{"id":8450,"date":"2026-05-26T09:00:00","date_gmt":"2026-05-26T08:00:00","guid":{"rendered":"https:\/\/uplastech.com\/silicone-surface-treatment\/"},"modified":"2026-11-02T02:28:01","modified_gmt":"2026-11-02T02:28:01","slug":"silicone-surface-treatment","status":"publish","type":"post","link":"https:\/\/uplastech.com\/ja\/silicone-surface-treatment\/","title":{"rendered":"Silicone Surface Treatment: Plasma, Corona and Printability"},"content":{"rendered":"<style>\n.upl-blog{font-size:17px;line-height:1.78;color:#1f2937}\n.upl-blog p{margin:0 0 18px}\n.upl-blog h2{font-size:26px;line-height:1.3;color:#0b2b33;margin:46px 0 14px;font-weight:700;letter-spacing:-.015em}\n.upl-blog h3{font-size:19.5px;color:#0d3b47;margin:28px 0 10px;font-weight:700}\n.upl-blog ul,.upl-blog ol{margin:0 0 20px;padding-left:22px}\n.upl-blog li{margin:0 0 9px}\n.upl-blog figure{margin:0 0 34px}\n.upl-blog figure img{width:100%;height:auto;display:block;border-radius:10px}\n.upl-blog figcaption{font-size:13px;color:#6b7280;margin-top:10px;line-height:1.5}\n.upl-blog .toc{background:none;border:0;border-radius:0;padding:0;margin:0 0 34px}\n.upl-blog .toc .lwptoc{margin:0}\n.upl-blog .toc h4{margin:0 0 10px;font-size:13px;letter-spacing:.1em;text-transform:uppercase;color:#0d5563}\n.upl-blog .toc ol{margin:0;padding-left:18px;font-size:14.5px}\n.upl-blog .toc li{margin-bottom:6px}\n.upl-blog table{width:100%;border-collapse:collapse;font-size:14.5px;margin:0 0 10px}\n.upl-blog th{background:#0d3b47;color:#fff;text-align:left;padding:11px 13px;font-weight:600;font-size:13.5px;border:0}\n.upl-blog td{padding:11px 13px;border:0;border-bottom:1px solid #e8ebed;vertical-align:top}\n.upl-blog tbody tr:nth-child(even){background:#fafbfc}\n.upl-blog .tablecap{font-size:12.5px;color:#6b7280;margin:0 0 30px}\n.upl-blog .myth{background:#fff8ef;border:1px solid #f6ddbd;border-radius:8px;padding:16px 20px;margin:0 0 26px;font-size:15.5px}\n.upl-blog .myth b{color:#a85c10}\n.upl-blog .callout{background:#f2f8f9;border-radius:8px;padding:18px 22px;margin:0 0 26px;font-size:15.5px;border-left:3px solid #14707f}\n.upl-blog .faq h3{border-top:1px solid #eceff1;padding-top:22px;margin-top:0;font-size:18px}\n.upl-blog .faq h3:first-of-type{border-top:0;padding-top:0}\n.upl-blog .cta{background:linear-gradient(135deg,#0b2b33,#0d5563);color:#fff;border-radius:12px;padding:34px;margin:48px 0 30px}\n.upl-blog .cta h2,.upl-blog .cta .cta-h{color:#fff;margin:0 0 10px;font-size:24px;font-weight:700;line-height:1.3}\n.upl-blog .cta p{color:#c9dee3;margin:0 0 20px;font-size:16px}\n.upl-blog .btn{display:inline-block;background:#e07a1f;color:#fff;text-decoration:none;font-weight:700;padding:13px 26px;border-radius:8px;font-size:15.5px}\n.upl-blog .rel{border-top:1px solid #e8ebed;margin-top:40px;padding-top:26px}\n.upl-blog .rel h4{font-size:13px;letter-spacing:.1em;text-transform:uppercase;color:#6b7280;margin:0 0 14px}\n.upl-blog .rel ul{list-style:none;padding:0;margin:0}\n.upl-blog .rel li{padding:11px 0;border-bottom:1px dashed #e8ebed}\n.upl-blog .rel a{text-decoration:none;font-weight:600;font-size:15.5px}\n@media(max-width:640px){.upl-blog h2{font-size:22px}.upl-blog table{font-size:13px}.upl-blog .cta{padding:24px}}\n\/* \u5355\u7bc7\u9875\u9690\u85cf WhatsApp \u95ee\u5019\u5361\uff0c\u53ea\u4fdd\u7559\u5706\u5f62\u6c14\u6ce1\uff0c\u907f\u514d\u906e\u6321\u4fa7\u680f\u8be2\u76d8\u63d0\u4ea4\u6309\u94ae\u3002\n   \u6ce8\u610f\uff1aClick to Chat \u7684\u70b9\u51fb\u903b\u8f91\u662f\u300c\u95ee\u5019\u5361\u5143\u7d20\u5b58\u5728\u5c31\u4e0d\u8df3\u8f6c\u300d\uff0c\u53ea\u9760 CSS \u9690\u85cf\u4f1a\u8ba9\u6c14\u6ce1\u53d8\u6210\u6b7b\u94fe\u63a5\u3002\n   Code Snippets #9\u300cUPL single post: WhatsApp bubble jumps straight to chat\u300d\u8d1f\u8d23\u628a\u8be5\u8282\u70b9\u4ece DOM \u79fb\u9664\uff0c\n   \u4e0b\u9762\u8fd9\u6761 CSS \u53ea\u662f\u79fb\u9664\u524d\u7684\u89c6\u89c9\u515c\u5e95\u3002\u5220 #9 \u524d\u5fc5\u987b\u5148\u5220\u8fd9\u6761\u89c4\u5219\u3002 *\/\nbody.single-post .ht_ctc_chat_greetings_box{display:none !important}\n<\/style>\n<div class=\"upl-blog\">\n<figure>\n<img fetchpriority=\"high\" decoding=\"async\" src=\"https:\/\/uplastech.com\/wp-content\/uploads\/2026\/11\/silicone-surface-treatment.jpg\" alt=\"A technician in a grey apron holding a handheld plasma nozzle over a tray of black silicone O-rings, with a faint violet glow at the tip\" width=\"1536\" height=\"909\"><figcaption>Two seconds of plasma takes the contact angle from 112 degrees to 24. Holding it there is the harder part.<\/figcaption><\/figure>\n<div class=\"toc\"><\/div>\n<h2 id=\"why\">Why nothing sticks to silicone<\/h2>\n<p>Silicone surfaces sit at around 20 to 24 mN\/m surface energy, against 35 to 45 for most thermoplastics and 72 for water. Ink, adhesive and coating formulations are designed to wet surfaces in the thirties and forties. On silicone they do not wet at all, they bead, and a bead that does not wet cannot form a bond.<\/p>\n<p>The chemistry behind that number is the methyl groups on the polymer backbone. A cured silicone surface presents a dense layer of -CH3 groups, which are non-polar and have very little capacity for hydrogen bonding or dipole interaction. There is nothing for an adhesive to grab.<\/p>\n<p>There is a second problem that catches people out: silicone is a release material by nature. Even a formulation that wets the surface will often fail to bond, because the low surface energy means the adhesive cannot achieve the mechanical interlocking that carries most of the load in a joint. Activation has to create both a chemically receptive surface and a physically roughened one.<\/p>\n<p>This is why silicone is chosen for gaskets and why the same property makes it difficult to print. The property that makes the material useful is the property that makes it hard to decorate, and no additive fully resolves the conflict.<\/p>\n<h2 id=\"plasma\">What plasma actually does to the surface<\/h2>\n<p>An atmospheric plasma is a partially ionised gas at close to room temperature. When it touches a silicone surface, the energetic species in the discharge break Si-CH3 bonds and replace the methyl groups with silanol, carbonyl and hydroxyl groups. The surface becomes polar, and the surface energy rises.<\/p>\n<p>The change is confined to the top few nanometres. That is enough to change wetting and bonding, and it is also why the treatment is easy to overdo: a long exposure does not create a thicker activated layer, it starts to abrade and to create a weak boundary layer of low molecular weight debris that fails cohesively.<\/p>\n<p>The chart on the left is measured on a 60 Shore A silicone sheet. Untreated, the water contact angle is 112 degrees. Two seconds of air plasma brings it to 24 degrees, which is a fully wetting surface. Longer treatment barely improves it, and beyond about eight seconds the angle starts to climb again as the surface roughens and oxidises further.<\/p>\n<p>The practical implication is that plasma treatment is fast and that the process window is wide on the fast side and narrow on the slow side. There is no benefit to a longer dwell, and there is a real penalty in surface damage.<\/p>\n<h2 id=\"corona\">Corona and flame: cheaper, less even<\/h2>\n<p>Corona treatment uses a high voltage discharge between an electrode and a grounded roll. It works well on thin film because the film can be run through the gap at a controlled distance. On a three dimensional silicone part it is much less effective, because the discharge concentrates on the nearest surface and the rest of the part sees very little.<\/p>\n<p>Flame treatment passes the part through a gas flame, usually with a lean mixture and a high excess of oxygen. It works on complex shapes because the flame wraps around them, but it also heats the part, and silicone has a low thermal conductivity, so the surface can reach temperatures that cause depolymerisation and a chalky residue.<\/p>\n<p>On the same sheet, five seconds of corona brings the contact angle to about 48 degrees and flame to about 58. Both are below the 40 degree threshold that most inks need for reliable wetting only after longer treatment, and neither reaches the 24 degrees that plasma achieves in two seconds.<\/p>\n<p>The choice is therefore not about which is better in the abstract. Corona suits continuous film and simple profiles at high speed. Flame suits complex shapes where a robot can follow the contour. Plasma suits parts that need the highest surface energy with the least thermal load, which in practice means most precision silicone components.<\/p>\n<h2 id=\"ageing\">The ageing problem<\/h2>\n<p>Activated silicone does not stay activated. The polar groups created by the treatment are mobile, and the polymer chains rearrange to bury them below the surface. Over hours to days the contact angle climbs back towards its original value, and the bond strength falls with it.<\/p>\n<p>The right hand chart shows the decay measured on plasma treated sheet stored in a clean, dry room at 22 C. Bond strength is still 92 percent after one day, 78 percent after three days, 61 percent after a week, and 31 percent after a month. The 70 percent line is crossed somewhere between day three and day seven.<\/p>\n<p>Storage conditions change the rate. Heat accelerates the recovery. Humidity slows it slightly but introduces a different problem, because water adsorbed onto a polar surface competes with the adhesive. Handling is the worst offender: skin oils transfer onto the activated surface and block the sites the adhesive needed.<\/p>\n<p>The production rule that follows is simple and often ignored: treat immediately before the next operation, not at the end of the moulding shift. A batch treated on Friday and printed on Monday has lost more than half its bond strength before it reaches the press.<\/p>\n<figure>\n<img decoding=\"async\" src=\"https:\/\/uplastech.com\/wp-content\/uploads\/2026\/11\/silicone-surface-treatment-chart.jpg\" alt=\"Contact angle falling from 112 degrees to 24 degrees in two seconds of plasma treatment, and bond strength decaying from 100 percent to 31 percent over 30 days\" width=\"1536\" height=\"909\"><figcaption>Left: contact angle against treatment time for three methods. Right: how fast the activated surface loses its bond strength.<\/figcaption><\/figure>\n<h2 id=\"measure\">Measuring the treatment, not guessing<\/h2>\n<p>The only reliable way to know whether a surface is ready is to measure it. A dyne pen is the cheapest option: a felt pen filled with a liquid of known surface tension, drawn across the surface. If the line holds for three seconds without beading, the surface energy is at least that value. Pens come in 30, 34, 38, 42 and higher, and a 38 pen is a reasonable pass criterion for most inks.<\/p>\n<p>A contact angle goniometer is more precise and costs a few thousand euro. A 2 microlitre water drop on the surface, photographed against a backlight, gives an angle in seconds. Below 40 degrees is printable, below 25 is good for structural bonding. The instrument pays for itself the first time it stops a batch of parts being printed on an untreated surface.<\/p>\n<p>Whatever method is used, it has to be applied to the part, not to a test coupon. Plasma density varies with distance from the nozzle and with the geometry of the part, and a coupon treated at the nozzle centre tells you nothing about a shadowed face on a real component.<\/p>\n<table>\n<thead>\n<tr>\n<th>\u65b9\u6cd5<\/th>\n<th>Contact angle reached<\/th>\n<th>Time to reach it<\/th>\n<th>\u6700\u9069<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Atmospheric plasma, air<\/td>\n<td>20 to 25 deg<\/td>\n<td>1 to 3 s<\/td>\n<td>Precision parts, bonding, printing<\/td>\n<\/tr>\n<tr>\n<td>Atmospheric plasma, argon<\/td>\n<td>18 to 22 deg<\/td>\n<td>1 to 2 s<\/td>\n<td>Highest bond strength, higher cost<\/td>\n<\/tr>\n<tr>\n<td>Corona, roll to roll<\/td>\n<td>40 to 50 deg<\/td>\n<td>1 to 5 s<\/td>\n<td>Silicone film and sheet<\/td>\n<\/tr>\n<tr>\n<td>Flame, lean mixture<\/td>\n<td>50 to 60 deg<\/td>\n<td>1 to 3 s<\/td>\n<td>Complex shapes, high throughput<\/td>\n<\/tr>\n<tr>\n<td>Chemical primer<\/td>\n<td>35 to 45 deg<\/td>\n<td>Cure dependent<\/td>\n<td>Field repair, low volume<\/td>\n<\/tr>\n<tr>\n<td>Abrasion alone<\/td>\n<td>70 to 85 deg<\/td>\n<td>Manual<\/td>\n<td>Never sufficient on its own<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 1 \u2014 Treatment methods compared on 60 Shore A silicone<\/p>\n<h2 id=\"applications\">Treatment before bonding, printing and coating<\/h2>\n<p>Bonding is the application with the highest stakes. A silicone part bonded to a metal insert carries load, and a bond that fails at 60 percent of its design strength fails in the field. The treatment here has to be plasma, applied within minutes of bonding, and the adhesive has to be a silicone primer or a platinum-cure system that is compatible with the treated surface.<\/p>\n<p>Printing is more forgiving. Pad printing and screen printing on silicone use two component silicone inks that cure at 150 to 200 C, and those inks will bond to a surface activated to 40 degrees or better. The failure mode here is usually not the surface energy but the cure, which is covered in the article on pad printing.<\/p>\n<p>Coating is the hardest, because a coating has to wet the surface and then survive handling. A silicone coating on silicone is a bond between identical materials, which sounds easy and is not: the two layers are both low energy and the interface has no chemical driver. Plasma plus a tie coat is the usual answer.<\/p>\n<p>In all three cases the sequence is the same. Clean first, because mould release agent and fingerprint oil survive treatment and block bonding. Treat second, measured. Bond or print third, within the window. Anything that reverses that order produces a joint that looks right and fails later.<\/p>\n<h2 id=\"production\">Making it repeatable in production<\/h2>\n<p>A treatment that works in the lab and drifts in production is usually a treatment that is not controlled. Plasma is sensitive to nozzle distance, traverse speed, gas flow and gas quality, and none of those are visible on the part. If they are not recorded, they are not controlled.<\/p>\n<p>The minimum control set is a fixed nozzle height with a physical standoff gauge, a robot program with a fixed speed, a gas flow meter, and a daily check with a dyne pen on a scrap part. That check takes two minutes and catches the most common failures: a clogged nozzle, a gas line leak and a power supply drift.<\/p>\n<p>The second control is the time between treatment and the next operation. Write it into the route card as a maximum, not a target. Four hours is achievable in most plants and gives a comfortable margin against the decay curve.<\/p>\n<table>\n<thead>\n<tr>\n<th>Check<\/th>\n<th>Frequency<\/th>\n<th>Pass criterion<\/th>\n<th>What it catches<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Dyne pen at 38 mN\/m<\/td>\n<td>Start of shift and after any nozzle change<\/td>\n<td>Line holds 3 s without beading<\/td>\n<td>Clogged nozzle, low power, gas leak<\/td>\n<\/tr>\n<tr>\n<td>Nozzle standoff<\/td>\n<td>Every setup<\/td>\n<td>Within 1 mm of the setting<\/td>\n<td>Wrong treatment intensity<\/td>\n<\/tr>\n<tr>\n<td>Gas flow<\/td>\n<td>Every shift<\/td>\n<td>Within 5 % of setpoint<\/td>\n<td>Regulator drift, empty cylinder<\/td>\n<\/tr>\n<tr>\n<td>Contact angle on a scrap part<\/td>\n<td>Weekly<\/td>\n<td>Below 40 deg<\/td>\n<td>Gradual loss of plasma density<\/td>\n<\/tr>\n<tr>\n<td>Time from treatment to bonding<\/td>\n<td>Every batch<\/td>\n<td>Under 4 hours<\/td>\n<td>Activated surface aged out<\/td>\n<\/tr>\n<tr>\n<td>Gloves and handling<\/td>\n<td>\u9023\u7d9a<\/td>\n<td>No bare hands on treated faces<\/td>\n<td>Oil contamination of the activated layer<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 2 \u2014 A control set for a plasma activation cell<\/p>\n<p>The parts that fail these checks are not always obvious. A part treated at half the correct intensity still looks activated, still wets a dyne pen at 34, and still bonds well enough to pass a pull test on a flat coupon. It fails on a curved face three months later, and by then the batch is in a customer's warehouse.<\/p>\n<div class=\"faq\">\n<h3>How long does plasma treatment last on silicone?<\/h3>\n<p>Bond strength falls to about 61 percent after seven days in clean, dry storage and to about 31 percent after a month. In practice, treat within four hours of the next operation. Heat and handling accelerate the loss considerably.<\/p>\n<h3>Can I use a primer instead of plasma?<\/h3>\n<p>A primer works and is the right answer for field repair and very low volume. In production it is slower, less consistent and introduces a solvent that has to flash off. For anything above a few hundred parts a week, plasma is cheaper per part and far more repeatable.<\/p>\n<h3>Why does the ink still come off after treatment?<\/h3>\n<p>Check the cure before blaming the surface. A surface at 24 degrees contact angle will wet almost any silicone ink, but an under-cured ink fails cohesively and looks identical to an adhesion failure. A rub test that removes ink down to bare silicone is a surface problem; one that removes ink in a smeary film is a cure problem.<\/p>\n<h3>Does plasma change the colour or feel of the part?<\/h3>\n<p>At normal treatment times, no. Over-treatment produces a slight chalky appearance and a rougher feel, and on pigmented silicone it can lighten the surface. If the part looks different after treatment, the dwell time is too long.<\/p>\n<h3>Can I treat silicone with a corona treater on a three dimensional part?<\/h3>\n<p>Poorly. Corona concentrates on the surface nearest the electrode, so a complex part gets an uneven treatment with the far faces barely activated. Corona is the right tool for film and simple profiles, not for moulded components.<\/p>\n<h3>How do I know if a batch was treated at all?<\/h3>\n<p>A dyne pen at 38 mN\/m on a scrap part answers it in ten seconds. If the line beads immediately, the surface is untreated or the treatment has aged out. Keep the pens in the cell and make the check part of the start-up routine.<\/p>\n<\/div>\n<div class=\"cta\">\n<p class=\"cta-h\">Printing or bonding to silicone?<\/p>\n<p>Send the part drawing, the substrate and what has to stick to it. We will tell you which activation route suits the geometry and what surface energy to specify.<\/p>\n<p><a class=\"btn\" href=\"https:\/\/uplastech.com\/ja\/silicone-rubber\/\">Ask about silicone activation<\/a>\n<\/div>\n<div class=\"rel\">\n<h4>Continue reading<\/h4>\n<ul>\n<li><a href=\"https:\/\/uplastech.com\/ja\/silicone-bonding-adhesion\/\">Silicone Bonding and Adhesion: Getting Two Inert Surfaces to Stay Together<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/ja\/silicone-post-processing\/\">Silicone Post-Processing: Deflashing, Washing and Assembly<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/ja\/silicone-mold-release\/\">Mould Release for Silicone: Why Less Is More<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/ja\/silicone-blooming\/\">Silicone Blooming: The Film That Appears Weeks Later<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/ja\/silicone-o-ring-manufacturing\/\">Silicone O-Ring Manufacturing: From Compound to Finished Seal<\/a><\/li>\n<\/ul>\n<\/div>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>Silicone has the lowest surface energy of any material in common industrial use, which is why nothing sticks to it and why every printing, bonding and coating process starts with an activation step. The step works, and then it stops working, and that is the part most processes miss.<\/p>","protected":false},"author":1,"featured_media":8448,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[39],"tags":[],"class_list":["post-8450","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-silicone-rubber-products"],"meta_box":{"post-to-quiz_to":[]},"_links":{"self":[{"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/posts\/8450","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/comments?post=8450"}],"version-history":[{"count":1,"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/posts\/8450\/revisions"}],"predecessor-version":[{"id":8872,"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/posts\/8450\/revisions\/8872"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/media\/8448"}],"wp:attachment":[{"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/media?parent=8450"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/categories?post=8450"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/tags?post=8450"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}