| As a kind of one-dimensional nanomaterials, carbon nanotubes (CNTs) with their unique structure and excellent performance are showing a broad application in the field of functional polymer composites. Polymer/CNTs nanocomposites have emerged very good mechanical, electrical and fire-retardant properties. In this thesis, CNTs were used to modify extrinsic flame retardant polymer ethylene/vinyl acetate copolymer (EVA) and intrinsic flame retardant polymer polymer polyphenylene sulfide (PPS). The following aspects were mainly studied.Firstly, high density polyethylene(HDPE) was added in EVA to improve the mechanical properties. When the HDPE content was 10%, The tensile strength(TS) and elongation at break(EB) reached maximum of 27.6 MPa and 1917.9%,78.7% and 9.4% higher than EVA, respectively. For improving the compatibility between EVA and HDPE, EVA grafted with maleic anhydride(EVA-g-MAH) and PE grafted with maleic anhydride(PE-g-MAH) were selected to fill in EVA/HDPE (90/10). It was found that these two kinds of compatibilizer can enhance the TS of EVA/HDPE blend. The compatibizing effect of EVA-g-MAH was better than PE-g-MAH.Secondly, phosphorus and nitrogen macromolecules intumescent flame retardant(NPS) was selected as fire retardant, multi-walled carbon nanotubes (MWNTs) were used as flame retardant synergist to modify EVA. Effects of NPS and MWNTs on the properties of EVA composites were investigated.The results indicated that the flame retardancy was improved,while the mechanical properties decreased with the increase of NPS. With the addition of MWNTs which have a good synergistic effect in combination with NPS to improve their efficiency, so the loading of NPS can be significantly decreased. When the NPS content was 29.5% and MWNTs was 0.5%, LOI and TS could reach 33.6% and 12.4 MPa. TGA and SEM data showed that MWNTs could enhance the thermal stability and improve the quality of residual carbon layer. Furthermore, the system remained good electrical insulating performance. These properties meet the industry standard for the use of halogen-free flame retardant EVA wire and cable materials.Finally, using epoxy resin (E51) as the interfacial modifier and MWNTs as nano-functional modifier to prepare PPS nanocomposites. When the content of E51 was 5%, the EB increased to 31.2%,6 times higher than PPS, showing excellent toughening effect. FT-IR and TGA results indicated that E51 was completely participated in the chain-extension reaction of PPS. But the TS and Young's modulus decreased. The glass transition temperature(Tg) is 15.7? lower than PPS. DSC indicated that both crystallization temperature and melting temperature of the system reduced 14.4? and 12.1?,respectively. After MWNTs reinforced PPS/E51 system, the TS and flexural strength increased, Young's modulus and flexural modulus increased as well. When filling 0.25% of MWNTs, the TS and flexural strength of PPS nanocomposite reached 71.6MPa and 117MPa, EB was 23.7%.According to the dynamic mechanical analysis(DMA), the addition of MWNTs made the Tg of the system increase about 4?12?,as well as storage modulus. Meanwhile crystallization temperature of the system increased by nearly 10?, but little change on melting point.The DTG curves of PPS nanocomposites shifted to higher temperature section, and lower the maximum mass loss rate. By observing the TEM photos, it was found that single or small beam tubular structure of MWNTs distributed in the matrix. In a word, E51 and MWNTs have a good synergistic effect on the strengthening and toughening for PPS. |
PDF Full Text Request