Novel technology for titanium dioxide modification and full-dull polyamide-6 polymers preparation

Titanium dioxide has recently found applications in many areas including cosmetics, paints, and papers owing to their excellent properties. In particular, it is an essential element in the preparation of polyamide-6 and polyester for the fabrication of functional dull polymers and fibers. Generally, the excellent performance of the resulting polymers and fibers is achieved titanium dioxide content is above 2.4wt%. However, titanium dioxide has poor dispersion property in polyamide-6 polymers hence production of full-dull polyamide-6 products at high titanium dioxide content is a great challenge. Recently, surface modification of titanium dioxide has been identified as a promising solution for solving the above problem.

To this end, Yu-ting Yang and Professor Chun-wang Yi from Hunan Normal University looked at using aluminate coupling agents as a suitable titanium dioxide modifier for the fabrication of full-dull polyamide-6 polymers and fibers. Unlike other coupling agents, it is widely preferred due to its low cost and high whiteness property. Their work is currently published in  Journal of Materials Science.

The authors commenced their work by developing a new surface modification approach for the preparation of nanoscale titanium oxide based on the aluminate coupling agents. Next, the reaction temperature and the content of the aluminate coupling agent were optimized to obtain modified titanium oxide particles. Also, the effects of the content of the aluminate coupling agent on the size of titanium oxide particles during the modification process were investigated at a constant temperature. The modified titanium oxide particles displayed better dispersion and smaller sizes in toluene attributed to the replacement of the exposed hydroxyls on the surface with hydrophobic bonds.

It was worth noting that for a suitable ratio range, an increase in the aluminate coupling content resulted in a corresponding decrease in the size of the modifies titanium oxide particles. Consequently, an increase in the coating temperature from 15°C to 30°C resulted in a sharp decline of the titanium oxide particles initiated by the high activity of the aluminate coupling agent at high temperatures. Further increase in the temperature induced particle regression.

The aluminate coupling agent reacted with the titanium oxide to change the particles from hydrophilic to super-hydrophobic state at a static water contact angle of 151.39°. According to the authors, the addition of a 6wt% aluminum coupling agent at a coating temperature of 30°C was the best condition for the preparation of modified titanium oxide. This condition can produce modified particles with an average size of 32.37nm and PDI of 0.214.

To validate the presented surface modification approach, the dispersion behavior and morphologies of both titanium oxide and modified titanium oxide particles in different solvents were studied. Modified titanium oxide was observed to be well dispersed in hot liquid caprolactam which is suitable for the preparation of full-dull polyamide-6 polymers. In addition, the modified titanium oxide particles showed well dispersion throughout the PA6 matrix. Altogether, the study by Yu-ting Yang and Professor Chun-wang Yi provides essential information that will pave way for enhancing the polymer distribution and optimizing the modification process for the preparation of different full-dull polyamide-6 fibers and polymers.