Use of purified and modified bentonites in linear low‐density polyethylene/organoclay/compatibilizer nanocomposites

Abstract

Polyethylene-based ternary nanocomposites were prepared with different clay structures, obtained by the modification of purified Resadiye bentonite as the reinforcement, a random terpolymer of ethylene, butyl acrylate, and maleic anhydride with the trade name Lotader3210 as the compatibilizer, and linear low-density polyethylene (LLDPE) as the polymer matrix in an intensive batch mixer. The quaternary ammonium/phosphonium salts used for the modification of bentonite were dimethyldioctadecyl ammonium (DMDA) chloride (Cl), tetrakisdecyl ammonium (TKA) bromide (Br), and tributylhexadecyl phosphonium (TBHP) Br. The effects of the physical properties and structure of the organoclay on the clay dispersion were studied at different clay contents (2 and 5 wt %) and at a compatibilizer/organoclay ratio of 2.5. The extent of organoclay dispersion was determined by X-ray diffraction (XRD) and was verified by transmission electron microscopy (TEM), mechanical testing, and rheological analysis. XRD analysis showed that the nanocomposite with the organoclay DMDA contained intercalated silicate layers, as also verified by TEM. The TEM analysis of the nanocomposites with TBHP exhibited intercalated/partially exfoliated clay dispersion. TKA, with a crowded alkyl environment, sheltered and hindered the intercalation of polymer chains through the silicate layers. In comparison to pure LLDPE, nanocomposites with a 33-41% higher Young's modulus, 16-9% higher tensile strength, and 75-144% higher elongation at break were produced with DMDA and TBHP, respectively (at 5 wt % organoclay). The storage modulus increased by 807-1393%, and the dynamic viscosity increased by 196-339% with respect to pure LLDPE at low frequencies for the samples with DMDA and TBHP (at 5 wt % organoclay).

Nanoclay dispersion into a thermosetting binder using sonication and intensive mixing methods

“…The applications of thermosetting resins in general and epoxy resins in particular can be broadened further upon incorporation of various inorganic and organic reinforcements and fillers to especially improve the stiffness, toughness, and mold shrinkage of the resulting thermosetting composites, as well as possibly reduce costs 2–6. Among the inorganic nanofillers, nanoclays offer potentially improved heat resistance, moduli and optical properties, decreased permeability, and flammability 4, 7–17. However, the incorporation of the nanoclay particles into the thermosetting matrix via solution processing, in situ polymerization and polymer melt processing, is a challenge 4, 18–27.…”

Production of modified clays and their use in polypropylene‐based nanocomposites

“…For this aim, firstly unpurified (raw) bentonite was modified with two quaternary ammonium salts [HDA][Br] and [TKA] [Br] and then used in the production of ternary nanocomposites of PP by twin screw extrusion. DMDA was used in organoclay production 16,17 and in nanocomposites with PE 18,19 and PP matrices. In the second set of experiments, the raw bentonite was purified and then modified with two quaternary ammonium salts [DMDA][Cl] and [TKA] [Br], and one phosphonium salt [TBHP] [Br].…”

“…DMDA was used in organoclay production 16,17 and in nanocomposites with PE 18,19 and PP matrices. In this study, functionalization of PP or DMDA organoclay were not needed differing from the work of Manias et al 21 Also, TBHP organoclay was used in LLDPE matrix 19,22 but not in PP matrix nanocomposites. In this study, DMDA is used without grafting a silane and a detailed characterization is conducted.…”

“…In the set with neat PP, DMDA was modified with semifluorinated alkyltrichlorosilane. In this study, functionalization of PP or DMDA organoclay were not needed differing from the work of Manias et al 21 Also, TBHP organoclay was used in LLDPE matrix 19,22 but not in PP matrix nanocomposites.…”

“…In the second set of experiments, the raw bentonite was purified and then modified with two quaternary ammonium salts [DMDA][Cl] and [TKA] [Br], and one phosphonium salt [TBHP] [Br]. DMDA was used in organoclay production 16,17 and in nanocomposites with PE 18,19 and PP matrices. 20 Lee et al 20 grafted organosilane to DMDA organoclay and then used it in PP matrix.…”