ABSTRACT
Polytetrafluoroethylene/poly(methyl methacrylate) (PTFE/PMMA) composites were prepared by a self-curing method. The influence of heat treatment processes on the friction and wear behaviors of PTFE/PMMA composites against bearing steel balls were studied by a ball-on-disk tribometer. The thermal performance of PTFE/PMMA composites with heat treatment was analyzed by Thermogravimetric Analysis (TGA). The surface morphologies and element distribution of PTFE/PMMA composites in a PMMA matrix were detected by Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive Spectroscopy (EDS). The results indicated that the wear rates of PTFE/PMMA composites with different heat treatments significantly declined compared with the unheated treatment composite. The wear rate of the PTFE/PMMA composite decreased firstly and then increased with molding temperature and time increasing, and reduced with the molding pressure increasing. The main wear mechanisms of PTFE/PMMA composites with different heat treatments were fatigue wear and abrasive wear.
ABSTRACT
Polytetrafluoroethylene/Poly(methyl methacrylate) (PTFE/PMMA) composite was prepared by mixing PTFE into PMMA matrix which synthesized by the PMMA powder mixture and methyl methacrylate (MMA) liquid mixture. The effects of the filling mass ratio of PTFE and powder/liquid (P/L) ratio on the friction and wear properties of PTFE/PMMA composites against bearing steel were studied by a ball-on-disk tribometer. Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDS) were used to characterize the synthesis of PTFE/PMMA composite. The shore hardness and glass transition temperature (Tg) were obtained respectively by shore hardness tester and differential scanning calorimetry (DSC). The results show that the friction coefficient and wear rate of PMMA based composite, comparing with the unfilled PMMA, can be significantly reduced by filling with PTFE. With the increasing of PTFE filling mass ratio, the wear rate of PTFE/PMMA composite increases. The friction coefficient and wear rate of the unfilled PMMA and PTFE/PMMA composite generally decrease with the P/L ratio increasing. The main wear mechanism of the unfilled PMMA is adhesive wear. While the main wear mechanisms of PTFE/PMMA composites are fatigue wear and abrasive wear.
ABSTRACT
The dry reciprocating sliding properties of two weaves, reinforced twill 2/2 (RT) and basket weave 3/3 (BW), of hybrid PTFE/Kevlar fabric composites were investigated using a pin-on-flat configuration along the selected orientations of 0°, 30°, 45°, 60° and 90° which were the reciprocating sliding directions of pin to weft yarn (PTFE). The morphologies of the worn surfaces of the composites were analyzed by means of Scanning Electron Microscopy (SEM). The PTFE transfer film and F element on the counterface were observed and analyzed respectively by SEM and Energy Dispersive X-ray Spectroscopy (EDS). The results showed that the orientations and weaves played an important role in the friction reduction and antiwear properties of PTFE/Kevlar fabric composites. Contrasting to BW PTFE/Kevlar fabric composites, RT PTFE/Kevlar fabric composites showed significant advantages in the antiwear performance along all the selected orientations. The main damage forms of PTFE/Kevlar fabric composites include fatigue wear and adhesive wear of the polymer matrix, and lifted, wrinkled and breakage of the fibers.
ABSTRACT
A cavity ring-down spectrometer was built up using a CW tunable Ti: sapphire laser. The experiments show that not only the spectral resolution is up to the 10(-4) cm(-1) level, but the detecting sensitivity also exceeds 10(-10) cm(-1). With the measurements of the absorption spectroscopy of C2H2 near 12,696.4 cm(-1), the quantitative capability of the instrument was demonstrated. Through the spectroscopy of the samples mixed with trace C2H2 in N2 gas, the detection limit of C2H2 was determined to be 0.2 ppm.
