Starch nanocrystals and starch nanoparticles from waxy maize as nanoreinforcement: A comparative study

• Starch nanocrystals (SNCs) and starch nanoparticles (SNPs) from waxy maize were prepared.
• The morphology, crystallinity, colloidal properties and reinforcing potential were investigated and compared.
• The inclusion of SNCs in a ductile polymer matrix was shown to bring about stronger reinforcing effect than that of SNPs.

The morphological, structural and thermal behavior of starch nanocrystals (SNCs) extracted from waxy maize starch through an acid hydrolysis were compared with those of starch nanoparticles (SNPs) obtained through an ultrasound treatment starting from the same waxy maize starch. The SNPs were found to be completely amorphous, slightly smaller and had no surface charge, whereas the SNCs had the expected platelet-like morphology with a negative surface charge introduced as a result of the use of sulphuric acid in the acid hydrolysis step. SNCs also showed better thermal stability than SNPs in the presence of water. As a result of their platelet-like morphology, the SNCs performed better in reinforcing a polymer film. On the other hand, SNPs reduced the transparency of the nanocomposite films to a lesser extent than the SNCs due to their smaller size.