Tensile and Impact Bending Properties of Chemically Modified Scots Pine

Abstract

This study deals with the influence of chemical modification on elasto-mechanical properties of Scots pine (Pinus sylvestris L.). The elasto-mechanical properties examined were impact bending strength, determined by impact bending test; tensile strength; and work to maximum load in traction, determined by tensile tests. The modification agents used were one melamine-formaldehyde resin (MF), one low molecular weight phenol-formaldehyde resin, one higher molecular weight phenol-formaldehyde resin, and a dimethylol dihydroxyethyleneurea (DMDHEU). Special attention was paid to the influence of the solution concentration (0.5%, 5%, and 20%). With an increase in the concentration of each modification agent, the elasto-mechanical properties decreased as compared to the control specimens. Especially impact bending strength decreased greatly by modifications with the 0.5% solutions of each agent (by 37% to 47%). Modification with DMDHEU resulted in the highest overall reduction of the elasto-mechanical properties examined (up to 81% in work to maximum load in traction at 20% solution concentration). The results indicate that embrittlement is not primarily related to the degree of modification depended on used solution concentration. It is therefore assumed that molecular size and the resulting ability to penetrate into the cell wall could be crucial. The results show that, in the application of chemically modified wood, impact and tensile loads should be avoided even after treatment with low concentrations.

Chemical, Biological and Mechanical Characterization of Wood Treated with Propolis Extract and Silicon Compounds

“…The wood treated with chitosan solution exhibited an increase of the modulus of elasticity and no significant changes in the modulus of rupture compared to untreated wood [73]. The pine wood modified with methyl-etherified melamine formaldehyde resin, a low molecular weight phenol-formaldehyde resin, a higher molecular weight phenol-formaldehyde resin and dimethylol dihydroxyethyleneurea showed significantly lower bending strength values than control specimens [71]. In turn, the treatment with tetraethoxysilane showed no effect on the mechanical properties of pine wood compared to untreated samples [72].…”

“…However, the ethanolic solution does not affect on the cell wall S2 layer, which is one of the main factors determining the strength properties of wood [69]. The impregnation of wood with chemical preservatives caused changes in the mechanical properties of wood [70][71][72]. The pine wood impregnated with ionic liquids showed a lower value of bending strength and modulus of elasticity compared to untreated wood [70].…”

Bending Strength of Wood Treated with Propolis Extract and Silicon Compounds

“…Changes in mechanical parameters after wood treatment with various chemicals have already been described. However, the research concerned other agents than these described in this paper, e.g., ionic liquids [ 30 ], chitosan solutions [ 40 ], or resins [ 41 ]. The increase in MOR and MOE by 12% and 16%, respectively, was indicated by Ming-Li et al [ 42 ], after impregnating the wood with sodium silicate solution compared to the control sample.…”