Study On The Preparation And Modification Of ZrWMoO₈ And Its Composites With PTFE And PMMA

Negative Thermal Expansion materials have attracted widespread attention because their special performance. ZrWMoO8 has been studied extensively because its thermal stability and negative thermal expansion in a wide temperature range.According to the characteristics of the large coefficients of thermal expansion(CTE)of polymers, this article has studied on the improving of the thermal expansion properties of the polymers by filling modified ZrWMoO8. And so, the application area of the polymers would be made broader. The main contents of this paper are as follows:(1). Different shapes of ZrWMoO8 powders were prepared by hydrothermal synthesis and co precipitation synthesis. The powder prepared by co precipitation synthesis is shapeless with the size of 2μm~10μm. The powder prepared by hydrothermal synthesis is rod like with the size of 0.4μm × 4μm. Through the examine of the variable temperature X-ray diffraction(XRD), we can find that both of the powders prepared by the above methods have negative thermal expansion performance, the CTE is-5.12×10-6 K-1 and-6.39×10-6 K-1 respectively.(2). ZrWMoO8 powders were modified by the surface modifier of 3-Aminopropyltriethoxysilane(kh-550). We can find the Si—O bond in the sample by mean of the examine of Fourier transform infrared spectroscopy(FT-IR). The Contact Angle testing proves the hydrophilic is reduced, and the dispensability of the sample in organic solvents is improved.(3). By filling the modified ZrWMoO8 powders in(PTFE), ZrWMoO8/PTFE composite is prepared and characterized by the methods of XRD, scanning electron microscope(SEM), FT-IR, thermal mechanical analysis(TMA), high-speed reciprocating friction tester and surface profiler. The dates show that the two materials don’t have crystal structure change and chemical reaction, moreover, the two materials dispersed evenly. The result of TMA examines shows that the CTE of the samples reduced gradually with the increasing of the loading of the modified ZrWMoO8. In comparison of the effects of both kinds of ZrWMoO8, the rod like ZrWMoO8 is better than the shapeless in reducing the CTE of PTFE. When the loading of the rod like ZrWMoO8 reaches 50 wt%, the CTE of PTFE is 4.53 × 10-5K-1, 56.9% lower than the original 10.5 × 10-5 K-1. Whereas, when the loading of shapeless ZrWMoO8 reach 50 wt%, The CTE of PTFE is 7.1 × 10-5 K-1, 32.4% lower than the original. The study of friction and wear properties of composite shows thatthe friction coefficient and wear rate are reduced when loading the two shapes ZrWMoO8, and the effect of rod like ZrWMoO8 is also better.(4). ZrWMoO8/PMMA composite is prepared through in situ polymerization,The samples were characterized using XRD, FT-IR and SEM, the dates show that the two materials don’t have crystal structure change and chemical reaction, moreover,the two materials dispersed evenly. The CTE of composite is characterized by TMA,the result shows the CTE of the composite reach 7.8 × 10-5 K-1 when loading with 10wt% irregular ZrWMoO8 powders, and is 26.4% lower than of the pure PMMA which is 10.6 × 10-5 K-1. The CTE of composite loading with rod like ZrWMoO8 powders reach the lowest 7.9 × 10-5 K-1when loading 20 wt%.