Preparation and Flammability Properties of Polyethylene/Organoclay Nanocomposites

Abstract

Polyethylene (PE) nanocomposites were prepared by melt intercalation, in order to evaluate the flame retardant effect of this material. For the development of nanocomposites were used the montmorillonite clay (MMT), organoclay (OMMT) and flame retardant product (FRP) with the percentage of 1, 3, 6 and 9 wt%. Grafted polyethylene with maleic anhydride (PE-g-MA) was used as a compatibilizer of the systems. PE and its systems were evaluated: XRD, TEM, TG and flammability (UL94HB, oxygen index (LOI) and cone calorimetry). The X-ray diffraction showed a partial intercalation and exfoliation as well as formation of microcomposite. The phase morphology of the systems was observed by TEM that it showed that the system with 1% OMMT clay presented a predominance of exfoliation. Already the system with 3% OMMT showed partial exfoliation and this exfoliation reduced as the clay content increased. By TG it was seen that MMT, OMMT and FRP acted improving the thermal behavior of the nanocomposites compared to PE matrix. The results obtained for the oxygen index showed that both PE and its systems presented flame retardancy behavior. By means of the horizontal flammability tests, it was found that the presence of 1% MMT clay reduced 25% the flammability of PE. By cone calorimetry it was found that the system that contains 9% of OMMT clay decreased by about 33% the flammability of PE.

Green Highly Clay-Filled Polyethylene Composites as Coating Materials for Cable Industry—A New Application Route of Non-Organophilised Natural Montmorillonites in Polymeric Materials

“…%) decreased that parameter by 73% as well as positively affected mechanical parameters of PE. Lower values of PHRR of PE/OMMT (vs. PE) were also reported in [ 3 , 18 ]. Interestingly, samples containing 5 wt.…”

“…Modern polymeric materials for cable sheaths should exhibit low flammability and smoke production as well as no emission of toxic gases during their combustion [ 1 , 2 ]. Fire resistance of thermoplastics can be improved by incorporation of appropriate additives (e.g., P-based compounds [ 3 , 4 , 5 ]) and/or throughout chemical modification of a polymeric matrix [ 6 ]. One of the most commonly used thermoplastics in the cable industry is polyethylene (PE) due to its relatively high electrical resistivity, easy processing, and lack of halogen elements, however, it is a highly flammable material and must be flame retarded.…”

“…More interesting results have been reported in the latter paper: medium HRR values for PE containing 9 wt. % of (i) an OMMT, (ii) a MMT-Na, or (iii) a commercial nitrogen-phosphorus flame retardant were almost similar (198–219 kW/m 2 ) [ 3 ]. Limited oxygen index (LOI) values also show that OMMTs do not reduce the flammability of polyolefins markedly more efficiently than non-organophilised MMTs.…”

“…Only insignificant increments of interlayer spacing values—resulted from polymeric chains migration into platelet–platelet gaps (an intercalation process)—were described in these and many other papers. It shows that organophilisation of MMTs and their further dispergation in PE (using designed dispergation agents, for example, PE-g-MA [ 3 , 16 , 19 ]) do not usually allow one to produce nanocomposite-type polymeric materials with extraordinary better features than PE/MMT-Na systems. Moreover, the initial form of the clay is significantly cheaper than an OMMT, which is crucial for industrial applications.…”

“…Many research groups investigated various polymeric composites with MMTs-Na [ 3 , 18 , 20 , 22 ], but compositions with calcium montmorillonites (MMTs-Ca; the naturally occurring less hydrophilic MMTs) were not widely described in the literature. It should be noted that MMTs-Na (before their organophilisation) are often formed via MMTs-Ca activation/cation exchange processes using soda.…”