Experimental investigation of flame retardancy and mechanical properties of APP/EG/TPU multilayer composites prepared by microlayer coextrusion technology

Abstract

In this paper, ammonium polyphosphate(APP)/expandable graphite(EG)/thermoplastic polyurethane (TPU) composites were prepared by microlayer coextrusion technology, APP and EG fillers had good synergistic flame retardancy and excellent dispersion in TPU matrix, which greatly improved the flame retardancy and mechanical properties of multilayer composites. The dispersion of APP and EG in TPU was characterized by using SEM, the flame retardancy of composites was characterized by using UL94 and LOI, the thermal stability of composites was characterized by using TGA and DTG, and tensile test was used to characterized the mechanical properties of composites. SEM showed that the microlayer coextrusion technology significantly improved the dispersion of APP and EG in TPU. As showed by the experimental results, the vertical combustion level of ordinary blended composites reached V‐2 after adding only one kind of filler either APP or EG, and the vertical combustion level of ordinary blended composites reached V‐0 with APP and EG applied together, while the vertical combustion level of microlayer coextruded composites all reached V‐0 when the total addition of APP and EG was 15%. In particular, the LOI value of microlayer coextruded composites was 30.9%, while the LOI value of ordinary blended composites only was 27.9% when APP: EG = 1: 1. At this time, the flame retardancy level of APP/EG/TPU composites was the best. In addition, the thermal stability and mechanical properties of microlayer coextruded composites were far superior to ordinary blended composites. In conclusion, the synergistic flame retardancy of APP and EG fillers and the dispersion of APP and EG fillers in TPU matrix played a significant role in enhancing flame retardancy and mechanical properties.

Surface Modification of Ammonium Polyphosphate for Enhancing Flame-Retardant Properties of Thermoplastic Polyurethane

“…The results showed that the tensile strength (T s ) of pure TPU was 28.9 ± 2.3 MPa, and elongation at break (E b ) was 1310 ± 42%. The introduction of APP significantly reduced the T s and E b of TPU composites, which may be due to the stress concentration caused by the accumulation of APP in the TPU matrix, making the composites prone to cracks [ 30 ]. Furthermore, compared with TPU/5%APP, the T s and E b of TPU/5%APP-Cu increased by 25% and 12%, and the T s and E b of TPU/5%APP-Cu@PDA increased by 43% and 37%.…”

Recent Advances in Halogen-Free Flame Retardants for Polyolefin Cable Sheath Materials

“…However, the charred layer formed during combustion is very loose and easily falls off due to the “popcorn effect”. Thus, a number of investigations are focused on cooperative effects of EG with other additives to overcome this disadvantage [ 226 ], such as APP [ 227 , 228 , 229 ], MH [ 230 , 231 ], and LDH [ 232 , 233 ].…”

Thermoplastic polyurethane composites based on aluminum hypophosphite/modified iron tailings system with outstanding fire performance

“…34 The chemical components of unmodified IT are given in Table 2 35 The flame retardancy of polymer materials is improved by adding metal oxides/ metal hydroxides as flame retardants or synergistic agents into the polymer matrix. [36][37][38][39][40] Figure 2 gives the FTIR spectra of IT before and after modification. The figure shows that 3411 cm À1 is the characteristic peak of -OH asymmetric stretching vibration in crystal water.…”