Morphology and thermal degradation studies of melt-mixed poly(hydroxybutyrate-co-valerate) (PHBV)/poly(ε-caprolactone) (PCL) biodegradable polymer blend nanocomposites with TiO2 as filler (original) (raw)
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Polymer Testing, 2015
The morphology and thermal stability of melt-mixed poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blend nanocomposites with small amounts of TiO 2 nanoparticles were investigated. The nanoparticles were mostly located in the PLA phase, with good dispersion of individual particles, although significant aggregation was also visible. The thermal stability and degradation behaviour of the different samples were studied using thermogravimetric analysis (TGA) and TGA-Fourier-transform infrared (FTIR) spectroscopy. Neat PCL showed better thermal stability than PLA, but the degradation kinetics revealed that PLA had a higher activation energy of degradation than PCL, indicating its degradation rate more strongly depends on temperature, probably because of a more complex degradation mechanism based on chain scission and re-formation. Blending of PLA and PCL reduced the thermal stabilities of both polymers, but the presence of TiO 2 nanoparticles improved their thermal stability. The nanoparticles also influenced the volatilization of the degradation products from the blend, acted as degradation catalyst and/or retarded the escape of volatile degradation products.
Poly(hydroxybutyrate- co -hydroxyvalerate)/titanium dioxide nanocomposites: A degradation study
Journal of Applied Polymer Science, 2009
Nanocomposites, based on a poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) matrix and titanium dioxide (TiO 2 ) nanoparticles and fabricated with a solventcasting technique, were characterized with differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The content of TiO 2 nanoparticles varied between 0.5 and 10 wt %. Degradation studies, including hydrolytic degradation in a strong base medium (1N NaOH) and degradation under ultraviolet light at 365 nm, were performed. It was confirmed that the inorganic filler had no great influence on thermal properties such as the melting and crystallization temperatures. Improved degra-dation temperatures were also confirmed with the increase in the filler content. Degradation observations confirmed significant increases in hydrolytic erosion with the filler content increasing in comparison with the degradation of a pure PHBV film. Also, the photocatalytic activity of the inorganic filler TiO 2 in all investigated composites [irradiated at k ¼ 365 nm and immersed in a liquid medium (H 2 O)] was evaluated. The degraded samples were analyzed with Fourier transform infrared spectroscopy, which confirmed their increased crystallinity.
Crystals, 2018
New poly (δ-valerolactone)/titanium dioxide (PDVL/TiO2) nanocomposites with different TiO2 nanoparticle loadings were prepared by the solvent-casting method and characterized by Fourier transform infra-red, differential scanning calorimetry, X-ray diffraction and scanning electron microscopy, and thermogravimetry analyses. The results obtained reveal good dispersion of TiO2 nanoparticles in the polymer matrix and non-formation of new crystalline structures indicating the stability of the crystallinity of TiO2 in the composite. A significant increase in the degree of crystallinity was observed with increasing TiO2 content. The non-isothermal crystallization kinetics of the PDVL/TiO2 system indicate that the crystallization process involves the simultaneous occurrence of two- and three-dimensional spherulitic growths. The thermal degradation analysis of this nanocomposite reveals a significant improvement in the thermal stability with increasing TiO2 loading.
Poly(b-hydroxybutyrate) [PHB] is a biodegradable and biocompatible polymer produced by some bacteria genders. To improve mechanical properties, PHB has been blended with other polymers. Compression-molded blends of PHB and poly(e-capro-lactone) [PCL] (70/30 mass ratio) were cooled to room temperature following five different thermal treatments after molding at 180 8C. Blends processed with higher cooling rates were easier to biodegrade, nevertheless elongation at break and tensile strength decreased. Slower cooling kinetics and isothermal treatments increased perfection of crystals, as seen in differential scanning calorimetry and X-ray diffraction and spherulites size. A descriptive model is proposed herein where thermal, biodegradation, tensile properties, and crystal features were related to cooling kinetics applied. It is proposed that properties of 70/30 (PHB/PCL) blends can be predetermined by an adequate control of thermal conditions during processing.
Prodegradant effect of titanium dioxide nanoparticulates on polypropylene-polyhydroxybutyrate blends
Journal of Applied Polymer Science, 2018
Polymers are gradually replacing conventional materials in various sectors of the economy because of their low cost and broad functionality. However, the high stability of polymers under most environmental conditions can lead to their accumulation in the form of waste. Polyhydroxybutyrate (PHB) is an alternative because of its biodegradability, but it is usually expensive and brittle. These aspects can be improved through the formation of blends, such as with polypropylene (PP). The objective of this study was to investigate the possibility of using titanium dioxide (TiO 2) nanoparticles as a prodegradant agent in the PP-PHB-TiO 2 system through the evaluation of the effects of these nanoparticles under UV light on the structure and properties of the materials. Samples were produced through extrusion and injection molding and were characterized by their mechanical and thermal properties and structural analyses. The results show that the TiO 2 nanoparticles were able to act as a prodegradant agent for the PP-PHB blend; they also successfully improved some of the mechanical and dynamic mechanical properties of the blend. However, a TiO 2 nanoparticle content higher than 7.5 wt % was not able to extend the photodegradation process further, possibly as a consequence of the agglomeration of nanoparticles during the processing of these more concentrated blends.
Thermochimica Acta, 2011
Poly(3-hydroxybutyrate) (PHB)/organically modified clay nanocomposites were prepared by the melt mixing method and were characterized using wide-angle X-ray diffraction. Their thermal degradation kinetics was investigated using thermogravimetric analysis at various heating rates. Further kinetic analysis was performed using isoconversional methods and the invariant kinetic parameters method was used to estimate the so-called 'true' kinetic parameters, i.e. the pre-exponential factor, A and the activation energy, E, as well as the reaction model. It was found that intercalated structures are formed and the thermal stability of the material is improved by the addition of the nano-filler. From the isoconversional analysis, it was found that the activation energy does not vary significantly with the degree of degradation denoting degradation in one step with similar values for pure PHB and for all nanocomposites. Using the invariant kinetic parameters method, it was found that the model that best describes the experimental data was that of Sestak-Berggren's with f(a) =˛n(1 −˛) m , where the value of n is always larger than m and is increasing with the amount of the nano-filler. The value of the 'true' activation energy was found to be about 100 kJ mol −1 for all nanocomposites and the pre-exponential factor for PHB was estimated equal to 5.35 × 10 9 min −1 . Finally, the values of the kinetic rate constant k were found to decrease with the amount of the nano-filler up to 3 wt%, while for amounts larger than 3 wt% k increased reaching a value greater than that of pure PHB for the 10 wt% nanocomposites. (D.S. Achilias). meric materials in commercial products . That is why improving the thermal stability of PHB is very important. There are several approaches to overcome these drawbacks of PHB: (a) biosynthesize series of copolymers containing hydroxyalcanoate units other than 3-hydroxybutyrate units, (b) prepare miscible blends of PHB with another bio-degradable polymer with suitable properties or plasticizer, and (c) synthesize block copolymers based on PHB. As an alternative to these conventional methods, the preparation of PHB nanocomposites is investigated here.
Polymer International, 2006
New poly (δ-valerolactone)/titanium dioxide (PDVL/TiO 2) nanocomposites with different TiO 2 nanoparticle loadings were prepared by the solvent-casting method and characterized by Fourier transform infra-red, differential scanning calorimetry, X-ray diffraction and scanning electron microscopy, and thermogravimetry analyses. The results obtained reveal good dispersion of TiO 2 nanoparticles in the polymer matrix and non-formation of new crystalline structures indicating the stability of the crystallinity of TiO 2 in the composite. A significant increase in the degree of crystallinity was observed with increasing TiO 2 content. The non-isothermal crystallization kinetics of the PDVL/TiO 2 system indicate that the crystallization process involves the simultaneous occurrence of two-and three-dimensional spherulitic growths. The thermal degradation analysis of this nanocomposite reveals a significant improvement in the thermal stability with increasing TiO 2 loading.
Polymers, 2020
Compositions of polylactide (PLA) and poly(3-hydroxybutyrate) (PHB) thermoplastic polyesters originated from the nature raw have been obtained by blending under shear deformations and electrospinning methods in the form of films and nanofibers as well as unwoven nanofibrous materials, respectively. The degrees of crystallinity calculated on the base of melting enthalpies and thermal transition temperatures for glassy state, cold crystallization, and melting point for individual biopolymers and ternary polymer blends PLA-PHB- poly(ethyleneglycol) (PEG) have been evaluated. It has been shown that the mechanical properties of compositions depend on the presence of plasticizers PEG with different molar masses in interval of 400–1000. The experiments on the action of mold fungi on the films have shown that PHB is a fully biodegradable polymer unlike PLA, whereas the biodegradability of the obtained composites is determined by their composition. The sorption activity of PLA–PHB nanofibers...
Polymer Degradation and Stability, 2006
Blends of poly (3-hydroxybutyrate) (PHB) with poly (ethylene glycol) (PEG), (PHB/PEG), in different proportions of 100/0, 98/2, 95/5, 90/ 10, 80/20 and 60/40 wt%, respectively, were investigated for their thermal properties (using differential scanning calorimetry and thermogravimetric analysis), tensile properties, water vapor transmission rate, enzymatic biodegradation (using light microscopy) and mass retention. The addition of plasticizer did not alter the thermal stability of the blends, although an increase in the PEG content reduced the tensile strength and increased the elongation at break of pure PHB.