Synthesis And Application Of Phenyl Substituted Dihydrazide Nucleating Agents For Isotactic Polypropylene

The novel a nucleating agents of phenyl substituted dihydrazides(DCDH)were developed in this work.The nucleating agents of C2-C10 dicarboxylic diphenyl dihydrazides(DCDH-Ph-n,n=0-8)were prepared and characterized by FT-IR,1H-NMR,HRMS and DSC.The effects of C2-C10 dicarboxylic diphenyl dihydrazides on the crystallization,melting behavior and crystallization kinetics of isotactic polypropylene(iPP)were studied.At the same time,the influences of a/p compound nucleating agents based on N,N’-bis(benzoyl)azelaic acid dihydrazide(α/β-NAs)on the crystallization,melting behavior and crystallization kinetics of iPP were also analyzed.Firstly,the nucleation efficiency of phenyl substituted dihydrazide nucleating agents was investigated.It was found that the N,N’-bis(benzoyl)adipic acid dihydrazide(DCDH-Ph-4),N,N’-bis(benzoyl)suberic acid dihydrazide(DCDH-Ph-6),N,N’-bis(benzoyl)azelaic acid dihydrazide(DCDH-Ph-7),N,N’-bis(benzoyl)azelaic acid dihydrazide(DCDH-Ph-8)have better nucleating efficiency and increased the crystallization temperatures of iPP to 9-12℃.Based on this reasons,the effects of addition concentrations on the crystallization properties of iPP were studied.The optimum addition concentrations of DCDH-Ph-4,DCDH-Ph-6,DCDH-Ph-7 and DCDH-Ph-8 were 0.15wt%,0.1 wt%,0.3wt%and 0.06wt%,respectively.At this time,the crystallization temperatures of iPP was increased by 10.0℃,12.3℃,9.0℃,and 11.9℃,respectively.It can be found that characteristic peak appears around 163℃ from the melting curves and characteristic diffraction peaks appear at 20=14.0°,16.7°,18.4°,21.00 and 21.70 from WAXD patterns.Therefore,these nucleating agents are all a nucleating agents.As DCDH-Ph-8 is an a nucleating agent with high good nucleation efficiency,the DCDH-Ph-8 was compounded with three β nucleating agents,namely,amide nucleating agent,calcium pinelate and rare earth nucleating agent to prepare different compound nucleating agents(designated as DCDH-TMB,DCDH-WBG and DCDH-CaPi,respectively).The effects of these a/p compounds nucleating agents on the crystallization and melting behavior of iPP were studied.It was found that the crystallization temperatures of iPP nucleated with DCDH-TMB,DCDH-WBG and DCDH-CaPi were increased by 11.3℃,10.8℃ and 11.2℃,respectively.The relative content of β-crystals of DCDH-TMB,DCDH-WBG and DCDH-CaPi by DSC and WAXD were 0.4348,0.3713,<0.05 and 0.5121,0.4608,0.2519,respectively.In addition,the effects of different cooling rates and crystallization temperatures in isothermal crystallization on the relative content of p-crystals in iPP were also investigated.The faster the cooling rate,the higher the relative content of p crystals is.However,the crystallization temperatures in isothermal crystallization have different effects on iPP nucleating different α/β compound nucleating agents.Based on this reasons,the principles and methods for controlling the crystallization of iPP nucleated with a/p compound nucleating agents were proposed.The smaller the differences in nucleation efficiencys of each nucleating agents,the more intense the competition-induced iPP crystallization,and the greater the influence of external conditions is.The isothermal crystallization kinetics of iPP nucleated with phenyl substituted dihydrazide nucleating agents and α/β compound nucleating agents were studied by the Avarmi method.The Avrami exponents of pure iPP and iPP nucleated with DCDH-Ph-4,DCDH-Ph-6,DCDH-Ph-7,DCDH-Ph-8,DCDH-TMB,DCDH-WBG and DCDH-CaPi were relatively close,indicating that the addition of these nucleating agents does not change the crystal growth mode of iPP.The nucleating agents can significantly increase the crystallization rates of iPP.The crystallization rate of iPP/DCDH-Ph-n was in the order of iPP/DCDH-Ph-6 ≈iPP/DCDH-Ph-8>iPP/DCDH-Ph-7>iPP/DCDH-Ph-4.The crystallization rate of iPP/(α/β-NAs)was in the order of iPP/DCDH-TMB>iPP/DCDH-CaPi>iPP/DCDH-WBG.The non-isothermal crystallization kinetics of iPP nucleated with phenyl substituted dihydrazide nucleating agents and α/β compound nucleating agents were studied by Caze method and Mo method.According to Caze method,the Avrami exponents of pure iPP and iPP nucleated with DCDH-Ph-4,DCDH-Ph-65 DCDH-Ph-7,DCDH-Ph-8,DCDH-TMB,DCDH-WBG and DCDH-CaPi have differences,obviously.The differences indicate that the addition of the nucleating agents changes the crystal growth mode.According to the Mo method,under the same relative crystallinity,the required cooling rate of pure iPP is much larger than that of nucleated iPP.Then,the crystallization rate of iPP/DCDH-Ph-n was in the order of iPP/DCDH-Ph-6≈iPP/DCDH-Ph-8>iPP/DCDH-Ph-7>iPP/DCDH-Ph-4.The crystallization rate of iPP/(α/β-NAs)was in the order of iPP/DCDH-TMB>iPP/DCDH-CaPi>iPP/DCDH-WBG.The results obtained by the two methods are consistent.