چكيده به لاتين
In this study, polypropylene (PP) was reinforced using mica nanoparticles as a reinforcement to improve its mechanical properties. For this purpose, mica was organically modified using a vinyl functional modifier, i.e. diacetone acrylamide (DAAM), to increase the interaction between the polymer chains and mica silicate layers. X-ray diffraction (XRD) patterns exhibited the intercalation of the modifier molecules inside the mica's gallery. Maleic anhydride-grafted polypropylene (PP-g-MAH) was grafted on the organically modified mica (OMM) in an organic suspension media at different temperatures, 100, 120 and 130°C. Fourier transform infrared spectroscopy was used to characterize OMM and the organically modified-grafted mica (OMGM). Various amounts of OMGM nanoparticles, 0–3 wt%, were used to reinforce PP. The effect of OMGM level on the crystallinity, tensile properties, impact and fracture toughness of resulting nanocomposites was investigated. The results showed that adding 1 wt% OMGM prepared at grafting temperature of 120°C enhanced the tensile strength 12% and notched impact strength 58%, while changed the critical stress intensity factor (K1C) slightly (5%) when compared to PP. Partial exfoliation of OMGM layers in the PP matrix was indicated using transmission electron microscopy. Further increase of OMGM lowered the mechanical properties and fracture toughness due to OMGM nanoparticle agglomeration. PP was also reinforced using Cloisite15A (C15A) along with the organically modified-grafted mica (OMGM) as debonding rigid nanoparticles to improve its impact resistance with the advantage of increasing its Young's modulus and crack growth resistance. Various amounts of C15A, 0–3 wt% along with 1 wt% OMGM were used to reinforce the PP matrix. The effect of C15A content on the crystallinity degree, fracture morphology and mechanical properties of resultant hybrid nanocomposites was investigated. The results showed that the incorporation of 1 wt% OMGM and 0.5 wt% C15A resulted in the highest impact resistance (68%) and fracture toughness (6.2%) when compared to neat PP. In addition, the elastic modulus and yield stress were increased 12 and 14.5%, respectively. Transmission electron microscopy exhibited a fairly good dispersion of smaller C15A and longer OMGM tactiods in the resultant hybrid nanocomposite, while increasing of C15A content caused the nanoparticle agglomeration and lowering the impact resistance. The highest fracture toughness and the slowest crack growth rate was observed. The results showed the highest impact strength enhancement of 68% and Young's modulus of 12% for hybrid nanocomposite containing 1 wt% OMGM and 0.5 wt% C15A when compared to neat PP. In order to considerably improve the impact strength of PP with advantage of elastic modulus enhancement, PP was melt blended with above-mentioned amounts of OMGM and C15A and different contents of ethylene-1-butene copolymer (EBR), 0–10 wt%. The dispersion of low- and high-aspect ratio layered silicate tactoids and EBR nanoparticles in the polymer matrix was studied using transmission electron microscopy. The effect of EBR level on the crystallization behavior, tensile properties, impact strength, and fracture toughness of the resultant toughened hybrid nanocomposite was investigated. The presence of EBR nanoparticles did not show any sufficient effect on the melting and crystallization temperatures of the toughened PP and hybrid nanocomposites. However, the impact results indicated that the addition of EBR to neat PP remarkably increased the toughness while sharply decreased its Young's modulus. The incorporation of 7 wt% EBR in the hybrid nanocomposite containing 1 wt% OMGM and 0.5 wt% C15A considerably enhanced impact strength 119% and 30% in comparison to neat PP and its hybrid nanocomposite, respectively. Additionally, the incorporation of EBR nanoparticle in the presence of the silicate layered nanoparticles prevented significant decreasing in Young's modulus of the matrix.
