Study On The Preparation And Properties Of PVC/ Diatomite Composites

Organic and inorganic composites combine the processability and high toughness of organic phase and the high rigidity,corrosion resistance and heat resistance of inorganic phase,so it has wide application prospect.Various kinds of inorganic fillers have been extensively applied in plastics and rubber,so that the composites have many excellent properties.However,the surface hydrophobic of inorganic filler is very weak,and its compatibility with polymer is poor.The inorganic filler has large specific surface area,and it is easy to aggregate,which seriously affects the performance of organic and inorganic composites.The modification of the surface of inorganic filler is an effective approach to promote the compatibility between the inorganic particles and the polymer matrix.This method is able to promote the interfacial interaction between inorganic particles and the polymer matrix,so it has attracted wide attention.In order to improve the compatibility between diatomite and PVC resin,we first remove the impurities which are on the surface of diatomite by acid treatment,and expect to activate the silicon hydroxyl on its surface.And then KH570 is grafted onto the surface of diatomite to make the surface covered by a layer of hydrophobic chain segment,which improves the compatibility between diatomite and PVC matrix,and makes the modified diatomite dispersed in the matrix more uniform.Then,PVC powder,the modified diatomite and other processing aids are made into PVC/modified diatomite composites by melt blending using two-roll mill.The results of FTIR and TGA show that KH570 is successfully grafted onto the surface of diatomite through covalent bonding.The thermal stability of the composites increases with the addition of KH570 modified diatomite.When the 1 phr modified diatomite is added,the maximum weight loss temperature(T_max)of the PVC composites increases by 20°C.Because of the stronger interface interaction between the PVC matrix and the modified diatomite,the PVC/modified diatomite composites exhibit better mechanical properties.When 0.5 phr and 1 phr modified diatomite are added into the PVC matrix,the impact strength of the composites reaches 988.9 J/m and 828.2 J/m,which increases by 33.1%and 26.8%,respectively,than that of the unmodified diatomite.The apparent shear yield deformation can be observed in the scanning electron microscope images of the composites impact fracture surface.The effect of the mixing ratio of diatomite and light calcium carbonate on the properties of composites is also investigated in this paper.The experimental results show that with the increase of the proportion of light calcium carbonate in the compound filler,the impact strength of the composites increases and the elongation at break rises.The impact fracture surface is very smooth in the scanning images.With the increase of the proportion of light calcium carbonate,the thermal stability of the composites increases.The 5%weight loss temperature(T_5%)and the maximum weight loss temperature(T_max)of the composites increase by 7.77°C and 8.67°C respectively.The storage modulus of the composites decreases gradually and the glass transition temperature moves towards the low temperature,the loss factor?tan??of the composites increases.