Study On PA-6/304 Stainless Steel Micro-Nano Pressing Integration Technology

As the lightweight and low VOC(volatile organic compounds)emissions of traffic and transport instrument have been proposed,more and more researchers pay attention to the integration molding of plastic and metal without bonding agent.The principle of micro mechanical interlock structure formation between plastic interface and metal nano holes layer was used in this paper,PA-6/304 stainless steel micro-nano pressing integration technology MNPT(Micro Nano Pressing Technology)was explored.304 stainless steel is easy to form pitting corrosion with halogen ions,the stainless steel surface treating fluid formula was controlled and optimized,eventually,the stainless steel surface generated nano holes layer which the pore size is 70-120 nm,hole depth is about 100 nm,hole distribution density is about 100 holes per square micron,specific surface area is 14.78%(before chemical etching specific surface area is 2.23%).The pressing die and plastic-metal lap test specimen was designed,the polymer surface melt flow into the metal surface nano holes layer in advance through controlling the parameters such as temperature,pressure and holding time,finally the micro mechanical interlock structure produced between the plastic and metal interface,so that micro-nano pressing integration was successfully implemented.Lapping experiments was finished which was conducted between each of polypropylene(PP),polycarbonate(PC),Poly Acrylonitrile-butadiene-styrene(ABS),nylon-6(PA-6),polyphenylene sulfide(PPS)the five kinds polymer and each of 304 stainless steel treated by mechanical polishing(P-304),304 stainless steel treated by mechanical polishing+chemical etching(P/E-304),304 stainless steel treated by mechanical polishing+chemical etching+annealing(P/E/A-304)the three kinds 304 stainless steel of process,the results showed that PA-6 and PPS can realize MNPT requirements.Dynamic rheological properties experiments showed that the dynamic rheological rules varied widely between PA-6,PPS the two kinds polymer and the other three ones within the pressing shear frequency 1-10rad/s,the analysis suggests that storage modulus,loss modulus,loss factor and complex viscosity of polymer melt vary from different ones,the differences may reflect the capacity of polymer chain motioning and freezing in the micro-channel which largely determines polymer whether meet the MNPT demands.The Differential Scanning Calorimetry(DSC)experimental results of PP,PC,ABS,PA-6 and PPS was contrast analyzed,it was found that polymer crystallizing contribute to molecular chain delay glasstransition in the micro-channel with the movement,namely the interface formed between polymer surface and metal nano holes layer is easy to produce micro mechanical interlock structure within certain conditions.Lap specimen tensile shear test results showed that the maximum tensile shear strength of lap joint of PA-6 bonded with P-304(P-SSN6)which served a contrast was 3.56 MPa,the maximum fracture work shown 3.14 KJ/m2;the maximum tensile shear strength of the lap joint of PA-6 bonded with P/E-304(P/E-SSN6)reached to 11.02 MPa,increased by 214%,the maximum fracture work got to 16.65 KJ/m2,increased by 430%;the maximum tensile shear strength of the lap joint of PA-6 bonded with P/E/A-304(P/E/A-SSN6)reached to 18.9MPa,increased by 431%,the maximum fracture work got to 31.29 KJ/m2,increased by896%.The surfaces of P/E-304,P-304 and P/E/A-304 were progressive characterized by Confocal Laser Scanning Microscope(CLSM),Scanning Electron Microscope(SEM)and Atomic Force Microscope(AFM),experiments of SEM and AFM to the failure interfaces of P-SSN6,P/E-SSN6 and P/E/A-SSN6 were conducted,the morphology showed that the P-SSN6 presented mainly adhesion failure,P/E-SSN6 displayed primary adhesive and cohesive mixed failure,the central failure of P/E/A-SSN6 is cohesive invalidation mode.Fourier Transform Infrared spectrum(FTIR)experiments showed that the-NH2 of PA-6 is likely to form chemical bonds with the nano hole surface oxide layer of P/E-304 and P/E/A-304,and the reason that PA-6 was bonded with P-304 is just physical adsorption.Energy Dispersive X-ray(EDX),Laser Raman spectroscopy(LRS)and X-ray diffraction(XRD)experiments further confirmed that the interface between PA-6 and P-304 results form mainly physical adsorption,the micro mechanical interlock structure greatly contributes to the interface between PA-6 and P/E-304,and the interface between PA-6 and P/E/A-304 is central caused by the micro mechanical interlock structure and chemical bonds together.Contact Angle results showed that the surface wettability of P-304,P/E-304 and P/E/A-304 reduced in turn.In conclusion,nano hole layer of 304 stainless steel surface was successful fabricated.With 304 stainless steel of different processing,the lap joint with PA-6 specimen tensile shear strength increased significantly,the mechanism why PA-6 and PPS satisfy the requirement of MNPT was analyzed,surface characterization of the P-304,P/E-304 and P/E/A-304 were completed,as well as the comparison characterization of failure interface of P-SSN6,P/E-SSN6 and P/E/A-SSN6 were implemented,and the adhesion mechanism between PA-6 and 304 stainless steel of different treatment processing was comprehensive analyzed.