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

Abstract

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 Namontmorillonite (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.

Phase Change Material with Gelation Imparting Shape Stability

“…In this region, G * of composite SSPCMs exceeded 4–5 times that of the unfilled SSPCM. This result is consistent with that reported in ref ( 53 ), where it is shown that the degree of mechanical properties improvement induced by the incorporation of fillers into a liquid-crystalline matrix increases with the decrease of the matrix order. The carbonaceous fillers slightly affected the thermal stability of the SSPCM, causing melting temperature growth by ∼1.0° and 1.5 °C for SSPCM filled with MWCNTs and GnPs, respectively.…”

Rheological Properties and Electrospinnability of High-Amylose Starch in Formic Acid

“…In this case, G ″ was higher than G ′, but the elastic modulus plateau appeared in the region of low frequencies, reflecting strong structuration in the system. This behavior is typical for filled polymer melts and solutions . Decreased G ′ values at high frequencies reflect weakening of the formed entanglement network, which can be attributed to a concentration drop of the dissolved polymer fraction.…”

“…This behavior is typical for filled polymer melts and solutions. 55 Decreased G′ values at high frequencies reflect weakening of the formed entanglement network, which can be attributed to a concentration drop of the dissolved polymer fraction. Figure 6 shows the evolution of shear viscosity (η) and elastic modulus (G′) with time for the 17 wt % HS dispersions.…”

“…This behavior is typical for filled polymer melts and solutions. 55 Decreased G′ values at high frequencies reflect weakening of the formed entanglement network, which can be attributed to a concentration drop of the dissolved polymer fraction.…”

Intercalated clay structures and amorphous behavior of solution cast and melt pressed poly(ethylene oxide)–clay nanocomposites

“…This W cg value represents that the bilayer structure of PEO or helical structure arranged in flattened arrangements can be accommodated because the trans ‐conformation of PEO chain has an expansion of about 0.4 nm . The intercalated 0.80 nm wide trans ‐gauche‐ trans double layers structures of PEO and poly(ethylene glycol) (PEG) are the most stable arrangement from steric consideration . Further increase of MMT concentration in the solution cast nanocomposite films, the observed W cg values range from 0.686–0.855 nm (Table ), which also confirms the existence of flattened bilayers arrangement of PEO structures in the MMT galleries.…”