Kaolinite (Kaol) and halloysite nanotubes (HNT) are both aluminosilicate clays with similar chemical formulation and different microshapes. In this article, nanotubular HNT and nanoplate Kaol together were introduced into polypropylene (PP) containing intumescent flame retardant (IFR). The flammability of the PP composites was characterized by limiting oxygen index (LOI), vertical burning (UL-94), and cone calorimeter tests (CCT). The results showed that for the composite with 75 wt % PP and 25 wt % IFR, its LOI was 31.0% and it obtained a UL-94 grade of V-2. For the composite of 75 wt % PP, 23.5 wt % IFR, and 1.5 wt % (Kaol/HNT 5 9/1), its LOI increased to 36.9 and it obtained a UL-94 grade of V-0; at the same time, its peak heat release rate value in CCT decreased by 82.2% compared to neat PP. The thermostability analysis indicated that the mixture of Kaol/HNT could improve the thermostability and final char yield. The char residues were comprehensively analyzed by scanning electron microscopy and Fourier transform infrared spectroscopy. The results illustrated that the Kaol/HNT combination was beneficial to forming a crosslinked network and promoting formation of a compact char with higher strength. V C 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46507.
Nitrate intercalated hydrotalcite (NO 3 − -HTC) was first prepared as precursor; a schiff base derivative containing N, P, and S was synthesized and its structure was characterized. Later the schiff base derivative was used as intercalation to replace NO 3 − in hydrotalcite. The final product was schiff base derivative intercalated hydrotalcite, which was named as benzaldehyde-taurine-hypophosphorous (BTP)-HTC. The results showed both NO 3 − -HTC and BTP-HTC can effectively improve the flame retardant and thermostability of ethylene vinyl acetate (EVA). In cone calorimeter test, the peak heat release rate of EVA was 1421.2 kW/m 2 and reduced sharply to 746.1/584.5 kW/m 2 for 20 wt% NO 3 − -HTC/ BTP-HTC adding, respectively. At same time, the total heat release was also decreased from 120.6 MJ/m 2 for EVA to 81.0/70.0 MJ/m 2 , respectively. Morphology observation and composition analysis by scanning electron microscopy (SEM)/X-ray spectroscopy (EDS) documented the residue left after combustion of EVA/NO 3 − -HTC was just ash containing Mg and Al; but for EVA/BTP-HTC, coherent char layer containing Mg, Al, and P was left. Thermogravimetric analysis indicated that the thermal degradation of EVA was prolonged by either NO 3 − -HTC or BTP-HTC; and char content was kept to 8.6% and 11.0%, respectively. The whole results documented either NO 3 − -HTC or BTP-HTC improved the combustion behavior and thermostability of EVA, and BTP-HTC showed excellent effect. J. VINYL ADDIT. TECHNOL., 25:255-261, 2019.
Ammonium polyphosphate (APP) is an effective flame retardant in thermoplastic polyurethane (TPU). In order to further enhance the flame retardant efficiency of APP, it was coated with graphene oxide (GO) and melamine formaldehyde (MF) successively, by using 5 wt% end product of MF‐GO@APP in TPU, the sample produced little dripping during burning and reached UL‐94V‐0 grade, peak smoke production rate was reduced from 0.132 m2/s in TPU to 0.051 m2/s, that was 61.4% decrease. Neat TPU burned out with little residue left, but by the help of 5 wt% MF‐GO@APP, 24.4 wt% of char was left. These results were tried to be analyzed as relative higher heat conductivity of GO, in heating GO transferred more heat to APP and MF, resulting in earlier degradation of APP and MF, the decomposed product of MF and APP cross‐linked together to form more compact char above substrate. MF‐GO@APP acted as an integrated intumescent flame retardant.
A rapid, green, and cost‐effective route for the preparation of graphene nanosheets (GRNs) from their layered bulks by the ultrasonic together with mechanical grinding was reported. The whole exfoliation process of synthesizing GRNs lasted just 2 hours without involvement of any acid solvent or other organic solvents; only one kind of waste biomass as adhesive could be used. The structure and morphology of GRNs were characterized and then was then introduced into polypropylene by melt blending, and the cone calorimetry test results indicated that the presence of GRNs could enhance the flame retardancy of PP composite.
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