Research On The Polypropylene/Nylon66/Grafted Polypropylene/Graphite Binary And Multicomponent Electrically Conductive Nanocomposites

In attempt to prepare and investigate the novel high-performance electrically conductive polymer composites, the binary and multicomponent electrically conductive nanocomposites as well as the combined nano and in-situ composites were prepared with polypropylene (PP) served as the matrix, expanded graphite (EG) as a conductive filler, nylon 66 (PA66) as a modifier, and maleic anhydride grafted polypropylene as an EG intercalater and the compatibilizer of PP-PA66, based on the state-of-art development in the realm of polymer/inorganic nanocomposites and polymer/polymer in-situ composites domestically and overseas. The main outcomes are obtained as follows:1. The gPP/EG electrically conductive nanocomposites were firstly prepared via solution intercalation. The percolation threshold at room temperature (?C) of the nanocomposites was merely 0.67 vol% (1.6 wt%), which was much lower than that of gPP/EG and PP/EG electrically conductive composites (3. 82 vol%, 5. 48 vol%) prepared via conventional melt-mixing. The critical index (b) was up to 9.61, which was much higher than that of PP/carbon black electrically conductive composites (2. 84~3. 79). This demonstrates that gPP molecules have intercalated into the nanoscale interlayers of graphite sheets as well as the pores (from nanoscale to microscale) of EG networks. The large structure-occupation of the formed EG-gPP networks results in low ?c, high b and excellent conductivity of the nanocomposites, for instance, the electrical conductivity at room temperature is up to 2.49X10-3 S/cm at 3.90 vol% EG content.2. The PP/gPP/EG electrically conductive nanocomposites with ?c of 6 wt%, which was much lower than that of corresponding electrically conductive composites (11 wt%) prepared via conventional melt-mixing, were firstly achieved via solution intercalation. At EG content of 8 wt%, the volume resistivity at room temperature of the former was only 3.81X 107 ?cm, whereas that of the latter was 3.22 X 1016 ?cm. This demonstrates that during solution intercalation, partial PP molecules intercalate into the pores of EG networks together with gPP molecules by means of their favorable compatibility, which leads to the stable EG-gPP-PP nanocomposite networks with larger structure occupation volume. As a result, the nanocomposites have lower ?c and higher conductivity.3. The PP/PA 66/gPP/EG electrically conductive nanocomposites with ?C of 4 wt%, which was lower than that of nanocomposites (6 wt%) without PA66, were firstly prepared via melt-mixing PP/PA66 pre-blends with gPP/EG master batches obtained via solution intercalation. This demonstrates that fractional PA66 intercalates into the EG-gPP-PP nanocomposite networks in the form of particles, which results in the increase of structure-occupation volume of the network, while the other PA66 particles are dispersed in the PP matrix, enhancing the EG concentration in PP matrix and consequently presenting the double percolation effect. The two effects mentioned above make the ?c of composites play down.4. The reinforced and toughened PP/PA66 and PP/PA66/gPP in-situ composites were firstly prepared via extrusion-drawing-injection method. The tensile strength (?t=34.0, 38.6 MPa) of PP/PA66/gPP=85/15/0 and 85/15/4 in-situ composites are enhanced by 10% and 25% than that of PP (?t=31. 0 MPa) respectively, and their Izod impact strength ( a k=6. 6, 5. 2 kJ/m2) are improved by 47% and 16% than that of PP (a k=4. 5 kJ/m2) respectively. The new phenomena, never previously reported in the references, of the PA66 phase morphology in the PP/PA66 in-situ composites varying with PA66 contents (Cd) are revealed as follows: the diameter or width of PA66 fibers has dispersity, which becomes smaller first and then larger lately with Cd. Additionally, the number of PA66 unfibrillized paticles increases with Cd. This can interpret the variation of ?t with Cd.5. The PP/PA66/gPP/EG combined in-situ and nano electrically conductive composites with ?C of 4 wt%, which was lower than that (?C =6wt%) of composites without PA66...