EVA nanocomposites based on South African Koppies clay

Abstract

South African Koppies bentonite was organo-modified with single tail and double tail alkyl ammonium cationic surfactants with the latter intercalated both below and above the clay CEC.Corresponding poly(ethylene-co-vinylacetate) nanocomposites were prepared by twin-screw melt compounding. Transmission electron microscopy indicated the presence of mixed nano-and micron-sized clay morphologies. X-ray diffraction studies revealed that the crystallinity of the particles improved and that the d-spacing values increased on incorporating the clays in the polymer matrix. It is postulated that, rather than indicating polymer co-intercalation, this is caused by further intercalation of either excess surfactants or surfactant residues that were released by shear delamination of the clays during compounding. Improved mechanical properties were realized especially when using the clay containing the longer double tail surfactant intercalated at levels in excess of the cation exchange capacity of the clay. The nanocomposites showed improved tensile modulus and elongation at break values at the

Calcium carbonate and ammonium polyphosphate flame retardant additives formulated to protect ethylene vinyl acetate copolymer against fire: Hydrated or carbonated calcium?

“…Strictly speaking, the elastic modulus only applies to the linear elastic section of the stress‐strain curve. [ 33 ] In cases where it is difficult to judge the linear elastic section from the curved part, as is the case here, the secant modulus of elasticity is alternatively used. Stress and strain typically have a nonlinear relationship, but the relationship can be considered the linear elastic section at a lower stress level.…”

Synergistic effects of modified hydrotalcite on improving the fire resistance of ethylene vinyl acetate containing intumescent flame retardants

“…Ethylene vinyl acetate (EVA) copolymer is extensively used as an insulator in the wire, adhesive and cable industry due to its desirable physico-chemical properties and its easy acceptance of additives [1][2][3][4]. The ease of ignition and subsequent combustion with the release of large volumes of toxic smoke prohibits the application of EVAbased materials [5][6][7].…”