Preparation And Performances Of Selective Laser Sintering Inorganic Fullerene Reinforced Polyamide Composites

With the rapid development of 3D printing technology,the range of applications for printable polymer composites is gradually expanding.Widely used polymer materials are often flammable,which can increase the risk of fire and may lead to direct personal injury and property damage.Therefore,it is of great scientific and practical importance to study 3D printed（additive manufacturing）polymer materials and to develop,design and prepare polymer composites with flame retardant features,and will provide new ideas for the further promotion and application of 3D printing technology.There are many studies on the reinforcing phases of polymer composites,including organic phases,inorganic phases and organic-inorganic hybrid materials.Researchers have conducted in-depth studies on inorganic phase transition metal sulphide reinforced phase materials,especially the hot inorganic fullerene-like tungsten disulphide（IF-WS₂）nanomaterials,as well as on their enhanced mechanical properties of polymer composites,which have proven their unique advantages.However,less research has been reported on the preparation of composites using IF-WS₂ and its derivatives as the reinforcing phase for selective laser sintering technology for 3D printing,and there are still many technical challenges in the multifaceted composite of IF-WS₂nanoparticles with polymers.Therefore,this thesis investigated the use of various organic modifiers for improving the interfacial compatibility of IF-WS₂nanoparticles with polymer matrix,using modified IF-WS₂ nanoparticles combined with carbon nanotubes（CNT）and metal organic frameworks to develop a variety of novel composites.This work focuses on the dispersion of IF-WS₂ and its derivatives in the polymer matrix,and on the thermal and mechanical properties of the obtained polymer composites,as well as their impact on fire safety performance.The research will provide a theoretical and experimental basis for research and practical applications of selective laser sintering of polymeric flame-retardant composites.The research results achieved are as follows:1.In response to the problem that the traditional physical blending of powders tends to cause agglomeration of IF-WS₂ nanoparticles in PA12 powder and affects the dispersion,the stable coating of IF-WS₂ nanoparticles on the surface of PA12 was achieved in this work using a solution blending process.In combination with selective laser sintering techniques,nanocomposites with different components of IF-WS₂ nanoparticles reinforced with PA12 matrix were prepared.Compared to pure PA12,the addition of IF-WS₂ nanoparticles imparted static and dynamic mechanical properties to the selective laser sintered nanocomposites,with a 14.6%increase in tensile strength and a 10.1%increase in energy storage modulus for PA12/IF-WS₂（2%）.the PA12/IF-WS₂（4%）composite,compared to PA12,had a peak heat release rate（p HRR）value was reduced by 19.7%,and the peak smoke production rate（SPR）and total smoke yield（TSR）were reduced by 30.9%and 21.9%respectively,effectively reducing the production of the toxic gas CO,indicating that IF-WS₂nanoparticles have excellent flame retardancy.2.IF-WS₂ nanoparticles were chemically treated with polyethylene glycol（PEG）to generate F-IF-WS₂（chemically modified IF-WS₂）nanoparticles rich in-OH groups on their surface to improve the surface inert behaviour of IF-WS₂nanoparticles.the FTIR results verified the existence of hydrogen bonding behaviour of F-IF-WS₂ nanoparticles with PA12 matrix.Compared to pure PA12,the PA12/F-IF-WS₂（2%）nanocomposites showed a 12%increase in energy storage modulus and a 33%increase in tensile strength.In addition,PA12/F-IF-WS₂（4%）significantly enhanced the flame-retardant efficiency of PA12 with a reduction in p HRR（37.31%）and a reduction in TSR and p SPR values by 14.6%and 23%,respectively.It indicates that F-IF-WS₂ nanoparticles not only improve the flame-retardant properties,but also confer excellent mechanical properties to the selective laser sintered polymer composites.3.The combination of F-IF-WS₂ nanoparticles and Hummers-modified carbon nanotubes（F-CNT）was explored to obtain a new flame-retardant composite system for developing efficient 3D printed flame-retardant composites.Compared with pure PA12,PA12/3C/1W,the tensile strength increased by 19.4%,the energy storage modulus increased by 14.5%,the glass transition temperature increased by 5.8°,the p HRR decreased by 18.2%,the THR decreased by 20.14%and the TSR decreased by 22.7%.the three-dimensional hydrogen bonding network formed by the functional groups on the surface of F-CNT,F-IF-WS₂ with PA12 has improved the flame-retardant performance of the composites and reduced the release of toxic gases.4.The first in-situ synthesis of metal-organic framework HKUST-1/polyvinyl pyrrolidone（PVP）-modified IF-WS₂ hybrids using a hydrothermal reaction was used to develop PA12 composites with excellent mechanical and fire safety properties.The addition of HKUST-1@PVP-IF-WS₂ at 2%resulted in a 10.5%increase in tensile strength,a 10.8%increase in energy storage modulus,a 14.5%decrease in p HRR and a 28.4%decrease in p SPR.The introduction of the organic-inorganic flame-retardant hybrid HKUST-1/PVP-IF-WS₂ significantly improved the fire safety performance of the PA12 matrix.the catalytic effect of HKUST-1 and the thermal barrier effect of PVP-IF-WS₂nanoparticles played a key role in the flame-retardant PA12 matrix.