A molecular model for reversible and irreversible hygroscopicity changes by thermal wood modification

Tutkimustuotos: Lehtiartikkeli

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@article{68bd07838e1c450f91b83d5fb6f69a90,
title = "A molecular model for reversible and irreversible hygroscopicity changes by thermal wood modification",
abstract = "Heat treatment (HT) is a well-known means to reduce the equilibrium wood moisture content (EMC) at a specified relative humidity (RH). EMC is profoundly decreased by the loss of accessible hydroxyl groups (OHacc) in the wood matrix by thermochemical reactions. However, the obtained EMC reduction after HT can be partly reversible, depending on the ability of the wood matrix polymers to fully mechanically relax during HT. We discuss the results of our earlier experimental study on the OHacc content and the associated EMC decrease at 93{\%} RH by a relaxation inhibiting dry-HT vs. a relaxation enabling wet-HT. New experimental results, showing that OHacc does not significantly change during reversible EMC changes, are added to the discussion. This study quantitatively supports a molecular explanation of the reversible EMC, in which wood moisture is principally bound at sorption sites, composed of two functional groups, constituting a hydrogen-donor/acceptor pair, involving at least one OHacc group. The irreversible part of EMC reduction is assigned to the thermochemical removal of OHacc from the wood matrix. The reversible part is attributed to a process of wood polymer conformal rearrangements, bringing an isolated OHacc group in proximity of another free hydrogen-bonding functional group, creating a site for water sorption.",
keywords = "crosslinks, equilibrium moisture content, heat treatment, mechanical relaxation, sorption sites",
author = "Wim Willems and Michael Altgen and Lauri Rautkari",
note = "HUOM! T{\"a}h{\"a}n pit{\"a}{\"a} lis{\"a}t{\"a} lopullinen versio kun se julkaistu. T{\"a}m{\"a} kustantajan lehdiss{\"a} saa lopullisen aukaista 12 kuukautta virallisesta julkaisemisesta.",
year = "2019",
month = "8",
day = "14",
doi = "10.1515/hf-2019-0057",
language = "English",
journal = "Holzforschung",
issn = "0018-3830",

}

RIS - Lataa

TY - JOUR

T1 - A molecular model for reversible and irreversible hygroscopicity changes by thermal wood modification

AU - Willems, Wim

AU - Altgen, Michael

AU - Rautkari, Lauri

N1 - HUOM! Tähän pitää lisätä lopullinen versio kun se julkaistu. Tämä kustantajan lehdissä saa lopullisen aukaista 12 kuukautta virallisesta julkaisemisesta.

PY - 2019/8/14

Y1 - 2019/8/14

N2 - Heat treatment (HT) is a well-known means to reduce the equilibrium wood moisture content (EMC) at a specified relative humidity (RH). EMC is profoundly decreased by the loss of accessible hydroxyl groups (OHacc) in the wood matrix by thermochemical reactions. However, the obtained EMC reduction after HT can be partly reversible, depending on the ability of the wood matrix polymers to fully mechanically relax during HT. We discuss the results of our earlier experimental study on the OHacc content and the associated EMC decrease at 93% RH by a relaxation inhibiting dry-HT vs. a relaxation enabling wet-HT. New experimental results, showing that OHacc does not significantly change during reversible EMC changes, are added to the discussion. This study quantitatively supports a molecular explanation of the reversible EMC, in which wood moisture is principally bound at sorption sites, composed of two functional groups, constituting a hydrogen-donor/acceptor pair, involving at least one OHacc group. The irreversible part of EMC reduction is assigned to the thermochemical removal of OHacc from the wood matrix. The reversible part is attributed to a process of wood polymer conformal rearrangements, bringing an isolated OHacc group in proximity of another free hydrogen-bonding functional group, creating a site for water sorption.

AB - Heat treatment (HT) is a well-known means to reduce the equilibrium wood moisture content (EMC) at a specified relative humidity (RH). EMC is profoundly decreased by the loss of accessible hydroxyl groups (OHacc) in the wood matrix by thermochemical reactions. However, the obtained EMC reduction after HT can be partly reversible, depending on the ability of the wood matrix polymers to fully mechanically relax during HT. We discuss the results of our earlier experimental study on the OHacc content and the associated EMC decrease at 93% RH by a relaxation inhibiting dry-HT vs. a relaxation enabling wet-HT. New experimental results, showing that OHacc does not significantly change during reversible EMC changes, are added to the discussion. This study quantitatively supports a molecular explanation of the reversible EMC, in which wood moisture is principally bound at sorption sites, composed of two functional groups, constituting a hydrogen-donor/acceptor pair, involving at least one OHacc group. The irreversible part of EMC reduction is assigned to the thermochemical removal of OHacc from the wood matrix. The reversible part is attributed to a process of wood polymer conformal rearrangements, bringing an isolated OHacc group in proximity of another free hydrogen-bonding functional group, creating a site for water sorption.

KW - crosslinks

KW - equilibrium moisture content

KW - heat treatment

KW - mechanical relaxation

KW - sorption sites

U2 - 10.1515/hf-2019-0057

DO - 10.1515/hf-2019-0057

M3 - Article

JO - Holzforschung

JF - Holzforschung

SN - 0018-3830

ER -

ID: 36039273