Development And Application Research Of Zinc Adipate As ?-nucleating Agent For Polypropylene

Polypropylene?PP?is one of the most widely used thermoplastic synthetic resins,and its comprehensive performance is comparable to that of some engineering plastics.However,the impact toughness of PP is poor,which limits its further application in some areas where high impact toughness is required.Among the many toughening modification methods,the addition of?-nucleating agent is a simple and efficient toughening modification method,which is suitable for large-scale production in industry and has great development potential.In recent years,some researchers have found that the zinc adipate synthesized by in-situ method is a kind of?-nucleating agent with excellent nucleation performance,but they have not systematically studied the nucleating properties of zinc adipate and explore its application value.Therefore,the zinc adipate as?-nucleating agent have many problems to be solved from industrial applications.Based on the current research results and existing problems of zinc adipate as?-nucleating agent,the in-situ method was used to synthesize zinc adipate in this paper.The effect of zinc adipate prepared by different in-situ synthesis methods on the nucleation performance of PP was systematically studied,and its non-isothermal crystallization performance and rheological properties were further explored.Finally,the influence of common processing aids on the nucleation performance of zinc adipate was discussed,which laid a good foundation for the application of such nucleating agents in industrial production of PP.The main contents of the study and the results obtained were summarized as follows:1)The zinc adipate as?-nucleating agent was synthesized by in-situ method.First,the effects of different zinc compounds and the ratio of zinc compounds and adipic acid on the nucleation performance of zinc adipate were studied.Then,the commercial amide?-nucleating agent?name it CNA?was used as reference to study the application value of zinc adipate.The results showed that:?1?For equimolar zinc compounds and adipic acid,the nucleation ability of zinc adipate?Adi-Zn?OH?₂?1:1??synthesized by in-situ method using zinc hydroxide and adipic acid as raw materials was better than the zinc adipate?Adi-ZnO?1:1??synthesized from zinc oxide and adipic acid as raw materials.The maximum impact strength of isotactic polypropylene?iPP?nucleated by Adi-Zn?OH?₂?1:1?was obtained at 0.2 wt%,and its maximum impact strength was about 9%and 147%higher than the maximum impact strength of iPP nucleated by Adi-ZnO?1:1?and the impact strength of pure iPP,respectively.?2?When the molar ratio between adipic acid and zinc hydroxide was 1:2?Adi-Zn?OH?₂?1:2??,the in situ synthesized zinc adipate had the best?-nucleation performance.At the optimum addition amount of 0.2 wt%,the impact strength of the sample was increased by 163%compared with pure iPP,and its?_?reached 88.05%of the maximum value.?3?The impact strength of Adi-Zn?OH?₂?1:2?nucleated iPP was higher than that of CNA nucleated iPP throughout the test.The maximum impact strength of iPP nucleated by Adi-Zn?OH?₂?1:2?was about 42%higher than the maximum impact strength of iPP nucleated by CNA.2)The non-isothermal crystallization kinetics of pure iPP and Adi-Zn?OH?₂?1:2?nucleated iPP were studied by the Caze method.Then,the effects of shear rate and melt temperature on the viscosity of pure iPP and Adi-Zn?OH?₂?1:2?nucleated iPP were investigated.The results displayed that:?1?The Avrami index?n?of pure iPP was 3.84 and was very close to 4,which belonged to homogeneous nucleation,and the growth mode of spherulites was three-dimensional.With the increase of Adi-Zn?OH?₂?1:2?,the semi-crystallization time(t_1/2)of nucleated iPP was significantly shortened.In addition,the Avrami exponent n decreased with the increase of Adi-Zn?OH?₂?1:2?,decreased from 3.84 of pure iPP to 3.38,and gradually approached 3,which concluded that the addition of Adi-Zn?OH?₂?1:2?caused the formation of crystal nucleus to change from homogeneous nucleation to heterogeneous nucleation.?2?Moreover,the addition of Adi-Zn?OH?₂?1:2?did not reduce the crystallization activation energy of iPP,but increased its the crystallization activation energy.The increase in crystallization activation energy was due to the interaction between the nucleating agent molecule and the molecular chain of iPP,which hindered the free movement of the molecular chain of iPP.This result was also well explained by the fact that the addition of nucleating agent increases the consistency coefficient?K?and the viscous flow activation energy???_??of the melt of iPP.3)The matching of halogen absorber and Adi-Zn?OH?₂?1:2?was studied by impact strength,tensile strength,flexural modulus,melt index and oxidation induction period.The results revealed that:?1?Calcium stearate had a significant inhibitory effect on the nucleation properties of Adi-Zn?OH?₂?1:2?.With the increasing amount of calcium stearate,the impact strength of iPP nucleated by Adi-Zn?OH?₂?1:2?decreased almost linearly,,while the tensile strength and flexural modulus showed a opposite trend to the impact strength.?2?Zinc stearate had a weak inhibitory effect on the nucleating properties of Adi-Zn?OH?₂?1:2?.When the addition amount of zinc stearate was less than 0.04 wt%,the impact strength of iPP nucleated by Adi-Zn?OH?₂?1:2?remained almost the same.When the addition amount of zinc stearate exceeded 0.04 wt%,the impact strength of Adi-Zn?OH?₂?1:2?nucleated iPP decreased sharply.?3?With the increasing amount of zinc stearate,the oxidation induction period and melt index of iPP nucleated by Adi-Zn?OH?₂?1:2?increased first and then decreased gradually,which showed that zinc stearate can not only prevent the aging degradation of materials,but also to lubricate and improve the processing.Zinc stearate and Adi-Zn?OH?₂?1:2?have good matching in the range of commonl y used additions,which can meet the needs of general industrial applications.