Morphological hierarchy of butadieneacrylonitrile/montmorillonite nanocomposite

Systematic Literature Review of the Effect of Layered Double Hydroxides on the Mechanical Properties of Rubber

Layered double hydroxides (LDHs) have attracted interest as reinforcing fillers in elastomers due to their ease of synthesis and customisability. A systematic review was performed on the effect of LDHs on the mechanical properties of elastomers using the Scopus database. Of the 61 articles relevant to the search criteria, the majority were published on polyurethane (PU) and nitrile butadiene rubber (NBR). Mg-Al LDH was used in most of the studies and Zn-Al LDH was used second most common. LDH can act as a reinforcing filler, typically increasing tensile strength even at low concentrations, so it could be used as an alternative to traditional reinforcing fillers for elastomers. LDH can also be made a functional filler by selecting the right metals and interlayer anions. It was found that Mg-Al LDH and Zn-Al LDH can both participate in crosslinking reactions and can replace MgO and ZnO, respectively. Less Zn ions are required for crosslinking when LDH is used than when ZnO is used, making LDH more environmentally friendly. Organic modification is usually required to improve compatibility with the elastomer matrix, especially in non-polar elastomers. It enables exfoliation of the LDH and intercalation of polymer chains into the LDH interlayer to occur. Organic modifiers can also be used to functionalise the LDH. Stearic acid used in crosslinking systems can be replaced by stearate anions from stearate-modified LDH.

Intercalation of a block co-polymer in kaolinite

Intercalates of kaolinite/Polyethylene-block-poly (ethylene glycol) were successfully prepared by melt intercalation of the polymer with a kaolinite: dimethyl sulfoxide pre-intercalate. Powder X-ray diffraction gives an 11.05 Å d-spacing which remains after washing the material with water. Thermal gravimetric analysis and nuclear magnetic resonance confirm the presence of the polymer in the prepared material. Perturbation of the kaolinite hydroxyl stretch and the polymer's CH2 bending modes in the materials' infrared spectrum suggest strong interaction between the aluminol clay sheet and the ethylene glycol units in the polymer. Dipolar dephasing studies show both polymer blocks experience a significant loss in mobility in the prepared material, indicative of intercalation. The presence of highly hydrophobic polyethylene inside kaolinite is expected to drastically modify the nature of the interlayer space, and could be of interest for applications where retention or sequestration of hydrophobic species is required.

Influence of miscibility phenomenon on crystalline polymorph transition in poly(vinylidene fluoride)/acrylic rubber/clay nanocomposite hybrid

In this paper, intercalation of nanoclay in the miscible polymer blend of poly(vinylidene fluoride) (PVDF) and acrylic rubber(ACM) was studied. X-ray diffraction was used to investigate the formation of nanoscale polymer blend/clay hybrid. Infrared spectroscopy and X-ray analysis revealed the coexistence of β and γ crystalline forms in PVDF/Clay nanocomposite while α crystalline form was found to be dominant in PVDF/ACM/Clay miscible hybrids. Flory-Huggins interaction parameter (B) was used to further explain the miscibility phenomenon observed. The B parameter was determined by combining the melting point depression and the binary interaction model. The estimated B values for the ternary PVDF/ACM/Clay and PVDF/ACM pairs were all negative, showing both proper intercalation of the polymer melt into the nanoclay galleries and the good miscibility of PVDF and ACM blend. The B value for the PVDF/ACM blend was almost the same as that measured for the PVDF/ACM/Clay hybrid, suggesting that PVDF chains in nanocomposite hybrids interact with ACM chains and that nanoclay in hybrid systems is wrapped by ACM molecules.