The aim of this study was to obtaining an adhesive made of dimethacrylate copolymer and clay particles in different concentrations. The samples were prepared by light curing and were evaluated by XRD, FTIR and TGA as well as by measuring flexural strength, elasticity modulus and tensile resistance. The XRD and the mechanical test results indicated that the system with 0.2% clay is exfoliated, while the highest concentrations showed the agglomeration of these clays. FTIR was used to determine the conversion, and showed that use of clays particles are unable to significantly alter the polymerization until 1.0%. However, for the group containing 1.5%, there was a decline in this index. In the thermogravimetric analysis, only the groups with 0.2% of clays showed increased thermal resistance. In conclusion, the incorporation of clay at 0.2% concentration produces a well-dispersed system and can be applied as a dental adhesive.

Poly (ε-caprolactone) (PCL) based hybrids containing different amounts of modified (Aerosil® R972) and unmodified (Aerosil® A200) silica oxide were prepared employing the solution method, using chloroform. The relationships of the amount of nanofillers, organic coating, molecular structure and intermolecular interaction of the hybrid materials were investigated mainly using low-field nuclear magnetic resonance (NMR). The NMR analyses involved the hydrogen spin-lattice relaxation time (T1H) and hydrogen spin-lattice relaxation time in the rotating frame (T1ρH). The spin-lattice relaxation time measurements revealed that the PCL/silica oxide hybrids were heterogeneous, meaning their components were well dispersed. X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also employed. The DSC data showed that all the materials had lower crystallization temperature (Tc) and melting temperature (Tm), so the crystallinity degree of the PCL decreased in the hybrids. The TGA analysis demonstrated that the addition of modified and unmodified silica oxide does not cause considerable changes to PCL's thermal stability, since no significant variations in the maximum temperature (Tmax) were observed in relation to the neat polymer.

This article reports the preparation of composites and nanocomposites of polypropylene and titanium dioxide particles, with our without surface modification, to obtain photodegradable or photostable materials with less severe environmental impacts. The modification of the titanium dioxide was carried out in the laboratory using propionic acid to improve the interaction of titanium dioxide with the polymer matrix. The composites and nanocomposites were prepared by melt extrusion using a single-screw extruder. The materials obtained were characterized by nuclear magnetic resonance relaxometry, X-ray diffraction, Raman spectroscopy, thermogravimetric analysis and mechanical analysis (tension). The results showed that the surface modification of the titanium dioxide particles promoted their better dispersion, distribution and interaction with the polypropylene matrix, generating a nanocomposite material. The NMR relaxometry results showed that the modified particles changed the molecular dynamics, indicating the formation of nanocomposites. In the Raman spectra, peaks related to the titanium dioxide only appeared at a concentration of 1%, and there was an inversion between crystalline and amorphous phase regions in the samples with the organophilic titanium dioxide, indicating the formation of a nanocomposite. The best modified PP/TiO2 compositions were those containing 0.25 and 0.50% modified TiO2 particles. The incorporation of the titanium dioxide particles, in rutile form, promoted photostabilization of the composites and nanocomposites at all ratios, and the composition containing 0.50% modified TiO2 presented the best photostabilization.