Study On The Rheological Behaviour And Properties Of The Anti-dripping Fiber From Bottle Grade Recycled PET

Besides fiber production, polyethylene terephthalate (PET) is applied in food, beverages containers and packaging films manufacturing in large quantity. The reuse and recycling of bottle grade PET is of great importance in terms of environmental protection and resources saving. In addition, polyester fibers are thermoplastic and flammable, when burning they tend to form molten drops, which can bring burns and other secondary damages, so the modification of polyester fibers is necessary to improve the performance of anti-dripping.In this paper, the rheological properties of bottle (rPET) and fiber grade polyester were analyzed and compared, then an anti-dripping resin was added to rPET resin and the rheological properties of melt blends were studied. At last, the rPET/anti-dripping resin blended fibers were prepared. The thermoplastic anti-dripping copolymer in polyester fiber will hydrolyze and crosslink into a three-dimensional thermosetting network after putting blended fibers in the water. The thermosetting anti-dripping resin can warp the melting drops and then accelerate charring, and thus the anti-dripping effect was achieved. The melt rheological properties of blends, performance of the blending fiber and anti-dripping fiber were studied by means of melt flow rate indexer, double capillary rheometer RH 7D, SEM, FTIR, XRD, TG, DSC, KES-G1 MULTI-PURPOSE TENSILE TESTER and anti-dropping tests.The main research contents and conclusions are listed as follows:(1) The melt rheological properties of bottle and fiber grade polyester were comparatively studied by double capillary rheometer RH 7D. The influence of shear rate and temperature on the apparent viscosity, non-Newtonian index, structural viscosity index, and activation energy for viscous flow were discussed. The results show that the two kinds of melt belong to non-Newtonian pseudoplastic fluid and the apparent viscosity decreases with the increasing of shear rate and temperature. At the same temperature, the non-Newtonian index of bottle grade melt is smaller than that of fiber grade polyester, but the structural viscosity index is larger than fiber grade polyester. The activation energy for viscous flow of two kinds of melt decreases with the increasing of shear rate.(2) The melt rheological properties of rPET and blends of rPET/anti-dripping resin were studied by melt flow rate indexer and double capillary rheometer RH 7D. The results show that the melt index of rPET/anti-dripping resin blends increased along with increasing of the anti-dripping resin content; the apparent viscosity gradually decreased with raising temperature and shear rate, their melts showed non-Newtonian pseudoplastic fluid characteristics; the non-Newton index gradually increased with the increasing of temperature; the structural viscosity index decreases with the increasing of temperature. The activation energy for viscous flow of melt decreases with the increasing of shear rate. Within the framework of the study, with the increase of anti-dripping resin content, non-Newton index of rPET/anti-dripping resin blends melt increased, the structural viscosity index, zero shear viscosity and the activation energy of viscosity flow reduced.(3) SEM, XRD results showed that the blending fibers' surface was rough compared with the traditional pure rPET fibers, and the crystal structure of blending fibers was unchanged with the addition of anti-dripping resin. The crystallinity decreased to 26% when the ratio of anti-dripping resin was 27.18%. The results of KES-G1 showed that the fracture intensity of anti-dripping polyester fibers was 134.49Mpa that was lower than pure polyester fibers'. TG, DSC and the anti-dripping performance test indicated that the melting point, the maximum thermal decomposition rate of the blending fibers and the number of drops of the anti-dripping fibers in unit time (1min) were decreased with the increase of anti-dripping resin content. The char residue of blending fibers was increased and the anti-dripping effect got gradually strengthened when raised the content of anti-dripping resin.