| In order to solve environmental problems generated by petrochemical products, many researchers have focused their attentions on the natural polymers. Among these polymers, chitosan and starch have been considered as the promising candidates due to theirs attractive properties of low-cost, abundant, renewable, biocompatible and biodegradable, which make them superior to synthetic polymers and particularly useful in disposable plastics, food, and medicine applications. However, the main disadvantage of chitosan/starch-based products is hydrophilic character, which makes them low stability in the humid environment. In addition, chitosan/starch-based materials have poor mechanical, barrier and thermal characteristics. Therefore, in order to obtain the high performance chitosan/starch-based products, we carried out the works as follows:(1) Three types of zirconium phosphonate (org-ZrP) with different functional groups (-COOH,-SO3H,-NO2) were prepared first, and then added them into chitosan (CS) matrix, respectively. The FTIR spectroscopy revealed that org-ZrP had intense interactions with chitosan in the composites because of introducing functional groups on the fillers, resulting in the improved mechanical properties of composite films. Zirconium sulfophenyl phosphonate (ZrSP) exhibited the best among the org-ZrP. These differences of reinforcement effect appeared to be caused by the different adhesion between the org-ZrP fillers and matrix. The stronger the interfacial interactions were, the better the reinforcement effect was. In addition, the moisture uptake (Mu) of CS/org-ZrP-n composite films also determined. It was found that zirconium nitrophenyl phosphonate (ZrNP) showed better moisture barrier property than the other org-ZrP due to its poor adsorbability for water molecules.(2) The composite films (CS/TiP-n) were successfully prepared, and their structures, morphologies and properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and tensile tests. The interactions between titanium phosphate (TiP) and chitosan (CS) were analyzed by Fourier transform infrared spectroscopy (FTIR). The result revealed that hydrogen bonding formed in the composite films, which led to the good compatibility between TiP fillers and chitosan matrix. The SEM results indicated that the fillers could be dispersed well at low TiP loading but obvious aggregations existed at high TiP loading. In addition, with an addition of only 0.4 wt% TiP, the tensile strength (σb) and elongation at break (εb) of the TiP-reinforced chitosan composites were improved by 35.1% and 37.0%, respectively. The moisture uptake (Mu) of composite films with 0.8 wt% TiP was reduced by 41.7%. Meanwhile, it was found that the CS/TiP-n composite films exhibited higher thermal stability than neat CS.(3) A new type of titanium glycine-N, N-dimethylphosphonate (TGDMP), with the functional groups -COOH, has been prepared first and then characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Subsequently, chitosan/titanium glycine-N,N-dimethylphosphonate (CS/TGDMP-n) nanocomposite films of various compositions were prepared by solution casting method. The results showed that the mechanical, thermal stability and moisture barrier properties of chitosan films were improved by the incorporation of TGDMP, and the samples kept at moisture environment showed the larger elongation and lower tensile strength than the dried counterparts.(4) Glycerol-plasticized pea starch/graphene oxide (PS/GO-n) biocomposite films with different loading levels of graphene oxide (GO) were prepared by solution casting method. The structure, morphologies and properties of biocomposite films were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), thermal gravimetric analysis (TGA), Ultraviolet-visible (UV-vis) and tensile tests. The results revealed that hydrogen bonding formed in the biocomposite films, which improved compatibility between GO fillers and starch matrix. The tensile strength (σb) and Young's modulus (E) of starch films containing 2.0 wt% GO increased from 4.56 MPa,0.11 GPa to 13.79 MPa,1.05 GPa, respectively, while the elongation at break (εb) decreased from 36.06% to 12.11%. The introduction of GO also reduced the moisture uptake (Mu) and UV transmittance of starch films. In addition, TGA showed that the thermal stability of biocomposite films was better than that of neat starch film.
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