Influence of Modification on the ABS Plastics Using Atmospheric UV Irradiation as Plating Pretreatment

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1 Journal of Materials Science and Engineering B 7 (11-12) (2017) doi: / / D DAVID PUBLISHING Influence of Modification on the ABS Plastics Using Atmospheric UV Irradiation as Plating Pretreatment Yuki Nakabayashi 1,2, Yasushi Umeda 2,3, Katsuhiko Tashiro 2,3, Hideo Honma 2 and Hiroaki Kozai 3,4 1. Graduate School of Engineering, Kanto Gakuin University, Mutsurahigashi , Kanazawa-ku, Yokohama, Kanagawa, Japan 2. Materials and Surface Engineering Research Institute, Kanto Gakuin University, Ogikubo , Odawara, Kanagawa, Japan 3. Kanto Gakuin University Research Advancement and Management Organization, Mutsurahigashi , Kanazawa-ku, Yokohama, Kanagawa, Japan 4. College of Science and Engineering, Kanto Gakuin University, Mutsurahigashi , Kanazawa-ku, Yokohama, Kanagawa, Japan Abstract: Plating on the plastic is one of the important technologies to decorate exterior automotive parts and electronic devices. Conventionally, etching solution contained carcinogen hexavalent chromium obtained high adhesion strength between metal film and plastic surface to decorative the plating. On the other hand, health damage and environmental pollution from waste etching solution are occurring. For the above reasons, development of chromium free pretreatment is an urgent problem to solve this issue. In this study, we concentrated the environmentally friendly surface modification process in which atmospheric UV treatment was used to investigate effect of surface morphology and state on the ABS (acrylonitrile butadiene styrene) plastic. As a result, morphology of ABS surface was kept smooth after UV irradiation treatment. The conversion from hydrophobic to hydrophilic on the ABS surface state was confirmed by contact angle test and FT-IR spectra. Moreover, it was confirmed that appropriate amount of oxidation was necessary for metal plating on the ABS plastic, in order to obtain high adhesion strength between metal film and plastics surface. Key words: Atmospheric UV treatment, surface modification, ABS plastic, plating pretreatment. 1. Introduction ABS plastics have been widely used in various fields because it has excellent properties such as workability, impact resistance and dimensional stability. Deposited metal plating on ABS plastics surface is utilized to increase the weather resistance and impart metallic luster. By conventionally plating method, chromic acid-sulfuric acid mixed solutions are applied to improve the high adhesion strength between metal plating layer and plastic surface [1, 2]. However, heavy risk of environmental pollution occurs because of the including carcinogen hexavalent chromium in plating process. Therefore, it should remove the hexavalent chromium from plating process [3, 4]. Corresponding author: Yuki Nakabayashi, Ph.D. student, research fields: plating and surface modification. In recent years, there were many reports about the substitute methods of etching without chromic acid to the plating pretreatment on plastic materials [5-8]. Previously, we achieved the possibility to high adhesion strength between metal plating and smooth surface on the plastic materials using atmospheric UV treatment [9, 10]. This process was the formation of surface modification layer on the plastics surface for plating pretreatment. The moderate modification layer was effective to achieve the result of high adhesion strength between metal plating and plastics surface. In this study, atmospheric UV treatment was applied as a pretreatment on ABS plastics for metal plating. We confirmed that the effect of surface modification layer on the ABS plating achieved the high adhesion strength of metal plating. In addition, we were comparing the surface condition on the different type ABS plastic materials modified by

2 Influence of Modification on the ABS Plastics Using Atmospheric UV Irradiation as Plating Pretreatment 273 atmospheric UV treatment method. 2. Experimental Methods 2.1 Substrates The samples used commercial type ABS plastics that were SUNLOID EAR003 (ABS-S, Sumitomo Bakelite Co., Ltd. Japan), HISHIPLATE Y-268 (ABS-H, Mitsubishi Chemical, Inc., Japan), and UMG 3001M (ABS-U, UMG ABS, Ltd. Japan). 2.2 Surface Modification and Plating Procedures The equipment used for surface modification was low pressure mercury vapor lamp (KOL1-300S, Koto Electric Co., Ltd. Japan) that emitted with a wavelength of 185 nm and 254 nm. The distance between UV lamp and ABS surface was set to 30 mm. Table 1 shows the plating procedure of the ABS plastics. Heat treatment was performed before and after UV irradiation. Moreover, alkaline treatment and conditioning were immersed to improve the absorption amount of catalyst. Palladium ion performed absorption on the surface as the catalyst for electroless plating. After the accelerating step, ABS plastics were immersed to electroless Ni-P plating bath for 5 min. The thickness of Ni-P plating film was deposited about 0.2 µm on the surface. Finally, copper film 20 µm thickness was deposited on the Ni-P film using electro copper sulfate acid bath as the current density 3 A/dm 2 under room temperature. Composition of copper sulfate acid bath contained 0.3 mol/l of copper sulfate and 1.8 mol/l of sulfuric acid. Moreover, plating additives used commercial type CUBRITE-21 and STB (JCU Co., Japan). 2.3 Evaluation of Adhesion Strength The copper plating film was cut with 10 mm width for peeling tests. In order to investigate the adhesion strength of plating film on the ABS surface, universal testing machine (Strograph E2-L05 Toyo Seiki Seisaku-sho, Ltd. Japan) was used. In addition, the average of adhesion strength was calculated from 3 times measurement in each sample. 2.4 Characterization Before and after the atmospheric UV treatment, the surfaces were observed by SEM (Scanning Electron Microscopy, Quanta 3D 200i, FEI Inc., USA) and SPM (Scanning Probe Microscopy, E-sweep, Seiko Instruments Inc. Japan) to examine the surface morphologies of the each sample. To obtain topographic images of the ABS plastics, SPM was operated in AFM (Atomic Force Microscopy) mode. In addition, the arithmetic average roughness (Ra) and 10 points average roughness (Rzjis) were measured in an area of 10 µm square. The AFM cantilever used a standard contact mode type (SI-AF-01, Seiko Instruments Inc. Japan). Table 1 Experimental procedure. Atmospheric UV treatment Alkaline treatment,65 C, 3 min (NaOH 50 g/dm 3 ) Conditioning, 45 C, 2 min (CC vol%, ROHM and HAAS) Catalyzing, 45 C, 5 min (PdCl g/dm 3 ) Accelerating, 45 C, 1 min (NaH 2 PO 2 H 2 O 35 g/dm 3 ) Electroless Ni-P plating, 0.2 μmt Electro Cu plating, 20 μmt : Rinsing : No rinse

3 274 Influence of Modification on the ABS Plasticss Using Atmospheric UV Irradiation as Plating Pretreatment The surface analysis of wettability was applied by the water contact angle measurement in which it was measured by automatic contact angle meters (DMe-201, Kyowa Interface Science Co., Ltd. Japan) with fixed water droplet size of 1.0 µl. Surface functional groups were analyzed using Fourier Transform Infrared Spectroscopy (FT-IR, FT/IR4100, JASCO Co., Japan) equipment fitted with ATR diamond prism (PKS-D 470 with ATR PRO450-S, JASCO Co., Japan). The measurement range of wave number was defined 4,000 cm -1 to 1,000 cm -1. Moreover, for comparison with amount of carbonyl production, carbonyl index value was used. The carbonyl index was calculated as the ratio of the carbonyl band at 1,715 cm -1 and nitrile group band at 2,240 cm -1 respectively [ 11]. Oxidation states among the samples were compared and analyzed by CL (chemical luminescence) intensity. The CL intensity measurements used Chemiluminescence analyzer (CLA-SF4 Tohoku Electronics Industry Co., Ltd., Japan) 5 min continuously under N 2 at 160 C in a sample chamber. ABS-H obtained the highest adhesion strength over 1.0 kn/m. The other two types of ABS-SS and ABS-U showed maximum adhesion strength of about 0.7 kn/ /m by atmospheric UV treatment Moreover, we UV treatment time. confirmed that the change of the adhesion strength was not constant with increasing 3.2 Observation of Surface Morphology for 1 min. 2 showss SEM images before and after the surfaces modified by atmospheric UV treatment. The surfaces morphologies were confirmed that fine dimples were scattered before and after atmospheric UV treatment ABS plasticss surfaces [12, 13]. The surface morphology showed a little change before and after atmospheric UV treatment observation by SEM images. 3 shows AFM images before and after the 3. Results and Discussion 3.1 Influencee of Adhesion Strength by Atmospheric UV Treatment In order to quantitatively evaluate adhesion strength between the metal plating layer and ABS plastics quantitatively, peel test was used. 1 showss the effect of UV treatment time on the adhesion strength with the copper film on the various ABS plastics. Electroless Ni-P plating film was deposited on the untreated ABS plastics confirmed by visual. However, adhesion strength of untreated ABS plastics could not be measured because deposited metal film was blister after sulfuric copper plating. This reason was perhaps that untreated surface didd not have modification layer to obtain adhesion strength. When UV treated ABS plastics, it was possible to measure adhesion strength between metal film and plastic surface. There were three types of commercial materials, among them 1 Effect of UV treatment time to the adhesion strength with the copper film on the various ABS plastics. 2 SEM images of the ABS plastic surface. (a) Untreated of ABS-S, (b) Untreated of ABS-H, (c) Untreated of ABS-U, (d) After UV treatment 1 min of ABS-S, (e) After UV treatment 1 min of ABS-H, (f) After UV treatment 1 min of ABS-U.

4 Influence of Modification on the ABS Plasticss Using Atmospheric UV Irradiation as Plating Pretreatment 275 surfaces modified by atmospheric UV treatment. Untreated ABS plastics surfaces were smooth topographic images as with SEM images. After atmospheric UV treatment, increasing and decreasing in arithmetic average roughness (Ra) and 10 points average roughness (Rzjis) were -3.9 nm to 1.7 nm and nm to 10.5 nm, respectively. The changes of nanoscale surface properties were very smooth. It was suggested that adhesion strength of metal plating was obtained without micro anchor effect. Therefore, surface morphology by atmospheric UV treatmentt had lesser impact on adhesion strength and before and after the UV treatment, the surface roughness was not almost changed. 3.3 Characteristic of Surface State 4 shows that it depends on atmospheric UV treatment time to the water contact angle measurement on the ABS plastics. The surface states on the ABS plastics were hydrophobic without the atmospheric UV treatment, and the water contact angles of ABS-S, ABS-H and ABS-U were 82.3, 85.7 and 86.2, respectively. The water contact angle of ABS-T was greatly decreased at UV 1 min and it was more affected by atmospheric UV treatment than other samples. These results showed that surface wettability properties arose throughh the presence of hydrophilic group by using atmospheric UV treatment. Moreover, ABS plastics showed the similar result of wettability at UV 10 min, water contact angle becomes in the vicinity We confirmed that UV modified ABS plastics has lower limit of water contact angle. 5 shows measurement of the FT-IR spectra results on the ABS-S with different atmospheric UV treatment time. After atmospheric UV treatment, the IR spectra showed adsorption bands of carbonyl group at 1,715 cm -1 and hydroxyl group at 3,300 cm -1. The above functional groups were increased with increasing UV treatment time [8]. It was confirmed that the other two types of ABS-H and ABS-U had similar spectra of above result from 0 min to 5 min treated. However, FT-IR spectra from UV treatmentt time of 10 min had the different result for carbonyl group. For the above reason, carbonyl index was calculated from FT-IR spectra and compared with each sample. 3 AFM images of the ABS plastic surface. (a) Untreated of ABS-S, (b) Untreated of ABS-H, (c) Untreated of ABS-U, (d) After UV treatment 1 min of ABS-S, (e) After UV treatment 1 min of ABS-H, (f) After UV treatment 1 min of ABS-U. 4 Dependence of atmospheric UV treatment time on the water contact angle measurement on the ABS plastic. 5 FT-IR spectra of the ABS-S surface before and after UV treatment.

5 276 Influence of Modification on the ABS Plastics Using Atmospheric UV Irradiation as Plating Pretreatment 6 shows relation between the atmospheric UV treatment time and the carbonyl index. The values of the carbonyl index on the ABS-S were maximum value after UV treated 5 min and it was decreased when UV treated 10 min. For that reasons, carbonyl group at 1715 cm -1 was shifted to the low wave number in ABS-S. Moreover, there was the difference in the value of the adhesion strength in each sample, but the increase rate of the carbonyl index was almost the same. Therefore, surface hydrophilic groups were necessary for plating on the ABS plastics and it was uncertain to correlate with the density of adhesion strength. 7 shows relation between the total CL intensity on the various ABS plastics. The amount of chemical luminescence was emitted from degraded peroxide and it was arranged by descending order ABS-S, ABS-H and ABS-U respectively. As the above results, amount of carbonyl index was not too much difference, but we confirmed that each sample had obvious difference for CL intensity. We considered that oxidized butadiene component and amount of oxidation inhibitor of additives in ABS plastics influenced chemical luminescence species. For above reasons, ABS-S was susceptible to oxidation and ABS-U was insusceptible to oxidation in these three materials. It was suggested that for ABS-U there existed less butadiene on the surface or contained more oxidation inhibitor of additives than other samples [14]. On the other hand, amount of chemical luminescence intensity of ABS-H was intermediate value between ABS-U and ABS-T. At the same time, it was suggested that surface state was becoming sufficient oxidation for modification by using atmospheric UV treatment. Therefore, for the above results, ABS-H was suitable for UV surface modification process and it obtained high adhesion strength between metal plating and plastic. Moreover, it was possible that appropriate amount of oxidation was necessary for metallization on the ABS plastics. 6 Relation between the atmospheric UV treatment time and the carbonyl index. 7 Relation between the total CL intensity and the various ABS plastics. 4. Conclusions The surface roughness of ABS plastics was changed by nanometer scale before and after UV treatment. For this reason, surface morphology by atmospheric UV treatment has lesser impact on adhesion strength between plating metal film and ABS plastics. Carbonyl group of all samples was increased with increasing atmospheric UV treatment time. Therefore, the change in surface state from hydrophobic to hydrophilic was attributed to appear of polar functional groups. However, approximately there was not too much difference in increasing rate of carbonyl index each sample after atmospheric UV treatment. We considered that oxidized butadiene component and amount of oxidation inhibitor of additives in ABS plastics were influenced to oxidation degree of deterioration. Moreover, in order to form high adhesion strength plating on the ABS plastics, it was necessary to have appropriate amount of oxidation state. For above reasons, while maintaining the

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