The modification of magnesium hydroxide (MH) with triethoxy vinyl silane (TVS) was carried out via three different methods and the results are discussed with respect to their effect on the flame retardant and the tensile properties of high density polyethylene (HDPE) nanocomposites. Via a xylene suspension of MH and TVS, via a water suspension of MH and TVS, and via powder mixing of MH and TVS. It was found that in all three cases, SiAOAMg bonds formed on the MH particles surface. Also, this silane modification induced a certain level of particle agglomeration, but without modifying their morphology or particle size. It was also found that the flame retardant properties of the HDPE nanocomposites did not improve because of the use of silane modified MH. During the flame retardant tests, all nanocomposites passed the UL-94-HB, but it was observed that the flame permanence time was longer when using modified MH. The tensile properties were negatively affected by the addition of unmodified MH; the nanocomposites became hard and brittle, with reduced flexibility. This negative effect was diminished when using silane modified MH.

Álvarez (2015) Preparation and characterization of Polyethylene/Clay/Silver nanocomposites using functionalized polyethylenes as an adhesion promoter,The performance of Polyethylene (PE)/Clay/Silver nanocomposites is dependent to a great extent on the properties of filler-matrix interface. To improve the interfacial properties in PE/Clay/Silver composites, different types of compatibilizers or adhesion promoters were introduced. The compatibilization provided by maleic anhydride (MA), itaconic acid (IA) and 2-[2-(dimethylamine)-ethoxy] ethanol (DMAE) functionalized PEs for forming PE-based nanocomposites was studied and compared. IA was grafted into PE by melt mixing to obtain PEgIA (compatibilizer 1), thereafter, PEgIA and PEgMA (compatibilizer 2) were reacted with DMAE also by melt mixing to obtain PEgI-DMAE (compatibilizer 3) and PEgM-DMAE (compatibilizer 4). These compatibilizers were reacted using ultrasound with a solution of AgNO 3 0.04 M and ethylene glycol. Ammonium hydroxide was added in a ratio of 2:1 M with respect to silver nitrate. These silver coated compatibilizers were mixed with PE and with a quaternary ammonium modified montmorillonite clay (Nanomer I28E), thus forming the different hybrid PE/Clay/Silver nanocomposites. FTIR confirmed the formation of these compatibilizers. All the DMAE compatibilized nanocomposites had better filler (clay and silver) dispersion and exfoliation. XRD, oxygen and water transmission rate as well as antimicrobial properties attained showed that the PEgI-DMAE produced the better dispersed PE, clay and silver nanocomposites. The obtained nanocomposites showed enhanced barrier properties and outstanding antimicrobial properties against bacteria, E. coli. PEgI-DMAE offers an outstanding capability for preparing nanocomposites with highly exfoliated and dispersed filler into the PE matrix that offers a new option for obtaining hybrid nanocomposites with enhanced properties to be used in packaging applications.

The effect of graphene oxide (GO) functionalized with 3‐amino‐propyl‐triethoxy‐silane(APTS), organo‐vermiculite(OVMT), and magnesium hydroxide (MH) combinations on mechanical, thermal, and flame retardant (FR) properties of polypropylene (PP) was studied. GO was obtained via a slight modification of the Hummers method and then chemically surface functionalized with APTS. VMT clay was modified with maleic anhydride (MA) via a chemical reaction with acetic acid to increase its inter‐laminar spacing. The results of Fourier‐transform infrared analysis, X‐ray diffraction, and transmission electron microscopy demonstrated that APTS had been successfully attached to the GO and that VMT was modified with MA. Subsequently, each functionalized filler was incorporated in combination with MH to the flame‐retardant‐polypropylene system. The performance of PP composites with each filler as well as with their combinations, including a reduced “30 wt% of MH” were compared with the reference PP composite with 55 wt% of MH as the only FR additive. PP grafted with MA (PP‐gMA) and PP grafted with amine‐alcohol(PP‐gDMAE) were used as compatibilizer agents between each filler and the polymer matrix. The results obtained confirmed a better mechanical and FR performance when using PP‐gDMAE. Composites with 30 wt% MH combined with very low contents of GO (0.5 and 1.0 wt%) showed improved FR properties, similar to the reference sample, with an evident reduction in peak of the heat release rate (pHRR) and total heat release and increased limiting oxygen index (LOI) values. The combination of MH and GO showed the best FR and mechanical properties: LOI of 22.5% and pHRR of 540 kW/m2 which were very similar to the reference sample. In addition, PP‐gDMAE improved the OVMT exfoliation with a slight increase in the intergallery spacing but OVMT and modified GO combinations did not significantly improve the FR and mechanical properties compared with the effect of MH and modified GO combinations. The combination of MH and modified GO makes it possible to reduce the total MH filler content from 55 to 30 wt% to accomplish the FR requirements and with enhanced mechanical properties. This filler combination promoted the formation of a continuous, intact residual char layer on the PP surface, which acts as an insulating barrier to protect the base material. These filler combinations offer an option to meet the FR properties using halogen‐free FR with better mechanical properties.

No abstract

Transformers are very expensive apparatuses and are vital to make the whole power system run normally. The failures in such apparatuses could leave them out of service, causing severe economic losses. The life of a transformer can be effectively determined by the life of the insulating paper. In the present work, we show an alternative diagnostic technique to determine the ageing condition of transformer paper by the use of FTIR spectroscopy and an empirical model. This method has the advantage of using a microsample that could be extracted from the transformer on-site. The proposed technique offers an approximation quantitative evaluation of the degree of polymerization of dielectric papers and could be used for transformer diagnosis and remaining life estimation.