Parallel-plate rheology of latex films bonded to wood
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Francisco López-Suevos
Abstract
A parallel-plate rheological analysis was developed for two types of cross-linking poly(vinyl acetate) latex films: solid freestanding films (neat), and solid films bonded directly to wood substrates (composites). The composite sample glass transition was increased by 5°C relative to the neat films, suggesting a strong interaction through polymer adsorption. Time-temperature equivalence was used to evaluate the mechanical response and the distribution of relaxation times in both systems. The resulting master curves revealed significant differences in the mechanical response during the glass transition: the neat films exhibited a 2.5–3-decade change in storage modulus and a damping factor of 1.65, while the composite samples showed a much smaller transition (approx. 0.3 decades and tan δ=0.4, respectively). The coupling model of Plazek and Ngai adequately described segmental relaxations in the glass transition. It was found that wood caused a small but significant decrease in segmental coupling (n=0.32±0.01) relative to that of the neat PVAc films (n=0.37±0.01). This finding was independently confirmed by directly fitting the Gram-Charlier statistical model to evaluate the distribution breadth. That wood caused an increase in the poly(vinyl acetate) glass transition, but a decrease in the related segmental coupling seems counterintuitive. The decrease in segmental coupling may result from reduced cross-linking in the composite films relative to the neat films; perhaps wood absorbs water-soluble reactive chains that would otherwise increase cross-linking in the neat films.
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Articles in the same Issue
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Articles in the same Issue
- Chemical changes in silver birch (Betula pendula Roth) wood caused by hydrogen peroxide bleaching and monitored by color measurement (CIELab) and UV-Vis, FTIR and UVRR spectroscopy
- Hydrophobisation and densification of wood by different chemical treatments
- Functionalisation of wood by reaction with 3-isocyanatopropyltriethoxysilane: Grafting and hydrolysis of the triethoxysilane end groups
- Isolation and fractionation of lignosulfonates by amine extraction and ultrafiltration: A comparative study
- Bioactive phenolic substances in industrially important tree species. Part 4: Identification of two new 7-hydroxy divanillyl butyrolactol lignans in some spruce, fir, and pine species
- Characterization of physiological functions of sapwood IV: Formation and accumulation of lignans in sapwood of Cryptomeria japonica (L.f.) D. Don after felling
- X-ray scattering studies of thermally modified Scots pine (Pinus sylvestris L.)
- Differences in acoustic velocity by resonance and transit-time methods in an anisotropic laminated wood medium
- Parallel-plate rheology of latex films bonded to wood
- An assessment of the feasibility of ultrasound as a defect detector in lumber
- Vibrational properties of green wood in high-temperature water vapor
- The stiffness modulus in Norway spruce as a function of year ring
- Strain analysis in bulk forming of wood
- Decay fungi from playground wood products in service using 28S rDNA sequence analysis
- Effect of climatic variables on chromated copper arsenate (CCA) leaching during above-ground exposure
- Protic ionic liquids with organic anion as wood preservative
