Effect of the Incorporation of Modified Silicas on the Final Properties of Wood Adhesives

Enhancement of Polyvinyl Acetate (PVAc) Adhesion Performance by SiO2 and TiO2 Nanoparticles

Post press processes include various types of bonding and adhesives, depending upon the nature of adherends, the end use performance requirements and the adhesive bonding processes. Polyvinyl acetate (PVAc) adhesive is a widely used adhesive in the graphic industry for paper, board, leather and cloth. In this study, the enhancement of PVAc adhesion performance by adding different concentrations (1%, 2% and 3%) of silica (SiO2) and titanium dioxide (TiO2) nanoparticles was investigated. The morphology of investigated paper-adhesive samples was analyzed by SEM microscopy and FTIR spectroscopy. In addition, the optimal adhesion at the interface of paper and adhesive was found according to calculated adhesion parameters by contact angle measurements (work of adhesion, surface free energy of interphase, wetting coefficient). According to obtained surface free energy (SFE) results, optimum nanoparticles concentration was 1%. The wettability of the paper-adhesive surface and low SFE of interphase turned out as a key for a good adhesion performance. The end use T-peel resistance test of adhesive joints confirmed enhancement of adhesion performance. The highest strength improvement was achieved with 1% of SiO2 nanoparticles in PVAc adhesive.

Co-encapsulation of CdSe/ZnS and CeO2 nanoparticles in waterborne polymer dispersions: enhancement of fluorescence emission under sunlight

Hybrid core/shell polymer particles with co-encapsulated quantum dots (QDs) (CdSe/ZnS) and CeO₂ nanoparticles have been synthesized in a two stage semi-batch emulsion polymerization process. In the first stage, both inorganic nanoparticles are incorporated into cross-linked polystyrene (PS) particles by miniemulsion polymerization. This hybrid dispersion is then used as the seed to produce the core/shell particles by starved feeding of methyl methacrylate and divinylbenzene (MMA/DVB) monomers. The core/shell hybrid dispersions maintained in the dark exhibit stable fluorescence emission over time, and notably their fluorescence intensity increases under sunlight, likely due to the effect of the co-encapsulated CeO₂ nanoparticles that change the optical properties of the environment of the quantum dot particles. The fluorescence increase depends on the QD : CeO₂ ratio, with the 1 : 2 ratio resulting in the highest increase (280%). Furthermore, a film forming hybrid latex has been synthesized using the former core/shell PS/QD/CeO₂/PMMA particles as seeds and feeding under semi-batch conditions methyl methacrylate, butyl acrylate and acrylic acid. Films cast from this core/shell/shell hybrid dispersion also exhibit fluorescence, and as for the core/shell latex the fluorescence increases under sunlight exposure. Interestingly, the increase in the film is at least two times higher than that in the latex, which is attributed to the additional effect of the neighboring coalesced particles containing CeO₂ affecting the environment of the QDs.