Surface treatment of titanium dioxide nanoparticles in rutile crystale structure and it\u27s influence on UV absorption properties of polymer nanocomposite.

Polimerni kompoziti, ki se uporabljajo tudi v premaznih sredstvih, estetsko spreminjajo okolje, v katerem živimo, obenem pa jih uporabljamo tudi za zaščito površin, ki lahko propadajo zaradi škodljivih zunanjih vplivov, npr. zaradi izpostave UV svetlobi. Nove tehnološke rešitve zaradi izboljšanja funkcionalne lastnosti, kot je npr. UV zaščita, se v industriji polimernih kompozitov uvajajo tudi s pomočjo nanotehnologije, v tem primeru z vgradnjo nanodelcev TiO2. Pomembno vlogo v skupini nanodelcev, ki se uporabljajo v polimernih kompozitih, predstavljajo nanodelci TiO2. Veliko raziskav je bilo usmerjenih v študij posebnih lastnosti nanodelcev TiO2, ki omogočajo doseganje posebnih funkcijskih lastnosti in transparentnosti polimernih kompozitov. Nanodelci TiO2 rutilne kristalne strukture so odlični UV absorberji, zato se dodajajo različnim polimernim kompozitom za doseganje izboljšane UV in vremenske obstojnosti. Za optimalno izkoriščanje posebnih lastnosti nanodelcev v polimernih kompozitih je ključni problem tendenca aglomeracije nanodelcev zaradi London - van der Waals - ovih interakcij v disperziji. To je mogoče preprečiti z ustrezno stabilizacijo nanodelcev v disperziji, kar zagotavlja tudi ozko porazdelitev velikosti delcev in posledično omogoča zadostno transparentnost polimernega kompozita ter učinkovitost UV zaščite. Eden izmed načinov stabilizacije nanodelcev TiO2 rutilne kristalne strukture v disperziji je površinska obdelava z anorganskimi ter organskimi snovmi. Površinska obdelava površine rutilnih TiO2 nanodelcev z anorganskimi oksidi je pomembna zaradi izboljšanja disperzbilnosti ter zmanjšanja fotokatalitske aktivnosti. Prav tako anorganski sloj na površini nanodelcev poveča njihovo specifično površino v primerjavi z neobdelanim nanodelcem. Po apliciranju anorganskega oksida na površini TiO2 je le ta v vodni disperziji obdelan še z organskimi reagenti – površinsko aktivnimi sredstvi, ki omogočajo stabilizacijo v topilu oziroma polimeru in vzpostavijo odbojne sile med posameznimi delci ter posledično izboljšajo funkcionalno učinkovitost sistema. Doktorski študij temelji na izvedbi dveh inovativnih sklopov dodatne površinske obdelave nanodelcev TiO2 rutilne kristalne strukture ter določitvi vpliva na aplikacijske lastnosti in UV absorpcijsko učinkovitost polimernih nanokompozitov. V ta namen smo uporabili s koprecipitacijsko metodo sintetizirane nanodelce TiO2 rutilne kristalne strukture. Poleg klasične stabilizacije nanodelcev TiO2 s polidimetilsiloksani smo razvili dodatna komplementarna postopka površinske obdelave. Z namenom izboljšanje stabilnosti nanodelcev v vodni ter polimerni disperziji smo v prvem sklopu raziskav nanodelce TiO2 dodatno površinsko obdelali z 3 – glicidil oksipropil trimetoksi silanom (GLYMO), v drugem pa z anorganskim oksidom - Fe2O3. Študirali smo vpliv razmerja TiO2/GLYMO ter procesnih pogojev priprave disperzij kot sta čas in temperatura površinske obdelave z GLYMO ter vpliv ut. % dodatka - Fe2O3 na stabilnost disperzije nanodelcev TiO2. V tretjem delu doktorske disertacije smo namesto nepravilne oblike TiO2 nanodelcev površinsko obdelali nanodelce TiO2 riževe strukture. Najprej so na TiO2 nanodelce precipitirali Al2O3. Nato smo jih površinsko obdelali z trisilanolnimi poliedrični oligomerni silseskvioksani (POSS). Študirali smo vpliv površinske obdelave TiO2 nanodelcev z POSS molekulami na transparenco ter UV zaščito polimernih nanokompozitov. S postopkom dodatne površinske obdelave nanodelcev TiO2 rutilne kristalne strukture smo potrdili postavljene teze o vplivu površinske obdelave na UV absorpcijske lastnosti kot tudi transparenco polimernega kompozita. Tako smo z dodatno površinsko obdelavo z -Fe2O3 dosegli višjo UV zaščito polimernega nanokompozita, v primeru dodatne površinske obdelave z GLYMO pa višjo transparenco polimernega nanokompozita. Končna polimerna disperzija z integriranimi površinsko obdelanimi nanodelci TiO2 rutilne kristalne strukture ima tudi ustrezne apPolymer composites, used in paints, are aesthetically changing the environment, in which we are living. At the same time we are using paints for surface protection, since the surface can be damaged by harmful exterier environment, for example UV light exposure. New technological solutions for improving functional properties like UV protection are in polymer composite industry introduced with the help of the nanotechnology, in this case with incorporation of TiO2 nanoparticles. Important role among the nanoparticles, used in polymer composites, have TiO2 nanoparticles. A lot of research is focused on studying properties of TiO2 nanoparticles, which enable to accomplish required functional properties and transparency of polymer composites. TiO2 nanoparticles with rutile crystaline structure are excellent UV absorbers. For this reason they are used for incorporation in polymer composites to accomplish improved UV and weathering protection. For optimal exploitation special properties of nanoparticles in polymer composites it is very important to prevent nanoparticles tendency to agglomeration because of London – van der Waals interactions in dispersion. This is possible to achieve by suitable nanoparticles stabilization in dispersion, which is also assured by narrow particles size distribution that consequently provides sufficient tranasparency and UV protection of polymer composite. One of the possibilities to stabilize in dispersion TiO2 nanoparticles in rutile crystaline stucture is surface treatment with inorganic and organic components. Surface treatment of rutile TiO2 nanoaprticles is imporatant for improving dispersibility and to diminish photocatalytic activity. Inorganic coating on the nanoparticles surface also increases their specific surface area when compared with untreated nanoparticles. After application of inorganic coating on TiO2 surface additional surface treatment with organic compounds is used. Treatment with surface active agent enables stabilization in solvent or polymer dispersion. The repulsion forces are being estabilshed among the particles and consequently the functional efficiency is being improved. In the presented disertation two innovative additional surface treatment procedures of TiO2 nanoparticles in rutile crystaline structure were used. We have investigated the influence of surface treatment on application properties and UV absorption efficiency of polymer nanocomposites. For this reason we have used TiO2 nanoparticles in rutile crystaline structure synthesized with coprecipitation method. In addition to classical polydimethylsiloxane surface treatment of TiO2 nanoaprticles we have developed two additional complementary surface treatment procedures. In order to improve nanoparticles stability in water and polymer dispersion, we have treated TiO2 nanoparticles surface with 3-glycidyloxypropyltrimethoxysilane (GLYMO) in the first and with inorganic oxide - Fe2O3 in the second part of our reasearch. We have studied the influence of GLYMO/TiO2 ratio and the surface treatment procedure conditions like time and temperature and the influence of wt. % of - Fe2O3 addition on the TiO2 nanoparticles dispersion stability. Third surface treatment procedure was perfomed on TiO2 nanoparticles of rice structure in comparison with before used spherical shape of nanoparticles. First Al2O3 was precipitated on TiO2 surface. Than we have used trisilanol polyhedral oligomeric silsesquioxanes (POSS) for additional surface treatment of TiO2 nanoparticles. We have studied the influence of TiO2 surface treatment with POSS on transparency and UV efficiency of polymer nanocomposite. With additional surface treatment of TiO2 nanoparticles in rutile crystaline structure we have confirmed our hypotheses about the surface treatment influence on UV absorption properties as well as on the transparency of polymer composite. Final polymer dispersion with integrated surface treated TiO2 nanoparticles in rutile crystaline structure has suitable application properties for external wood protectio