35 2.25 0.35 4 Control 4 (N1&N2) -- -- -- 3-layer panels Core - N1 -- -- -- Surface - 35F2C2 35 2.0 0.35 5 Control 5 (N1&N2) -- -- -- 3-layer panels Core - N1 -- -- -- Surface - 35F3C2 35 2.25 0.35 Core - 25F2C1A 25 2.0 0.25 Surface - 35F3C2 35 2.25 0.35 Dry (b) Wet (b) Dry (c) Wet (c) Batch IB IB MOR MOR MOE (c) TS (d) 1 (*) (**) NS NS NS (**) Homogeneous NS (**) NS NS NS (**) panels (**) (**) NS NS NS (**) (*) (**) NS NS NS (**) 2 (*) (**) NS (**) (*) (**) Homogeneous (*) (**) NS (**) NS (**) panels NS (**) NS NS NS (**) 3 (**) (**) NS NS NS (**) Homogeneous NS (**) NS NS NS (**) panels NS (**) NS NS NS (**) 4 NS NS NS NS NS (**) 3-layer panels NS NS NS NS NS (**) 5 (**) NS NS NS (**) (**) 3-layer panels (**) (**) NS (**) NS (**) (**) (**) NS NS NS (**) (a) Replicate: 2 panels NS = not significant (*)= significant at 0.05 level (**)= highly significant at 0.01 level. (b) n = 12. (c) n = 6. (d) n = 4.
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F. CHAN (*), B. RIEDL (*), X.-M. WANG (*)
(*.) Forest Products Society Member.
The authors are, respectively, Research Associate, Pyrovac Inst. Inc. (PI), 333 rue Franquet, Ste-Foy, QC, Canada GiP 4C7; Professor, Universite Laval (UL), Dept of Wood Sci. and CERSIM, Ste-Foy, QC, Canada GiK 7P4; Research Scientist, Forintek Canada Corp., Eastern Div., 319, rue Franquet, Ste-Foy, QC, Canada G1P 4R4; Research Associate, P1; Chemist, Valspar (Vermicolor) Corp. AG, Im Tobel 4, Hodlikom, CH-8340 Hinwil, Switzerland; and President, P1. The authors are grateful to the Natural Sciences and Engineering Research Council (NSERC) of Canada and to the Ministry of Industry and Commerce and the Ministry of Environment/FPGST Program, for their financial support of Universite Laval and Pyrovac Inst., respectively, and to Dynea (formerly Neste Resins Canada) for providing the resin samples. This paper was received for publication in December 2000. Reprint No. 9230.
[c] Forest Products Society 2002.
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|Title Annotation:||oriented strandboard|
|Author:||Chan, F.; Riedl, B.; Wang, X.-M.; Lu, X.; Amen-Chen, C.; Roy, C.|
|Publication:||Forest Products Journal|
|Article Type:||Statistical Data Included|
|Date:||Apr 1, 2002|
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