The Investigation On Preparation And Properties Of Thermal-conductive Nylon 6 Filled With Magnesium Hydroxide

Filled thermal conductive composites are an active research field at present.Generally,inorganic fillers with high thermal conductivity are used to modify the bulk resin.Although a wide variety of inorganic fillers can be selected,they are confronted with the problems of difficult processing and production,imperfect construction of composite thermal conduction pathway and high cost under the condition of high filling.With the twin screw extruder as the processing equipment,magnesium hydroxide as the main inorganic filler,the melt blending modification of nylon 6 resin matrix can expand the application of nylon 6 resin in the field of heat conduction.Firstly,60wt%magnesium hydroxide filled nylon 6 resin matrix was selected as formula A?filling system?,20wt%glass fiber reinforced nylon 6 resin matrix was selected as formula B?reinforcing system?,the processing temperature of the extruder was fixed,the feeding amount was fixed,and the effects of different screw combinations and screw speed on the properties of the composite were investigated.In the aspect of screw assembly,the influence of changing the number of the melt plasticizing section and the continuous combination of the shear blocks in the mixing section on formula A was investigated.The effect of screw assembly replacing mixed segment shear element with the same number of dispersing elements on formula B was investigated.In terms of screw speed,300rpm and 400rpm were selected as two variables to investigate the influence on formulations A and B.Through infrared thermal imaging,mechanical properties testing,thermal stability analysis and scanning electron microscopy and other characterization means,respectively,formula A and formula B were tested under different technological conditions.For the filling system,the shear block in the melt plasticized section has the greatest influence on the shear heat of the composite melt,followed by the shear block in the mixed section.On the premise of fully plasticizing the materials in the formula,the thin shear blocks in the mixing section are added to facilitate the dispersion of the fillers in the filling system,so as to improve the mechanical properties of the composite materials.For the reinforcing system,the use of miter tooth block in the mixing section can make the composite material have a higher short glass fiber retention length than the shear block,thus improving the mechanical properties of the composite material.Then,the fixed process conditions were used to fill the PA6 with magnesium hydroxide as the main filler,and the total additive amount of the filler was determined to be 60 wt%.From the perspective of building thermal path,the effect of the characteristic parameters of inorganic filler such as different particle sizes and structures on the performance of the final thermal conductive composite was investigated.The first step is to investigate the effects of magnesium hydroxide dosage and particle size.The results showed that the thermal conductivity of the composite increased with the increase of magnesium hydroxide amount.At the same filler loading,the filled composite with larger particle exhibited higher thermal conductivity.The thermal conductivity of the composite was further enhanced when the composite was filled with three sizes of particles?weight ration of 1:1:1?.The second step is to investigate the effect of different amount of boron nitride on the composite.When the boron nitride content increased from 0 to 20 wt%,the thermal conductivity of the composites increased first and then decreased.When 1 wt%boron nitride was introduced to replace magnesium hydroxide,the thermal conductivity of the composite increased by 9.8%.When boron nitride content increased to 15 wt%,the thermal conductivity of the composites decreased.In the third step,the effect of different components and dosage of fiber on the composite was investigated.The effect on the construction of heat conducting network of composite materials was investigated through the blending of spherical granules,flake and fibrous filler.Finally,a optimized formulation has been obtained.The filler content is 60 wt.%,which consists of 56 wt%magnesium hydroxide,1 wt%boron nitride,3 wt%tin silver alloy.The thermal conductivity of the optimized formulation reached 2.01 W(m^-1k^-1),which was 10times that of neat PA6 resin.