Preparation Of Acetylacetone-based PVC Auxiliary Thermal Stabilizer And Performance Study

Polyvinyl chloride（PVC）is one of the earliest industrialized resin varieties in the world and has been widely used in various industries.However,PVC itself has structural defects,thermal sensitivity and easy thermal degradation.Therefore,stabilizers must be added in practical applications to improve the stability of heat and light.Acetylacetone is aβ-diketone substance,which has a synergistic effect when used together with a calcium/zinc stearate（CaSt₂/ZnSt₂） composite thermal stabilizer,and inhibits the occurrence of“zinc burning”.Due to the lower boiling point of acetylacetone（133～140℃）,it is easy to be volatile when used directly,and the loss is high.,it can only be used after making salt,such as calcium salt,zinc salt,magnesium salt and aluminum salt.In this dissertation,calcium acetylacetonate（Ca（acac）₂） and magnesium acetylacetonate（Mg（acac）₂） were prepared by one step heterogeneous precipitation method.Study the effects of reaction conditions on product purity and whiteness,and analyze the structure of the product,and study on the thermal stability and thermal stability mechanism of acetylacetone-based auxiliary thermal stabilizer.The specific research contents are as follows:1.One-stepheterogeneousprecipitationconversionmethod:Calcium acetylacetone was synthesized by the reaction of acetylacetone with calcium oxide at 65℃ for 2 h,and the molar ratio of acetylacetone to calcium oxide was 2:1.The acetylacetone with a molar ratio of 2:1 and magnesium hydroxide were placed in a solvent ethanol,and reacted at 75℃ for 3 h to obtain the product magnesium acetylacetonate.Under the above conditions,the purity and whiteness of calcium acetylacetone and magnesium acetylacetone were the best.2.The structure of the product was analyzed by X-ray diffractometer（XRD）,scanning electron microscope（SEM）,fourier transform infrared analyzer（FTIR）,element analyzer,thermogravimetric analysis（TG）,inductively coupled plasma spectrometer（ICP）and laser particle size analyzer.The results showed that the samples of calcium acetylacetonate and magnesium acetylacetonate were successfully prepared.3.Through static thermal aging test and Congo red test,it concluded that calcium acetylacetone and magnesium acetylacetone have synergistic effect when used as auxiliary thermal stabilizers with metal soap thermal stabilizers at the same time.The total mass of the main thermal stabilizer is 1% of PVC powder,and the synergistic effect of calcium stearate/zinc stearate is the best when the ratio of calcium stearate/zinc stearate is 3:1.When the content of calcium acetylacetone is 0.4%of the mass of PVC powder and the mass ratio of calcium acetylacetone to the main thermal stabilizer is 2:5,the thermal stability of PVC is the best.When the total mass of the main thermal stabilizer is 1% of PVC powder and the ratio of calcium stearate/zinc stearate is 3:1,the synergistic effect with magnesium acetylacetone is the best.When the content of magnesium acetylacetone is 0.6% of the mass of PVC powder and the mass ratio of magnesium acetylacetone to the main thermal stabilizer is 2:5,the thermal stability of PVC is the best.4.When the acetylacetone metal compound is used together with the main thermal stabilizer,acetylacetone metal compounds can not only react with HCl molecules and restrain the self-degradation of PVC large subchains,but also react with allyl chloride on PVC macromolecular chain to inhibit the occurrence of discoloration reaction.At the same time,the acetylacetone metal compound can undergo a displacement reaction with the ZnCl₂ molecule,reduce the content of the ZnCl₂ molecule,and inhibit the occurrence of the"zinc burning" reaction.