Polyamide 6 Toughened And Synergistic Flame-retarded By Core-shell Poly(siloxane-acrylate)

Polyamide 6(PA6)is an important thermoplastic with attractive mechanical performance,thermal properties and processability.It has been widely used in the mechanical,electronic and electrical industries.However,PA6 belongs to notch-sensitive materials with poor resistance to crack propagation,high brittleness at low temperatures.At the same time,PA6 is a flammable material.These defects restrict the wider application of PA6.Therefore,it is necessary to prepare toughened and flame-retarded PA6.In this paper,core-shell poly(siloxane-acrylate)(SiBMG)was used for toughening and flame-retarding PA6.The relationship between modification effect,structure and properties was mainly studied.SiBMG takes polysiloxane with low glass transition temperature(T_g)as the core layer,and graft copolymerized methyl methacrylate(MMA)and glycidyl methacrylate(GMA)as the shell layer.SiBMG was used as a synergistic agent in flame-retarding PA6 with aluminium diethylphosphinate(AlPi),which realized the application of SiBMG in toughening and flame-retarding PA6.It provides a new technical route for the simultaneous industrialization of toughened and flame-retarded engineering plastics,which is of scientific significance and practical value.In this paper,SiBMG was used as toughening modifier and bisphenol A type epoxy resin(DGEBA)as compatibilizer.PA6/SiBMG/DGEBA blends were prepared by melt blend extrusion.The effects of SiBMG and DGEBA amounts on the processability,crystallization property and mechanical properties of the blends were investigated,and toughening mechanism of the blends was discussed in depth.The results showed that SiBMG has a certain toughening effect on PA6.After the addition of DGEBA in PA6/SiBMG blends,toughness of the blends at room temperature and low temperature was further improved.With the addition of 10.0 wt%SiBMG and 2.0 wt%DGEBA,the notched impact strength at room temperature and low temperature of PA6/SiBMG-10/DGEBA-2.0 blend were 280.9 J/m and117.6 J/m,respectively,which were higher than pure PA6 by 301%and 168%respectively.It was indicated that SiBMG and DGEBA have a significant toughening effect on PA6.SiBMG Synergistic halogen-free flame-retarded PA6 was studied.When only AlPi was applied for halogen-free flame-retarding PA6,PA6/AlPi-11 with 11.0 wt%AlPi can achieve UL-94 V-1@3.2 mm rating,and PA6/AlPi-13 with 13.0 wt%AlPi can reach UL-94 V-0@3.2mm rating.SiBMG was combined with AlPi to prepare halogen-free flame-retarded PA6.PA6/AlPi-10/SiBMG-1.0 with 1.0 wt%SiBMG and 10.0 wt%AlPi can pass the same UL-94V-0@3.2 mm rating.From the cone calorimeter results,with the same amount of flame retardant,the peak heat release rate(pHRR)and the total heat release(THR)of PA6/AlPi-10/SiBMG-1.0 decreased compared with that of PA6/AlPi-11,and the peak smoke release rate(pRSR)decreased from 10.5(m~2/s)/m~2 to 7.6(m~2/s)/m~2 of PA6/AlPi-11.In addition,the average mass loss rate(mMLR)of PA6/AlPi-10/SiBMG-1.0 was significantly lower than that of PA6/AlPi-11,resulting in the higher final carbon residue rate.From the X-ray energy spectrum(EDX),it was found that the contents of Si and O elements increased from 0.38%and 29.18%in the inner carbon layer to 0.99%and 39.26%in the outer carbon layer respectively,indicating that SiBMG would migrate from the inside to the surface of the material.Moreover,the result of thermogravimetry-fourier transform infrared spectroscopy(TG-FTIR)analysis showed that Si element of SiBMG was not released into the gas phase,but remained in the condensed phase.The flame ratardancy mechanism of PA6/AlPi-10/SiBMG-1.0 was a combination of gas phase and condensed phase flame ratardancy.Because SiBMG has obvious toughening effect on PA6,the impact performance of flame-retarded PA6 with SiBMG and AlPi is better than that of AlPi flame-retarded PA6.Compared with the PA6/AlPi-13 which has the same UL-94 V-0@3.2 mm rating,the notched impact strength of PA6/AlPi-10/SiBMG-1.0 was increased by 16%,the melt flow rate was increased by 29%.Both mechanical properties and processability of the synergistic flame-retarded PA6 were improved.