Preparation And Properties Of UHMWPE Thermal Conductive Materials Based On Dopamine Modification

Ultra-high molecular weight polyethylene?UHMWPE?usually refers to polyethylene with a viscosity average molecular weight of more than 1.5 million.Its high molecular weight and entanglement density endow it with unique properties different from ordinary polyethylene,and its excellent wear resistance.Lubricity and impact resistance make it have broad application prospects in aerospace,ship transportation,military defense and other fields.However,due to UHMWPE has a linear structure,low thermal conductivity and poor heat resistance,as the same as ordinary polyethylene,its heat distortion temperature is only 85°C.When transported as a pipe,the material and the pipe are easily rubbed and heated.which easily causes deformation and reduces the service life of the pipe,greatly limits its application and development.Therefore,on the basis of retaining the original advantages of UHMWPE,enhancing its heat resistance is the key to solving the above problems.In this paper,the dopamine?DA?via in-situ polymerization was used to modify UHMWPE,?-flaky alumina??-Al₂O₃?and nano-graphite sheets?GNPs?,and the UHMWPE was modified with inorganic fillers.And the thermal and mechanical properties of UHMWPE and its composites was reaserched.In this paper,the physical properties of modified?-Al₂O₃ and UHMWPE/?-Al₂O₃ are measured by means of thermal conductivity,thermogravimetry?TG?,scanning electron microscopy?SEM?,Fourier transform infrared spectroscopy,Raman spectroscopy and X-ray photoelectron spectroscopy.The thermal conductivity and mechanical properties of Al₂O₃ composites were characterized.The main conclusions obtained are as follows:?1?Using DA in-situ polymerization,Surface polymerization of UHMWPE nascent powder to form PDA coating,UHMWPE/PDA with different PDA content was reaserched by different polymerization time,and its mechanical properties,rheological properties and thermal properties were studied.The experimental results show that PDA-modified UHMWPE has higher tensile strength and elongation at break than that of UHMWPE because of the active group and adhesion of PDA.When the PDA coating is increased to a certain extent,The mechanical strength of UHMWPE/PDA will decrease.?2?Al₂O₃was selected as the thermal conductive filler to modified UHMWPE,and DA was formed in situ on the surface of Al₂O₃ to form PDA-Al₂O₃,which was added to UHMWPE for filling modification.Firstly,nano-scale,1?m,10?m and 30?m Al₂O₃ were selecte to modify UHMWPE.The experimental results show that with the increase of Al₂O₃ particle size,the thermal conductivity of UHMWPE/Al₂O₃ is gradually increased,while the mechanical properties are decreased.Considering the thermal conductivity and mechanical properties,select 1?m Al₂O₃ as the subsequent modified filler in this chapter Secondly,unmodified Al₂O₃ and PDA modified 1?m Al₂O₃ were added to UHMWPE according to different mass fractions.The experimental results show that when the addition amount is 1wt%,The tensile strength and elongation at break of UHMWPE/PDA-Al₂O₃ composites were 62.508 MPa and 462%,respectively,which were 1.96 and1.98 times that of UHMWPE,respectively.When the addition amount is increased to 20wt%,the tensile strength of UHMWPE/PDA-Al₂O₃ composite reaches 40 MPa,which is similar to that of UHMWPE.The thermal conductivity of UHMWPE/PDA-Al₂O₃composite increases from 0.38 W/?mK?to 0.52 W/?mK?.The results show that the PDA-Al₂O₃ powder can simultaneously improve the mechanical properties and thermal conductivity of UHMWPE.?3?Using graphene nanoplates?GNPs?as thermal conductive fillers,The PDA via in-situ polymerization on the surface of graphene nanoplates are prepared.and to modify unmodified GNPs.The GNPs,PDA-GNPs were added to UHMWPE with different mass fractions.The experimental results show that when the addition of GNPs reaches 3 wt%,the thermal conductivity of UHMWPE/GNPs composites is 0.75 W/?mK?,while the thermal conductivity of UHMWPE/PDA-GNPs composites is only 0.65 W/?mK?,but the mechanical properties of UHMWPE/PDA-GNPs composites are better than that of UHMWPE/GNPs composites under the same addition.It is indicated that the thermal conductive filler GNPs can significantly improve the thermal conductivity of UHMWPE composites,and PDA can enhance the mechanical properties of composites.