Structure, Morphology and Properties of Benzyl Starch Nanocrystals

Starch nanocrystals of platelet nanoparticles 50–100 nm are prepared by acid hydrolysis of natural starch. To improve both the dispersion stability of starch nanocrystals and the interphase compatibility with polymer matrix, hydrophobic benzyl groups were introduced for the surface modification. The modified benzyl starch nanocrystals were characterized using Fourier transform infrared spectra, proton nuclear magnetic resonance spectroscopy (1H NMR) and X-ray diffraction. The characterization results showed that the molecular structure and crystalline structure of prepared benzyl starch nanocrystals have little changes and that the degree of substitution of benzyl starch nanocrystals was about 0.05. The morphology study indicated that after modification the nanoparticles’ size decreased and the homogenous distribution of size increased. Wettability tests showed that the low substituted benzyl starch nanocrystals have appropriate hydrophilicity and can be uniformly dispersed in water. Since its excellent reinforcing effect and antistatic properties of benzyl starch nanoparticles, it can be used in rubber composites. The composites were prepared by co-mixing the benzyl starch nanocrystals with the natural rubber and silica. The mechanical properties and the antistatic properties of benzyl starch nanocrystals/natural rubber nanocomposites were dramatically enhanced. As expected the benzyl starch nanocrystals obtained is a new functional biopolymer filler or additive for the polymer composites.