Synergistic effect of carbon fibers and carbon nanotubes on improving thermal stability and flame retardancy of polypropylene: a combination of a physical network and chemical crosslinking

Abstract

Recently, an intensive research effort has been devoted to the fabrication of polymer composites with enhanced physical and chemical properties. In this work, the combination of carbon fibers (CFs) and carbon nanotubes (CNTs) was demonstrated to show a synergistic effect on improving thermal stability 10 and flame retardancy of polypropylene (PP). The results of morphology characterization indicated that both CFs and CNTs were well dispersed in the PP matrix. The temperature at the maximum weight loss rate of PP under air atmosphere was dramatically increased by 93.4 o C, and the peak value of heat release rate measured by cone calorimeter was significantly reduced by 71.7%. The remarkably improved thermal stability and flame retardancy of PP were partially owing to the accelerated oxidation 15 crosslinking reaction of PP radicals by CNTs (chemical effect), and partially to the in situ formation of dense and continuous CF/CNT hybrid protective layer (physical effect). This was because the CF/CNT hybrid protective layer not only hindered the diffusion of oxygen into PP and the migration of volatile decomposition products out of PP, but also acted as a thermal shield for energy feedback from the flame.

Flame Retardant Polypropylenes: A Review

“…Symbols are indicative of different types of carbonaceous flame retardant used. Here: ■ GN-2, m-GN-2 [ 106 ], m–rGNO-2, m–rGNO-2 [ 122 ], rGNO-2, m-rGNO-2, m-rGNO-2 [ 123 ], rGNO-2, m-rGNO-2 [ 112 ], GNO-2, m-GNO-0.5, m-GNO-1, m-GNO-2 [ 124 ], GN-2.5, GN-NiO-2.5, GN-NiCe x O y -2.5 [ 125 ], rGNO-2, m-rGNO-1, m-rGNO-2, m-rGNO-3 [ 126 ], m-rGNO-20 [ 58 ], EG(ES 350 F5)-10, EG(ES 700 F5)-10, EG(Nyagraph FP)-10, EG(TEG 315)-10, EG(Nyagraph KP251)-10 [ 127 ], CNT-1, m-CNT-0.5, m-CNT-1, m-CNT-2, m-CNT-4 [ 128 ], CNT-1, m-CNT-0.5, m-CNT-1, m-CNT-2 [ 129 ], MWCNT-1, MWCNT-3, MWCNT-5, m-MWCNT-1, m-MWCNT-3, m-MWCNT-5 [ 130 ], MWCNT-1, MWCNT-3 [ 131 ], MWCNT-3 [ 132 ], MWCNT-10, CF-10 [ 133 ], CF-3, CF-8, CB-5 [ 134 ], AC-7.5 [ 108 ], VGCNF-4, VGCNF-8, VGCNF-12 [ 6 ].…”

Multiscale Carbon Fibre–Carbon Nanotube Composites of Poly(Vinyl Chloride)—An Evaluation of Their Properties and Structure

“…On this basis, it can be concluded that the addition of CFs and CF_CNT has a slight effect on increasing the thermal stability of PVC composites, but the CF_CNT filler system improves this property to a minor extent. A significant increase in thermal stability was observed in the case of polypropylene (PP) composites containing both CF-and CF+CNT-modified maleic anhydride-grafted PP according to the authors due to the increase in a dense and continuous hybrid CF/CNT protective layer preventing PP decomposition [48]. The time of thermal stability assessed by the Congo red test [49,50] allows the determination of the stability time after which the PVC matrix decomposes with rapid HCl release, thus causing the discolouration of the indicator paper.…”

Themoxidative stability and char formation mechanism for the introduction of CNTs and MoS2 into halogen-free flame retarding TPEE

“…The formation of compact char during the burning process has proven to be an effective way to enhance the re retardancy of polymers. [11][12][13] In recent years, the incorporation of nano-llers with a high aspect ratio can obviously enhance the ame retardancy of polymers on account of the formation of a high-quality char during the burning process. 14,15 Carbon nanotubes (CNTs) have attracted considerable interest due to their unique structure, electronic, thermal and mechanical properties, 16 and thus have been used in various applications, including drug delivery, 17,18 chemical sensing, 19,20 electronic sensing 21,22 and as reinforced llers for polymers.…”