Thermorheological Complexity and Fragility in Plasticized Lignocellulose

Chowdhury, Sudip; Frazier, Charles E.

doi:10.1021/bm400080f

Cited by 17 publications

(25 citation statements)

References 43 publications

(147 reference statements)

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“…The shift factors of the amorphous thermoplastics commonly exhibited non-linear temperature (or moisture) dependencies, while the experimental value of r / log MC MC a , as a function of MC, was highly linear in this study ( Figure 5). The Arrhenius (linear) behavior has also been reported for ethylene glycol and N,N-dimethylformamide plasticized wood (Laborie et al 2004;Chowdhury and Frazier 2013), and attributed to intermolecular cooperativity within polymeric materials. When the wood MC is around 0.6%, a slight relaxation occurs at 30-80°C , which may explain why Figure 6 shows the typical changes in frequency-dependent E′′ during the moisture adsorption processes when the temperatures were 30 and 80°C.…”

Section: Storage Modulusmentioning

confidence: 66%

“…Hence, the changes in stiffness by altering the temperature are somewhat similar to those caused by frequency changes. The time-temperature superposition principle (TTSP) is widely applied to predict the rheological properties of polymers at wide ranges of frequency or time (Chevali et al 2009;Townsend et al 2011;Chowdhury and Frazier 2013;Sirk et al 2013;Tan and Guo 2013;Arbe et al 2016). According to TTSP, a master curve is obtained by shifting a series of multiplexed frequency scans relative to a reference curve.…”

Section: Introductionmentioning

confidence: 99%

“…Numerous wood-TTSP studies have been carried out using both static and dynamic methods (Samarasinghe et al 1994;Lenth and Kamke 2001;Laborie et al 2004;Frazier 2005, 2006;Placet et al 2007;Dlouhá et al 2009;Peng et al 2017;Wang et al 2017;Hsieh and Chang 2018). TTSP is effective for analyzing the in situ softening of lignin and for improving the understanding of structure/property relationships in plasticized lignocellulose (Salmén 1984;Laborie et al 2004;Chowdhury and Frazier 2013). However, the applicability of TTSP to wood is still controversial, and some researchers stated that it was applicable only under limited conditions (Salmén 1984;Kelley et al 1987;Nakano 1995Nakano , 2013.…”

Section: Introductionmentioning

confidence: 99%

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Frequency-dependent viscoelastic properties of Chinese fir (Cunninghamia lanceolata) under hygrothermal conditions. Part 1: moisture adsorption

Zhan

Jiang

et al. 2019

Holzforschung

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To elucidate the frequency-dependent viscoelasticity of wood under a moisture non-equilibrium state, changes in stiffness and damping as a function of frequency were investigated during the moisture adsorption process. The moisture adsorption processes were carried out at six temperatures (30–80°C) and three relative humidity levels (30, 60 and 90% RH). During the moisture adsorption process, the wood stiffness decreased, and damping increased with the increment of moisture content (MC). Regardless of the moisture adsorption time, the wood stiffness increased, and damping decreased with the increasing testing frequency. Based on the re-organized Williams-Landel-Ferry (WLF) model, the time-moisture superposition (TMS) relation was assumed to be applicable for developing a master curve of wood stiffness during the moisture adsorption process. The frequency ranges of the stiffness master curves spanned from 16 to 23 orders of magnitude at temperatures ranging from 30 to 80°C. However, the TMS relation was not able to predict the wood damping properties during the moisture adsorption process due to the multi-relaxation system of the wood and the non-proportional relationship between free volume and MC at transient moisture conditions.

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Section: Storage Modulusmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Frequency-dependent viscoelastic properties of Chinese fir (Cunninghamia lanceolata) under hygrothermal conditions. Part 1: moisture adsorption

Zhan

Jiang

et al. 2019

Holzforschung

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“…Hook], an important commercial conifer species planted in China, was submitted to CS treatment at 140°C, 160°C and 180°C under the compression ratios of 25% and 50%. The viscoelastic behavior of the samples was studied by dynamic mechanical analysis (DMA), (Placet et al 2007;Jiang et al 2008;Chowdhury and Frazier 2013;Salmén and Olsson 2016). Ethylene glycol (EG) was applied as a softening agent, which facilitates a better determination of the T g even above 100°C ( Wennerblom et al 1996).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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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 (T g ) and apparent activation energy (ΔH a ) 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. T g and ΔH a of the lignin softening were nearly unaffected by the compression ratio, but were highly influenced by the steam temperature. The T g decreased significantly with CS treatments at or above 160 o C, but showed no appreciable change, compared to the native wood, at the lower steaming temperature of 140 o C. ΔH a increased at higher steam temperatures, while ΔH a showed a decreasing tendency with decreasing T g . This indicates that lignin undergoes a simultaneous depolymerization as well as a condensation during CS treatment.

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“…For each reference temperature (T ref ), the segmental relaxation time was calculated as τ α = 1/2πf max , where f max is the frequency at which the tan δ value reaches its maximum. 70,71 3. RESULTS AND DISCUSSION 3.1.…”

Section: Methodsmentioning

confidence: 99%

Relationship between Segmental Relaxation of Polystyrene Films and Stick–Slip Behavior during Dynamic Wetting of Liquid Droplets on Their Surfaces

Zuo

Wang

et al. 2015

J. Phys. Chem. B

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A novel method was previously reported for detecting the glass transition of thin polystyrene (PS) films by correlating the relationships between the temperature-dependent viscoelasticity of the PS films and stick-slip behavior on their surfaces during dynamic wetting of liquid droplets. In the present study, the frequency dependence of the stick-slip behavior is investigated. The results show that the stick-slip behavior of liquid dynamic wetting on PS films is dependent on the contact line velocity, which is related to the deformation frequency of the PS surface during the moving liquid front. The stick-slip behavior was revealed to be determined by a dimensionless parameter (ξ), which is the ratio of the PS segmental relaxation time (τα) and the characteristic time (τc) for PS surface deformation near the droplet contact line. When ξ is close to 1 (τα ≈ τc), the Δθ (jumping angle), a scale of the stick-slip behavior, reaches a maximum. This correlation between Δθ and ξ demonstrates that the stick-slip behavior is related to the energy dissipation caused by the PS α-relaxation process, and the peak temperature (or frequency) in Δθ corresponds to the α-relaxation temperature (time) of the polymer. These results strongly demonstrate that the utilization of the stick-slip behavior is a creditable method, similar to dynamic viscoelastic measurement, for probing the glass transition and segmental relaxation of thin polymer films.

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Thermorheological Complexity and Fragility in Plasticized Lignocellulose

Cited by 17 publications

References 43 publications

Frequency-dependent viscoelastic properties of Chinese fir (Cunninghamia lanceolata) under hygrothermal conditions. Part 1: moisture adsorption

Frequency-dependent viscoelastic properties of Chinese fir (Cunninghamia lanceolata) under hygrothermal conditions. Part 1: moisture adsorption

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

Relationship between Segmental Relaxation of Polystyrene Films and Stick–Slip Behavior during Dynamic Wetting of Liquid Droplets on Their Surfaces

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