RESUMO
Most adhesives used in the wood-based panel (WBP) industry are petroleum-based and are associated with environmental impact and price fluctuations. Furthermore, most have potential adverse health impacts, such as formaldehyde emissions. This has led to interest from the WBP industry in developing adhesives with bio-based and/or non-hazardous components. This research focuses on the replacement of phenol-formaldehyde resins by Kraft lignin for phenol substitution and 5-hydroxymethylfurfural (5-HMF) for formaldehyde substitution. Resin development and optimization was carried out regarding varying parameters such as molar ratio, temperature or pH. The adhesive properties were analyzed using a rheometer, gel timer and a differential scanning calorimeter (DSC). The bonding performances were evaluated using an Automated Bonding Evaluation System (ABES). Particleboards were produced using a hot press, and their internal bond strength (IB) was evaluated according to SN EN 319. Hardening of the adhesive could be achieved at low temperatures by increasing or decreasing the pH. The most promising results were obtained at pH 13.7. The adhesive performances were improved by adding filler and extender (up to 28.6% based on dry resin) and several boards were produced reaching P1 requirements. A particleboard achieved a mean IB of 0.29 N/mm2, almost reaching almost P2 requirements. However, adhesive reactivity and strength must be improved for industrial use.
RESUMO
Nanocomposites comprising a polymer matrix and metallic nanoparticles (NPs) can merge the structural features of the matrix material with the functional characteristics of the NPs. While such materials are promising for a wide range of applications, their preparation typically requires multi-step processes that can be difficult to control. Alternatively, materials with NPs can be directly accessed in a controlled manner by exploiting zero-valent metallosupramolecular polymer (MSP) precursors. We here report how the nature of the polymer and its molecular weight affect the nanocomposite formation and structure. Poly(tetrahydrofuran)-based macromonomers with suitable ligands are used to prepare MSPs based on bis(η2-alkyne)platinum(0) complexes. Heating these materials causes disassembly of the complexes and, upon the release of Pt0-atoms, Pt-NPs form in the matrix polymer. The Pt content in the MSP influences the NP formation and thereby the characteristics of the nanocomposites. It is also possible to trigger the complex dissociation and NP formation by exposure to UV light. This allows photolithographic processing and thus the preparation of nanocomposites that contain Pt-NPs in a spatially controlled manner.
RESUMO
Nanocomposites consisting of a polymer matrix and metallic nanoparticles can merge the functional, structural, and mechanical properties of the two components and are useful for applications that range from catalysis to soft electronics. Gaining spatial control over the nanoparticle incorporation is useful, for example to confine catalytic sites or create electrically conducting pathways. Here, we show that this is possible by the controlled disassembly of a metallosupramolecular polymer containing zerovalent platinum complexes to form nanoparticles in situ. To achieve this, a telechelic poly(ethylene-co-butylene) was end-functionalized with diphenylacetylene ligands and chain-extended through the formation of bis(η2-alkyne)Pt0 complexes. These complexes are stable at ambient conditions, but they can be dissociated upon heating or exposure to ultraviolet light, which allows producing Pt nanoparticles when and where needed and without auxiliary reagents or formation of byproducts. This approach was exploited to create objects with well-defined catalytically active areas.
