No abstract

A new kind of polypropylene (PP)/CaCO 3 composites was prepared on a twin screw extruder with the nanoparticle content of 5 wt % and the 2500 mesh microparticle content of 15 wt %. The mechanical property of four different samples [pure PP (1), PP filled with 15 wt % microCaCO 3 particle composites (2), PP filled with 5 wt % nanoCaCO 3 particle composites (3) and PP filled with micro/nano-CaCO 3 complex size particle composites (4)] was investigated through tensile tests, notched Izod impact tests and SEM. The results indicated that the sample 4 had the best mechanical property. The proofs of SEM showed that the high impact energy could lead to debonding and creating microcavitation between the nanoparticle and polymer interface if the polymer was filled with the nanoparticles. This process could absorb a lot of mechanical failure energy, but too much mechanical failure energy would lead to the enlargement of microcavitation and the destruction of the composites in sample 3. In sample 4, the microparticle could be used to prevent the enlargement of microcavitation in the matrix polymer under the higher impact failure energy. In this article, the model of the impacting failure process of micro/nanoCaCO 3 /PP composites was established.

The subject of this study was the crystallization behavior and thermal properties of polypropylene (PP)/maleic anhydride (MAH) modified nano calcium carbonate (nano-CaCO 3 ) composites. In this study, 5 wt % nano-CaCO 3 modified with different contents of MAH was filled into a PP matrix. X-ray diffraction and differential scanning calorimetry were used to characterize the crystal morphology and crystallization kinetics of a series of composites. The results demonstrate that the nanoCaCO 3 modified with MAH had an important effect on the thermal and morphological properties of the nanocomposites. The Avrami exponent of the pure PP was an integer, but those of the composites were not integers, but the crystallization rate constant decreased as the content of MAH in the nano-CaCO 3 filler increased in isothermal crystallization. In nonisothermal crystallization, the kinetic parameter F(T) and the degree of crystallinity of pure PP were compared with those of the PP composites filled with nano-CaCO 3 . We suggest that heterogeneous nucleation existed in the PP composites and that the transformation and retention of the b-form crystal into the a-form crystal took place in the composite system and the b-form crystal had a higher nucleation rate and growth process than the a-form crystal in the PP composites.

A thiolated chitosan (CS) derivative was synthesized by the introduction of thioglycolic acid to CS via amide‐bond formation mediated by carbodiimide. The chemical structure of the CS derivative was confirmed by Fourier transform infrared spectroscopy and 1H‐NMR spectroscopy. The solubility test showed that the thiolated CS derivative was water‐soluble. The X‐ray pattern of the CS derivative showed an obvious disappearance or shift of crystalline peaks compared to that of CS. Thermogravimetric analysis indicated that the degradation peak temperature of the thiolated CS derivative was much higher than that of CS and implied an improved thermal stability at higher temperatures. Moreover, the antimicrobial activity of the thiolated CS derivative was comparable to that of CS. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

No abstract