Specific functionalization and polymer grafting on multiwalled carbon nanotubes to fabricate advanced nylon 12 composites

This paper deals with polymer grafting of multi-walled carbon nanotubes (MWCNTs) via ultraviolet/ozone (UV/O₃) assisted polymer grafting (UVOG) in order to improve the filler efficiency and thus giving a highly homogeneous dispersion, strong filler-matrix interactions and excellent distribution of individual nanotubes in the polymer matrix. Though several chemical procedures of grafting have been developed to obtain dispersible CNTs, grafting by a fast, low cost, non hazardous and controllable process is still under active research. 2-Acrylamido-2-methylpropane sulfonic acid (AMPS) monomers were employed for grafting onto MWCNTs due to their very hydrophilic and reactive sulfonic (SO₃H) end groups. The structural and morphological changes in poly-AMPS grafted MWCNTs (PAG-MWCNTs) were characterized by FTIR spectroscopy, XPS, Raman spectroscopy, TEM and FESEM. When the PAG-MWCNTs were incorporated into nylon 12, the results showed excellent uniform dispersion of individual MWCNTs throughout the matrix and improved the mechanical properties of the composites. Addition of only 0.75 wt% PAG-MWCNTs showed an improvement of tensile strength and Young's modulus by ∼43% and 33%, respectively, compared with those of neat nylon 12. Moreover, the PAG-MWCNTs/nylon 12 composites exhibited a ∼12 °C improvement in the glass transition temperature (T_g) compared to the raw MWCNTs/nylon 12 composites. From a literature survey, these results are found to be quite promising. Therefore, we believe that the polymer grafting of MWCNTs presented herein will be a useful technique to produce novel filler materials for preparing various advanced nanocomposites. Moreover, this grafting technique may also be employed to introduce other functional polymers onto the surface of MWCNTs.