Modification Of Black Shale And Its Application In Polymer Composites

There is a large amount of black shale in northern Guangxi exposed in the mountains,which makes it easy and inexpensive to exploit.The black shale in northern Guangxi is mainly composed of silica,clay,organic carbon,and a small amount of pyrite.Decompose of pyrite makes an unpleasant odor during high-temperature processing resulting in the difficulty of application of black shale.At the same time,the black shale is highly hydrophilic leading to the formation of air bubbles in polymer composites,which can seriously damage the performance of the composites.On the other hand,the presence of small amounts of organic matter in black shale breaks the interfacial bond between the shale and the polymer matrix resulting in a reduction in the mechanical properties of the composite.Therefore,the modification of black shale composition and surface properties is of great significance for the development and utilization of black shale.The research on the modification of black shale in northern Guangxi not only expands the application of shale in composite materials but also promises to eliminate the problem of soil acidification caused by the natural weathering of shale,providing a solution for environmental protection in northern Guangxi.Taking advantage of the easy decomposition of pyrite after heating,we effectively remove sulfide and remove a small amount of organic matter by high-temperature calcination.The surface modification of calcined shale was then carried out using coupling agents.Calcined modified shale/HDPE and calcined modified shale/PVC composites were prepared to investigate the difference in properties of the powders after modification.This work contains four parts as following:1.Calcination study of black shale.Shale powders were calcined at 300°C,450°C,and600°C.The shale was found to be still black after calcination at 300°C,turning earthy yellow after calcination at 450°C,and maroon after calcination at 600°C.XRD tests showed that the powder was still mainly composed of silica after calcination at 450°C and above,but the diffraction peaks of sulfide ferrite disappeared.Infrared spectroscopy and thermogravimetric analysis indicate that organic matter is removed from the powder after calcination at temperatures above 450°C.2.Surface modification study of post-calcined shale.Coupling agents such as KH550,KH560,KH570,KH792,and NDZ201 were selected for wet modification of the surface of post-calcined shale.The highest settling volume,activation,and lower surface hydroxyl number were measured for 5%NDZ201/BS450.This indicates that the surface of the calcined powder was covered by coupling agents,which increased lipophilicity and improved the compatibility and dispersion of the shale with the polymeric material.3.The preparation of calcined modified shale/HDPE composites was studied.The effects of different fillings of calcined modified shale on the melt index,tensile strength,and elongation at the break of the composites were investigated.The results showed that the composites could maintain a tensile strength of 24.41 MPa when the filling amount of modified shale reached 50parts.The thermal analysis shows that the filling of black shale does not affect the decomposition temperature.The thermal analysis shows that the filling of black shale does not affect the decomposition temperature.The cross-sectional scan photograph shows that the modified shale forms an obvious interfacial bond with the matrix,thus maintaining the mechanical properties.4.Preparation of calcined modified shale/soft PVC composites.The effect of different filler amounts on the properties of calcined modified shale/soft PVC composites was investigated and compared with the properties of the original shale and Ca CO₃ filled soft PVC composites.The tensile strength of the calcined modified shale/soft PVC composites was 10.69MPa,compared to 11.05 MPa for the Ca CO₃ filled and 9.02 MPa for the unmodified shale filled,under the same conditions of other components and at a filling level of 50 phr;the elongation at break of the modified powder increased by 37.1%to 187%compared to the unmodified filled soft PVC.Scanning electron microscope characterization illustrates the strong bonding of calcined modified shale to the PVC interface.