scholarly journals Production of plywood panels from Pinus taeda using veneers of differing densities and phenol-formaldehyde resin with high and low molecular weights

CERNE ◽  
2013 ◽  
Vol 19 (2) ◽  
pp. 315-321
Author(s):  
Graciela Ines Bolzon de Muniz ◽  
Setsuo Iwakiri ◽  
Lívia Cássia Viana ◽  
Mário Andrade ◽  
Cristiane Weber ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Pinus Taeda ◽  
Cold Water ◽  
Phenol Formaldehyde ◽  
Water Immersion ◽  
Line Strength ◽  
Formaldehyde Resin ◽  
Low Molecular Weight ◽  
Bonding Quality

This study aimed to evaluate the bonding quality of plywood panels from Pinus taeda using low and high molecular weight phenol-formaldehyde resin and veneers from three different density classes. The experiment consisted of six treatments, each of which produced three panels (replicates). Tests were conducted to evaluate glue line strength to shear stress after two boiling cycles and after 24 hours of cold water immersion. Also determined was the percentage of defects in wood samples. Results indicated that the density classes being assessed differed statistically. However, no significant difference was found between panels produced with high and panels produced with low molecular weight resin as to the mean values of glue line strength, whether subjecting them to two boiling cycles or after 24 hours of cold water immersion. Interactions between different density classes and adhesive formulations were found not significant either. Low molecular weight resin (BPM) and panels produced with higher density veneers were found to have better behavior, regarding both bonding strength and percentage of defects. It was concluded that the bonding quality of plywood panels from Pinus taeda was satisfactory after using different densities of veneer and also high and low molecular weight phenolic resins. All treatments were found to comply with minimum requirements established in European standard EN 314-1/1993, which addresses bonding quality of plywood panels.

The Chemistry of Phenol-Formaldehyde Resin Vulcanization of EPDM: Part I. Evidence for Methylene Crosslinks

1995 ◽  
Vol 68 (5) ◽  
pp. 717-727 ◽  
Author(s):  
Martin van Duin ◽  
Aniko Souphanthong
Keyword(s):  
Molecular Weight ◽  
Phenol Formaldehyde ◽  
Polymer System ◽  
Phenol Formaldehyde Resin ◽  
Formaldehyde Resin ◽  
Low Molecular Weight ◽  
Hydroxyl Groups ◽  
Reaction Products ◽  
Cure Reaction ◽  
Weight Model

Abstract The application of phenol-formaldehyde resins as crosslinking agents is increasing in importance due to the good high temperature properties of the corresponding vulcanizate and the use in thermoplastic vulcanizates. With respect to the chemistry of phenol-formaldehyde cure (reaction mechanism and structure of crosslink) there are still problems that have to be resolved. The reaction products of the phenol-formaldehyde resin curing of EPDM, contain 2-ethylidene norbornene (ENB) as the third monomer, have been studied. Since such an investigation is rather difficult to perform for the polymer system, a low molecular weight model for EPDM was used: 2-ethylidene norbornane (ENBH). Reaction of ENBH and a resole results in scission of the dimethylene ether bridges, i.e. in degradation of the resole into mono-, bis- and terisooctylphenol units. These are consequently converted into products, consisting of two ENBH molecules linked by mono-, bis- and terisooctylphenol units. The solid resole seems to be a technological solution for storing phenol in combination with formaldehyde. These results support the use of 2-hydroxymethylphenol (HMP) as a low molecular weight model for the resole. At low temperatures and/or short reaction times HMP oligomers (= resoles) and HMP oligomers linked to one ENBH molecule are formed, which are converted into ENBH/HMP (1:1) condensation products. The reaction products of ENBH with both the resole and HMP are shown to contain methylene linked structures, as demonstrated by the formation of monisooctylphenol crosslinks and the presence of residual unsaturation and hydroxyl groups, besides chroman linked structures. This is the first experimental evidence that during phenol-formaldehyde resin cure of rubber, formation of methylene bridges occurs.

scholarly journals A comparison between the properties of low and medium molecular weight phenol formaldehyde resin-treated laminated compreg oil palm wood

2017 ◽  
Vol 19 (3) ◽  
pp. 1-11 ◽  
Author(s):  
G. Aizat ◽  
A. Zaidon ◽  
S. H. Lee ◽  
S. B. Edi ◽  
B. Paiman
Keyword(s):  
Molecular Weight ◽  
Oil Palm ◽  
Phenolic Resin ◽  
Phenol Formaldehyde ◽  
Phenol Formaldehyde Resin ◽  
Formaldehyde Resin ◽  
Low Molecular Weight ◽  
Hot Press ◽  
Plastic Bag ◽  
Better Than

In order to improve the inherently poor properties of oil palm wood (OPW), this study examines the effects of resin molecular weight, diffusion time and compression ratio on the properties of laminated compreg OPW. Treating solutions used were medium molecular weight phenol formaldehyde (MmwPF) and low molecular weight phenol formaldehyde (LmwPF). OPW strips were soaked in the treating solutions for 24 h before wrapping in a plastic bag and leaving them for diffusion for 2, 4 and 6 days, respectively. Then, three-layer laminated compreg OPW were fabricated and compressed in hot press at 150°C for 20 minutes to achieve compression ratios of 55%, 70% and 80%. Results indicated that dimensional stability and mechanical properties of the phenolic resin treated laminated compreg OPW were significantly better than the untreated laminates. MmwPF-treated laminates exhibited inferior properties in comparison to that of LmwPF-treated laminates. Nevertheless, MmwPF-treated laminated compreg OPW emitted significantly lesser formaldehyde.

scholarly journals Bolt-Bearing Yield Strength of Three-Layered Cross-Laminated Timber Treated with Phenol Formaldehyde Resin

Forests ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 551 ◽  
Author(s):  
Wengang Hu ◽  
Jilei Zhang
Keyword(s):  
Yield Strength ◽  
Pinus Taeda ◽  
Phenol Formaldehyde ◽  
Core Layer ◽  
Phenol Formaldehyde Resin ◽  
Formaldehyde Resin ◽  
Low Molecular Weight ◽  
Southern Pine ◽  
Cross Laminated Timber ◽  
Loading Direction

The effect of impregnation treatment of low molecular weight phenol formaldehyde (MWPF) resin on the bolt-bearing yield strength (BBYS) of a three-layered cross-laminated timber (CLT) composed of two face layers of southern pine (Pinus taeda) and one core layer of sweetgum (Liquidambar styraciflua) was investigated together with two additional factors of material type and loading direction. Experimental results indicated that the amount of low MWPF resins penetrating into sweetgum was more than the ones into southern pine. Sweetgum had more uniform distribution of low MWPF resins penetrating longitudinally than southern pine. Impregnation treatment using a low MWPF resin at a concentration of 20% can enhance the BBYS of three-layered CLTs with a 60% increase. The BBYS of a core layer material in three-layered CLTs can significantly alter the overall BBYS of the three-layered CLTs.

The Chemistry of Phenol-Formaldehyde Resin Crosslinking of EPDM as Studied with Low-Molecular-Weight Models: Part II. Formation of Inert Species, Crosslink Precursors and Crosslinks

2000 ◽  
Vol 73 (4) ◽  
pp. 706-719 ◽  
Author(s):  
Martin van Duin
Keyword(s):  
Molecular Weight ◽  
Phenol Formaldehyde ◽  
Chemical Mechanism ◽  
Formaldehyde Resin ◽  
Low Molecular Weight ◽  
Model Compounds ◽  
Dynamic Vulcanization ◽  
Ethylene Propylene ◽  
Chemical Structures ◽  
End Groups

Abstract Phenol-formaldehyde resins (resols) are the preferred crosslinking agents for the dynamic vulcanization of blends of polypropylene and ethylene—propylene—diene rubber (PP/EPDM) for the production of thermoplastic vulcanizates (TPVs). The goals of this study were to elucidate in detail the chemical structures formed using low-molecular-weight model compounds and to elaborate on the chemical mechanism of resol cure of EPDM as presented in our previous study. The use of model compounds for EPDM (2-ethylidenenorbornane [ENBH] and 4-methylheptane), but also for resol (2-hydroxymethylphenol [HMP] and 2,6-di(hydroxymethyl)-p-cresol) allowed the characterization of the chemical structures formed with the aid of gas chromatography/mass spectrometry (GC/MS). In combination with derivatization of unreacted hydroxyls a large variety of species could be distinguished with the general structure of R−phenol-[-CH2−phenol-]n−R′ (n=0, 1 or 2). R and R′ can be inert end groups resulting from degradation or disproportionation, viz. —H, —CH3 or —CHO, reactive end groups, viz. —CH2OH, and products of addition to ENBH (C9H14), viz. —CH2—C9H13. When either R or R′ is —CH2—C9H13 a model crosslink precursor is formed, when both are —CH2—C9H13 a model crosslink is formed. It has been demonstrated beyond doubt that both chroman and methylene bridged species are produced. It is still unclear what parameters determine the selectivity for chroman versus methylene bridged structures (presence of activators, structure of olefin etc.). The two major model crosslink products of HMP and ENBH have also been characterized with nuclear magnetic resonance, which confirmed the chroman and methylene bridged structures and showed that the addition of the phenol predominantly occurs at the least sterically hindered C-8 of ENBH. The yield of the reaction of resol with ENBH is enhanced by temperature increase and/or the addition of SnCl2·2H2O. 4-Methylheptane does not react with HMP. This indicates that in a PP/EPDM based TPV only crosslinking of EPDM via the residual diene unsaturation occurs and that tertiary C-atoms of PP or of the ethylene—propylene rubber (EPM) chain of EPDM are not involved. The high reactivity of ENBH compared with 1-decene or hydrogenated dicyclopentadiene supports a cationic mechanism.

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