Metallization Of Poly Ether Ether Ketone And Its Multi-walled Carbon Nanotubes Composites

Poly(ether ether ketone)(PEEK)has a high volume resistivity and surface resistance.Though they could be decreased by incorporation of carbon nanotubes,the volume resistivity and surface resistance were still much higher than metal.This restricts their use in some electronic fields,such as electromagnetic interference shielding.In this research,we used PEEK and Poly(ether ether ketone)/multiwalled carbon nanotubes(PEEK/MWCNT)composites as substrate materials.PEEK and PEEK/MWCNT were pretreated by environmentally friendly chemical etching method.Ni-P and Cu were deposited on the surface of PEEK and PEEK/MWCNT by three different processes.The main contents of this research as follows:(1)Noble metal Pd as catalyst induced the electroless Ni-P plating.The surface morphology of PEEK/MWCNT was sensitive to the concentration of H2SO4.An interconnected micro-pores structure can be formed on the surface,only when the H2SO4 concentration was higher than 90wt%.In swelling treatment,temperature,time and sonication had little effect on the surface morphology.The swelling ratio of both the PEEK/ MWCNT and PEEK samples increased with the increase of the swelling time.However,for the same swelling time,the swelling ratio of the PEEK/MWCNT composite was smaller than that of PEEK.The surface roughness increased significantly after swelling treatment.The etching effect of MnO2-NaH2PO4-H2SO4 system was stronger than that of MnO2-H2SO4 system.With the increasing of etching time,the interconnected micro-pores structure was destroyed gradually and MWCNT was exposed on the surface.After etching by MnO2-NaH2PO4-H2SO4 system for 5min,not only were interconnected micro-pores structure and partially exposed MWCNT obtained but also the percentage of hydrophilic groups on the surface was increased.The roughness of the etched samples was a little smaller than that of the swelled samples,but it was still much higher than that of original samples.After electroless plating,Ni-P alloy was embedded in the micro-pores structure and direct contact with the exposed MWCNT.An interconnected anchorage effect was formed between the substrate and Ni-P coating with a cauliflower structure.The volume resistivity in direction of thickness was decreased rapidly after electroless deposition.And the sheet resistance decreased with increasing the plating time.The adhesion of the coating reached the highest 5 B scale(ASTM D3359).(2)Sodium borohydride(Na BH4)induced the electroless plating directly.NaBH4 was directly absorbed on the wall of the interconnected micro-pores formed by swelling PEEK/MWCNT composites surface,and then the dried composites were put into electroless Ni-P plating bath.NaBH4 reduced the Ni2+ ions in the electroless plating bath to Ni0 species in situ and simultaneously the Ni0 initiated the electroless Ni-P plating.Almost no induction period was observed.Once the pretreated sample was put into Ni-P plating bath,the deposition of Ni-P was started.With the increase of temperature,the deposition rate was increased and the sheet resistance was decreased.At the same temperature,the sheet resistance decreased with increasing the plating time.The volume resistivity in direction of thickness was decreased by six orders of magnitude after electroless Ni-P deposition.The adhesion of the Ni-P coating reached the highest 5 B scale(ASTM D3359)because of the interconnected anchorage effect.In electroless copper plating,NaBH4 absorbed on surface of PEEK/MWCNT reduced Cu2+ to Cu0 in situ and the Cu0 as catalyst initiated the electroless copper plating.The volume resistivity in direction of thickness was decreased by six orders of magnitude after electroless copper plating.The sheet resistance decreased with increasing the plating time.The adhesion of the copper coating reached the highest 5 B scale(ASTM D3359).(3)Ni and Cu as catalyst induced the electroless Ni-P and Cu plating respectively.To avoid NaBH4 into the plating bath and ensure the stability of the plating process,Ni and Cu catalysts were adhered on the surface in advance.After swelling treatment,a regular porous network layer at the micron scale was produced on the surface of PEEK and PEEK/MWCNT.The swelling treatment made the surface rough and increased the surface area.After sonicating,part of the swelling layer where the strength was relatively weak was removed and the regular porous network morphology changed into irregular micro/nano porous structure.And the surface area increased further.The water contact angle was increased after swelling treatment.What's more,compared with the swelled samples,it was increased significantly by sonicating treatment(>125°).In this study,the sonicated samples were put into a NaBH4-NaOH solution followed by blow-drying.Then the dried samples were immersed into NiSO4 solution.In this process,the BH4-reacted with the Ni2+ to form Ni0.Both the size and the number of Ni0 particles on the sonicated surface were a little bigger than that on the swelled surface.The Ni0 initiated the electroless Ni-P plating.The deposition rate on the sonicated surface was slightly higher than that on the swelled surface.The adhesion of the Ni-P coating deposited on the sonicated surface(4.3 MPa)was much higher than that deposited on the surface only with swelling treatment.The addition of MWCNT in PEEK didn't improve the adhesion of Ni-P coating and even decreased the adhesion a little.For PEEK/MWCNT,the volume resistivity in direction of thickness was decreased by six orders of magnitude after electroless Ni-P deposition.However,for PEEK,the volume resistivity in direction of thickness was increased by one order of magnitude after electroless Ni-P deposition.When NaBH4 absorbed samples were put into the CuSO4 solution,the BH4-reacted with the Cu2+ to form Cu0 and the Cu0 as catalyst initiated the electroless copper plating.With the increase of NaBH4 concentration in pretratment,the Cu0 catalysts gradually changed from small spherical particles to large polyhedral particles and the content of Cu0 catalysts increased.The deposition rate of copper coating was increased and the sheet resistance of copper coated composite was decreased with the increase of NaBH4 concentration in pretratment.For PEEK/MWCNT,the volume resistivity in direction of thickness was decreased by six orders of magnitude after electroless copper plating.The adhesion of the copper coating reached the highest 5 B scale(ASTM D3359).(4)The pretreatment of PEEK by wet chemistry and its effect on the surface morphology were studied.The effects of sulfuric acid concentration in swelling treatment,solution temperature in cleaning treatment,the kind and concentration of cleaning solution on the surface morphology of PEEK were studied.Through controlling those influential factors,the PEEK with different surface morphology(holes' structure,density and wall thickness)was obtained.This is helpful for further studying the combination of PEEK with metal coating,bone,resin and other materials.