{"id":7988,"date":"2025-12-29T09:00:00","date_gmt":"2025-12-29T09:00:00","guid":{"rendered":"https:\/\/uplastech.com\/silicone-vulcanization-temperature\/"},"modified":"2025-12-29T09:00:00","modified_gmt":"2025-12-29T09:00:00","slug":"silicone-vulcanization-temperature","status":"publish","type":"post","link":"https:\/\/uplastech.com\/fr\/silicone-vulcanization-temperature\/","title":{"rendered":"Vulcanisation Temperature and Time: The Cure Curve Behind Every Part"},"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\/10\/silicone-vulcanization-temperature.jpg\" alt=\"Cure time against temperature on a log scale, and tensile strength against cure state\" width=\"1536\" height=\"909\"><figcaption>Cure time falls from 60 seconds at 120 C to 15 at 160, and a part cured to 90 percent of t90 keeps only 97 percent of its tensile strength.<\/figcaption><\/figure>\n<div class=\"toc\"><\/div>\n<h2 id=\"curve\">The cure curve is a rate, not a time<\/h2>\n<p>Silicone vulcanisation is a chemical reaction, and like most reactions it speeds up with temperature. What a data sheet calls the cure time is really a point on a curve: the time to reach a given state of cure at a given temperature.<\/p>\n<p>The useful measure is t90, the time to reach 90 percent of the maximum torque on a moving die rheometer. It is a standard test, it is reproducible, and it gives a single number that can be compared between compounds and between batches.<\/p>\n<p>On a log axis, t90 against temperature is close to a straight line, which means the relationship is exponential. That is convenient to remember and dangerous to extrapolate: a cure schedule developed at 160 C does not scale linearly to 200 C, and a part that cures in 15 seconds at 160 may scorch in 5 at 200.<\/p>\n<h2 id=\"halving\">Twenty degrees halves the cure<\/h2>\n<p>For a typical addition-cure silicone, t90 goes from 60 seconds at 120 C to 42 at 130, 30 at 140, 21 at 150, 15 at 160 and 10.5 at 170. Twenty degrees halves it: 60 at 120 becomes 30 at 140 and 15 at 160.<\/p>\n<p>The rule is a useful planning tool, and it has limits. Below about 110 C the reaction is slow enough that the inhibitor dominates and the relationship flattens. Above about 190 C the cure is fast enough that the thermal mass of the part matters more than the oven setting, and a thick part will be overcured on the surface before the centre is cured.<\/p>\n<p>That is why cure schedules are quoted with a thickness. A 2 mm section can be cured at 180 C for 10 seconds; a 10 mm section at the same temperature will have a fully cured skin and an undercured core, and no amount of extra time at that temperature will fix it without degrading the skin.<\/p>\n<table>\n<thead>\n<tr>\n<th>Temp\u00e9rature<\/th>\n<th>t90<\/th>\n<th>Relative<\/th>\n<th>Note<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>120 C<\/td>\n<td>60 s<\/td>\n<td>1.00<\/td>\n<td>Slow, good for thick sections<\/td>\n<\/tr>\n<tr>\n<td>130 C<\/td>\n<td>42 s<\/td>\n<td>0.70<\/td>\n<td>Long cycles<\/td>\n<\/tr>\n<tr>\n<td>140 C<\/td>\n<td>30 s<\/td>\n<td>0.50<\/td>\n<td>General purpose<\/td>\n<\/tr>\n<tr>\n<td>150 C<\/td>\n<td>21 s<\/td>\n<td>0.35<\/td>\n<td>Production default<\/td>\n<\/tr>\n<tr>\n<td>160 C<\/td>\n<td>15 s<\/td>\n<td>0.25<\/td>\n<td>Thin sections, fast cycles<\/td>\n<\/tr>\n<tr>\n<td>170 C<\/td>\n<td>10.5 s<\/td>\n<td>0.18<\/td>\n<td>Near the practical limit<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 1 \u2014 t90 against temperature, and the halving at every twenty degrees.<\/p>\n<h2 id=\"properties\">Properties follow the cure state<\/h2>\n<p>Tensile strength develops with cure state and it develops unevenly. At 50 percent of t90 the material has about 60 percent of its strength, at 70 percent it has 85, at 90 percent it has 97 and at 100 percent it has 100. Past 100 percent there is nothing to gain, and a slow loss begins.<\/p>\n<p>The shape of that curve is why under-cure is the expensive side. A part cured to 70 percent looks and feels like a part cured to 100, passes a visual inspection, and fails a tensile test by 15 percent. The defect is invisible until the part is loaded.<\/p>\n<p>Over-cure is less damaging but not harmless. Beyond about 110 percent of t90 the network continues to crosslink and the material stiffens, the elongation falls and the compression set starts to rise. At 130 percent the part is measurably harder than specification, which on a sealing part is a functional failure.<\/p>\n<h2 id=\"measure\">How to know where you are<\/h2>\n<p>A cure schedule is only as good as the measurement behind it. The three practical methods are a rheometer curve on the compound, a hardness check on the part, and a solvent swell test.<\/p>\n<p>The rheometer is the reference: it gives t90 for the compound at the production temperature, and the schedule is set from it with a margin. The hardness check is the shop-floor method, and it catches gross under-cure but not a 10 percent shortfall. The swell test is the most sensitive, because an incomplete network absorbs more solvent, and it is the one to use when a part passes hardness and fails in service.<\/p>\n<p>The measurement has to be on the part, not on a slab. A slab cured in a laboratory press at 5 mm thickness and a production part at 12 mm have completely different thermal histories, and the part is what the customer receives.<\/p>\n<div class=\"callout\">Log the cure temperature and dwell for every batch, and keep a hardness and swell result against the first and last part of the run. That is enough to catch a drift before it becomes a recall.<\/div>\n<h2 id=\"thick\">Thick sections and the thermal lag<\/h2>\n<p>Heat travels slowly through rubber. Silicone has a thermal diffusivity of about 1 x 10 to the minus 7 square metres per second, which means a 10 mm section takes minutes, not seconds, to reach the mould temperature at its centre.<\/p>\n<table>\n<thead>\n<tr>\n<th>Section thickness<\/th>\n<th>Schedule<\/th>\n<th>Pourquoi<\/th>\n<th>Risk if rushed<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Up to 3 mm<\/td>\n<td>160 C for 15 s<\/td>\n<td>Thermal lag is negligible<\/td>\n<td>Over-cure of the skin<\/td>\n<\/tr>\n<tr>\n<td>3 to 6 mm<\/td>\n<td>150 C for 60 s<\/td>\n<td>Core needs time to reach temperature<\/td>\n<td>Undercured core<\/td>\n<\/tr>\n<tr>\n<td>6 to 10 mm<\/td>\n<td>140 C for 3 min<\/td>\n<td>Heat has to diffuse through<\/td>\n<td>Skin degradation<\/td>\n<\/tr>\n<tr>\n<td>10 to 20 mm<\/td>\n<td>130 C for 10 min plus post-cure<\/td>\n<td>Press cure only skins the part<\/td>\n<td>A part that looks cured and is not<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 2 \u2014 Cure schedules by section thickness, and what happens if they are shortened.<\/p>\n<p>So a thick part is cured from the outside in, and the surface sees far more heat history than the core. The usual solution is a lower temperature for longer, which lets the core catch up before the surface degrades. A 10 mm part might run at 130 C for 10 minutes where a 2 mm part runs at 170 C for 15 seconds.<\/p>\n<p>The alternative is a two-stage cure: a short press cure to give the part enough green strength to be handled, followed by an oven post-cure that brings the whole section to temperature evenly. That is standard for thick mouldings and it is covered separately under post-curing.<\/p>\n<h2 id=\"set\">Setting a cure schedule that repeats<\/h2>\n<p>A schedule that works once and drifts is worse than no schedule, because it produces intermittent scrap. Four things make it repeat.<\/p>\n<ol>\n<li>Measure t90 on the actual compound at the actual production temperature, not from the data sheet.<\/li>\n<li>Set the dwell at t90 plus 20 to 30 percent, which covers the thermal lag without overcuring.<\/li>\n<li>Control the mould temperature with a controller, not with a dial, and log it.<\/li>\n<li>Check hardness and swell on the first and last part of every run.<\/li>\n<li>Recalibrate when the compound lot changes, because t90 varies by 10 to 15 percent between lots.<\/li>\n<\/ol>\n<p>The lot-to-lot variation is the item most often missed. A compound from a different batch can have a t90 15 percent longer than the one the schedule was set on, and the result is a run of parts that are technically cured but 5 percent short of full strength.<\/p>\n<div class=\"faq\">\n<h3>What is t90 in silicone vulcanisation?<\/h3>\n<p>The time to reach 90 percent of the maximum torque on a moving die rheometer. It is the standard measure of cure speed and the basis for setting a cure schedule.<\/p>\n<h3>How much does temperature change cure time?<\/h3>\n<p>Twenty degrees halves it. Sixty seconds at 120 C becomes 30 at 140 and 15 at 160, on a typical addition-cure compound.<\/p>\n<h3>What happens if silicone is under-cured?<\/h3>\n<p>Tensile strength and compression set are worse, and the part looks and feels normal. At 90 percent of t90 it keeps 97 percent of its strength; at 70 percent it keeps 85.<\/p>\n<h3>Can silicone be over-cured?<\/h3>\n<p>Yes. Past about 110 percent of t90 the material stiffens, elongation falls and compression set rises. On a seal that is a functional failure.<\/p>\n<h3>Why does a thick part need a different schedule?<\/h3>\n<p>Because heat takes minutes to reach the centre of a 10 mm section. A high temperature cures the skin before the core, so thick parts run cooler and longer, or use a press cure plus an oven post-cure.<\/p>\n<h3>Does t90 vary between compound lots?<\/h3>\n<p>By 10 to 15 percent. That is enough to leave a part 5 percent short of full strength, so the schedule should be rechecked when the lot changes.<\/p>\n<\/div>\n<div class=\"cta\">\n<p class=\"cta-h\">Cure schedule that will not repeat?<\/p>\n<p>Send the compound, the part thickness and the current temperature and dwell. We will check the schedule against t90 and tell you where the margin is.<\/p>\n<p><a class=\"btn\" href=\"https:\/\/uplastech.com\/fr\/silicone-rubber-products\/\">Ask about silicone curing<\/a>\n<\/div>\n<div class=\"rel\">\n<h4>Continue reading<\/h4>\n<ul>\n<li><a href=\"https:\/\/uplastech.com\/fr\/platinum-cure-vs-peroxide-cure\/\">Platinum Versus Peroxide Cure: Speed, Purity and Inhibition<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/fr\/silicone-compression-molding\/\">Silicone Compression Molding: Pressure, Venting and Cure<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/fr\/silicone-compound-formulation\/\">Silicone Compound Formulation: Filler, Catalyst and Inhibitor<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/fr\/hcr-solid-silicone-rubber\/\">HCR Solid Silicone Rubber: Compound, Milling and Moulding<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/fr\/silicone-mixing-two-roll-mill\/\">Two-Roll Mill Mixing: Adding Filler, Curative and Heat History<\/a><\/li>\n<\/ul>\n<\/div>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>Twenty degrees halves the cure time, so 60 seconds at 120 C becomes 30 at 140 and 15 at 160. A part cured to 70 percent of t90 keeps 85 percent of its strength, and over-cure buys nothing.<\/p>","protected":false},"author":1,"featured_media":7987,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_seopress_titles_title":"Silicone Vulcanisation: Temperature and t90","_seopress_titles_desc":"Silicone vulcanisation explained: cure time against temperature, the twenty degree halving rule, t90 and property development, under-cure and over-cure, and how","_seopress_robots_index":"","_seopress_robots_follow":"","_seopress_robots_imageindex":"","_seopress_robots_snippet":"","_seopress_robots_primary_cat":"39","_seopress_robots_breadcrumbs":"","_seopress_robots_freeze_modified_date":"","_seopress_robots_custom_modified_date":"","_seopress_robots_canonical":"","_seopress_social_fb_title":"","_seopress_social_fb_desc":"","_seopress_social_fb_img":"","_seopress_social_fb_img_attachment_id":0,"_seopress_social_fb_img_width":0,"_seopress_social_fb_img_height":0,"_seopress_social_twitter_title":"","_seopress_social_twitter_desc":"","_seopress_social_twitter_img":"","_seopress_social_twitter_img_attachment_id":0,"_seopress_social_twitter_img_width":0,"_seopress_social_twitter_img_height":0,"_seopress_redirections_value":"","_seopress_redirections_enabled":"","_seopress_redirections_enabled_regex":"","_seopress_redirections_logged_status":"","_seopress_redirections_param":"","_seopress_redirections_type":0,"_seopress_analysis_target_kw":"","footnotes":""},"categories":[39],"tags":[],"class_list":["post-7988","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\/fr\/wp-json\/wp\/v2\/posts\/7988","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/comments?post=7988"}],"version-history":[{"count":0,"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/posts\/7988\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/media\/7987"}],"wp:attachment":[{"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/media?parent=7988"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/categories?post=7988"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/tags?post=7988"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}