Effects of thermo-hygro-mechanical (THM) treatment on the viscoelasticity of in-situ lignin

Holzforschung ◽  
2017 ◽  
Vol 71 (6) ◽  
pp. 455-460 ◽  
Author(s):  
Juan Guo ◽  
Jiangping Yin ◽  
Yonggang Zhang ◽  
Lennart Salmén ◽  
Yafang Yin
Keyword(s):  
Compression Ratio ◽  
Softening Temperature ◽  
Mechanical Analysis ◽  
Wood Products ◽  
Steam Treatment ◽  
Steam Temperature ◽  
Appreciable Change ◽  
Treatment Conditions ◽  
Softening Process

Abstract For producing wood products without fractures based on thermo-hygro-mechanical (THM) treatments, it is essential to understand how steaming and compression change the wood softening and cell wall components. In this paper, the effects of compression combined with steam treatment (CS) on the viscoelasticity of the in-situ lignin of Chinese fir has been investigated through dynamic mechanical analysis (DMA) under fully saturated conditions. Several variations were studied, such as the softening temperature (Tg) and apparent activation energy (ΔHa) of the softening process in response to CS treatment conditions (such as steam temperature and compression ratio) under separate consideration of earlywood (EW) and latewood (LW). No difference between EW and LW with respect to the viscoelasticity was noted. Tg and ΔHa of the lignin softening were nearly unaffected by the compression ratio, but were highly influenced by the steam temperature. The Tg decreased significantly with CS treatments at or above 160oC, but showed no appreciable change, compared to the native wood, at the lower steaming temperature of 140oC. ΔHa increased at higher steam temperatures, while ΔHa showed a decreasing tendency with decreasing Tg. This indicates that lignin undergoes a simultaneous depolymerization as well as a condensation during CS treatment.

Influence of Acid-Treated Carbon Nano-Tubes on the Microstructure and Properties of Carbon Nano-Tubes Polyurethane Composites

2010 ◽  
Vol 146-147 ◽  
pp. 805-809
Author(s):  
Ji You Gu ◽  
Lan Zhang ◽  
Xian Kai Jiang
Keyword(s):  
Photoelectron Spectroscopy ◽  
Acid Treatment ◽  
In Situ Polymerization ◽  
Mechanical Analysis ◽  
X Ray ◽  
Carbon Nano Tubes ◽  
Dynamic Storage ◽  
Treated Carbon ◽  
Polyurethane Composites

The investigations including the acid treatment to multi-walled carbon nano-tubes (MWNTs) and the synthesis of MWNTs/polyurethane composites via in situ polymerization were done. X-ray Photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA) were utilized for evaluating the effects of acid-treated MWNTs on the properties and microstructure of the composites. The results indicated that carboxyl groups could be successfully introduced onto the surface of MWNTs by acid treatment. The dynamic storage modulus and glass transition temperature of composites increased with the existence of MWNTs. The improvement of polyurethane by acid-treated MWNTs performed better compared to raw MWNTs.

Viscoelastic properties of woody hemp core

Holzforschung ◽  
2011 ◽  
Vol 65 (2) ◽  
Author(s):  
Rahime Bag ◽  
Johnny Beaugrand ◽  
Patrice Dole ◽  
Bernard Kurek
Keyword(s):  
Cell Wall ◽  
Viscoelastic Properties ◽  
Specific Effect ◽  
Mechanical Analysis ◽  
Low Molecular Weight ◽  
Dielectric Analysis ◽  
Technological Transformation ◽  
Chain Mobility ◽  
Cell Wall Polymers

Abstract The aim of this study was to determine the effect of removing extractives from the woody core of hemp (chènevotte) on the chain mobility of hemicelluloses and lignins, which can react during technological transformation such as de-fibering and/or composite materials production. Extractives are molecules with low molecular weight, which are present in the cell wall matrix and can be readily removed by solvents. In the present paper, the nature and amounts of extractives, removed under different conditions and with solvents of different polarities, were determined. The mobility and structural relaxations of lignins and hemicelluloses were stu-died in situ by dynamic mechanical analysis and dielectric analysis under controlled moisture content. Extractions at low temperature led to rigidification of lignins and plasticizing of hemicelluloses, probably due to local changes by the selective removal of molecules interacting with the polymers. Probably, the accessibility of hemicelluloses to plasticizing water was increased at controlled humidity. In contrast, hot extractions including water induced rigidification of the hemi-celluloses and plasticizing of lignins. This could be related to a combination of molecule extractions and chemical modi-fications of both polymers. This interpretation is supported by the variation of activation energy for relaxation of hemi-celluloses. It can be concluded that each type of extraction has a clear specific effect on the relaxation properties of the amorphous cell wall polymers.

scholarly journals Morphology, Thermal, Mechanical Properties and Rheological Behavior of Biodegradable Poly(butylene succinate)/poly(lactic acid) In-Situ Submicrofibrillar Composites

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2422 ◽  
Author(s):  
Zhiwen Zhu ◽  
Hezhi He ◽  
Bin Xue ◽  
Zhiming Zhan ◽  
Guozhen Wang ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Cold Drawing ◽  
Mechanical Analysis ◽  
Poly Lactic Acid ◽  
Fiber Morphology ◽  
Molding Process ◽  
Butylene Succinate ◽  
Low Frequencies ◽  
Biodegradable Poly

In this study, biodegradable poly(butylene succinate)/poly(lactic acid) (PBS/PLA) in-situ submicrofibrillar composites with various PLA content were successfully produced by a triple-screw extruder followed by a hot stretching−cold drawing−compression molding process. This study aimed to investigate the effects of dispersed PLA submicro-fibrils on the thermal, mechanical and rheological properties of PBS/PLA composites. Morphological observations demonstrated that the PLA phases are fibrillated to submicro-fibrils in the PBS/PLA composites, and all the PLA submicro-fibrils produced seem to have a uniform diameter of about 200nm. As rheological measurements revealed, at low frequencies, the storage modulus (G’) of PBS/PLA composites has been increased by more than four orders of magnitude with the inclusion of high concentrations (15 wt % and 20 wt %) of PLA submicro-fibrils, which indicates a significant improvement in the elastic responses of PBS melt. Dynamic Mechanical Analysis (DMA) results showed that the glass transition temperature (Tg) of PBS phase slightly shifted to the higher temperature after the inclusion of PLA. DSC experiments proved that fiber morphology of PLA has obvious heterogeneous nucleation effect on the crystallization of PBS. The tensile properties of the PBS/PLA in-situ submicrofibrillar composites are also improved compared to neat PBS.

scholarly journals Focused ion beam preparation of microbeams for in situ mechanical analysis of electroplated nanotwinned copper with probe type indenters

2020 ◽  
Vol 279 (3) ◽  
pp. 212-216
Author(s):  
STUART ROBERTSON ◽  
SCOTT DOAK ◽  
FU‐LONG SUN ◽  
ZHI‐QUAN LIU ◽  
CHANGQING LIU ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Mechanical Analysis ◽  
Probe Type

Catecholated graphene-filled polyimide with enhanced mechanical, thermal, and tribological properties

2020 ◽  
pp. 095400832094035
Author(s):  
Xing Wu ◽  
Zhengyu Jin ◽  
Yuejin Zhu ◽  
Haichao Zhao
Keyword(s):  
Friction And Wear ◽  
In Situ Polymerization ◽  
Cycloaddition Reaction ◽  
Mechanical Analysis ◽  
Dipolar Cycloaddition ◽  
Wear Properties ◽  
Comprehensive Properties ◽  
Transmission Electron ◽  
Friction And Wear Tests

In order to achieve good dispersion of graphene in polyimide (PI), catecholated graphene (G-Cat) was prepared by 1,3-dipolar cycloaddition reaction of N-methylglycine and 3,4-dihydroxybenzaldehyde with graphene sheets. G-Cat/PI composites were prepared by in situ polymerization with pyromellitic dianhydride and 4,4-oxydianiline in the presence of G-Cat. The successful modification of graphene was proved by infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy. The comprehensive properties of G-Cat/PI composites were studied by tensile, dynamic mechanical analysis, thermogravimetric analysis, and friction and wear tests. By observing the morphology of wear marks, the friction and wear properties of the composites were emphatically analyzed. Therefore, graphene/PI composites were expected to have broad application prospects in lubrication and wear resistance.

scholarly journals In Situ Mechanical Analysis of the Nanoscopic Solid Electrolyte Interphase on Anodes of Li‐Ion Batteries

2019 ◽  
Vol 6 (16) ◽  
pp. 1900190 ◽  
Author(s):  
Boaz Moeremans ◽  
Hsiu‐Wei Cheng ◽  
Claudia Merola ◽  
Qingyun Hu ◽  
Mehtap Oezaslan ◽  
...  
Keyword(s):  
Solid Electrolyte ◽  
Solid Electrolyte Interphase ◽  
Mechanical Analysis ◽  
Li Ion Batteries ◽  
Li Ion

In-Situ FT-IR Monitoring of a Solar Flux Induced Chemical Process

1997 ◽  
Vol 119 (3) ◽  
pp. 219-224 ◽  
Author(s):  
J. R. Markham ◽  
J. E. Cosgrove ◽  
C. M. Nelson ◽  
A. S. Bonanno ◽  
R. E. Schlief ◽  
...  
Keyword(s):  
Flow Reactor ◽  
Hydrogen Bromide ◽  
Solar Flux ◽  
Solar Furnace ◽  
Critical Parameters ◽  
Steam Temperature ◽  
Photochemical Process ◽  
Ft Ir ◽  
Formed Hydrogen

The capability to perform in-situ, on-line monitoring of processes induced by concentrated solar flux will enhance the development and utilization of solar technologies. Temperature measurements and chemical concentration measurements provide an understanding of the ongoing chemistry, process limits, and process reproducibility. A Fourier transform infrared (FT-IR) spectrometer was optically coupled to a quartz flow reactor at the High Flux Solar Furnace of the National Renewable Energy Laboratory in Golden, CO. In-situ emission/transmission spectroscopy was utilized to simultaneously monitor steam temperature and the concentration of formed hydrogen bromide during the solar flux induced reaction of steam and bromine. The photochemical process is being investigated for the production of industrial quantities of hydrogen and oxygen, where downstream electrolysis of the formed hydrogen bromide provides the hydrogen and regenerates bromine. Steam temperature was measured to increase upon the addition of bromine to the reactor. Gas temperature increases of 200°C to 400°C were observed. Hydrogen bromide concentrations up to ten percent of the reactor gas volume were measured. The FT-IR system provided quantitative information of two critical parameters of the measured process and serves to accelerate this technology area.

scholarly journals Melanocyte pigmentation stiffens murine cardiac tricuspid valve leaflet

2009 ◽  
Vol 6 (40) ◽  
pp. 1097-1102 ◽  
Author(s):  
Kantesh Balani ◽  
Flavia C. Brito ◽  
Lidia Kos ◽  
Arvind Agarwal
Keyword(s):  
Mechanical Properties ◽  
Storage Modulus ◽  
Tricuspid Valve ◽  
Viscoelastic Properties ◽  
Mechanical Analysis ◽  
Current Work ◽  
Valve Leaflet ◽  
Stiffness Measurement ◽  
Proper Functioning

Pigmentation of murine cardiac tricuspid valve leaflet is associated with melanocyte concentration, which affects its stiffness. Owing to its biological and viscoelastic nature, estimation of the in situ stiffness measurement becomes a challenging task. Therefore, quasi-static and nanodynamic mechanical analysis of the leaflets of the mouse tricuspid valve is performed in the current work. The mechanical properties along the leaflet vary with the degree of pigmentation. Pigmented regions of the valve leaflet that contain melanocytes displayed higher storage modulus (7–10 GPa) than non-pigmented areas (2.5–4 GPa). These results suggest that the presence of melanocytes affects the viscoelastic properties of the mouse atrioventricular valves and are important for their proper functioning in the organism.

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