Research Of Structure And Properties For Long Chain Branched Polycarbonate

As one of the most important engineering plastics, polycarbonate (PC) exhibits excellent comprehensive properties including high impact strength, transparency, ageing resistance, fatigue resistance, electrical insulation, etc. It has been widely used in electronic and equipment, automobile, construction, machinery, aerospace, medical instruments and so on. However. PC has some drawbacks because of the limitation of polymer molecular structure such as difficult to process, notch sensitivity, the poor scratch and environmental crack resistance. In this research, we start with the improvement of polymer melt processability. With the help of gamma irradiation, we prepared a series of long-chain branched polycarbonate and studied the changes of its topological structures and properties. The main research works includes:1. A series of long-chain branched polycarbonates was prepared from linear PC precursor through gamma radiation with addition of difunctional monomer, divinyl benzene (DVB) of various amounts. The topological structures of linear PCs and LCB-PCs were measured by size-exclusion chromatography coupled with a multiangle light scattering detector (SEC-MALLS) and rheology. SEC-MALLS measurements showed that the topological structures of PCs were changed with the introduction of LCB structures. Rheological measurements showed that the LCB structures of LCB-PCs contributed to the enhancements of storage modulus, complex viscosity, relaxation time and the changes of relaxation behavior.2. Changes of the thermodynamic performance with the introduction of long-chain branched structures is researched by differential scanning calorimetry (DSC). In order to distinguish the process of glass transition and enthalpy relaxation, the modulated mode is employed. Meanwhile, the influence of annealing time on thermal properties of linear PC and LCB-PCs is studied. On the other hand, the influence of LCB structures on the environmental stress cracking (ESC) property of LCB-PCs was further explored and the results showed that the ESC property of LCB-PCs could be enhanced with the introduction of LCB structures.