Papers by Author: Hao Gu

Abstract: The extraction of tea seed oil obtained from wild camellia seed using supercritical CO2 extraction has been investigated. The extraction was carried out under operation pressures of 20, 30, 35, 40 and 50 MPas at 45°C, with a supercritical fluid flow rate of 5mL•min-1. The collected extracts were analyzed and the relative compositions of the tea oil were determined by gas chromatography-mass spectrometry(GC-MS). The purpose of this work was to investigate the effect of operation pressure on the extraction yield, extraction time, and extract composition. The results from supercritical CO2 fluid extraction (SFE) showed that the extraction pressure positively related to the extraction yield and negatively and linearly related to the extraction time. Only 5 constituents were found in the extract under the pressure of 20 MPa. However, about 20 constituents in the extract were obtained under the pressure of 35 MPa, approximately the same as those under 50 MPa. The curve of the extraction pressure versus the extraction yield demonstrated that the extractable constituents of wide camellia seeds have two states: a free state and a bound state. In the bound state, extractable constituents can only be extracted under an extraction pressure above the threshold. Taking into consideration of the extraction yield, equipment, and operation, the appropriate pressure of the SFE is between 36.4 MPa and 40 MPa.

Abstract: Thermogravimetry (TG) analysis was employed to investigate the effects of antioxidants on the temperature response of PEG200 at 5% and 10% weight loss respectively, and to compare the TG profiles of cutting fluid 010 with that of PEG200 adulterated with antioxidants. Thermal aging method was utilized to survey the electrical conductivity, pH value and relative viscosity of PEG600 stock solution. Meanwhile, effects of 13 antioxidants on the anti-thermal oxidation activity of PEG600 was studied and the properties of the antioxidant-modified PEG were compared with that stipulated by the trade standard of silicon wafer cutting fluid in terms of electrical conductivity, pH value and relative viscosity. The results showed that addition of antioxidants such as 626, 1098, B900 and p-hydroxyanisole increased the temperature of PEG200 at weight loss significantly. A large disparity was displayed between the thermal gravity curves of cutting fluid 010 and that of antioxidants-containing PEG200. Electrical conductivities for all 13 PEG600 samples with anti-oxidants after thermal aging excel that of the manufacture’s standard. All antioxidant-modified PEG600 samples, except that containing DLTP and 626, satisfy the criteria of pH value by the manufacture’s standard. The viscosity of PEG600 changed little after adding antioxidants 1010 and B225, which revealed that these two antioxidants posses certain property of inhibiting polymerization of PEG600.