Synthesis of carbon nanotubes by orifice-chemical vapor deposition reactor and applications in styrene polymerization and nanocomposites

A new generation of catalytic chemical vapor deposition reactor was designed and fabricated locally at the department of chemical engineering, and it is called orifice chemical vapor deposition (O-CVD) reactor, to produce well aligned multiwall carbon nanotube (MWCNT) with high aspect ratio. Reaction parameters such as reaction temperature, reaction time, hydrogen flowrate, hydrocarbon flowrate and orifice diameter were varied in order to study their effect and to find the best parameters for producing MWCNTs with high quality and high aspect ratio. MWCNTs with purity of 97.6% and high aspect ratio (1mm long) were produced at hydrogen flowrate of 240 ml/min, acetylene flowrate of 155 ml/min, orifice diameter of 6 mm, 800°C reaction temperature and 30 minutes reaction time. The production rate was 1.9 gram/hr with total cost of only 6 ;MWCNT were functionalized by different types of functional groups such as, carboxylic, dodecylamine, phenol and 1-octadecanol functional groups in order to enhance the dispersion of CNTs in styrene monomer solution during polymerization process. The non functionalized MWCNTs and modified MWCNTs-Amine and MWCNT-COOH showed a clear reduction in the conversion of styrene monomer to polystyrene at high temperature (115 °C), which indicated that they could be good candidates as polymerization inhibitors by adding them to the styrene monomer solution. MWCNT-Amine was the best in polymerization inhibition.;Polystyrene (PS)/CNT nanocomposites were prepared by thermal bulk polymerization without any initiator at different loadings of CNT. The mechanical, thermal and rheological properties of the nanocomposites were studied. The tensile tests showed that the addition of 5 wt.% of CNT-COOH results in 68% increase in Young's modulus. The DSC measurements showed a decrease in glass transition temperature (Tg) of PS in the composites. The rheological studies at 190°C showed that the addition of untreated CNTs increase the viscoelastic behavior of the PS matrix, while the functionalized CNT act as plasticizer at low loadings. Thermogravimetric analysis indicated that the incorporation of CNT into PS enhanced the thermal properties of the matrix polymer. A comparison between commercial short MWCNTs and long MWCNTs produced by O-CVD was carried out to evaluate the effect of increasing the aspect ratio on the mechanical properties of PS/CNT nanocomposites.