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

Holzforschung ◽  
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.

scholarly journals Extended-pour and conventional alginates: effect of storage time on dimensional accuracy and maintenance of details

2021 ◽  
Vol 26 (3) ◽  
Author(s):  
Sandro Basso BITENCOURT ◽  
Isabela Araguê CATANOZE ◽  
Emily Vivianne Freitas da SILVA ◽  
Karina Helga Leal TURCIO ◽  
Daniela Micheline dos SANTOS ◽  
...  
Keyword(s):  
Dimensional Stability ◽  
High Stability ◽  
Digital Camera ◽  
Dimensional Accuracy ◽  
Dimensional Change ◽  
Clinical Results ◽  
Dimensional Changes ◽  
Plastic Bags ◽  
Significant Difference ◽  
Student’S T

ABSTRACT Objective: This study aimed to evaluate the dimensional stability and maintenance of details of conventional and high stability alginates up to 5-day storage. Methods: Two types of alginates were selected (n=10) for this study, conventional (Hydrogum) and high stability alginates (Hydrogum 5), which were produced with the aid of a cylindrical metal block and a ring-shaped metal mold (Specifications 18, 19, and 25, ANSI/ADA). Ten images were obtained from the molds for the dimensional stability test, which were taken immediately after their production and at each different storage periods (15 min, 24 h, 48 h, 72 h, 96 h, and 120 h) by a digital camera. The specimens were kept hermetically sealed in plastic bags (23°C) and then used to obtain 140 (n=70) dental stone models, used in the detail reproduction test, in which the angular accuracy of three grooves (20 µm, 50 µm, and 75 µm) was observed at each period. The details reproduction accuracy was classified using a predetermined score classification. Measurements of dimensional changes were made in the Corel DRAW X6 program. The data were submitted to the Student’s t-test (α?#8197;= 0.05). Results: A statistically significant difference concerning the size of the matrix was observed after 24h for both alginates, and a statistically significant negative linear dimensional change (contraction) was verified after 24 h of storage (1.52% for the high stability alginate, and 1.32% for the conventional alginate). The high stability alginate kept the full details for 72 hours, while the conventional alginate, for 24 h. Both alginates reproduced the 75 µm groove at all storage periods. Conclusion: Impressions made with both alginates presented satisfactory clinical results when the alginates were immediately poured.

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

Holzforschung ◽  
2016 ◽  
Vol 70 (12) ◽  
pp. 1191-1199 ◽  
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.

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

Materials ◽  
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).

Comparison of dynamic sorption and hygroexpansion of wood by different cyclic hygrothermal changing effects II

2017 ◽  
Vol 41 (4) ◽  
pp. 360-376 ◽  
Author(s):  
Tiantian Yang ◽  
Jiamin Wang ◽  
Nan Sheng ◽  
Erni Ma
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Average Rate ◽  
Dimensional Change ◽  
Dimensional Changes ◽  
Wood Processing ◽  
Content Change ◽  
Period 2 ◽  
Two Factors ◽  
Temperature Constant

Dynamic wood sorption and hygroexpansion by different cyclic hygrothermal changing effects were investigated. Poplar ( populus euramericana Cv.) specimens, 20 mm in radial (R) and tangential (T) directions with two thicknesses of 4 and 10 mm along the grain, were subjected to three rounds under control of these two factors. In the first round, relative humidity changed sinusoidally between 75% and 45% with temperature constant at 20°C. In the second round, temperature changed sinusoidally between 5°C and 35°C with relative humidity constant at 60%. In the third round, relative humidity changed sinusoidally between 75% and 45%, simultaneously temperature changed between 5°C and 35°C. In each round, three sinusoidal change cyclic periods were operated: 1, 6, and 24 h. The measurement of moisture and dimensional responses showed the following results: (1) moisture and dimensional changes were both presented generally in sinusoidal mode. Their amplitudes were lower for thicker specimens exposed to shorter cyclic period. (2) Comparing with the effect brought by changing a single parameter, that is, changing relative humidity or temperature alone, changing relative humidity and temperature together brought greater impact on the specimens. Under a typical air-dry condition at 20°C and 60% relative humidity, this comparison was more obvious, especially for dimensional changes. (3) When the amplitudes resulted in changing relative humidity and changing temperature were superposed, its value was higher than which brought by changing relative humidity and temperature together with the maximum ratio of 1.48. (4) Moisture-content change (ΔMC) and variation of T-dimensional change (ΔT) were all linearly correlated with treating time. Less time was needed to reach a given ΔMC or ΔT, namely, larger ΔMC or ΔT could be attained within the same time by changing relative humidity and temperature together, where the greatest average rate of wood sorption and hygroexpansion could be observed. All these results indicated that in practice, sinusoidally controlling the changes in relative humidity and temperature together was most efficient to adjust the moisture content and deformation in wood processing and application.

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

Holzforschung ◽  
2018 ◽  
Vol 72 (11) ◽  
pp. 943-950 ◽  
Author(s):  
Tiantian Yang ◽  
Erni Ma ◽  
Jinzhen Cao
Keyword(s):  
Moisture Sorption ◽  
Tangential Direction ◽  
Hydroxyl Groups ◽  
Phase Lag ◽  
Matrix Stiffness ◽  
Poplar Wood ◽  
Positive Relation ◽  
Dimensional Changes ◽  
Opposite Trend ◽  
Expansion Coefficients

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%.

scholarly journals Dimensional stability of stored extended-pour irreversible hydrocolloids materials

2021 ◽  
Vol 10 (16) ◽  
pp. e192101623338
Author(s):  
Rudys Rodolfo de Jesus Tavarez ◽  
Etevaldo Matos Maia-Filho ◽  
Adriana Santos Malheiros ◽  
Oswaldo Serra Santos-Neto ◽  
Shelon Cristina Souza Pinto ◽  
...  
Keyword(s):  
Dimensional Stability ◽  
Digital Camera ◽  
Multiple Comparisons ◽  
Dimensional Change ◽  
Dimensional Changes ◽  
Parallel Lines ◽  
Significant Difference ◽  
Adobe Photoshop ◽  
Equivalent Distance ◽  
Storage Times

The purpose of this study was to evaluate the linear dimensional stability of four extended-pour irreversible hydrocolloids (EPIHs). Material and Methods: Five samples per material (Cavex ColorChange, Cavex Orthotrace, Jeltrate Plus, and Orthoprint) were prepared following the manufacturers’ instructions. The samples were prepared using a cylindrical matrix coupled with a nylon-polyamide ring. Two parallel, 25-mm equidistant lines were made on its surface following ANSI/American Dental Association (ADA) Specification 18 for plaster reproducibility and compatibility and Specification 19 for linear dimensional change. The samples were stored in an environment with a relative humidity of 70% (± 3) and temperature of 28°C (± 2). Photo images were obtained using a digital camera to record images for 120 hours, with a standardized distance of 80cm between the lens and the specimen. Adobe Photoshop CS3 software was used for the measurement of the recorded images. The measurements refer to the equivalent distance between the two parallel lines printed on the samples. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey’s test for multiple comparisons between the means of the groups. Results: There was no statistically significant difference (p > 0.05) when EPIHs were compared at the same time of evaluation. Orthoprint, Cavex Orthotrace, and Cavex Colorchange presented with least dimensional stability up to 24 hours (p > 0.05) of storage, followed by Jeltrate Plus (48 hours). Conclusions: Storage of EPIHs for more than 24 hours for Cavex ColorChange and 48 hours for others EPIHs studied produces significant dimensional changes in the impressions stored at a humidity of 70% (± 3) and temperature of 28°C (± 2). Extended storage times produce large dimensional changes.

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