Study On Polypropylene/Intercalated LDHs Nanocomposites

Mg-Al layered double Hydroxides(LDHs) has been modified by sodium dodecylsulfonate(LDHs2),sodium bitartrate monohydrate(LDHs3),itaconic acid(LDHs4),sodium dodecylsulfonate& sodium bitartrate monohydrate(LDHs5) and sodium dodecylsulfonate& itaconic acid(LDHs6) using ion exchange method. Thermal stabilization and d-space of modified LDHs have been studied.Raw LDHs(LDHs1) and three kinds of LDHs(LDHs2,LDHs5,LDHs6) which have better properties,were used to prepare Polypropylene(PP)/LDHs nanocomposites.The trademark of Polypropylene usd as matrix is F401(PP1),usd as intercalation is K7726(PP2).PP-g-(MAH-co-St) is usd as compatibilizer.PP1/LDHs(100/3) and PP1/PP-g-(MAH-co-St)/LDHs(100/10/3) nanocomposites were prepared by melting method.PP-g-(MAH-co-St) were gained by melt grafting method.The grafting ratio and crystallization properties of PP-g-(MAH-co-St) is researched.Four kinds of PP2/LDHs(100/30) masterbatch were prepared by solution-intercalated method,and its crystallization properties were researched.Then PP2/LDHs(100/30) masterbatch were added to PP1 matrix to prepare PP1/PP2/LDHs(100/10/3) nanocomposites.Rheology,mechanical properties,crystallization properties,processing properties,fire retardation and layer space of PP1/LDHs,PP1/PP-g-(MAH-co-St)/LDHs and PP1/PP2/LDHs nanocomposites were studied,and contrast with each other.The research resaults of modified LDHs indicate that five modifiers can enter into the layers of LDHs.Layer space of LDHs are all enhanced.Layer space of Modified LDHs which contain sodium dodecylsulfonate is bigger than others. Itaconic acid has capability to distroy the regularity of sodium dodecylsulfonate in the layer space of LDHs.By contraries,sodium bitartrate monohydrate can improve the regularity of sodium dodecylsulfonate.Starting decomposion temperature of-OH in LDHs is boosted by itaconic acid.Because of especial crystallization properties of PP2 and a large amount of LDHs,starting crystallization temperature of PP2/LDHs(100/30) masterbatch is lower than pure PP2.LDHs in masterbatch has no heterogeneous nucleation.At the same time,the number of nucleus formed by heterogeneous nucleation become less. Crystallization activation energies,enthalpy and relative crystallinity of PP2/LDHs (100/30) masterbatch become lower and lower with cooling rate becomes slower.15℃/min cooling rate is a turning point for Avrami index.The research resaults of PP1/LDHs,PP1/PP-g-(MAH-co-St)/LDHs and PP1/PP2/LDHs nanocomposites show that:(1) In three kind nanocomposites, Crystal grain porosity size distribution of PP1/PP2/LDHs is narrowest,total crystallization rate is fastest,and the number of nucleus formed by heterogeneous nucleation is most.(2)Flexural strength and flexural Modulus of nanocomposites which contain LDHs5 are highest in the same kind of nanocomposites.(3)Burning time of PP1/LDHs is longest in air.(4) Thermal stability of PP1/LDHs1,PP1/LDHs5 and PP1/LDHs6 are better than pure PP1 in N₂.(5)Layer space of unmodified LDHs is unchanged in nanocomposites.LDHs modified by sodium dodecylsulfonate& itaconic acid is exfoliated.And LDHs modified by sodium dodecylsulfonate,sodium dodecylsulfonate& sodium bitartrate monohydrate is exfoliated or intercalative.