Studies On Modification Of PBS And Its Swelling And Foaming Properties In Supercritical Carbon Dioxide

Poly(butylenes succinate)(PBS) is a kind of aliphatic ester with excellent mechanical and biodegradable properties. Studies on PBS has received a large amount of attention in recent years. Researchers focused on synthesis, processing and modification of PBS to broaden its applications. This thesis aims at the modifications of PBS, solubilities of supercritical CO2in various PBS, and its foaming properties.Amorphous nylon PA6IcoT and PBS were reactively blended in a twin screw extruder with the aid of supercritical CO2. Meanwhile, the2,2-(1,3-phenylene)bis(2-oxazoline)(PBO), as chain extender, was added to improve the melt strength. The structure of chain extension was validated by solubility experiment, FT-IR,1-NMR and13C-NMR. Scanning electron microscope(SEM) was used to analyze the morphology. The results supported that PBO was an effective chain extender. The properties of products of chain extension, such as crystalline, thermal performance, mechanic and biodegradation properties, were systematically researched. It had been shown that the PA6IcoT inhabit the crystallization of PBS, resulting in higher activation energy, slow crystal growth, low crystallinity, spherulite size decreasing and more blurred interface between the two phase. At the same time, for the non-isothermal crystallization process, Jeziorny and Ozawa method could not describe the process, while Mo’s method performed well, the chain extension products possess improved thermal and mechanic properties. It was found that the rate of polymer degradation depended on the amorphous region. The higher randomness and lower crystallinity could accelerate the degradation rate. Therefore, the chain extension products not only improved the thermal and mechanic performance, but also maintained well biodegradability relatively.This thesis investigated the foaming property under scCO2at various temperatures and pressures. The results showed that the expansion ratio of LPBS was about7at temperatures from110℃to120℃and pressure up to20MPa. The modified PBS have a significant improvement in foamability and stability. The cell distribution of modified PBS is more uniform than raw PBS.The solubilities and swelling characteristics of PBS were also investigated. The solubilities of CO2in line-chain and branched-chain PBS was measured at temperatures from353.15K to383.15K and pressure up to10MP. The results demonstrated that the solubilities of CO2In PBS increased with the elevated pressure and decreased with temperature. The experimental results also were correlated by Sanchez-Lacombe equation of state(SL EOS) with temperature-dependent binary interaction parameter k12. The results showed that SL EOS was a suitable model to predict the solubility of CO2in PBS, where the average relatively deviations between experimental data and calculated results were less than5%. The binary interaction parameters for line-chain and branched-chain PBS were correlated with temperature. The results presented well linear relationship, which were helpful to predict the solubilities and swelling in others conditions. The experiment further found that the swelling of CO2have significant impact on the degree of crystallinity of PBS. The results revealed that the induced-crystallization was much easier at higher pressures and temperatures at certain range. There were no induced-crystallization at lower pressures and temperatures. Moreover, with the prolongation of the swelling time, the degree of crystallization is increased. All of experiment proved that the crystal forms were keep unchangeable, but the crystal morphology become more perfect.