Dynamic viscoelastic properties of Chinese fir (Cunninghamia lanceolata) during moisture desorption processes

Abstract The viscoelasticity of Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) during moisture desorption processes were examined at 30°C and two relative humidity (RH) modes: RHramp-down mode from 85 to 0% RH, and RHisohume mode at 0, 30, and 60% RH, respectively. Dynamic viscoelastic properties were determined in a multi-frequency range of 1, 2, 5, 10, and 20 Hz. In both RH modes, desorption of water resulted in increasing stiffness and decreasing damping. The reduction in moisture content caused an unstable state in the cell wall due to the formation of free volumes in cell wall and rearrangement of hydrogen bonds within the polymer networks. Higher ramping rates resulted in greater destabilization, and the unstable state was more pronounced at a lower frequency. The ratio of storage modulus at 1 and 20 Hz remained unchanged during both RH modes. The ratios of loss modulus and loss factor at 1 and 20 Hz increased during the RHramp-down and decreased during the RHisohume period. The changes of loss modulus or loss factor ratios at two frequencies were suitable for evaluation of the unstable state. The instability was aggravated with reducing RH and slightly recovered at constant RH.

Download Full-text

Influence of hygrothermal condition on dynamic viscoelasticity of Chinese fir (Cunninghamia lanceolata). Part 2: moisture desorption

Holzforschung ◽

10.1515/hf-2017-0130 ◽

2018 ◽

Vol 72 (7) ◽

pp. 579-588 ◽

Cited By ~ 7

Author(s):

Tianyi Zhan ◽

Jiali Jiang ◽

Jianxiong Lu ◽

Yaoli Zhang ◽

Jianmin Chang

Keyword(s):

Cell Wall ◽

Loss Modulus ◽

Adsorbed Water ◽

Chinese Fir ◽

Cunninghamia Lanceolata ◽

Dynamic Viscoelasticity ◽

Heating Effects ◽

Plateau Area ◽

Set Up ◽

Moisture Desorption

AbstractThe influence of hygrothermal condition on dynamic viscoelasticity of Chinese fir (Cunninghamia lanceolata) during the moisture desorption (MDes) process was investigated. The ambient hygrothermal environments were set up as a series of constant temperatures and two relative humidity (RH) modes (RHramp-downand RHisohume). The MDesprovided space for the rearrangement of the hydrogen bonds (Re-HB) and caused a mechano-sorptive (MS) effect. The enhancement of the Re-HB effect negatively correlated with the increment of loss modulus, while the elevation of the MS and the heating effects intensified the loss modulus. Lower values of RHc, determining the plateau area of loss modulus, were obtained at higher temperatures or greater RH ramping rates. The residual instability in the wood cell wall was quantitatively characterized by the extent of the MS effect. Residual instability was inversely proportional to the RHisohumelevel during the MDesprocess. The study of time dependent viscoelastic properties under moisture changing process provided insight into the condition of adsorbed water in the cell wall and optimized the manufacturing technique involved in the thermo-hygro-mechanical treatment of wood.

Download Full-text

Moisture-dependent orthotropic viscoelastic properties of Chinese fir wood during quenching in the temperature range of 20 to −120°C

Holzforschung ◽

10.1515/hf-2018-0281 ◽

2019 ◽

Vol 74 (1) ◽

pp. 10-19 ◽

Cited By ~ 3

Author(s):

Zhu Li ◽

Jiali Jiang ◽

Jianxiong Lyu

Keyword(s):

Cell Wall ◽

Viscoelastic Properties ◽

Wood Cell Wall ◽

Bound Water ◽

Free Water ◽

Chinese Fir ◽

High Temperature Side ◽

Temperature Spectrum ◽

Β Relaxation ◽

Temperature Side

AbstractAn understanding of wood’s moisture-dependent viscoelastic properties under various temperature conditions is important for assessing its utilization and product quality. In this study, we investigated the influence of moisture content (MC) on the orthotropic viscoelasticity of Chinese fir wood (Cunninghamia lanceolata [Lamb.] Hook.) during quenching ranging from 20 to −120°C. The storage modulus (E′) and loss factor (tan δ) of the longitudinal (L), radial (R) and tangential (T) specimens were determined for nine MC levels ranging from 0.6 to 60.0%. The results showed that E′ generally decreased with increasing amount of bound water in all orthotropic directions, regardless of the temperature. In contrast, a sharp increase in E′ was observed at temperatures below 0°C when free water was present, due to the formation of ice within the cell lumens. The γ-relaxation and β-relaxation were observed in the temperature spectrum. A comparison demonstrates that the β-relaxation showed evident grain orientation. When only bound water was present in the wood cell wall, one clear γ-relaxation was found for all orthotropic directions. In contrast, only the high-temperature side of the γ-relaxation was observed in the three anatomic directions in specimens with free water, which might be related to the amorphous wood cell wall coupling with the frozen free water during the quenching process. In addition, the differences in peak temperatures of the γ-relaxation among the three main directions diminished with increasing bound water.

Download Full-text

Viscoelastic Properties of the Chinese Fir (Cunninghamia lanceolata) during Moisture Sorption Processes Determined by Harmonic Tests

Materials ◽

10.3390/ma9121020 ◽

2016 ◽

Vol 9 (12) ◽

pp. 1020 ◽

Cited By ~ 10

Author(s):

Tianyi Zhan ◽

Jianxiong Lu ◽

Jiali Jiang ◽

Hui Peng ◽

Anxin Li ◽

...

Keyword(s):

Viscoelastic Properties ◽

Moisture Sorption ◽

Chinese Fir ◽

Cunninghamia Lanceolata

Download Full-text

Dynamic Rheological Behaviors of the Bone Scaffold Reinforced by Chitin Fibres

Materials Science Forum ◽

10.4028/www.scientific.net/msf.475-479.2387 ◽

2005 ◽

Vol 475-479 ◽

pp. 2387-2390 ◽

Cited By ~ 13

Author(s):

X.M. Li ◽

Qing Ling Feng

Keyword(s):

Viscoelastic Properties ◽

Loss Factor ◽

Complex Modulus ◽

Loss Modulus ◽

Complex Viscosity ◽

Materials Processing ◽

Bone Scaffold ◽

Rheological Behaviors ◽

Wide Range ◽

Yielding Behavior

In this study, a novel bioabsorbable porous bone scaffold reinforced by chitin fibres was prepared, the porosity of which is about 90 % and the pore size is approximately 200µm. The Advanced Rheological Enlarged System (ARES) was used to study the dynamic rheological behaviors of the ropy materials which would be made into the reinforced scaffold. The increase of the fibres’ volume content (Cf) enhanced the complex modulus (G*) and complex viscosity (h*) of the materials, the reason of which is that the fibres formed networks in the materials. When Cf increased from 35 % to 45 %, the storage modulus (G’) and loss modulus (G’’) curve showed obvious yielding behavior, which indicates that G’ and G’’ of the materials are hardly variable in a wide range. When Cf was more than 35 %, the loss factor (tand) was obviously lower than 1 and the materials exhibited viscoelastic properties, which result in a disadvantage for materials’ processing.

Download Full-text

Frequency-dependent viscoelastic properties of Chinese fir (Cunninghamia lanceolata) under hygrothermal conditions. Part 2: moisture desorption

Holzforschung ◽

10.1515/hf-2018-0209 ◽

2019 ◽

Vol 73 (8) ◽

pp. 737-746 ◽

Cited By ~ 4

Author(s):

Tianyi Zhan ◽

Jiali Jiang ◽

Jianxiong Lu ◽

Yaoli Zhang ◽

Jianmin Chang

Keyword(s):

Shift Factor ◽

Chinese Fir ◽

Cunninghamia Lanceolata ◽

Damping Properties ◽

Master Curves ◽

Frequency Dependent ◽

Wood Stiffness ◽

Set Up ◽

Stiffness And Damping ◽

Moisture Desorption

AbstractThe frequency-dependent viscoelasticity of Chinese fir (Cunninghamia lanceolata) during moisture desorption was investigated and the applicability of the time-moisture superposition (TMS) relation on wood stiffness and damping during the moisture desorption was verified. The hygrothermal conditions for the moisture desorption were set up as six constant temperatures ranging from 30 to 80°C and three relative humidity (RH) levels at 0, 30 and 60%. Due to the elimination of water during the moisture desorption, the stiffness of the Chinese fir increased, whereas the damping decreased. With the increase in frequency, increased stiffness and decreased damping were observed. Utilizing the TMS relation, it was possible to construct master curves of wood stiffness at temperatures ranging from 30 to 80°C. The linear relationship between the shift factor and the moisture content (MC) manifested a low intermolecular cooperativity between the polymers and a narrow relaxation window. However, the TMS relation was not able to predict the wood damping properties during the moisture desorption, because wood is a multi-relaxation system. The non-proportional relationship between the free volume and MC during the moisture desorption may also explain why the TMS relation failed to construct master curves of the wood damping properties.

Download Full-text

Dynamic Mechanical Analysis of Polyurethane-Epoxy Interpenetrating Polymer Networks

High Performance Polymers ◽

10.1177/0954008309339940 ◽

2009 ◽

Vol 21 (5) ◽

pp. 608-623 ◽

Cited By ~ 45

Author(s):

Mariana Cristea ◽

Sorin Ibanescu ◽

Constantin N. Cascaval ◽

Dan Rosu

Keyword(s):

Activation Energy ◽

Molecular Dynamics ◽

Dynamic Mechanical Analysis ◽

Loss Factor ◽

Loss Modulus ◽

Polymer Networks ◽

Mechanical Analysis ◽

Interpenetrating Polymer Networks ◽

Dynamic Mechanical ◽

Tan Δ

A series of semi-interpenetrated polymer networks based on bisphenol A epoxy resin and polyurethane was synthesized by sequential procedure. The molecular dynamics of polyurethane incorporated in the resin network with increasing amounts of resin was followed by dynamic mechanical analysis. All phenomena that concur in the material are evaluated by cross-examination of the storage modulus ( E'), loss modulus ( E'') and loss factor (tan δ) variation with temperature. Complex aspects were elucidated in consecutive heating-cooling-heating cycles and by calculating the apparent activation energy of relaxations in multiplex experiments.

Download Full-text

Orthotropic Viscoelastic Properties of Chinese Fir Wood Saturated with Water in Frozen and Non-frozen States

Forest Products Journal ◽

10.13073/fpj-d-20-00069 ◽

2021 ◽

Vol 71 (1) ◽

pp. 77-83

Author(s):

Zhu Li ◽

Jiali Jiang ◽

Jianxiong Lyu ◽

Jinzhen Cao

Keyword(s):

Viscoelastic Properties ◽

Initial Temperature ◽

Loss Modulus ◽

Viscoelastic Behavior ◽

Free Water ◽

Chinese Fir ◽

Enhancement Effect ◽

Wood Industry ◽

Order Of Magnitude ◽

Water Saturated

Abstract In order to better understand the differences in orthotropic viscoelastic properties of Chinese fir (Cunninghamia lanceolata) in frozen and non-frozen states, the storage modulus (E′) and loss modulus (E″) of the longitudinal, radial, and tangential specimens were investigated under water-saturated conditions with temperatures ranging from −120°C (or 30°C) to 280°C. Results revealed that the order of magnitude in E′ for each orientation was consistent for temperatures below 0°C, while the anisotropy in E′ was reduced due to the enhancement effect of ice. Frequency-dependent γ-relaxation was observed at approximately −96°C for all orthotropic directions. A sharp discontinuity in E′ occurred at approximately 0°C for each specimen, together with the corresponding sharp peak in the E″ spectrum. Furthermore, the frozen free water had an effect on the orthotropic viscoelastic behavior in the water-saturated specimens within the range of −120°C to 280°C. Specimens with a frozen history leveled off at the initial temperature ramping phase for each orientation, while a frozen history reduced the decline in stiffness of the wood specimens. Similar to the variations in E′, the dramatic loss of water increased the complexity of the E″ values. The loss of free water also had a pronounced effect on the viscoelastic properties during the temperature ramping process. Thus, in the wood industry, it necessary to consider the variations in the orthotropic viscoelastic performance of specimens under water-saturated conditions during the water loss process.

Download Full-text

Solubilization of aluminum-bound phosphorus by root cell walls: evidence from Chinese fir, Cunninghamia lanceolata

Canadian Journal of Forest Research ◽

10.1139/cjfr-2016-0310 ◽

2017 ◽

Vol 47 (4) ◽

pp. 419-423 ◽

Cited By ~ 3

Author(s):

Pengfei Wu ◽

Guang-Yu Wang ◽

Yousry A. El-Kassaby ◽

Pan Wang ◽

Xianhua Zou ◽

...

Keyword(s):

Cell Wall ◽

Cell Walls ◽

Chinese Fir ◽

Cunninghamia Lanceolata ◽

Tissue Type ◽

Wall Material ◽

Lateritic Soils ◽

Significant Difference ◽

Old Trees ◽

Solubilizing Activity

This paper considered whether it was possible to activate nonavailable phosphorus (P) with tree root organs in lateritic soils. We investigated the cell wall content and P-solubilizing activity of xylem and phloem from six different sizes of roots from 10, 22, and 34 year old plantations of the Chinese fir Cunninghamia lanceolata (Lamb.) Hook. We found that, on average, cell wall content accounted for 81.07% of the root biomass (dry mass), and the mean solubilization of aluminum-bound phosphate by cell wall preparations was 1.89 g·kg−1. Tissue type (i.e., phloem or xylem) had a significant effect on cell wall content, with more cell wall material in the xylem, whereas P-solubilizing activity was greater in the phloem. In addition, the cell wall content of xylem increased with increasing root diameter, but P-solubilizing activity did not. A significant difference was also observed among the P-solubilizing activity of the three age classes, with lower P-solubilizing activity in the roots of 10 year old trees than in those of 22 and 34 year old trees. Since the establishment of Chinese fir plantations is increasing in southern China, where lateritic soils are widely distributed, the findings of the present study undoubtedly provide pertinent information for improving the utilization of nonavailable P by the cell walls of tree roots.

Download Full-text