Preparation And Properties Of Modified Nylon-6 Microcellular Foaming Material

With the acceleration of automobile lightweight trend and the increasing demand of automobile plastics,Nylon 6,as the most widely used automobile plastics,has great potential and wide application prospect.However,the poor foamability has brought many limitations to the development of nylon foam materials,which is mainly determined by the linear molecular chain structure of Nylon 6 itself.This causes the low melt strength during the foaming process,which leads the cells to collapse and break easily at the cell growth stage.Therefore,it is a more effective and convenient way to improve the foamability of Nylon 6 by chemical modification for improving its melt strength and viscoelasticity compared with adjusting the foaming process.In general,mechanical properties of the lightweight microcellular material will be reduced in varying degrees,so it is also of great significance to enhance the mechanical properties of the microcellular foam materials in the actual production and application.In this paper,Nylon 6 was used as the matrix material.Firstly,the ionic polymer Surlyn and the chain extender BOZ were blended with Nylon 6 to obtain high melt strength Nylon products.It was found that the melt index of Nylon 6 can be reduced to 1.3g/10min by adding 1parts of Surlyn,which made better effect than the chain extender bisoxazoline with the increasing of viscosity.The rheological properties of modified nylon also show high viscoelasticity.In the second part,Nylon 6 foaming materials with different foaming ratio were successfully obtained by using batch foaming technique with supercritical CO₂ as foaming agent and adjusting the process conditions.It turns out that the highest foam density reaches 10⁹cells/cm³,the smallest foam size was 10?m,and the highest foam ratio of Surlyn modified foam samples comes up to 24times.At the same time,it is also found that temperature,saturation pressure,foaming time and other factors have great impacts on the foaming effect of modified Nylon 6.Finally,in the third part,on the basis of low-density modified Nylon 6 foaming products,two kinds of reinforcing fillers,organic montmorillonite and short glass fiber,were added to reinforce the mechanical properties of Nylon foaming products.Through the analysis of the changes of the morphology and mechanical properties of foaming materials caused by reinforcing fillers,it was found that the addition of montmorillonite and glass fiber both increased the density of the foam,decreased the size of the foam and the foaming ratio.At the same time,nano montmorillonite is used as the support point in the foam material matrix,and glass fiber act as micro rigid pillar in the polymer,which restricts the deformation ability of the foam material under the external force.With the same foam ratio of 6 times,compared with neat nylon foam,small amount of 0.5 parts of montmorillonite can increase the compression performance of the foam material by 131%,and the bending modulus by 112%;after adding 5 parts of glass fiber,the compression strength can be increased by 149%,and the bending modulus can be increased by 289%.