Preparation Of Polyamide-6/Graphene Composites By In Situ Polymerization Preparation And Their Thermal Conductivity Properties

In recent years, with the increasing application in electronics, heating exchanging system, and electromagnetic shielding materials, etc., the polymer materials are required to be of much higher thermal conductivity. As is known to all, almost all polymers show poor thermal conductivities of 0.1-0.5 Wm-1K-1, and thermal conductive fillers are commonly used to prepare polymer based composite to meet the requirement. The thermal conductivity of composite considerably depends on the filler. Graphene is getting extensive attention because of its outstanding thermal conductivity. However, such problems as dispersion, stability, and homogeneity of graphene in the resin martrix still remains to be improved.In this thesis, graphene oxide (GO), graphene (GE), and expanded graphite (EG) are selected as thermal conductive fillers to prepare a series of polyamide-6 (PA6) composites via in situ ring-opening polymerization of caprolactam monomer (CL). The impact of filler contents, dispersion, and preparation methods on the structures and thermal conductivities of the prepared composites were systematically investigated. The main results are provided bellow:1. In PA6/GO composites, the covalent bonds were proved to exist between the interface of GO sheets and PA6 chains, which favored the dispersion of GO in the composites. Compared with neat PA6, the thermal conductivity of the composites increased from 0.32 to 0.41 W m-1K-1 with 10.0 wt% GO loading due to the good dispersion and interfacial adhesion.2. Based on the results of using GO as dispersant to treat GE to get GE-GO complex, it could be adopted as filler to prepare PA6/GE-GO composites via in situ polymerization of CL. It was observed that the formation of π-π interaction between GO and GE was benefit for the dispersion of GE in PA6. With the addition of 10.0 wt% of the filler, the thermal conductivity of the prepared PA6/GE-GO composite got as high as 2.14 Wm-1K-1, which was improved 56% compared with the PA6/GO, and was almost 6 folders of neat PA6.3. Owing to the in situ intercalation polymerization of caprolactam cations (CL+) between the layers, the layers of EG were efficiently separated, and the PA6/EG-CL+ was then obtained via in situ polymerization. Because of the cation-π interaction between CL+ and the EG layers, CL+ was much easier to get into the EG layers and then separate the layers. The thermal conductivity of the PA6/EG-CL+ was 1.43 Wm-1K-1, with 10.0 wt% of EG was added, which was close to the value of PA6/GE.