Preparation And Properties Of Phosphate Ester Modified Anhydrite And Filled HDPE,PVC And PS Composites

There is a huge storage of anhydrite in China,but there are few application fields of it such as cement industry.And most of anhydrite has become mine waste,causing environmental pollution and resource waste.It is reported that anhydrite has excellent mechanical properties and stable chemical properties,which can meet requirements of polymer filler.However,the compatibility between anhydrous gypsum surface and polymer matrix is weak,causing unsatisfying dispersion.So it is necessary to modify the surface of anhydrite when filling it into polymer composites.Phosphate ester is a kind of material with both polar group such as phosphate and non-polar organic functional group.In this paper,phosphate ester was used to modify the surface of anhydrite,for a better application in polymer composites.The research contents are as follows1.The anhydrite modified by mono-dodecyl phosphate(MDP)and the by octadecyl phosphate(OP)are prepared by wet method,and the composites are made by filling HDPE with modified anhydrite.The results show that the fineness of the modified anhydrite powder is about 1000 mesh,and its weight loss is less than 0.5% at 190℃,the processing temperature of HDPE.The oil absorption value of anhydrite decreases to19.5 m L/100 g.The activity grade reaches 94%,and the water contact angle increases to 104°.The highest impact strength of HDPE composite filled with modified anhydrite is 21.511 k J/m2.With the adding of MDP,the flexural strength increases to 20.54 MPa.And the flexural strength increases to 20.20 MPa first and then decreases with the increase of OP.With the increase of MDP,the tensile strength increases to 30.4 MPa first and then decreases.The maximum melt flow rate of HDPE composites filled with modified anhydrite is 1.84 g/10 min.2.Anhydrite mixed butyl phosphate(MBP)modified is prepared by wet method.And then MBP modified anhydrite is used as filler to make composites with HDPE and PVC.The results show that the fineness of the modified anhydrite reaches 1300 mesh.The modified anhydrite has good thermal stability that less than 0.5% weight is lost at 190℃.The minimum oil absorption value of modified anhydrite is reduced to 24.2 m L/100 g.The maximum water contact angle is increased to 16°.And dispersibility of modified anhydrite in water is worse than that of unmodified powder,but it is better in naphtha and 1,2-dichloroethane.The addition of MBP has little effect on the flexural strength and impact strength of HDPE composites.The tensile strength decreases but the elongation at break increases up to 585.4%.The maximum melt flow rate reaches 1.68 g/10 min.In PVC composites,the addition of MBP has no obvious effect on the flexural strength and tensile strength,but the elongation at break increases to 20.0%.The impact strength of the composites increases to 15.082 k J/m2 first and then decreases with the increase of MBP content.And the melt flow rate increases with the increase of MBP content,reaching 3.21 g/10 min.3.The lignin-mixed butyl phosphate(L-MBP)composite is prepared by reactive extrusion,and the anhydrite modified by lignin-mixed butyl phosphate composite is prepared by dry method.Then the L-MBP modified anhydrite is filled into HDPE and PS by melt blending to prepare the composite.The results show that the particle size of the L-MBP modified anhydrite apparently increases,the fineness of 20 phr is only 250 mesh.The mass loss of the modified anhydrite is less than 1% at 200℃.The oil absorption value decreases slightly to 33.9 m L/100 g.And the maximum water contact angle is 40°.Its dispersibility in petroleum naphtha and xylene is better than that of the unmodified anhydrite powder,but its dispersibility in water is not good.In HDPE composites,the addition of L-MBP decreases the impact strength and flexural strength,but increases the tensile strength to 19.9 MPa,and slightly decreases the melt index to 1.71 g/10 min.In PS Composites,the addition of L-MBP decreases the impact strength and tensile properties.But the maximum flexural strength increases to 24.46 MPa,the maximum flexural modulus increases to 1.79 GPa.And the melt flow rate decreases to 4.31 g/10 min.