Hossein Behniafar, Mina Alimohammadi, Khaledeh Malekshahinezhad
Prog Org Coat 88, 150–154 (2015)
Publication year: 2015
In this work, TiO2 nanoparticles are surface modified by NH2-terminated organic moieties arised from 4,4-methylene diphenyl diisocyanate (MDI). These nanoparticles are incorporated into ether-based segmented polyurethane (SPU) matrix. MDI is utilized as monomer together with poly(tetramethyleneoxide) (PTMO) comonomer for preparing the final polymer as well. The NH2-functionalized TiO2 nanoparticles are covalently linked to the NCO terminals of the resulting SPU macromolecules during film preparation stage. Therefore, in addition to butylene glycol, these surface modified nanoparticles with enhanced organophilicity could play the role of the second chain extender of NCO-capped SPU macro-molecules through formation of urea linkages. Optical and thermal behaviors of the transparent andflexible film (SPU/TiO2–MDI) is compared with those of unmodified TiO2(SPU/TiO2) and TiO2-unloadedSPU films. Though the particle loading is only 5 wt.%, incorporation of TiO2and TiO2–MDI nanoparticles into the SPU polymer enhances significantly the light absorption in UV region at 300–400 nm. SEM images of the prepared films clearly show a considerable decrease in particle aggregation for TiO2–MDI into SPU matrix compared to that of unmodified TiO2. TG analyses indicate a one-step decomposition pattern with onset temperatures of about 360 and 380◦C for neat SPU and SPU/TiO2–MDI, respectively.Moreover, DTA thermograms of both nanocomposites show obviously two exothermic phase transitionsin the thermal range of 330–440 ◦C.