Mechanical and thermal properties of blends of low‐density polyethylene and ethylene vinyl acetate crosslinked by both dicumyl peroxide and ionizing radiation for wire and cable applications

Abstract

Formulations of chemically crosslinked and radiation-crosslinked low-density polyethylene (LDPE) containing an intumescent flame retardant such as ammonium polyphosphate were prepared. The influence of blending LDPE with a poly(ethylene vinyl acetate) copolymer (EVA) and the effects of various coadditives, including polyethylene grafted with maleic anhydride (PEgMA), vinyl silane with boric acid, and talc, on the mechanical and thermal properties were investigated. Chemical crosslinking by dicumyl peroxide and crosslinking by ionizing radiation from an electron-beam accelerator were both used and compared. Improved mechanical properties were observed by the partial replacement of LDPE with EVA. Similar mechanical or thermal properties were observed with coadditives such as PEgMA and vinyl silane with boric acid. The addition of a small amount of talc improved the tensile strength of the formulations. All crosslinked formulations showed good thermal stability on the basis of the retention of mechanical properties after thermal aging for 168 h at 1358C and a hot-set test.

Flame Retardancy and Mechanical Properties of Ethylene-vinyl Acetate Rubber with Expandable Graphite/Ammonium Polyphosphate/Dipentaerythritol System

“…Pure EVM is thermally stable under 300 • C and undergoes two degradation steps at higher temperature. [15] In the first step, at low temperature (300-400 • C), acetic acid was released by β-elimination forming double bonds and crosslinks. [16] The second step involves thermal decomposition of the unsaturated or crosslinked backbone by thermal dissociation and leads to the polymer volatilization, with the formation of stable residues of about 7.0 wt% above 500 • C. [17] The maximum mass loss rate of the first step was at 346 • C and the second step at 466 • C. Compared with pure EVM, the EVM/APP/DPER and EVM/APP/DPER/EG systems show similar decomposition behavior at lower temperature.…”

Poly(Ethylene Vinyl Acetate) (EVA)/Low Density Polyethylene (LDPE)/Ammonium Polyphosphate (APP) Composites Cross-linked by Dicumyl Peroxide for Wire and Cable Applications

“…Recently 17 we found PEgMA to be better compatibilizer than vinyl silane in LDPE/EVA/APP composites. Therefore, here we decided to use PEgMA to increase compatibility of additives with the resins.…”

“…At the same time a small amount of talc was used in all formulations in order to achieve higher tensile strength. 17 Tensile strength of prepared formulations is shown in Figure 1 and Table II. Generally, addition of additives to a resin leads to a decrease in tensile strength.…”

“…In recent work, 17 current authors demonstrated that crosslinking can increase tensile strength of polyethylene/ammonium polyphosphate composites and thus, at reasonable yield of cross-linking, improve their mechanical properties. Moreover it gives improvement in thermal stability as well.…”

“…Moreover it gives improvement in thermal stability as well. 17,18 In this paper various formulations containing EVA blended with LDPE and ammonium polyphosphate (APP) as an IFR were mixed with co-additives, stabilizer and cross-linking agents (see Table I) to develop LDPE/EVA/IFR composites with good mechanical and thermal properties and good flame retardancy. It is well known that presence of boron atom, from zinc borate or boroxosiloxanes, in combination with APP can improve action of APP in flame retardancy of polyolefins.…”