Papers by Author: Xin Deng

Abstract: Polyamide 6-polyurethane (PA6-PU) block copolymers filled with graphite particles were prepared by anionic polymerization process. The friction and wear experiments were conducted using a UMT-3 machine with the chromium steel ball sliding on surface of the composites at high sliding speeds of 500rpm, 1000rpm and 1500rpm and loads of 78.5N and 157N. With adding of graphite, coefficient of friction and wear rate values of the composites decreased firstly, and then increased. And the influence of the applied load and sliding speed on tribological properties of the composites was explored in this study. The results showed coefficient of friction and wear rate values increased with the increasing of load. Coefficient of friction decreased and wear rate values increased with increasing of sliding speed. Microstructure of wear surface of the tested composites was inspected by scanning electronic microscope(SEM) and wear mechanism of the composites was studied.

Abstract: Polyamide 6/polyurethane/graphite composites have been prepared by anionic polymerization process. The effect of graphite concentration on mechanical properties of the composites was investigated. The test results show that with increment of graphite content, tensile strength of the composites increases firstly, and then decreases, while notch impact strength decreases. The change of mechanical properties of the composites is attributed to the dispersion of graphite, the interfacial properties between the matrix and graphite and the nucleation effect of graphite. In addition, the relationships between loss factor(Tan δ), storage module(E’) and temperature were investigated using Dynamic Mechanical Analysis(DMTA), and the morphological characteristic of the composites were studied using Scanning Electronic Microscope (SEM).

Abstract: This thesis does thermal gravimetric analysis（TGA）studies on Chinese fir sawdust biomass by integrated thermal analyzer under vacuum conditions. Through the analysis on lostmass curve at different heating rate of 10, 15, 20 and 30°C/min, we found the process of Chinese fir sawdust vacuum pyrolysis can be mainly divided into three stages: evaporation of free water and combined water desorption, rapid lostmass of pyrolysis and slow decomposition of residues. The lostmass major temperature range is between 250 ~ 450°C, the peak temperature is between 365 ~ 400°C. When the pyrolysis temperature is 500°C, vacuum pyrolysis reaction of Chinese fir sawdust has basically completed. As the heating rate rises, the lostmass curve is moving to the right, the peak temperature is shifting to higher temperature, and the temperature range of thermal decomposition reaction widens significantly. According to experimental datas, we tried to obtain the vacuum pyrolysis dynamic parameters of Chinese fir sawdust, and the results are that the apparent activation energy of vacuum pyrolysis reaction of Chinese fir sawdust biomass is 128.34kJ/mol, with the pre-exponential factor being 6.42×109 and reaction order being 1.08, similar to first order reaction.

Abstract: A computer simulation model was established to analyze the curing and cooling of reaction injection molding process of nylon 6 based on theory of balance equation of energy, reaction kinetics and crystallization kinetics. The reasonable assumptions and simplifications were introduced in the model, and an explicit finite difference method with MATLAB software was applied to calculate and predict the conversion and temperature distribution within a plate type mold. The results show that the center position reaches the peak temperature about 45s. The effects of the feed temperature, wall temperature, and reaction rate constant on the temperature and conversion were discussed for searching the optimum processing conditions. The results suggests that the effect of reactive rate on crystallization, molecular weight and phase structure is decided by the value of reaction constant; the influence of the mold wall temperature on reactive rate and temperature near the boundary was great; and the control of feed temperature is important in condition of low mold temperature.