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.
PVC/wood flour composites were prepared by compression molding using sapwood and heartwood from Angelin Pedra as filler. The composites specimens were subjected to water immersion and impact tests. The results showed that the water absorption of all composites increased slightly with increasing immersion time and wood content. However, the values were considerably low compared with control sample, common solid woods and wood plastic composites reported in literature. PVC/sapwood composites showed slightly higher values for moisture absorption ability due to the difference in chemical constituents’ ratio. PVC compound and PVC/sapwood composite containing 10 phr of wood flour exhibited maximum water absorption in 63 days and it corresponded to 0.25 % and 0.58 % weight gain, respectively. In relation to impact test, the results indicated that impact property was affected by wood content and less by wood type. Composites containing 10 phr of wood content showed greater impact strength (decreased by around 60 %) than those prepared with 25 and 40 phr of wood flour content (decreased approximately by 75 %). In general the composites prepared with 10 phr of wood flour content exhibited a better performance in both parameters measured in this study.
In the last decades, the growing environmental awareness has resulted in a renewed interest in the use of natural materials for different applications. In this context, the use of wood in plastic to obtain composites has grown significantly. In the present work, heartwood and sapwood from Angelim Pedra (Hymenolobiun petraeum) were used to prepare PVC/wood composites. To study the composites with different wood types and filler contents the molecular dynamic was investigated through low field NMR by poton spin-lattice relaxation time measurements (T 1 H) and the thermal behavior was characterized by means of differential scanning calorimetry (DSC) focusing the glass transition temperature and thermogravimetric analyses (TGA) observing the changes in the thermal stability. It was found that increasing addition of wood flour (sapwood and heartwood) caused a small but progressive improvement of the decomposition temperature of the composites, whereas the glass transition temperature remains practically unchanged. In the molecular dynamic behavior, a gradual decrease in T 1 H values was observed with increasing sapwood and heartwood content, indicating that the composites became less rigid. The distribution curves of the domains showed a better interaction and phase dispersion between the composite components with higher filler content.
The focus of this work was to characterize the molecular dynamic of High Impact Polystyrene (HIPS -5% PB), wood -A (Vochysia divergens) and B (Erisma uncinatum) -and their composites, using solid state nuclear magnetic resonance (NMR), by measuring the proton spin-lattice relaxation time (T 1 H) using a low field NMR, and by thermal analysis as Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). DSC and TGA measurements show that both woods present the same molecular behavior. On the other hand, the spin-lattice relaxation time observed that the water is interfering in the packing and arrangements of cellulose chains due to inter and intra hydrogen molecular interactions, promoting the T 1 H values changed to high values. T 1 H shows that the sample B presents a higher rigidity than sample A. However, HIPS presents higher T 1 H values comparing to wood types. Analyzing the relaxation data for the composites, the values indicate that composites present an interaction between both components.
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