Preparation And Nucleation Effect Of Nucleating Agents Aliphatic Dicarboxylic Acid Salts For Isotactic Polypropylene

Isotactic polypropylene(iPP)has a good market prospect due to many advantages such as wide sources of raw materials,easy processing and so on.However,large spherulite size,low impact performance and other shortcomings limit its wide range of applications.At present,the most effective and simple modification methods is addition of nucleating agents.Aliphatic dicarboxylate nucleating agents have high research value due to relatively low cost and relatively simple synthesis method,which can promote the formation of a large number of?-crystal forms of iPP.48 kinds of aliphatic dicarboxylic salts were synthesized from aliphatic dicarboxylic acids and corresponding metal hydroxides or chlorides by neutralization or double decomposition reaction.The synthesized products were structurally characterized by infrared spectroscopy(FT-IR).The crystallization and melting behavior of iPP nucleated with aliphatic dicarboxylate nucleating agents were investigated by differential scanning calorimetry(DSC)and wide-angle X-ray diffraction(WAXD).Finally,the mechanical and thermal properties of nucleated iPP under optimum addition were discussed.The results of FT-IR showed that the anti-symmetric stretching vibration and the symmetric stretching vibration peaks of-COO-at 1550?1650 cm-1 and 1405 cm-1 were observed in the infrared spectrum of the salts of aliphatic dicarboxylic acids,respectively.But the C=O(in the carboxylic acids)stretching vibration peaks of the aliphatic dicarboxylic acids at 1695?1700 cm-1,the wide and strong stretching absorption peaks of-OH at 3300?2500 cm-1 and the C-O stretching vibration characteristic peaks of dibasic acid at 1272?1290 cm-1 and 1184?1190 cm-1 were not observed.Therefore the successful preparation of the target products was confirmed.The crystallization and melting behavior of iPP nucleated with different aliphatic dicarboxylate nucleating agents were investigated.The results showed that the crystallization peak temperature of iPP could be increased by the synthesized nucleating agents,moreover the aliphatic dicarboxylic acids itself had better effect on the crystallization peak temperature than its salts.In particular,when the number of carbon atoms were more than 5,the crystallization peak temperature of iPP nucleated with 0.2wt%aliphatic dicarboxylic acid could be increased by about 10?,and for the salts of aliphatic dicarboxylic acids nucleating agents could substantially improved 3?7? when compared to that of pure iPP.However,aliphatic dicarboxylic acids themselves do not have the ability to induce the ?-crystal form for iPP,and the induction of the ?-crystal form mainly depends on the metal ion species in the salts of aliphatic dicarboxylic acids.Aliphatic dicarboxylic acids and their monovalent metal salts(Na,Li)were mostly ?-crystal nucleating agents for iPP,but for most aliphatic dicarboxylic acid divalent metal salts(Ca,Mg,Ba and Zn),almost all were ?-crystal nucleating agents for iPP.Particularly for the calcium,barium and zinc salts,the ?-crystal form in iPP nucleated with these nucleating agents had a relatively large melting peak area,so they were high selectivity ?-crystal nucleating agents for iPP.The effect of the number of carbon atoms on the nucleation properties of iPP nucleated with barium,calcium and zinc salts of aliphatic dicarboxylic acids were showed that the relative content of ?-crystal and the nucleation ability of nucleated iPP were related to the number of carbon atoms in the aliphatic dibasic acid.Barium,calcium and zinc salts of aliphatic dicarboxylic acid with carbon atomic numbers of 5 to 8 had good nucleation ability for iPP except calcium adipate and zinc pimelate.Among them,barium glutarate(Glu-Ba),calcium suberate(Sub-Ca)and zinc suberate(Sub-Zn)were the most efficient nucleating agents of barium,calcium and zinc salts of aliphatic dicarboxylic acids,respectively.The optimal addition amounts of Glu-Ba,Sub-Ca and Sub-Zn were 0.1 wt%,0.1wt%,and 0.15wt%,respectively,and the crystallization peak temperature reached 127.1?,124.4? and 124.2?,respectively,increased by 9.50C,6.80C and 6.60C,when compared to that of pure iPP,the relative contents of ?-crystal calculated from DSC reached 0.9561,0.9351 and 0.9447,respectively,and those calculated from WAXD reached 0.8797,0.8370 and 0.8796,respectively.The results of the optimum addition amount obtained by the two methods were basically the same,which proves the correctness of the conclusion.Finally,the mechanical and thermal properties of iPP nucleated with Glu-Ba,Sub-Ca and Sub-Zn at optimum addition were investigated.The results showed that after adding 0.10wt%Glu-Ba,0.10wt%Sub-Ca and 0.15wt%Sub-Zn,the tensile strength,flexural modulus,and flexural strength were all reduced in different level.However,Izod impact strength of the nucleated iPP was increased by 71.32%,18.87%and 102.6%,respectively,the heat distortion temperature was increased by 10.3?,9.0? and 2.0?,respectively,when compared with pure iPP.Therefore,Glu-Ba,Sub-Ca and Sub-Zn decreased the rigidity,but improved the toughness and thermal properties of iPP.