Effects of lignin in wood on moisture sorption and hygroexpansion tested under dynamic conditions

AbstractEffects of lignin on dynamic sorption and hygroexpansion were investigated. Poplar wood (Populus cathay) [20×20×4 mm3(radial×tangential×longitudinal)] was delignified at three levels and subjected to dynamic humidity changes, where the relative humidity (RH) changed sinusoidally between 45% and 75% at 25°C during 1, 6 and 24 h. Moisture contents (MC) and dimensional responses were recorded automatically. Scanning electron microscopy (SEM) results show that lignin was partly removed. MC and dimensions also varied sinusoidally with RH. At higher delignification levels, amplitudes, moisture sorption coefficients and humidity expansion coefficients became higher, but the phase lag displayed an opposite trend. The effects were due to the removal of the relatively hydrophobic lignin layers, in the course of which more hydroxyl groups of cellulose and hemicelluloses were accessible to humidity. A linear positive relation was found between the delignification rate and MC, and dimensional changes in the tangential direction. Lignin had a significant effect on sorption and hygroexpansion and this effect was greater for static sorption. Delignification reduced the hysteresis due to matrix stiffness decrement of wood, especially in the RH range of 55–65%.

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Dynamic moisture sorption and dimensional stability of furfurylated wood with low lignin content

Holzforschung ◽

10.1515/hf-2019-0033 ◽

2019 ◽

Vol 74 (1) ◽

pp. 68-76

Author(s):

Tiantian Yang ◽

Erni Ma ◽

Jinzhen Cao

Keyword(s):

Relative Humidity ◽

Dimensional Stability ◽

Furfuryl Alcohol ◽

Lignin Content ◽

Moisture Sorption ◽

Dimensional Change ◽

Poplar Wood ◽

Sorption Coefficient ◽

Dimensional Changes ◽

Sinusoidal Shape

AbstractDegradation of lignin occurs naturally in wood due to the influence of microorganisms or photic radiation. To improve the properties of wood with low lignin content, furfuryl alcohol (FA) at the concentration of 25% was used to modify poplar wood (Populus euramericana Cv.) after partial delignification. Moisture sorption and dimensional stability of the samples were investigated under dynamic conditions where the relative humidity (RH) was changed sinusoidally between 45% and 75% at 25°C. Both the moisture content (MC) and the tangential dimensional change varied with a sinusoidal shape similar to the RH. Hygroscopicity and hygroexpansion increased after delignification, while furfurylation led to an inverse impact by reducing MC, dimensional changes, amplitudes of MC and dimensional changes, moisture sorption coefficient (MSC), and humidity expansion coefficient (HEC). After delignification and further furfurylation, the MC and the dimensional changes were reduced by about 20%, and the maximum drop in amplitudes of MC and dimensional changes was about 30%, while the MSC and the HEC decreased by over 15%. In addition, the furfurylated wood with low lignin content exhibited lower sorption hysteresis and swelling hysteresis.

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Influence of Moisture Sorption on Swelling of Mahogany (Swietenia macrophylla King) Wood

Holzforschung ◽

10.1515/hf.2001.096 ◽

2001 ◽

Vol 55 (6) ◽

pp. 590-594 ◽

Cited By ~ 6

Author(s):

R. Arévalo ◽

R.E. Hernández

Keyword(s):

Moisture Content ◽

Equilibrium Moisture Content ◽

Radial Direction ◽

Moisture Sorption ◽

Tangential Direction ◽

Order Effects ◽

Swelling Ratio ◽

Swietenia Macrophylla ◽

Dimensional Changes ◽

Moisture Conditions

Summary Samples of mahogany wood (Swietenia macrophylla King) from Peru were used for moisture sorption tests associated with swelling tests at 25°C. Seven adsorption and five desorption moisture conditions were investigated to study the differences in swelling between adsorption and desorption curves at a given equilibrium moisture content. The results demonstrated that dimensional changes in the tangential direction and in volume were greater for desorption than for adsorption. The presence of these second order effects of moisture sorption in mahogany wood were not detected in the radial direction. Finally, the tangential/radial swelling ratio of this wood was lower in both states of sorption, and was lower in adsorption than in the desorption state.

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Dimensional changes in pyrolytic graphite under fast-neutron irradiation

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1966.0028 ◽

1966 ◽

Vol 260 (1109) ◽

pp. 37-49 ◽

Cited By ~ 64

Keyword(s):

Thermal Expansion ◽

Fast Neutron ◽

Pyrolytic Graphite ◽

Irradiation Damage ◽

Polycrystalline Materials ◽

Dimensional Changes ◽

Thermal Expansion Coefficients ◽

Oriented Polycrystalline ◽

Expansion Coefficients ◽

High Doses

Measurements are reported of the principal strains and changes in principal thermal expansion coefficients of various grades of pyrolytic graphite after fast-neutron bombardment at constant temperatures in the range 150 to 650 °C. The pyrolytic graphites used in these studies possess properties approaching those of a monocrystal and the irradiation effects observed thus closely represent those expected in a crystal. The observations are compared with previous inferences of the behaviour of crystals in less well oriented polycrystalline materials under the same irradiation conditions and are discussed in terms of recent theories of the accumulation of irradiation damage in fast-neutron irradiated graphite. The existence of a new type of vacancy configuration is postulated to explain the crystal dimensional changes at high doses and high temperatures. A qualitative explanation of the changes in crystal thermal expansion coefficients is proposed.

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Dynamic moisture sorption and hygroexpansion of Populus euramericana Cv. under two cyclic hygrothermal conditions

Holzforschung ◽

10.1515/hf-2016-0015 ◽

2016 ◽

Vol 70 (12) ◽

pp. 1191-1199 ◽

Cited By ~ 6

Author(s):

Tiantian Yang ◽

Erni Ma ◽

Jianhui Zhang

Keyword(s):

Relative Humidity ◽

Moisture Content ◽

Environmental Conditions ◽

Moisture Sorption ◽

Longitudinal Direction ◽

Measured Data ◽

Populus Euramericana ◽

Dimensional Changes ◽

Unit Change ◽

Condition B

Abstract Poplar (Populus euramericana Cv.) specimens, 20 mm in radial (r) and tangential (t) directions with thicknesses of 4 mm and 10 mm along the longitudinal direction, were subjected to cyclic environmental conditions, in the course of which the relative humidity (RH) changed sinusoidally between 75% and 45% at 20°C (condition A), or the temperature (T) was changed sinusoidally within 5–35°C at 60% RH (condition B). Moisture content (MC), as well as the t- and r-dimensional changes were measured as a response to the dynamic environmental conditions. The measured data also changed sinusoidally but they lagged behind the triggering original RH or T data. This effect was much higher under condition A than under condition B. The observed equivalent RH and T changes at different ΔMCs or Δts served for comparison of the responses to RH and T, and the former were less pronounced than the latter. MC and t-dimensional changes per unit change of RH were greater than those per unit change of T but still lower than static values. In summary, the effects of dynamic RH change are larger than those of T, especially concerning MC responses compared to dimensional changes.

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Fragmentary Theory of Secularization and Religionization — Changes in the Family Structure as a Case Study

Politics and Religion ◽

10.1017/s1755048316000730 ◽

2016 ◽

Vol 10 (2) ◽

pp. 363-388 ◽

Cited By ~ 3

Author(s):

Netanel Fisher

Keyword(s):

Family Structure ◽

Dimensional Changes ◽

Civil Marriage ◽

Family Patterns ◽

Opposite Trend ◽

The Family ◽

Modern Family ◽

The One ◽

Central Claim

AbstractThe central claim of this article is that the multi-dimensional changes in the modern family structure may be explained as a manifestation of the simultaneous processes of secularization and religionization. On the one hand, the rising acceptance of secular alternatives to the traditional family structure indicates that modernization processes weaken religious behavior and authority, as the classical secularization thesis has claimed. On the other hand, ongoing loyalty to the religious family patterns, and even their relative intensification, reflect the opposite trend. Serving as a case study, the changes in the Israeli religious family structure — reflected by civil marriage, cohabitation, and out-of-wedlock children — clearly illustrate how modernization generates horizontal and vertical fragmental processes in which religion and secularism supplement as well as compete with each other, creating an increasingly divided society in which religiosity and secularism flourish side by side among various groups and within distinct realms.

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Effect of moisture sorption state on transverse dimensional changes in wood

European Journal of Wood and Wood Products ◽

10.1007/s00107-003-0437-y ◽

2004 ◽

Vol 62 (1) ◽

pp. 50-55 ◽

Cited By ~ 14

Author(s):

S. S. Chauhan ◽

P. Aggarwal

Keyword(s):

Moisture Sorption ◽

Dimensional Changes ◽

Effect Of Moisture

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On-line monitoring of hygroscopicity and dimensional changes of wood during thermal modification by means of neutron imaging methods

Holzforschung ◽

10.1515/hf-2014-0008 ◽

2015 ◽

Vol 69 (1) ◽

pp. 87-95 ◽

Cited By ~ 13

Author(s):

Walter Sonderegger ◽

David Mannes ◽

Anders Kaestner ◽

Jan Hovind ◽

Eberhard Lehmann

Keyword(s):

Water Saturation ◽

Sorption Isotherms ◽

European Beech ◽

Tangential Direction ◽

Thermal Modification ◽

Neutron Imaging ◽

Sorption Behaviour ◽

Dimensional Changes ◽

Colour Measurements ◽

Before And After

Abstract European beech (Fagus sylvatica L.) and Norway spruce [Picea abies (L.) Karst.] have been thermally modified in a combined air-steam atmosphere between 70°C and 150°C and pressures up to 4 bar, and the changes of dimensions and moisture contents (MC) of the samples were studied in-situ by means of neutron imaging (NI). This non-invasive testing method offers unique opportunities. NI is highly sensitive for hydrogen and thus well suited for monitoring the MC changes, although some metals (e.g., Al), indispensable for sample environments under high temperature and pressure, are practically transparent to neutrons. The results show that the modification induced changes of MC and dimensions both in radial and tangential direction can well be determined by NI. Dimensional changes from water saturation to oven-dry state, the sorption isotherms, and the differential swelling were observed. Additionally, the sorption behaviour at 20°C was investigated after thermal modification and colour measurements were carried out before and after the thermal treatment.

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Evaluation of the Dimensional Stability of Black Poplar Wood Modified Thermally in Nitrogen Atmosphere

Materials ◽

10.3390/ma14061491 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1491

Author(s):

Olga Bytner ◽

Agnieszka Laskowska ◽

Michał Drożdżek ◽

Paweł Kozakiewicz ◽

Janusz Zawadzki

Keyword(s):

Dimensional Stability ◽

Nitrogen Atmosphere ◽

Thermal Modification ◽

Poplar Wood ◽

Dimensional Changes ◽

Processing Times ◽

Modification Process ◽

Black Poplar ◽

Tangential Directions ◽

Modified Wood

Black poplar (Populus nigra L.) was thermally modified in nitrogen atmosphere. The effects of the modification process on poplar wood were evaluated for temperatures: 160 °C, 190 °C, and 220 °C applied for 2 h; and 160 °C and 190 °C for 6 h. The percentual impact of temperature and time of modification on the properties of modified wood was analysed. The study permitted the identification correlations between the chemical composition and selected physical properties of thermally modified poplar wood. The dimensional stability of poplar wood was improved after thermal modification in nitrogen. The higher the temperature of modification, the lower the equilibrium moisture content (EMC) of black poplar. At the temperature of 220 °C, EMC was two times lower than the EMC of non-modified black poplar. It is also possible to reduce the dimensional changes of wood two-fold (at the modification temperature of 220 °C), both in radial and tangential directions, independently of the acclimatization conditions (from 34% to 98% relative humidity, RH). Similar correlations have been found for wood that has been soaked in water. Higher modification temperatures and longer processing times contributed to a lower swelling anisotropy (SA).

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Effects of Thermo-Vibro-Mechanic® densification on the density and swelling of pre-treated Uludağ fir and black poplar wood

BioResources ◽

10.15376/biores.16.1.1581-1599 ◽

2021 ◽

Vol 16 (1) ◽

pp. 1581-1599

Author(s):

Mehmet Budakçı ◽

Süleyman Şenol ◽

Mustafa Korkmaz

Keyword(s):

Compression Ratio ◽

Tangential Direction ◽

Populus Nigra ◽

Low Density ◽

Poplar Wood ◽

Application Time ◽

Black Poplar ◽

Different Temperatures ◽

Tangential Directions ◽

Control Samples

The radial and tangential swelling as well as the fully dried density of low-density wood materials densified via the Thermo-Vibro-Mechanic® method were evaluated in response to applying wood stain and preservative. The samples obtained from Uludağ fir (Abies bornmüelleriana Mattf.) and black poplar (Populus nigra L.) in the radial and tangential direction were pre-treated with wood stain and preservative before undergoing Thermo-Vibro-Mechanic® densification. Thermo-Vibro-Mechanic® densification was performed at three different temperatures (100 °C ± 3 °C, 120 °C ± 3 °C, and 140 °C ± 3 °C), three different vibration pressures (0.60 MPa, 1.00 MPa, and 1.40 MPa), and three different vibration times (20 s, 60 s, and 100 s). Afterwards, changes in the fully dried density and swelling amounts in the radial and tangential directions of the samples were determined. The fully dried density increased by 15.4% to 38% and the radial and tangential swelling amounts increased by 73.2% to 242.6%, when the densified samples were compared to the control samples. In general, the fully dried density and swelling values increased depending on the Thermo-Vibro-Mechanic® densification parameters; higher values were found as the compression ratio and total application time increased.

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