Study On Structure And Properties Of The Ultrasonic-Assisted Hot-Pressed Plastics/Silane/Aluminum Alloys

With the rapid development of modern science and technology,polymer materials and polymer matrix composite materials had become the main application materials in the fields of automobiles,ships,construction,aerospace and electronics.The metal and plastic were connected to achieve the combined effect of the properties of the two materials,so that the composite part could not only achieve the desired strength,but also reduce the weight,and even generate additional specific properties.Traditional metal-plastic composite parts need to use adhesives or destructive welding methods to connect dissimilar materials,and composite parts would cause defects such as the release of harmful gases and stress concentration.This topic adopted a new method of ultrasonic-assisted thermocompression connection to realize the rapid connection of dissimilar materials.In the experiment,the selected plastic matrix was isotactic polypropylene,modified polypropylene and PC,and the metal surface treatment agent was ?-aminopropyl-triethoxysilane(KH550),Lapped with plastic.The effect of silane treatment on different plastic matrix composite parts was explored,and the connection mechanism of the composite parts was analyzed.1.Aluminum alloy surface pretreatmentThe surface of the aluminum alloy was pretreated by anodized.Under the optimal electrolytic parameters of anodized,an aluminum substrate with micro-nano structures on the surface was obtained.The morphology analysis of scanning electron microscopy(SEM)showed that there were uniform honeycomb micro-nano pores with pore size of60-210 nm and pore depth of about 4um on the pretreated surface of aluminum alloy.The uniform honeycomb-shaped micro-nano pores and the secondary micro-pores on the longitudinal pore walls provide a "split channel" for the drilling of plastics.The anodized aluminum alloy plate was immersed in a silane hydrolyzate with different volume fractions,and cured to obtain a silanized aluminum substrate.Energy spectrum analysis(EDS)analysis showed that with the increase of silane concentration,the content of silicon on the aluminum surface increased;X-ray photoelectron spectroscopy(XPS)results showed that the chemical reaction of silane on the aluminum alloy surface formed Al-O-Si bonds.2.Structure and properties of PP/silane/aluminum alloy composite partsWhen polypropylene(PP)was combined with aluminum alloy by ultrasonic assisted hot pressing,the tensile shear strength of PP/ aluminum alloy composite was about 19-21 MPa,while the bonded strength of PP/ aluminum alloy composite was19.54 MPa,indicated that silane treatment had no obvious enhancement effect on nonacute materials.SEM morphology analysis showed that the amount of resin drilling remains the same,and there was obvious resin drilling and failure.Large plastic deformation occured at the interface.XPS elemental analysis showed that Al-O-Si bonds were formed at the interface,but no other chemical bonds were found.Finally,it was concluded that the connection mechanism of the composite part was physical riveting,the failure mode was cohesive failure.3.Structure and properties of modified PP/silane/aluminum alloy composite partsPolypropylene grafted with maleic anhydride(PP-g-MAH)was used to polarize polypropylene,the bulk strength of PP was 40.58 MPa,and the bulk strength of 5wt %PP-g-MAH modified PP was 40.75 MPa.It was difficult to form,and finally 5wt% PPg-MAH modified resin was used as the matrix material,and the bonding strength of the composite made with aluminum alloy treated with silane was 17.40 MPa.The tensile shear strength test showed that the strength of the composite parts treated with 4%KH550 was the best,reached 21.02 MPa,and the strength showed a trend of increased first and then decreased.SEM morphology analysis showed that the resin drilling was the best when treated with 4% KH550.The failure was a combination of cohesive failure and interface failure.Through EDS and XPS elemental analysis,with the increase of silane concentration,the interface silicon element diffuses significantly,and XPS measures the formation of stable Al-O-Si at the interface when 4% KH550 was treated,Al-O-C,(C=O)-NH chemical bonds.The joining mechanism of the composite parts was physical riveting and chemical joining,and the failure mode was mixed failure4.Structure and properties of PC/silane/aluminum alloy composite partsWhen polar-resin polycarbonate(PC)was used as resin matrix,the tensile shear strength of aluminum alloy without silane treatment was 10.6 MPa.For aluminum alloy treated with silane,the bonding strength of composite parts increased first and then decreased with the increased of silane concentration,and reached the maximum bonding strength of 17.80 when treated with 4%KH550.SEM analysis showed that the resin penetrates the best when 4% KH550 was treated,and the interface failure was mixed failure;Through EDS and XPS elemental analysis,the interface elements diffuse obviously,formed stable Al-O-Si,Al-O-C,(C=O)-NH chemical bond.Finally,the connection mechanism was still physical riveting and chemical connection.To sum up,By adding Polypropylene grafted with maleic anhydride(PP-g-MAH)modified polar group or the active group on the selected polar resin to react with the silane coupling agent,the bonding strength of the composite parts can be effectively enhanced.At the same time,the micro-nano structure on the surface of the aluminum alloy provided a certain proportion of physical riveting for composite parts,so as to achieve the purpose of synergistic enhancement of physical riveting and chemical connection of composite parts.