The role of resol fortifiers in latex wood adhesives
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Francisco López-Suevos
Abstract
Static and dynamic rheological analyses using time/temperature equivalence were applied to freestanding poly(vinyl acetate-co-NMA) adhesive films and to wood-bonded films (composites), which were completely dry in all cases. Films and composites were prepared with two types of cross-linking: (1) cross-linking through AlCl3 catalysis of N-methylolacrylamide (NMA) comonomer; and (2) additional cross-linking using a resol phenolic (PF) additive, in addition to AlCl3 catalysis. Rheological experiments revealed that accelerated weathering (AW) significantly modified the mechanical response of films and composites lacking the PF additive. For samples lacking PF fortifier, AW caused a new thermal transition appearing as a major mechanical softening in the long time domain (creep master curves) or in the low-frequency region (dynamic master curves). This new transition correlated to a performance loss found with fracture testing in a previous publication. Here, the static and dynamic rheological data indicated that the AW-induced softening was a reversible transition. Differential scanning calorimetry analysis and the manipulation of physical aging effects demonstrated that the AW-induced softening was a glass transition. The calorimetric weakness and temperature of this transition indicated that it corresponds to the Tg of poly(vinyl alcohol) (PVOH), which is the emulsion polymerization interfacial agent. In contrast, all PF-formulated samples displayed only the base polymer Tg. Therefore, the PF additive prevented weathering effects that lead to PVOH softening. Atomic force and scanning electron microscopy provided visual evidence of the action of PF on PVOH at interparticle boundaries. We suggest that the PF fortifier enhances latex durability through the formation of hydrolytically stable PVOH cross-links at the interparticle boundaries.
References
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©2006 by Walter de Gruyter Berlin New York
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Articles in the same Issue
- A report from the 2005 Japanese-European Workshop on “Cellulose and Functional Polysaccharides”
- Determination of substituent distribution of viscoses by GPC
- Direct investigation of the structural properties of tension wood cellulose microfibrils using microbeam X-ray fibre diffraction
- Influence of amide content on the crystal structure of chitin
- Stepwise synthesis of chitooligosaccharides through a transition-state analogue substrate catalyzed by mutants of chitinase A1 from Bacillus circulans WL-12
- Synthesis of plantamajoside, a bioactive dihydroxyphenylethyl glycoside from Plantago major L.
- Diffusion of sulfide into Southern pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) particles and chips
- Laccase-catalysed functionalisation of TMP with tyramine
- Wood liquefaction by ionic liquids
- Studies on the dehydrogenative polymerizations of monolignol β-glycosides. Part 2: Horseradish peroxidase-catalyzed dehydrogenative polymerization of isoconiferin
- Phenolic compounds in silver birch (Betula pendula Roth) wood
- Analysis of fragrance compositions of precious coniferous woods grown in Taiwan
- Influences of hot pressing temperature and surface structure on VOC emissions from OSB made of Scots pine
- Dimensional stability and photostability of octanoylated wood
- Measurement of the shear modulus of wood by the square-plate twist method
- Dielectric relaxation of water adsorbed on chemically treated woods
- Influences of drying on internal checking of spruce (Picea abies L.) heat-treated at 212°C
- The role of resol fortifiers in latex wood adhesives
- A simple anisotropy correction procedure for acoustic wood tomography
- Evaluating growth strain of Eucalyptus globulus Labill. from SilviScan measurements
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