Influence of TiO2 nanofiller on the properties of polyacrylate systems

Polimerni nanokompoziti danas imaju široku primjenu. Glavni razlog su znatno bolja svojstva u usporedbi s čistim polimerom ili mikrokompozitom. Priprava ovakvih sustava ima za cilj jednoliku raspodjelu i dispergiranost punila u polimernoj matrici. Emulzije na bazi poliakrilata često se koriste kao premazi u drvnoj industriji gdje imaju ulogu zaštite drva od UV zračenja. Kod takvih nanokompozita kao punilo se često koriste nanočestice TiO2 koje imaju funkciju UV apsorbera. U ovom radu sintetizirane su poliakrilatne (PAK) i PAK/TiO2 emulzije in situ emulzijskom polimerizacijom i ex situ načinom priprave. Korištene su dvije vrste punila dispergiranih u vodi (DW i DN) i dvije vrste praškastog (PN i PM(PVP)) TiO2 nanopunila. Dobivenim emulzijama određena su reološka svojstva i raspodjela veličine čestica. Rezultati su pokazali bolju raspodjelu veličine čestica kod emulzija pripravljenih in situ načinom priprave, dok je emulzija s DW nanopunilom neovisno o načinu priprave pokazala najbolju raspodjelu. Sve emulzije pokazale su Newtonsko ponašanje, a zbog manje razlike u veličini čestica uočen je značajni utjecaj in situ načina priprave na viskoznost PAK emulzije od sustava pripravljenih ex situ načinom priprave. Iz dobivenih emulzija pripravljeni su tanki filmovi kojima je određena morfologija i mehanička svojstva, te toplinska svojstva diferencijalnom pretražnom kalorimetrijom (DSC) i termogravimetrijskom analizom (TGA). Morfologije dobivenih filmova u skladu su s rezultatima ispitivanja raspodjele veličine čestica emulzija. Svi pripravljeni filmovi, neovisno o načinu priprave imaju jednu temperaturu staklastog prijelaza (Tg). Dodatak svih vrsta punila neovisno o načinu priprave poboljšava toplinsku stabilnost poliakrilatne emulzije u početnim stadijima razgradnje.Polymer nanocomposites have nowadays a broad range of applications. The main reasons for this are their properties which are much better in comparison to the properties of pure polymers or microcomposites. The goal of the preparation of such systems is an even distribution and dispersion of fillers in the polymer matrix. Emulsions based on polyacrylates are often used as coatings in wood industry where they have the role of protecting the wood from UV radiation. With such nanocomposites TiO2 nanoparticles are usually used as fillers which have the function of UV absorbers. In this work, polyacrylate (PAK) and PAK/TiO2 emulsions were synthesised by the in situ emulsion polymerisation and by the ex situ preparation. Two kinds of fillers dispersed in water (DW and DN) and two kinds of a powder-like TiO2 nanofiller (PN and PM(PVP) were used. Rheological properties and the distribution of the particle sizes of the emulsions were determined. The results showed a better distribution of the particle sizes in emulsions prepared by the in situ mode of preparation, while the emulsion with a DW nanofiller showed the best distribution irrespective of the mode of preparation. All the emulsions showed Newtonian behaviour, and due to a smaller difference between the particle sizes, a significant influence of the in situ mode of preparation on the viscosity of the PAK emulsion in comparison to systems prepared by the ex situ mode of preparation was observed. From the obtained emulsions thin films were prepared, after which their morphology, their mechanical and thermal properties were determined using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The morphology of the obtained films are in line with the results of examining the distribution of the particle sizes in the emulsions. All the prepared films have one glass transition temperature (Tg) regardless of the mode of preparation. Adding fillers of all kinds enhances the thermal stability of a polyacrylate emulsion in the initial stages of degradation irrespective of the mode of preparation