An Investigation On Surface Modification And Flammability Of Ultra-high Molecular Weight Polyethylene (UHMWPE) Fiber/Fabric

Ultra-high molecular weight polyethylene (UHMWPE) fiber/fabric has been widely used in many areas due to its good self-lubricity, excellent water and wear resistance, high tensile strength, and strong shock resistance, non-sticky and chemical resistance. However, it’s inherent inflammability and low limit oxygen index (LOI) value of only 17.5% during combustion have restricted its application and development. Moreover, it not only releaseshigh amount heat release and smoking release, but also produces lots of dripping and release toxic gas, which could threat to public safety and cause environment pollution. Therefore, it is required to improve the flammability retardancy of UHMWPE.Pad-dry physical treatment, surface coating method and microwave induced grafting were used in this work to improve the fire resistance of UHMWPE fabric. The first two modifications were belong to physical adsorption method, and the third microwave induced grafting was chemical modification which could link flame retardant monomers onto UHMWPE fabric surface through covalent bonds,.The first part of this paper employed physical treatment method to modified UHMWPE fabric with three different fire retardancy systems (dissolves fire retardancy system, soluble fire retardancy system and multiple complex fire retardancy system). In addition, the effect of different kinds of flame retardant systems in UHMWPE fabric were analysied by combustion tests, and the effect of RDP in UHMWPE fabric was studied in soluble fire retardancy system. Moreover, the optimal formula was selected under the comprehensive results.In this part, effects of RDP concentration, padders pressure and immersion time were investigated. It was showed that the best efficiency of modification in the system was RDP concentration, padder pressure and immersion time about 20 wt%,60+40min and 0.1 MPa, respectively. Attenuated total reflection infrared spectroscopy (ATR-FTIR) and scanning electron microscope (SEM) showed that the RDP was absorbed in UHMWPE fabric successfully. And the thermogravimetric analysis (TGA) and comparison of combustion method indicated that the flame retardancy efficiency, such as ignition of time, dripping and so on, of UHMWPE fabric was improved obviously. The elongation at break and the tensile strength of the treated smaple have not shown significant changes compared with that of raw UHMWPE fabric.In the second part of this paper, surface coting method was employed to introduce AM-thiourea hydrogel system on the surface of UHMWPE fabric to improve the flame retardancy. ATR-FTIR and SEM showed that the fire resistance system was absorbed in UHMWPE fabric successfully. TGA date indicated the modification fabric had better thermal stability than raw fabric. The flammability was studied by LOI, vertical burning test (UL-94) and cone calorimeter test (CC). The LOI value of LOI was increased from 17.1% to 22.3% after treated with AM-thiourea hydrogel. The UL-94 showed that the time to dripping (from 10s to 17s after treated flame resistance system) and after flame time were decreased compare with sample. More importantly, the peak of heat release rate (PHRR) value of sample was reduced from 324Kw/m2 to 220 Kw/m2 after treated with AM-thiourea hydrogel. In addition, the tensile strength was decreased with the thiourea concentration, while the tensile strength of treated sample was better than that of the raw fabric.In the third part of this paper, microwave induced grafting was firstly introduced to surface modify UHMWPE fabric. AM was used as grafting monomer and potassium peroxydisulfate (KPS) was used as initiator. Effects of reaction time and reaction temperature, initiator concentration, monomer concentration, reaction time, and reaction temperature were investigated, and the optimal reaction conditions were as follows:the fabric was pre-reacted in 0.3 wt% initiator solution at 75℃ for 30 min then removed to the 20 wt% monomer solution to react at 75℃ for 30 min, and all the reaction were conducted under the microwave irradiation. Morphology and structure analysis by SEM and ATR-FTIR investigated. The flammability and thermal stability were investigated by comparison of combustion test and TGA. The TGA thermograms analysis indicated that modification sample could significantly improve the thermal stability of the fabric. However, melting dripping was reduced significantly after grafting treatment.