Effect of extractions on dynamic mechanical properties of white mulberry (Morus alba)

Abstract

International audienceVibrational properties of wood are affected by several parameters, of which extractives can be one of the most important ones. Wood for European musical instruments has been often studied, but traditional Middle Eastern ones had been left unnoticed. In this study white mulberry (Morus alba L.), the main material for long-necked lutes in Iran, was extracted by five solvents of various polarities (water included). Free-free bar forced vibrations were used to measure longitudinal (L) loss tangent (tanδ), storage (elastic) modulus (E′) and specific modulus (E′/γ) in the acoustic range. Their anisotropy between the 3 axes of orthotropy was determined by DMA (dynamic mechanical analysis). Native wood had a quite low EL′/γ but its tanδ was smaller than expected, and the anisotropy of tanδ and E′/γ was very low. Removal of extractives caused tanδ to increase and moduli to decrease. Acetone, the most effective solvent on damping despite a moderate extraction yield, increased tanδL by at least 20% but did not modify E′/γ as much. When used successively, its effects masked those of solvents used afterwards. Anisotropy of E′/γ was nearly unchanged after extraction in methanol or hot water, while tanδ was much more increased in R than in T direction. Results suggest that in white mulberry, damping is governed more by nature and localization of extractives rather than by their crud abundance

The effect of traditional hygro-thermal pretreatments on the acoustical characteristics of white mulberry wood (Morus alba)

“…It is based on three processes applied by Iranian makers on white mulberry (Morus alba), which is a dominant species for making long-necked lutes in Iran (Se Golpayegani et al 2012) as well as other types of lutes from the Middle East to Japan (Yoshikawa 2007). The authors previously reported on how the extractives of this species affected its dynamic mechanical properties (Se Golpayegani et al 2012) and also its toxicity and allergenic sideeffects (Se Golpayegani et al 2014).…”

“…It is based on three processes applied by Iranian makers on white mulberry (Morus alba), which is a dominant species for making long-necked lutes in Iran (Se Golpayegani et al 2012) as well as other types of lutes from the Middle East to Japan (Yoshikawa 2007). The authors previously reported on how the extractives of this species affected its dynamic mechanical properties (Se Golpayegani et al 2012) and also its toxicity and allergenic sideeffects (Se Golpayegani et al 2014). After interviewing some instrument makers, laboratory-scale protocols simulating traditional methods were applied to assess their effect on density (ρ) and on the vibrational properties which are classically expressed by E′/ρ (specific modulus of elasticity, where E′: dynamic flexural modulus of elasticity and ρ: Specific gravity) and damping coefficient (tanδ) Norimoto 1984, Obataya et al 2000).…”

The effect of extractives on acoustical properties of persian silk wood (Albizia julibrissin)

“…mulberry, maple, and walnut; but after some special hydrothermal treatments (Roohnia et al 2011, Segolpayegani et al 2012. Nowadays it has been revealed that hot water extraction of wood during traditional hydrothermal treatment, may withdraw some compounds which are not considered as stress supporting material in lignocellulose micro-structure.…”

“…This phenomenon, although, in lower quantities than cell wall constitutive polymers, is even reported in previous studies. To name an example, extractives of wood from Pernambuco (Caesalpinia echinata or Guilandina echinata) have previously been introduced , Matsunaga et al 2000a-b, Alves et al 2008, Segolpayegani et al 2012. It has been shown that the mechanical and acoustical properties of wood from Pernambuco weaken after extraction.…”

“…Furthermore, Albizia genus belongs to sub-family Mimosoideae, whereas Caesalpinia genus (to which belongs Pernambuco wood) is part of the Caesalpiniodeae sub-family. Meanwhile, other Iranian tone woods that were not from Leguminosae were previously investigated; Roohnia et al 2007, studied the Iranian stands of Arizona cypress, later in 2011, then after, Segolpayegani et al 2012, studied the acoustic properties of Mulberry wood (used in Iranian traditional musical instruments) in terms of extractives. Roohnia et al 2015, reported the acoustical performance of Maple wood before and after extraction.…”