{"id":4921,"date":"2026-09-08T00:00:00","date_gmt":"2026-09-07T16:00:00","guid":{"rendered":"https:\/\/ptfesuppliers.com\/ptfe-sheet-creep-dimensional-stability\/"},"modified":"2026-09-08T00:00:00","modified_gmt":"2026-09-07T16:00:00","slug":"ptfe-sheet-creep-dimensional-stability","status":"publish","type":"post","link":"https:\/\/ptfesuppliers.com\/ru\/ptfe-sheet-creep-dimensional-stability\/","title":{"rendered":"Creep Characteristics and Long-Term Dimensional Stability of PTFE Sheets"},"content":{"rendered":"<div class=\"container\">\n<p><strong>Creep in PTFE sheets is the slow, permanent deformation that continues under a constant load, even at room temperature.<\/strong> Unlike metals, PTFE (polytetrafluoroethylene) deforms continuously because its crystalline structure slips under stress. A sheet compressed at 10 MPa can lose 5\u201315% of its thickness within 1,000 hours at 23\u00b0C, and more as temperature rises. This article explains the mechanism, gives you a step-by-step method to predict and control creep, and shows the exact mistakes that cause seal and gasket failures. After reading, you will be able to estimate long-term thickness loss for a PTFE sheet and decide whether it fits your application.<\/p>\n<div class=\"toc\">\n<p><strong>Table of Contents<\/strong><\/p>\n<ul>\n<li><a href=\"#mechanism\">1. Why PTFE Creeps: The Mechanism<\/a><\/li>\n<li><a href=\"#predict\">2. How to Predict and Control Creep: Step-by-Step<\/a><\/li>\n<li><a href=\"#mistakes\">3. Common Mistakes and Fixes<\/a><\/li>\n<li><a href=\"#faq\">4. FAQ<\/a><\/li>\n<\/ul>\n<\/div>\n<h2 id=\"mechanism\">1. Why PTFE Creeps: The Mechanism<\/h2>\n<p><img decoding=\"async\" src=\"https:\/\/ptfesuppliers.com\/wp-content\/uploads\/2026\/09\/Creep_Characteristics_and_Long_00.jpg\" alt=\"PTFE sheet under compressive load showing creep deformation over time\" loading=\"lazy\" style=\"max-width:100%; border-radius:8px;\"><\/p>\n<p>PTFE is a semi-crystalline polymer. Its long chains slide past each other when stress is applied, and the crystalline regions gradually reorganize. This is why PTFE has a <strong>compressive creep rate roughly 10 to 100 times higher than filled grades or other engineering plastics<\/strong> such as POM or PEEK.<\/p>\n<p>Three variables control creep: <strong>stress, temperature, and time<\/strong>. Temperature matters most. Raising the temperature from 23\u00b0C to 100\u00b0C can increase creep by a factor of 5\u201310. Filler content matters too: adding 25% glass fiber or carbon reduces creep by 40\u201360% compared to <a href=\"https:\/\/ptfesuppliers.com\/ru\/product\/100-virgin-ptfe-skiving-sheet\/\">virgin PTFE skived sheet<\/a>.<\/p>\n<table>\n<caption>Typical compressive creep strain of virgin PTFE at 23\u00b0C (constant load)<\/caption>\n<thead>\n<tr>\n<th>Stress (MPa)<\/th>\n<th>100 h<\/th>\n<th>1,000 h<\/th>\n<th>10,000 h<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>5<\/td>\n<td>1.5%<\/td>\n<td>2.8%<\/td>\n<td>4.5%<\/td>\n<\/tr>\n<tr>\n<td>10<\/td>\n<td>3.2%<\/td>\n<td>6.0%<\/td>\n<td>9.5%<\/td>\n<\/tr>\n<tr>\n<td>20<\/td>\n<td>7.0%<\/td>\n<td>12.5%<\/td>\n<td>18.0%<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>These values follow a power law: strain at time <em>t<\/em> equals strain at 1 hour multiplied by <em>t<\/em><sup>n<\/sup>, where <em>n<\/em> is about 0.1\u20130.2 for PTFE. That means most creep happens early and then slows, but it never stops. For authoritative property data, see the <a href=\"https:\/\/www.nist.gov\/\" target=\"_blank\" rel=\"noopener\">NIST materials database<\/a> and the <a href=\"https:\/\/www.astm.org\/d2990-17.html\" target=\"_blank\" rel=\"noopener\">ASTM D2990 standard for tensile and compressive creep testing<\/a>.<\/p>\n<h2 id=\"predict\">2. How to Predict and Control Creep: Step-by-Step<\/h2>\n<p><img decoding=\"async\" src=\"https:\/\/ptfesuppliers.com\/wp-content\/uploads\/2026\/09\/Creep_Characteristics_and_Long_01.jpg\" alt=\"Engineer calculating PTFE sheet creep using stress and temperature data\" loading=\"lazy\" style=\"max-width:100%; border-radius:8px;\"><\/p>\n<p>Follow these steps to estimate long-term thickness loss and choose a design that stays stable.<\/p>\n<ol>\n<li><strong>Define your service conditions.<\/strong> Write down the compressive stress (MPa), the maximum continuous temperature (\u00b0C), and the required service life (hours). Example: 8 MPa, 60\u00b0C, 20,000 hours.<\/li>\n<li><strong>Find the base creep strain at 23\u00b0C.<\/strong> Use a creep table like the one above, or the manufacturer&#8217;s ISO 899-1 data. At 8 MPa and 1,000 hours, interpolate between 6.0% and 12.5% to get about 7.5%.<\/li>\n<li><strong>Apply the temperature correction factor.<\/strong> Multiply by the factor from your supplier&#8217;s curve. At 60\u00b0C the factor is typically 2.0\u20132.5. So 7.5% \u00d7 2.2 = 16.5%.<\/li>\n<li><strong>Extrapolate to your service life.<\/strong> Use the power law: strain at 20,000 h = strain at 1,000 h \u00d7 (20,000\/1,000)<sup>0.15<\/sup> = 16.5% \u00d7 1.57 = <strong>25.9%<\/strong>.<\/li>\n<li><strong>Compare to your allowable limit.<\/strong> If your seal can tolerate only 15% thickness loss, this design fails. Reduce stress to 4 MPa or switch to a 25% glass-filled PTFE sheet.<\/li>\n<li><strong>Verify with a test coupon.<\/strong> Compress a 25 mm \u00d7 25 mm sample under the same load and temperature for 500 hours. Measure thickness with a micrometer every 100 hours. Compare to your prediction; adjust the factor if the deviation exceeds 15%.<\/li>\n<li><strong>Set a re-torque interval.<\/strong> If you must use virgin PTFE, schedule bolt re-torquing every 2,000\u20133,000 hours to recover lost compression.<\/li>\n<\/ol>\n<p><strong>Decision rule:<\/strong> If predicted creep strain exceeds 10% of sheet thickness over the service life, use a filled grade or a different material. Do not rely on virgin PTFE for structural compression above 7 MPa at elevated temperature.<\/p>\n<h2 id=\"mistakes\">3. Common Mistakes and Fixes<\/h2>\n<p>These errors appear repeatedly in field failures. Each has a symptom and a concrete fix.<\/p>\n<ul>\n<li><strong>Mistake 1: Using room-temperature data for a hot application.<\/strong><br \/>\nSymptom: The joint leaks after 3\u20136 months at 80\u00b0C even though calculations at 23\u00b0C passed.<br \/>\nFix: Always multiply creep strain by the temperature factor. At 80\u00b0C, use a factor of 3.0 minimum for virgin PTFE.<\/li>\n<li><strong>Mistake 2: Ignoring the difference between virgin and filled PTFE.<\/strong><br \/>\nSymptom: A glass-filled sheet performs well, so you switch to virgin PTFE to save cost, and the seal fails.<br \/>\nFix: Keep a material substitution log. A <a href=\"https:\/\/ptfesuppliers.com\/ru\/product\/glass-microbead-filled-ptfe-sheet\/\">glass-microbead-filled PTFE sheet<\/a> has 40\u201360% less creep. Never substitute without recalculating.<\/li>\n<li><strong>Mistake 3: Assuming creep stops after the break-in period.<\/strong><br \/>\nSymptom: Thickness looks stable at 500 hours, so you stop monitoring. At 5,000 hours the seal has lost 20% thickness.<br \/>\nFix: Monitor for the full service life. PTFE creep follows a power law and continues indefinitely. Set a mid-life inspection at 50% of expected service hours.<\/li>\n<li><strong>Mistake 4: Over-torquing bolts to &#8220;compensate&#8221; for creep.<\/strong><br \/>\nSymptom: The sheet cold-flows out of the joint, causing extrusion and a new leak path.<br \/>\nFix: Torque to the manufacturer&#8217;s specification and re-torque at intervals instead of over-compressing at installation.<\/li>\n<\/ul>\n<h2 id=\"faq\">4. FAQ<\/h2>\n<p><strong>Q1: Does PTFE creep at room temperature?<\/strong><br \/>\nYes. At 23\u00b0C and 10 MPa, virgin PTFE creeps about 6% in 1,000 hours. It is slower than at high temperature but still significant for precision seals.<\/p>\n<p><strong>Q2: How do I stop PTFE from creeping?<\/strong><br \/>\nYou cannot stop it entirely, but you can reduce it. Use filled PTFE (glass, carbon, bronze), lower the stress below 7 MPa, keep temperature below 60\u00b0C, and add mechanical stops or metal backup rings to limit deformation.<\/p>\n<p><strong>Q3: What is the maximum compressive stress for a PTFE sheet?<\/strong><br \/>\nFor long-term stability, keep continuous compressive stress below 7 MPa for virgin PTFE and below 15 MPa for filled grades. Above these values, creep accelerates and cold flow becomes likely.<\/p>\n<p><strong>Q4: How long does it take for PTFE creep to stabilize?<\/strong><br \/>\nIt never fully stabilizes. About 50% of the 10,000-hour creep occurs in the first 100 hours, and 80% in the first 1,000 hours. Plan for continued movement over the full service life.<\/p>\n<p><strong>Q5: Can I predict PTFE creep without a lab test?<\/strong><br \/>\nYes, for a first estimate. Use the power law with published creep data and a temperature factor. Then verify with a 500-hour coupon test. The prediction is usually within 15\u201320% of measured values.<\/p>\n<p>For further reading on polymer creep testing methods, see the <a href=\"https:\/\/www.iso.org\/standard\/65710.html\" target=\"_blank\" rel=\"noopener\">ISO 899-1 standard<\/a> and the <a href=\"https:\/\/www.asme.org\/\" target=\"_blank\" rel=\"noopener\">ASME Boiler and Pressure Vessel Code<\/a> for gasket design guidance.<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>Learn how PTFE sheets creep under load and how to predict long-term dimensional stability using real test data, formulas, and practical design steps.<\/p>","protected":false},"author":1,"featured_media":4782,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[141],"class_list":["post-4921","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industry-news","tag-ptfe-sheet-creep-dimensional-stability"],"_links":{"self":[{"href":"https:\/\/ptfesuppliers.com\/ru\/wp-json\/wp\/v2\/posts\/4921","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ptfesuppliers.com\/ru\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ptfesuppliers.com\/ru\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ptfesuppliers.com\/ru\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ptfesuppliers.com\/ru\/wp-json\/wp\/v2\/comments?post=4921"}],"version-history":[{"count":0,"href":"https:\/\/ptfesuppliers.com\/ru\/wp-json\/wp\/v2\/posts\/4921\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/ptfesuppliers.com\/ru\/wp-json\/wp\/v2\/media\/4782"}],"wp:attachment":[{"href":"https:\/\/ptfesuppliers.com\/ru\/wp-json\/wp\/v2\/media?parent=4921"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ptfesuppliers.com\/ru\/wp-json\/wp\/v2\/categories?post=4921"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ptfesuppliers.com\/ru\/wp-json\/wp\/v2\/tags?post=4921"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}