Curing conditions effects on the characteristics of thermosetting adhesives-bonded wood joints

Lu, X.; Pizzi, A.

doi:10.1007/s001070050339

Cited by 15 publications

(5 citation statements)

References 9 publications

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“…The hardening of the resin can be evaluated using DLTMA (Lu and Pizzi 1998;Garcia and Pizzi 1998;Onic et al 1998). Wood beech plies of 0.6-mm thickness were cut into 14 × 5 mm samples.…”

Section: Dynamic Load Thermo-mechanical Analysis (Dltma)mentioning

confidence: 99%

Organosolv Wheat Straw Lignin as a Phenol Substitute for Green Phenolic Resins

Tachon¹,

Benjelloun-Mlayah²,

Delmas³

2016

BioResources

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Organosolv wheat straw lignin extracted using the CIMV process TM is a linear, low molecular weight, and natural phenolic oligomer. In this study, organosolv wheat straw lignin was tested as a substitute for 50% to 70% of the phenol in a phenol-formaldehyde-resol resin. The lignin was used without any chemical modification in a one-step synthesis reaction. Parameters such as reaction time and formaldehyde-to-phenol sources (phenol + lignin) mass ratios were optimized to achieve the requirements for industrial wood adhesives in terms of pH, viscosity, and dry matter. For the first time, the formaldehyde ratio was studied in order to reduce resin residual free formaldehyde below 1%. Lignin-phenol-formaldehyde resins were successfully synthesized up to a phenol substitution rate of 70% and showed physico-chemical properties close to standard phenolformaldehyde resins. The thermo-mechanical properties analyzed in dynamic load thermo mechanical analysis were similar to those of the reference resins. Plywood panels manufactured using these lignin-based resins reached the specifications for industrial panels according to the French standard for exterior plywood panels. Moreover, the formaldehyde content of these plywoods was low enough to satisfy even the most rigorous legislation.

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“…The hardening of the resin can be evaluated using DLTMA (Lu and Pizzi 1998;Garcia and Pizzi 1998;Onic et al 1998). Wood beech plies of 0.6-mm thickness were cut into 14 × 5 mm samples.…”

Section: Dynamic Load Thermo-mechanical Analysis (Dltma)mentioning

confidence: 99%

Organosolv Wheat Straw Lignin as a Phenol Substitute for Green Phenolic Resins

Tachon¹,

Benjelloun-Mlayah²,

Delmas³

2016

BioResources

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“…As expected, the maximum value of the MOE decreases with increase in the heating rate. The slower the heating rate applied, the later the MOE maximum presents itself 10–12. The curves describing the MOE increase and the maximum MOE values are always lower for the ammonium sulfate hardener than for the hexamine sulfate hardener.…”

Section: Discussionmentioning

confidence: 58%

“…The maximum value of mechanical resistance of a bonded wood joint is higher when the heating rate to cure is slower 10–12. This is the case both for aminoplastic and phenolic polycondensation resins.…”

Section: Discussionmentioning

confidence: 99%

“…The slower the resin cures, for whatever reason, the higher is the ultimate mechanical resistance of the joint bonded with it. The extent of this effect is considerable10–12: For example, the maximum value of the modulus of a resin, crosslinked at a heating rate of 40°C/min, is 30% lower than that observed at a heating rate of 5°C/min 10–12. Early immobilization of the resin in a less tightly crosslinked network10–12 is the cause of this.…”

Section: Discussionmentioning

confidence: 99%

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Upgrading of MUF polycondensation resins by buffering additives. II. Hexamine sulfate mechanisms and alternate buffers

Zanetti¹,

Pizzi²

2003

J of Applied Polymer Sci

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Iminoamino methylene bases intermediates are obtained by the decomposition of hexamethylenetetramine (hexamine). These are stabilized by the presence of strong anions such as SO 4 2Ϫ and HSO 4 Ϫ , that is, "hexamine sulfate." The effect of hexamine sulfate was closely linked to the strong buffering action it has on MUF resins. Its role is mainly to induce regularity of the reaction and the stability of conditions during resin networking, due to the buffer. Shifting of the polycondensation ª degradation equilibrium to the left appeared to be the determinant factor. This was a consequence of maintaining a higher, constant pH during curing, due to the buffer action. The modulus of elasticity (MOE) increases the curves of hexamine sulfate-catalyzed MUF resins, confirming this trend. The resins are faster curing than when catalyzed by ammonium sulfate. The effect is valid within the narrow buffering range of pH's used for resin hardening. Polycondensation is far too slow to occur at a much higher pH, and degradation is, instead, more predominant at much lower pH's. The network formed is then more crosslinked and less tainted by degradation when curing occurs within the correct pH range. The result is a much better performance of the wood board after water attack. The effects induced by hexamine sulfate effects are of longer duration than those of other potential buffers. This is due to the hexamine sulfate heat stability under standard hot curing conditions of the resin. Alternate systems were found and shown to have a comparable effect.

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“…1) shows a large curing exotherm in the DSC curve, which means that its curing reaction is sufficient, thus ensuring its good bonding strength and water resistance. In addition, the peak curing temperature of HUG2 is 105°C, which is similar to that of UF resins in industrial production [28,29]. Therefore, the HUG2 resin has real potential as a substitute for UF resin.…”

Section: Thermal Characteristics Analysismentioning

confidence: 83%

Preparation of Environmentally Friendly Urea-Hexanediamine-Glyoxal (HUG) Resin Wood Adhesive

Zhang¹,

Chen²,

Cao³

et al. 2024

JRM

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Using non-toxic, low-volatile glyoxal to completely replace formaldehyde for preparing urea-glyoxal (UG) resin adhesive is a hot research topic that could be of great interest for the wood industry. However, urea-glyoxal (UG) resins prepared by just using glyoxal instead of formaldehyde usually yields a lower degree of polymerization. This results in a poorer bonding performance and water resistance of UG resins. A good solution is to pre-react urea to preform polyurea molecules presenting already a certain degree of polymerization, and then to condense these with glyoxal to obtain a novel UG resin. Therefore, in this present work, the urea was reacted with hexamethylene diamine to form a polyurea named HU, and then this was used to react it with different amounts of glyoxal to synthesize hexamethylenediamine-urea-glyoxal (HUG) polycondensation resins, and to use this for bonding plywood. The results show that the glyoxal can well react with HU polyuria via addition and schiff base reaction, and also the HUG resin exhibits excellent bonding strength and water resistance. The shear strength of the plywood bonded with this HUG at 160°C hot press temperature as high as 1.93 MPa, 2.16 MPa and 1.61 MPa, respectively, which meets the requirement of the China national standard GB/T 9846-2015 (≥0.7 MPa), and can be a good choice as a wood adhesive for industrial application.

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Curing conditions effects on the characteristics of thermosetting adhesives-bonded wood joints

Cited by 15 publications

References 9 publications

Organosolv Wheat Straw Lignin as a Phenol Substitute for Green Phenolic Resins

Organosolv Wheat Straw Lignin as a Phenol Substitute for Green Phenolic Resins

Upgrading of MUF polycondensation resins by buffering additives. II. Hexamine sulfate mechanisms and alternate buffers

Preparation of Environmentally Friendly Urea-Hexanediamine-Glyoxal (HUG) Resin Wood Adhesive

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