Dispersion of single-walled carbon nanotubes in a non-polar polymer, poly(4-methyl-1-pentene)

Poly(4-methyl-1-pentene), PMP, a high melting polymer composed of hydrogen and carbon, has the potential to become an alternative to polyethylene (PE) as shielding material against Galactic Cosmic Radiation (GCR). PMP exhibits higher thermal stability than PE and is transparent in the UV/visible region of the electromagnetic spectrum. Single walled carbon nanotubes (SWNTs) were pretreated with a polar solvent, N,N-Dimethylformimide (DMF), and then dispersed in a halogenated hydrocarbon, cyclohexyl chloride, which also dissolved the non polar polymer, PMP. The composites were characterized via differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), microhardness measurements, and optical microscopy. DMA data revealed that the carbon nanotubes contributed to the enhancement of the high temperature a, relaxation which is thought to arise from motion around crystalline regions in the matrix. The storage modulus (60 Hz) increased from 2409 MPa in the neat PMP to 3716 MPa at -50 degrees C. The magnitude of the increase diminished near and above the glass transition region; the glassy matrix restricted motion of the crystalline regions. DSC data showed an increase in the percent crystallinity of the composite (75%) as compared to the neat polymer (68%). Low concentrations of nanotubes, when well dispersed, produced nanocomposites with varying degrees of transparency.