Morphology and rheology of composites based on anisotropic polymer matrix and different clays

• Published in: Journal of applied polymer science 2011-06, Vol.120 (6), p.3642-3653
• Main Authors: Vasilyev, G.B, Makarova, V.V, Rebrov, A.V, Picken, S.J, Smirnova, N.M, Malkin, A. Ya, Kulichikhin, V.G
• Format: Article
• Language: English
• Subjects: clay; Clays; Fillers; liquid-crystalline polymer; Loads (forces); Materials science; Morphology; nanocomposite; Polymers; Reproduction; Rheological properties; Surfactants; viscosity; Yield stress
• ISSN: 0021-8995; 1097-4628; 1097-4628
• DOI: 10.1002/app.33539

Structure and rheological properties of hybrids with polymer matrix and layered silicates as filler were studied. Solution containing 60% wt of hydroxypropylcellulose (HPC) in oligomeric polyethyleneglycol (PEG) was used as a matrix. The peculiarity of this study is that the matrix depending on temperature can form different phase states including liquid-crystalline (LC). So, a possibility of coexistence and superposition of different ordered structures can be realized at different temperatures. Three different fillers were used: natural Na-montmorillonite (MMT) and organoclays obtained by treating MMT with surfactants varying in polarity of their molecules. Depending on the type of clay, materials with different morphology can be obtained. X-ray data showed that PEG intercalates all types of clay used whereas penetration of HPC macromolecules into clay galleries during mixing does not occur. Clay modified with more polar surfactant should be treated as the most convenient material to be intercalated by PEG. Rheological studies (included steady-state and dynamic shear properties in a wide temperature range) demonstrate that composites are viscoplastic materials and the yield stress is observed already at 5% fillers loading. The level of the yield stress depends on the phase state of the matrix being induced by the superposition of structures formed by clay particles as well as by the LC phase (if it exists). The same conclusion can be made on the base of linear oscillatory measurements because the existence of the LC phase and/or the presence of filler lead to a pseudo solid-like behavior of a system as whole.