An Investigation on Synergistic Effect of EG with IFR in Polyethylene
Great concerns with environmental pollutions caused by halogen elements and heavy metals have been driving the development of eco-friendly wire and cable compounds, among which halogen-free low-smoke flame-retardant polyolefins are of great importance. Intumescent flame retardants (IFR) show better efficiency in flame retardant polyolefins (PO) than metal hydroxides, such as magnesium hydroxide and aluminum hydroxide, but the flame retardancy of IFR/PO is still limited. Recently, expandable graphite (EG), a promising eco-friendly flame retardant, has attracted much attention. In the paper, the synergistic effect of expandable graphite (EG) with intumescent flame retardants (IFR) on flame retardant polyethylene (PE) was investigated by limited oxygen index (LOI) and the investigations on the synergistic mechanism were performed by thermogravimetric (TG) and scanning electron microscope (SEM). The results showed that the flame retardant properties of PE/EG/IFR were greatly improved by the synergistic effect of EG with IFR. Compared with the cracking barrier on the combustion surface of PE/EG or PE/IFR, a very thick and compact char layer forming on the combustion surface of PE/EG/IFR was more in favor of preventing the transfer of oxygen and heat, thus leading to lower thermal degradation rate and more char left
Expandable Graphite Systems for Phosphorus‐Containing Unsaturated Polyester, 2
A series of flame-retardant-containing unsaturated polyesters have been developed. The flame retardants include expandable graphite (EG) and phosphorous-containing materials (ammonium polyphosphate (APP) and triphenyl phosphate (TPP)). The flame-retardant properties of these samples were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), and UL-94 tests. Moreover, the kinetic parameters of these flame-retardant-containing unsaturated polyesters were calculated by the Coats and Redfern method, the Ozawa method, and temperature modulated thermogravimetric analysis (MTGA). The differences and relationship among different analytical methodologies were investigated. Pyrolysis gas chromatography mass spectrometry (Py/GC/MS) was also used to investigate the pyrolysis products of the samples.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.