Influence of organically modified Ni[sbnd]Al layered double hydroxide (LDH) loading on the rheological properties of poly (methyl methacrylate) (PMMA)/LDH blend solution

Abstract

This work deals with the synthesis of organically modified NiAl layered double hydroxide (LDH) and the effect of NiAl LDH loading on the rheological behavior of PMMA/NiAl LDH blends prepared by solvent blending method. Firstly, NiAl LDH was synthesized by co-precipitation method at constant pH using their nitrate salts and subsequently modified using sodium dodecyl sulfate (SDS). Then, PMMA blends with various LDHs content (3 and 5wt.% with respect to PMMA) were prepared by solvent blending method using methylene chloride as a solvent. The structural properties of the modified NiAl LDH were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and FTIR analysis. The XRD analysis reveals that the d-spacing value of the modified LDH increases to 1.35nm from 0.80nm for the unmodified LDH, which confirms the insertion of SDS molecules into the NiAl LDH interlayers. The presence of sulfate groups in the modified LDH is confirmed by FTIR analysis. The rheological characteristics of PMMA/NiAl LDH blends were performed on rotational rheometer using HAAKE Rheostress RS1 with cup and cylinder geometry at room temperature. It is observed that the rheology of PMMA blends is affected by increasing LDH loading as well as shear rate. All the PMMA/LDH blends exhibit enhanced shear viscosity as compared to neat PMMA. In addition, the obtained rheological data are fitted with various models, like Power law, Herschel–Bulkley, Casson, Sisko, Cross, and Carreau models to explain the rheological behavior. The results clearly indicate that the Herschel–Bulkley model fits the rheological data better than other models.