Novel functionalized polyolefins as compatibilizers in polyolefin/polyamide 6 blends and polyethylene/metal hydroxide composites

Ricinoloxazoline maleinate (OXA) was grafted by melt free radical grafting onto polyolefins and elastomers to produce new compatibilizers for polymer blends. Effects of initial monomer and peroxide concentrations on the degree of grafting, on the amount of residual monomer, and on the side reactions were investigated. Reactive compatibilizers could be prepared with a suitable choice of processing conditions and initial concentrations. These oxazoline functionalized polyolefins and elastomers were found to act as effective compatibilizers in polymer blends. Blends of polyolefins and polyamide 6 were compatibilized with two novel types of compatibilizers: oxazoline functionalized polymers prepared by grafting and functionalized polyolefins prepared by copolymerization using metallocene catalysts. Comparison was made with commercial compatibilizers. Effects of the compatibilizers on blend morphology and thermal, tensile, and impact properties were studied. All of the functionalized polyolefins were effective compatibilizers in polyethylene/polyamide 6 blends. They were able to reduce the particle size and attach the particles more firmly to the matrix. The toughness was improved, though usually at the cost of stiffness. Only functionalized polyethylenes prepared with metallocene catalysts were able to improve the stiffness and strength along with toughness. In commercial polyolefin composites, fillers are usually coated with a fatty acid to make them organophilic. Replacement of fatty acid coatings with polymeric compatibilizers was studied in polyethylene/aluminum hydroxide (PE/ATH) and polyethylene/magnesium hydroxide (PE/MH) composites. The polymeric compatibilizers were oxazoline grafted polyethylene prepared by melt free radical grafting, hydroxyl and carboxylic acid functionalized polyethylenes prepared with metallocene catalysts, and commercial functionalized polyethylenes. Adhesion fracture changed to cohesion failure when the fatty acid coating was replaced through the addition of polymeric compatibilizers. Improvement in both stiffness and toughness was achieved, and improvements in flammability properties achieved with ATH or MH were preserved when polymeric compatibilizers were used as adhesion promoters.reviewe

Laccase Aided Modification of Nanofibrillated Cellulose with Dodecyl Gallate

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A Fast Method to Produce Strong NFC Filmas as a Platform for Barrier and Functional Materials

VK: T10413In this study we present a rapid method to prepare robust, solvent resistant nanofibrillated (NFC) cellulose films that can be further surface modified for functionality. The oxygen, water vapor and grease barrier properties of the films were measured and in addition mechanical properties in dry and wet state, and solvent resistance were evaluated. The pure unmodified NFC films were good barriers for oxygen gas and grease. At relative humidity below 65%, oxygen permeability of the pure and unmodified NFC film was below 0.6 cm3µmm-2d-1kPa-1, and no grease penetrated the film. However, the largest advantage of these films was their resistance to various solvents, like water, methanol, toluene and dimethylacetamide. Although they absorbed a substantial amount of solvent, the films could still be handled after 24h of solvent soaking. Hot-pressing was introduced as a convenient method to increase not only the drying speed of the films but also enhance the robustness of the films. The wet strength of films increased due to the pressing. Thus they can be chemically or physically modified through adsorption or direct chemical reaction in both aqueous and organic solvents. Through these modifications the properties of the film can be enhanced introducing e.g. functionality, hydrophobicity or bioactivity. Herein a simple method using surface coating with wax to improve hydrophobicity and oxygen barrier properties at very high humidity is described. Through this modification the oxygen permeability decreased further and was below 17 cm3µmm-2d-1kPa-1 even at 97.4 % RH and the water vapor transmission rate decreased from 600 to 40 g/m2day. The wax treatment did not deteriorate the dry strength of the film. Possible reasons for the unique properties are discussed. The developed robust NFC films can be used as a generic, environmentally sustainable platform for functional materials.Peer reviewe

Surface functionalization of nanofibrillated cellulose using click-chemistry approach in aqueous media

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