Revisiting the thermal relaxations of poly(vinyl alcohol)

González-Campos, J. Betzabé; García-Carvajal, Zaira Y.; Prokhorov, E.; Luna-Bárcenas, Gabriel; Mendoza-Duarte, J.M.; Lara‐Romero, Javier; Río, Rosa E. del; Sánchez, Isaac C.

doi:10.1002/app.33615

Cited by 15 publications

(14 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The change in relaxation time ( τ ) against RH for EPI film with different crosslinkers before and after the post-curing treatment is shown in Figure 12. The water molecules penetrating into EPI films form hydrogen bonds with the hydroxyl groups in the main component [31], by which the interchain and intra-chain bonding among amorphous chains in the polymer may be broken [32], and the τ magnitude descends by about 30–50% as RH increases from 0 to 80%. Furthermore, it was found that the relaxation time of EPI film lengthens with the increased polyisocyanate content, also verifying the effective cross-linking between NCO groups and active hydrogen in EPI.…”

Section: Resultsmentioning

confidence: 99%

Revealing the Mechanical Properties of Emulsion Polymer Isocyanate Film in Humid Environments

Guo

Zhang

et al. 2018

Polymers

View full text Add to dashboard Cite

Knowledge of the mechanical behaviors of polymer film in humid environments is of great significance for predicting the long-term performance of emulsion polymer isocyanate (EPI) as a high-performance wood adhesive. A tri-copolymer latex was cross-linked by the general polymeric methylene diisocyanate ( p -MDI) and aqueous emulsified isocyanate (EMDI) at different loadings for preparing EPI. Furthermore, a series of uniaxial tension tests under different relative humidity (RH) were carried out on cured EPI samples before and after post-curing treatment, and the corresponding chemical structure, as well as the microstructure of polymers, was investigated in detail. In addition, a constitutive equation was formulated to calculate the viscoelastic characteristics of the adhesive layer. The results indicate that the EPI films reveal various kinds of intrinsic deformation as RH increases, and the tensile rupture stress and stiffness would obviously decrease, even at cross-linker weight ratios of up to 20%. Furthermore, the moisture resistance could be markedly improved by increasing the isocyanate content and post-cure. Importantly, EMDI-cross-linked film not only exhibits much better mechanical properties than that containing p -MDI at 0–80% RH, but is also more sensitive to post-cure. Finally, the derived viscoelastic model could efficiently track moisture-dependent stress-strain curves of EPI films, and the obtained relaxation time further reveals the influence mechanism of isocyanate and post-cure on the mechanical response of the cured polymer under moist conditions.

show abstract

Section: Resultsmentioning

confidence: 99%

Revealing the Mechanical Properties of Emulsion Polymer Isocyanate Film in Humid Environments

Guo

Zhang

et al. 2018

Polymers

View full text Add to dashboard Cite

show abstract

“…On the other hand, in a previous work [19], it was shown by dielectric and dynamic mechanical analysis that the nature of pure PVA thermal relaxations was erroneously assigned, since improper water elimination and the narrow temperature range analyzed in all the previous reports have led to misinterpretation of thermal relaxations in pure PVA. Commonly, the molecular dynamics analysis of PVA composites, and its blends with other polymers and inorganic compounds has been carried out in a narrow temperature range and based on pure PVA thermal relaxations behavior; however, if the molecular dynamics of pure PVA has been misunderstood, it could also be the case of the molecular dynamics of its composites and blends.…”

Section: Introductionmentioning

confidence: 92%

Molecular Dynamics Analysis of PVA‐AgnP Composites by Dielectric Spectroscopy

González-Campos

Prokhorov²,

Sánchez

et al. 2012

Journal of Nanomaterials

Self Cite

View full text Add to dashboard Cite

The molecular dynamics of PVA/AgnP composites were studied by dielectric spectroscopy (DS) in the 20–300°C temperature range. Improper water elimination leads to misinterpretation of thermal relaxations in PVA composites in agreement with the previous report for pristine PVA. The evaporation of water and its plasticizing effect are more evident in pure PVA confirming the existence of strong interaction between OH groups of PVA chains and AgnP. Dry films show a single nonlinear VFT dependence (from 45°C until melting) associated to theα-relaxation and, therefore, to the glass transition phenomenon and from dielectric measurements, theTgof composites vary from 88°C for pristine PVA to 125°C for PVA/AgnP (5 wt%). Below 45°C, dry films exhibit a single Arrhenius behavior showing a 3D hopping conductivity as explained based on the variable range hopping model. PVA/AgnP composites have higher conductivity compared to pristine PVA, and it increases as AgnP weight percent increases. Finally, DMA measurements support the statement that a secondary relaxation was erroneously assigned as the glass transition of PVA and composites in previous reports.

show abstract

“…However, the same characteristics that endow PVA with hydrophilicity make it susceptible to plasticization in humid environments . Therefore, considerable efforts have been made in studying plasticizing effect caused by water on pristine PVA and PVA system by the various ways . López et al reported the water content dependence of the dynamics of PVA and PVA‐based composite films by means of dielectric spectroscopy (DS) and dynamic mechanical analysis (DMA) .…”

Section: Introductionmentioning

confidence: 99%

“…The simulation reveals the cooperative behavior of PVA and H 2 O which is responsible for the glass transition of the binary system. Recently, the plasticizing influence of water on the molecular dynamics of PVA was revisited by DS, DMA, TGA, and X‐ray diffraction (XRD) …”

Section: Introductionmentioning

confidence: 99%

Combined effect of relative humidity and temperature on dynamic viscoelastic properties and glass transition of poly(vinyl alcohol)

Zhang

et al. 2013

J of Applied Polymer Sci

View full text Add to dashboard Cite

On the basis of the experimental studies on viscoelastic properties of poly vinyl alcohol (PVA) films at various relative humidity (RH) and temperature conditions by dynamic mechanical analysis (DMA), the influence of both temperature and RH on the glass transition are discussed and an improved property model is developed to relate the dynamic modulus to RH and temperature. The results indicate that (1) with increasing the RH, the storage modulus of PVA decrease remarkably, while both loss modulus and tand sharply increase to reach the peak and then markedly drops. The intensity of this variation is highly dependent upon temperature. (2) Moisture increase will cause the glass transition of PVA at isothermal condition and the transition point can be detected by glass transition relative humidity (RH g ) that obtained by isothermal RH scans. (3) Similar to the relationship between T g and RH, the RH g of PVA vary linearly with temperature. The state diagram of RH g versus temperatures is nearly consistent with that of T g versus RH. (4)The present equation based on model of Mahieux and Reifsnider (Mahieux and Reifsnider, Polymer 2001, 42, 3281) can predict well the dynamic modulus of PVA at various RHs and temperatures.

show abstract

Revisiting the thermal relaxations of poly(vinyl alcohol)

Cited by 15 publications

References 33 publications

Revealing the Mechanical Properties of Emulsion Polymer Isocyanate Film in Humid Environments

Revealing the Mechanical Properties of Emulsion Polymer Isocyanate Film in Humid Environments

Molecular Dynamics Analysis of PVA‐AgnP Composites by Dielectric Spectroscopy

Combined effect of relative humidity and temperature on dynamic viscoelastic properties and glass transition of poly(vinyl alcohol)

Contact Info

Product

Resources

About