Influence of irradiation crosslinking on the flame‐retardant properties of polyolefin blends

Abstract

In the presence of flame retardants and other additives, halogen-free flame retardant (HFFR) shape-memory polymers were prepared using blends of ethylene vinyl acetate, ethylene propylene diene monomer, and low-density polyethylene. The HFFR compounds were irradiated using electron beam up to an absorbed dose of 150 kGy and characterized based on their mechanical, thermal, and electrical properties. Both the tensile strength (TS) and elongation at break (Eb) were found to increase as the levels of irradiation increased. This contrasted fact that, generally, Eb decreases as radiation doses increases because of polymer crosslinking capability. However, both TS and Eb decreased as the flame retardant content increased. The optimum mechanical properties were 13 MPa for TS and 200-350% for Eb. The versatile glass transition temperature greatly influenced the shape-memory impact. Nevertheless, the variable rubbery modulus had no significant influence. The limiting oxygen index was found to increase as the total flame retardant contents increased to values over the range of 30-35%. Hardness was about 92, and the retentions of TS and Eb after thermal aging at 136 C for 168 h were between 93-112 and 75-93%, respectively. UL94 ratings of V-0 and a volume resistivity of 3.21 × 10 15 to 3.49 × 10 15 Ωcm were obtained using these HFFR compounds.If a polymer is deformed by viscoelastic stretching, its molecular chains are reoriented, and elastic stress is experienced in the polymer matrix. When cooled in a stretched condition, the polymer re-enters a crystalline phase, and the elastic stress remains frozen in the polymer matrix, meaning that the expanded shape is retained. 5 Thermoplastic, thermoset, or elastomer materials may possess a shape-memory property after being crosslinked. The transformation temperature of SMPs can be either the melting temperature (T m ) or the glass transition (T g ) of a soft phase. 6 Upon deformation, mobile polymer chain segments are stretched in the loading direction, resulting in decreased entropy and simultaneous net elastic deformation. The overall result is an Additional Supporting Information may be found in the online version of this article.

Thermally resistant and strong shape memory bismaleimide resin with intrinsic halogen‐free and phosphorus‐free flame retardancy

“…Reviewing the literatures in the SCI database by June 6, 2022, there are 19 articles related on flame retardant SMPs including thermoplastics and thermosets (Table S1), [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] from which three problems are generally found. First, most SMPs get their flame retardancy from phosphorus-related flame retardants, however, phosphorusrelated flame retardants have been reported to cause eutrophication of the water bodies 24 ; moreover, they also tend to degrade thermal stability of thermally resistant resins.…”

“…First, most SMPs get their flame retardancy from phosphorus‐related flame retardants, however, phosphorus‐related flame retardants have been reported to cause eutrophication of the water bodies 24 ; moreover, they also tend to degrade thermal stability of thermally resistant resins 25,26 . Second, there are only 5 articles reported flame retardant SMPs through halogen‐free and phosphorus‐free strategy, 5–9 however the glass transition temperature ( T g ) of each SMP does not exceed 101°C except an epoxy resin ( T g = 220°C), 5 unfortunately, the epoxy resin has low shape memory recovery rate ( R f = 43.4%) and low initial thermal decomposition temperature ( T di = 290.5°C); in other words, no halogen‐free and phosphorus‐free flame retardant SMP with high thermal resistance and good shape memory properties has been reported so far. Third, only one literature reports the flexural and impact properties of flame retardant SMP, but the impact and flexural strengths are only 1.9 ± 0.3 kJ/m 2 and 54.9 ± 4.1 MPa, respectively 10 .…”

Ablation and thermal properties of ethylene propylene diene rubber/carbon fiber composites cured by ionizing radiation for heat shielding applications

“…The percentage burnet length for irradiated EPDM.SCFs/ATH composites at different of percent of ATH and concentrations of SCFs namely, 5 and 20 phr was presented in Figure 10(a) and (b) respectively. The irradiated composites take the same behavior of unirradiated ones except they have lower values for burnet length, this due to irradiation dose lead increase in flame retardancy [28].…”

Study on the Microstructure of Polyether Ether Ketone Films Irradiated with 170 keV Protons by Grazing Incidence Small Angle X-ray Scattering (GISAXS) Technology

“…Only a few papers mainly choose the gamma ray, heavy ion and electron irradiation sources to test and evaluate the chemical properties after irradiation, the mechanical behavior and the mechanism of the irradiated PEEK, of which the irradiated damage is only several microns and has not been studied [ 11 , 12 , 13 ]. The mechanical behavior of polymer insulating materials, especially a deep understanding of tensile deformation behavior, can help to evaluate the behavior of the material in orbit [ 14 ]. In recent years, synchrotron radiation X-ray scattering technology provides an effective method for detecting the microstructure changes of polymer materials [ 15 , 16 ].…”