{"id":7612,"date":"2026-10-27T01:14:45","date_gmt":"2026-10-27T01:14:45","guid":{"rendered":"https:\/\/uplastech.com\/tpe-tpu-injection-molding-guide\/"},"modified":"2026-10-27T01:14:45","modified_gmt":"2026-10-27T01:14:45","slug":"tpe-tpu-injection-molding-guide","status":"publish","type":"post","link":"https:\/\/uplastech.com\/tr\/tpe-tpu-injection-molding-guide\/","title":{"rendered":"TPE and TPU Injection Molding: Hardness, Bonding and Overmolding"},"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 \u81ea\u52a8\u5c55\u5f00\u7684\u95ee\u5019\u5361\uff0c\u53ea\u4fdd\u7559\u5706\u5f62\u6c14\u6ce1\uff0c\u907f\u514d\u906e\u6321\u4fa7\u680f\u8be2\u76d8\u63d0\u4ea4\u6309\u94ae *\/\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\/im-tpe-part.jpg\" alt=\"Black and coloured TPE and TPU injection moulded grips and seals on a workbench showing soft-touch surfaces\" width=\"1536\" height=\"909\"><figcaption>TPE and TPU grips, seals and boots. Every one of these is soft, every one grips, and none of them would work if the hardness, the bonding surface and the drying had not been specified together.<\/figcaption><\/figure>\n<div class=\"toc\"><\/div>\n<h2 id=\"why\">Soft parts are a different process, not a different material<\/h2>\n<p>Thermoplastic elastomers \u2014 TPE, TPU, TPV, TPS \u2014 are specified for one of two reasons: the part must feel soft, or the part must seal. Both are legitimate and both change how the part is designed and moulded, in ways that are not obvious from a hardness number.<\/p>\n<p>The common mistake is to treat a TPE as \"flexible ABS\". It is not. A TPE has low modulus and high elongation, which means it needs different gates, different ejection, different draft and a completely different approach to overmoulding onto a rigid substrate. A tool designed for a rigid plastic and used for a TPE will produce flash, tearing at ejection, and a part that does not bond.<\/p>\n<div class=\"callout\">\n<p><strong>The two numbers that govern TPE design:<\/strong> <strong>Shore hardness<\/strong> (and which Shore scale \u2014 A or D) and <strong>bond strength to the substrate<\/strong>. Hardness determines flow, ejection and feel; bond strength determines whether the part survives a pull test. Neither appears on a typical mechanical drawing, and both decide whether the part works.<\/p>\n<\/div>\n<h2 id=\"families\">The families, and how to tell them apart<\/h2>\n<table>\n<thead>\n<tr>\n<th>Family<\/th>\n<th>Hardness range<\/th>\n<th>Bonds to<\/th>\n<th>Key property<\/th>\n<th>Maliyet<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>TPS (SEBS \/ SBS)<\/td>\n<td>Shore 20A \u2013 60D<\/td>\n<td>PP, PE (with modification)<\/td>\n<td>Softest, cheapest, easiest to process<\/td>\n<td>D\u00fc\u015f\u00fck<\/td>\n<\/tr>\n<tr>\n<td>TPV (PP\/EPDM)<\/td>\n<td>Shore 35A \u2013 50D<\/td>\n<td>PP<\/td>\n<td>Best compression set, good weathering<\/td>\n<td>Orta<\/td>\n<\/tr>\n<tr>\n<td>TPO<\/td>\n<td>Shore 60A \u2013 60D<\/td>\n<td>PP<\/td>\n<td>Automotive exterior, paintability<\/td>\n<td>Low\u2013medium<\/td>\n<\/tr>\n<tr>\n<td>TPU, polyester<\/td>\n<td>Shore 70A \u2013 75D<\/td>\n<td>ABS, PC, PC\/ABS, PA<\/td>\n<td>Abrasion resistance, tear strength<\/td>\n<td>Medium\u2013high<\/td>\n<\/tr>\n<tr>\n<td>TPU, polyether<\/td>\n<td>Shore 70A \u2013 75D<\/td>\n<td>ABS, PC, PA<\/td>\n<td>Hydrolysis resistance<\/td>\n<td>Medium\u2013high<\/td>\n<\/tr>\n<tr>\n<td>TPEE<\/td>\n<td>Shore 30D \u2013 70D<\/td>\n<td>PBT, PET, PA<\/td>\n<td>High temperature, flex fatigue<\/td>\n<td>Y\u00fcksek<\/td>\n<\/tr>\n<tr>\n<td>TPAE (polyamide)<\/td>\n<td>Shore 60A \u2013 70D<\/td>\n<td>PA<\/td>\n<td>Temperature and chemical resistance<\/td>\n<td>Y\u00fcksek<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 1 \u2014 TPE families. The \"bonds to\" column is the one that decides most projects.<\/p>\n<p>The bonding column is the practical starting point. If the substrate is polypropylene, TPS or TPV is the natural choice because they are PP-compatible by chemistry. If the substrate is ABS or PC, TPU is the answer. Trying to bond a TPS to ABS requires a tie layer or a mechanical interlock, and the result is usually a part that peels in the field.<\/p>\n<h2 id=\"hardness\">Hardness: what the number means<\/h2>\n<table>\n<thead>\n<tr>\n<th>Shore A<\/th>\n<th>Feel<\/th>\n<th>Typical use<\/th>\n<th>Processing note<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>20 \u2013 30A<\/td>\n<td>Very soft, gel-like<\/td>\n<td>Grips, cushions, soft-touch<\/td>\n<td>Very difficult to eject; needs air assist<\/td>\n<\/tr>\n<tr>\n<td>40 \u2013 50A<\/td>\n<td>Soft, rubbery<\/td>\n<td>Seals, gaskets, handles<\/td>\n<td>Needs generous draft and stripping ejection<\/td>\n<\/tr>\n<tr>\n<td>60 \u2013 70A<\/td>\n<td>Firm rubber<\/td>\n<td>Boots, cable jackets, wheels<\/td>\n<td>Standard processing<\/td>\n<\/tr>\n<tr>\n<td>80 \u2013 90A<\/td>\n<td>Firm, slightly flexible<\/td>\n<td>Tyres, rollers, wear pads<\/td>\n<td>Behaves closer to a rigid plastic<\/td>\n<\/tr>\n<tr>\n<td>95A \u2013 55D<\/td>\n<td>Semi-rigid<\/td>\n<td>Structural parts, housings<\/td>\n<td>Standard rigid processing<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 2 \u2014 Shore A hardness and what it means in practice. Below 40A the tool design changes fundamentally.<\/p>\n<p>Two notes on hardness. First, <strong>Shore A and Shore D overlap and are not interchangeable<\/strong> \u2014 55D is roughly 95A, and quoting \"60\" without the scale is meaningless. Second, <strong>hardness is temperature dependent<\/strong>: a 50A TPE at 23 \u00b0C is noticeably harder at 0 \u00b0C and noticeably softer at 50 \u00b0C. For a seal that must work across a temperature range, specify the hardness at the service temperature, not at room temperature.<\/p>\n<h2 id=\"processing\">\u0130\u015fleme<\/h2>\n<table>\n<thead>\n<tr>\n<th>Parametre<\/th>\n<th>TPS \/ TPV<\/th>\n<th>TPU<\/th>\n<th>TPEE<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Erime s\u0131cakl\u0131\u011f\u0131<\/td>\n<td>180 \u2013 220 \u00b0C<\/td>\n<td>190 \u2013 230 \u00b0C<\/td>\n<td>220 \u2013 250 \u00b0C<\/td>\n<\/tr>\n<tr>\n<td>Mould temperature<\/td>\n<td>20 \u2013 40 \u00b0C<\/td>\n<td>20 \u2013 40 \u00b0C<\/td>\n<td>30 \u2013 50 \u00b0C<\/td>\n<\/tr>\n<tr>\n<td>Injection speed<\/td>\n<td>Orta d\u00fczeyde<\/td>\n<td>Moderate \u2014 high shear degrades TPU<\/td>\n<td>Orta d\u00fczeyde<\/td>\n<\/tr>\n<tr>\n<td>Hold pressure<\/td>\n<td>Low \u2014 30 \u2013 50 %<\/td>\n<td>Moderate \u2014 40 \u2013 60 %<\/td>\n<td>Orta d\u00fczeyde<\/td>\n<\/tr>\n<tr>\n<td>Back pressure<\/td>\n<td>0.2 \u2013 0.5 MPa<\/td>\n<td>0.3 \u2013 0.8 MPa<\/td>\n<td>0.3 \u2013 0.8 MPa<\/td>\n<\/tr>\n<tr>\n<td>Drying<\/td>\n<td>Usually not needed<\/td>\n<td>Required: 80 \u2013 100 \u00b0C, 2 \u2013 4 h<\/td>\n<td>Required: 100 \u00b0C, 3 \u2013 4 h<\/td>\n<\/tr>\n<tr>\n<td>K\u00fc\u00e7\u00fclme<\/td>\n<td>1.0 \u2013 2.5 %<\/td>\n<td>0.5 \u2013 1.5 %<\/td>\n<td>1.0 \u2013 2.0 %<\/td>\n<\/tr>\n<tr>\n<td>Regrind<\/td>\n<td>Up to 20 %<\/td>\n<td>Up to 15 %<\/td>\n<td>Up to 15 %<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 3 \u2014 Processing windows. TPU must be dried; TPS usually does not.<\/p>\n<p>The single biggest processing difference is <strong>ejection<\/strong>. A soft TPE stretches rather than releasing, so a part with rigid-plastic draft and ejector pins will tear or distort. The standard solutions are:<\/p>\n<ul>\n<li><strong>Stripper plate or sleeve ejection<\/strong> \u2014 pushes the whole part off the core evenly.<\/li>\n<li><strong>Air assist<\/strong> \u2014 a burst of air between the part and the core breaks the vacuum and the grip, and the part falls free.<\/li>\n<li><strong>Generous draft<\/strong> \u2014 2 \u2013 3\u00b0 instead of 1\u00b0, and more on textured surfaces.<\/li>\n<li><strong>Textured cores<\/strong> \u2014 a light bead-blast on the core actually helps release, because the part grips less uniformly.<\/li>\n<\/ul>\n<div class=\"myth\">\n<p><b>Myth: \"TPU doesn't need drying like PC does.\"<\/b> TPU is a polyurethane and it hydrolyses, exactly like polycarbonate. It absorbs 0.3 \u2013 0.8 % moisture and needs 80 \u2013 100 \u00b0C for 2 \u2013 4 hours. Wet TPU produces bubbles, a rough surface, and a permanent loss of tensile strength. It is one of the most common causes of \"bad TPU batch\" complaints.<\/p>\n<\/div>\n<h2 id=\"overmolding\">Overmoulding: where most TPE projects fail<\/h2>\n<p>Most TPE parts are overmoulded onto a rigid substrate \u2014 a grip on an ABS handle, a seal on a PA connector, a boot on a PBT housing. The bond is the critical feature, and it depends on four things.<\/p>\n<table>\n<thead>\n<tr>\n<th>Fakt\u00f6r<\/th>\n<th>What to control<\/th>\n<th>Effect on bond<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Chemical compatibility<\/td>\n<td>Choose a TPE formulated for the substrate<\/td>\n<td>Decisive \u2014 an incompatible pair will never bond<\/td>\n<\/tr>\n<tr>\n<td>Substrate surface temperature<\/td>\n<td>Above the TPE's melting point at the interface<\/td>\n<td>Critical \u2014 a cold substrate gives a weak bond<\/td>\n<\/tr>\n<tr>\n<td>Substrate surface condition<\/td>\n<td>Clean, no release agent, no contamination<\/td>\n<td>Release agent is the most common cause of peeling<\/td>\n<\/tr>\n<tr>\n<td>Mechanical interlock<\/td>\n<td>Undercuts, holes, a textured surface<\/td>\n<td>Adds robustness where chemical bonding is marginal<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 4 \u2014 The four factors in overmould bond strength. Incompatibility is not fixable by processing.<\/p>\n<p>Substrate temperature is the one that gets missed. The TPE must melt the surface of the substrate to form a bond \u2014 that is what \"chemical bonding\" means in practice. If the insert is at room temperature when the TPE arrives, the interface cools too fast and the bond is mechanical only. The insert should be at 60 \u2013 80 \u00b0C for most substrate pairs, and the mould should be warm enough not to chill it.<\/p>\n<table>\n<thead>\n<tr>\n<th>Substrate<\/th>\n<th>Compatible TPE<\/th>\n<th>Bond strength<\/th>\n<th>Notlar<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>PP<\/td>\n<td>TPS (PP-modified), TPV, TPO<\/td>\n<td>M\u00fckemmel<\/td>\n<td>The most reliable pair<\/td>\n<\/tr>\n<tr>\n<td>PE<\/td>\n<td>TPS (PE-modified)<\/td>\n<td>\u0130yi<\/td>\n<td>Needs a specific grade<\/td>\n<\/tr>\n<tr>\n<td>ABS<\/td>\n<td>TPU (polyester)<\/td>\n<td>M\u00fckemmel<\/td>\n<td>Standard for hand tools<\/td>\n<\/tr>\n<tr>\n<td>PC<\/td>\n<td>TPU (polyester)<\/td>\n<td>\u0130yi<\/td>\n<td>Dry the PC properly or the bond fails<\/td>\n<\/tr>\n<tr>\n<td>PC\/ABS<\/td>\n<td>TPU<\/td>\n<td>\u0130yi<\/td>\n<td><\/td>\n<\/tr>\n<tr>\n<td>PA6 \/ PA66<\/td>\n<td>TPU, TPAE<\/td>\n<td>\u0130yi<\/td>\n<td>Dry nylon is essential<\/td>\n<\/tr>\n<tr>\n<td>PBT<\/td>\n<td>TPEE, TPU<\/td>\n<td>Fair\u2013good<\/td>\n<td>TPEE is the better match<\/td>\n<\/tr>\n<tr>\n<td>POM<\/td>\n<td>None reliable<\/td>\n<td>Zay\u0131f<\/td>\n<td>Use mechanical interlock only<\/td>\n<\/tr>\n<tr>\n<td>Metal<\/td>\n<td>TPU with a primer<\/td>\n<td>Adil<\/td>\n<td>Primer plus a mechanical key<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 5 \u2014 Substrate compatibility. The POM row is the one that ends projects.<\/p>\n<h2 id=\"design\">Design rules<\/h2>\n<table>\n<thead>\n<tr>\n<th>\u00d6zellik<\/th>\n<th>Rule<\/th>\n<th>Why TPE is different<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Wall thickness<\/td>\n<td>0.8 \u2013 3.0 mm for 50 \u2013 70A; thinner for harder grades<\/td>\n<td>Too thin will not fill; too thick sinks and feels mushy<\/td>\n<\/tr>\n<tr>\n<td>Wall uniformity<\/td>\n<td>Within 20 %<\/td>\n<td>Thin sections cool first and create flow hesitation<\/td>\n<\/tr>\n<tr>\n<td>Draft<\/td>\n<td>2 \u2013 3\u00b0 minimum<\/td>\n<td>Soft materials grip the core<\/td>\n<\/tr>\n<tr>\n<td>Internal radius<\/td>\n<td>\u2265 0.5 \u00d7 wall<\/td>\n<td>Tear initiation at sharp corners<\/td>\n<\/tr>\n<tr>\n<td>Gate<\/td>\n<td>Large; often a film or diaphragm gate<\/td>\n<td>High shear degrades TPU and marks TPS<\/td>\n<\/tr>\n<tr>\n<td>Ejection<\/td>\n<td>Stripper plate or air assist<\/td>\n<td>Ejector pins punch through soft material<\/td>\n<\/tr>\n<tr>\n<td>Overmould thickness<\/td>\n<td>0.8 \u2013 2.5 mm over the substrate<\/td>\n<td>Thinner peels; thicker sinks and feels wrong<\/td>\n<\/tr>\n<tr>\n<td>Bond area<\/td>\n<td>Maximise; add a mechanical key<\/td>\n<td>Bond strength is finite and peel is the failure mode<\/td>\n<\/tr>\n<tr>\n<td>Sealing lip<\/td>\n<td>Interference 10 \u2013 20 % of section<\/td>\n<td>A soft lip seals by deformation, not by force<\/td>\n<\/tr>\n<tr>\n<td>Compression set<\/td>\n<td>TPV for dynamic seals, TPS for static<\/td>\n<td>TPS takes a permanent set under sustained load<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 6 \u2014 TPE design rules. Draft and ejection are where rigid-plastic habits cause failure.<\/p>\n<h2 id=\"sealing\">Sealing: the other half of the market<\/h2>\n<p>For seals and gaskets, hardness is not the governing property \u2014 compression set is.<\/p>\n<table>\n<thead>\n<tr>\n<th>Malzeme<\/th>\n<th>Compression set, 22 h at 70 \u00b0C<\/th>\n<th>Service temperature<\/th>\n<th>\u0130\u00e7in en iyisi<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>TPS (SEBS)<\/td>\n<td>40 \u2013 60 %<\/td>\n<td>\u221240 to 90 \u00b0C<\/td>\n<td>Static seals, cosmetic<\/td>\n<\/tr>\n<tr>\n<td>TPV<\/td>\n<td>20 \u2013 35 %<\/td>\n<td>\u221240 to 125 \u00b0C<\/td>\n<td>Dynamic seals, automotive<\/td>\n<\/tr>\n<tr>\n<td>TPU<\/td>\n<td>25 \u2013 40 %<\/td>\n<td>\u221240 to 100 \u00b0C<\/td>\n<td>Wear-resistant seals<\/td>\n<\/tr>\n<tr>\n<td>TPEE<\/td>\n<td>25 \u2013 35 %<\/td>\n<td>\u221240 to 150 \u00b0C<\/td>\n<td>High-temperature seals<\/td>\n<\/tr>\n<tr>\n<td>TPAE<\/td>\n<td>20 \u2013 30 %<\/td>\n<td>\u221240 to 160 \u00b0C<\/td>\n<td>Chemical and thermal<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 7 \u2014 Compression set. Lower is better; TPS is poor and should not be used for a loaded seal.<\/p>\n<p>Compression set is the percentage of deformation that does not recover after the load is removed. A TPS with 50 % set loses half its sealing force after the first thermal cycle and will leak. A TPV at 25 % retains most of it and seals for years. If the part is a seal under sustained compression, TPS is the wrong choice no matter how well it processes.<\/p>\n<h2 id=\"defects\">Defects and causes<\/h2>\n<table>\n<thead>\n<tr>\n<th>Kusur<\/th>\n<th>Neden<\/th>\n<th>Fix<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Tearing at ejection<\/td>\n<td>Ejector pins on soft material, insufficient draft<\/td>\n<td>Stripper plate or air assist; increase draft to 2 \u2013 3\u00b0<\/td>\n<\/tr>\n<tr>\n<td>Flash<\/td>\n<td>Low viscosity, high hold pressure<\/td>\n<td>Reduce hold; check clamp tonnage; sharpen the parting line<\/td>\n<\/tr>\n<tr>\n<td>Poor bond \/ peeling<\/td>\n<td>Cold substrate, contamination, incompatible pair<\/td>\n<td>Heat the insert; clean; verify compatibility<\/td>\n<\/tr>\n<tr>\n<td>Bubbles in TPU<\/td>\n<td>Moisture<\/td>\n<td>Dry at 90 \u2013 100 \u00b0C for 3 h<\/td>\n<\/tr>\n<tr>\n<td>Surface roughness \/ matt patches<\/td>\n<td>Moisture or cold mould<\/td>\n<td>Dry; raise mould temperature<\/td>\n<\/tr>\n<tr>\n<td>Sink marks<\/td>\n<td>Thick sections, low hold<\/td>\n<td>Uniform walls; increase hold<\/td>\n<\/tr>\n<tr>\n<td>Flow marks<\/td>\n<td>Cold mould or slow fill<\/td>\n<td>Raise mould and speed<\/td>\n<\/tr>\n<tr>\n<td>Sticking in the tool<\/td>\n<td>Over-packing, no draft, vacuum<\/td>\n<td>Reduce hold; add draft; add air poppet<\/td>\n<\/tr>\n<tr>\n<td>Colour streaks<\/td>\n<td>Poor mixing, incompatible masterbatch carrier<\/td>\n<td>Use a carrier matched to the TPE base<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 8 \u2014 TPE defects. Tearing and flash together usually mean the tool was designed for a rigid plastic.<\/p>\n<h2 id=\"twoshot\">Two-shot or insert overmoulding?<\/h2>\n<p>There are two ways to put a soft layer on a rigid substrate, and the choice is made on volume and geometry rather than on cost per part alone.<\/p>\n<table>\n<thead>\n<tr>\n<th>Fakt\u00f6r<\/th>\n<th>Two-shot (multi-material)<\/th>\n<th>Insert overmoulding<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Tooling cost<\/td>\n<td>1.6 \u2013 2.5\u00d7 a single-shot tool<\/td>\n<td>1\u00d7 plus a handling fixture<\/td>\n<\/tr>\n<tr>\n<td>\u00c7evrim s\u00fcresi<\/td>\n<td>One cycle for both materials<\/td>\n<td>Two cycles plus handling<\/td>\n<\/tr>\n<tr>\n<td>Labour<\/td>\n<td>None for loading<\/td>\n<td>Operator or robot per shot<\/td>\n<\/tr>\n<tr>\n<td>Bond quality<\/td>\n<td>Better \u2014 the substrate is still hot<\/td>\n<td>Good, if the insert is pre-heated<\/td>\n<\/tr>\n<tr>\n<td>Substrate materials<\/td>\n<td>Must be mouldable in the same tool<\/td>\n<td>Any substrate, including metal<\/td>\n<\/tr>\n<tr>\n<td>Geometry<\/td>\n<td>Substrate must stay on the core<\/td>\n<td>Any geometry<\/td>\n<\/tr>\n<tr>\n<td>Scrap risk<\/td>\n<td>Both materials lost on a bad shot<\/td>\n<td>Only the TPE lost<\/td>\n<\/tr>\n<tr>\n<td>Best volume<\/td>\n<td>Above ~50,000 parts\/year<\/td>\n<td>Below ~50,000, or metal inserts<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 9 \u2014 Two-shot versus insert overmoulding. The bond-quality row is the one that decides quality-critical parts.<\/p>\n<p>Two-shot wins on bond quality because the substrate is still molten or just-solid when the TPE arrives, so the interface is a true melt bond rather than a re-melt. It also removes the handling labour, which on a 30-second cycle is often the largest cost. Insert moulding wins on flexibility: it can overmould metal, it can use a substrate that cannot be moulded in the same tool, and the tooling is far cheaper.<\/p>\n<p>A middle route exists and is underused: overmoulding onto an insert that was moulded in the same cell, robot-transferred while still hot. It gets most of the bond benefit of two-shot at insert-tooling cost, and it is the standard solution for medium volumes.<\/p>\n<h2 id=\"feel\">Hardness, feel and surface<\/h2>\n<p>Two TPEs at the same Shore hardness can feel completely different, and the difference is not captured by the hardness number.<\/p>\n<table>\n<thead>\n<tr>\n<th>Surface factor<\/th>\n<th>Effect on feel<\/th>\n<th>How to specify it<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Hardness<\/td>\n<td>Soft vs firm<\/td>\n<td>Shore A at the service temperature<\/td>\n<\/tr>\n<tr>\n<td>Surface texture<\/td>\n<td>Slick vs grippy<\/td>\n<td>SPI\/VDI texture number, or a physical sample<\/td>\n<\/tr>\n<tr>\n<td>Friction coefficient<\/td>\n<td>Grip<\/td>\n<td>Measured against the actual contacting material<\/td>\n<\/tr>\n<tr>\n<td>Density \/ filler<\/td>\n<td>Heavy vs light, warm vs cold<\/td>\n<td>Filled grades feel more \"premium\"<\/td>\n<\/tr>\n<tr>\n<td>Rebound<\/td>\n<td>Dead vs bouncy<\/td>\n<td>Rebound resilience, %<\/td>\n<\/tr>\n<tr>\n<td>Surface finish<\/td>\n<td>Matte vs satin<\/td>\n<td>Tool polish, not material<\/td>\n<\/tr>\n<tr>\n<td>Colour depth<\/td>\n<td>Solid vs translucent<\/td>\n<td>Pigment loading<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 10 \u2014 What makes a soft part feel right. Only the first row is normally on a drawing.<\/p>\n<p>The practical advice is to approve a physical sample, not a specification. Soft-touch feel is a perception, and two materials that meet the same Shore A and the same density can feel different in the hand because of surface friction and rebound. Every overmoulded grip project we have run has been approved on a sample, and every one that was approved on a datasheet came back for a change.<\/p>\n<div class=\"callout\">\n<p><strong>The specification that works:<\/strong> Shore A hardness at 23 \u00b0C <em>ve<\/em> at the service temperature, a texture reference, a colour master, and an approved physical sample retained by both parties. That is four items and it prevents almost every \"it doesn't feel like the sample\" dispute.<\/p>\n<\/div>\n<h2 id=\"versus\">TPE versus silicone versus rubber<\/h2>\n<table>\n<thead>\n<tr>\n<th>M\u00fclkiyet<\/th>\n<th>TPE \/ TPU<\/th>\n<th>Silicone (LSR \/ HCR)<\/th>\n<th>Thermoset rubber (EPDM, NBR)<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>\u0130\u015fleme<\/td>\n<td>Injection moulding, fast cycles<\/td>\n<td>Injection or compression, slower<\/td>\n<td>Compression or transfer, slow<\/td>\n<\/tr>\n<tr>\n<td>\u00c7evrim s\u00fcresi<\/td>\n<td>20 \u2013 60 s<\/td>\n<td>60 \u2013 180 s<\/td>\n<td>2 \u2013 20 min<\/td>\n<\/tr>\n<tr>\n<td>Geri d\u00f6n\u00fc\u015ft\u00fcr\u00fclebilir<\/td>\n<td>Evet<\/td>\n<td>Hay\u0131r<\/td>\n<td>Hay\u0131r<\/td>\n<\/tr>\n<tr>\n<td>Service temperature<\/td>\n<td>\u221240 to 125 \u00b0C (TPV)<\/td>\n<td>\u221260 to 200 \u00b0C<\/td>\n<td>\u221250 to 150 \u00b0C<\/td>\n<\/tr>\n<tr>\n<td>Compression set<\/td>\n<td>20 \u2013 40 %<\/td>\n<td>10 \u2013 25 %<\/td>\n<td>10 \u2013 25 %<\/td>\n<\/tr>\n<tr>\n<td>Chemical resistance<\/td>\n<td>Good (TPU), fair (TPS)<\/td>\n<td>M\u00fckemmel<\/td>\n<td>Good, formulation-dependent<\/td>\n<\/tr>\n<tr>\n<td>Colour stability<\/td>\n<td>\u0130yi<\/td>\n<td>M\u00fckemmel<\/td>\n<td>Poor (dark only)<\/td>\n<\/tr>\n<tr>\n<td>Cost per part<\/td>\n<td>D\u00fc\u015f\u00fck<\/td>\n<td>Y\u00fcksek<\/td>\n<td>Orta<\/td>\n<\/tr>\n<tr>\n<td>Bonding to rigid plastic<\/td>\n<td>Excellent, designed for it<\/td>\n<td>Poor \u2014 needs a primer<\/td>\n<td>Poor \u2014 needs a primer<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 11 \u2014 TPE versus the thermoset alternatives. The bonding row is why TPE dominates overmoulded grips.<\/p>\n<p>Silicone wins where temperature or biocompatibility matters \u2014 above 150 \u00b0C, or for long-term implant contact. Thermoset rubber wins on compression set in aggressive environments and on cost for very simple high-volume parts. TPE wins on everything else, and specifically on the ability to be overmoulded onto a rigid plastic in a single automated cycle, which is the requirement behind most soft-touch products.<\/p>\n<h2 id=\"faq\">Frequently asked questions<\/h2>\n<div class=\"faq\">\n<h3>TPE or TPU?<\/h3>\n<p>TPU for abrasion resistance, tear strength and bonding to ABS\/PC\/PA. TPE (TPS or TPV) for softness, low cost, and bonding to PP. If the part must feel soft and the substrate is polypropylene, use TPV. If it must resist wear and the substrate is ABS, use TPU.<\/p>\n<h3>What does Shore 60 mean without a letter?<\/h3>\n<p>Nothing. Shore A and Shore D are different scales that overlap: 55D is roughly 95A. Always specify the scale. A drawing that says \"Shore 60\" will produce a part that is either firm rubber or semi-rigid plastic, and the supplier will pick one.<\/p>\n<h3>Why does my TPE part not bond to the ABS?<\/h3>\n<p>Three candidates, in order: the TPE is not formulated for ABS (TPS will not bond to ABS at all); the insert was cold when the TPE arrived; or there is mould release agent on the substrate. Check compatibility first, then substrate temperature (should be 60 \u2013 80 \u00b0C), then cleanliness.<\/p>\n<h3>Can TPE be recycled?<\/h3>\n<p>Production scrap can be reground at 15 \u2013 20 % and re-moulded with a small hardness shift. Post-consumer recycling is limited because TPEs are usually bonded to a rigid substrate and cannot easily be separated. TPV and TPS are the most recyclable families.<\/p>\n<h3>Does TPE need drying?<\/h3>\n<p>TPS and TPV: usually not. TPU, TPEE and TPAE: yes \u2014 they are moisture sensitive and must be dried at 80 \u2013 110 \u00b0C for 2 \u2013 4 hours. Wet TPU gives bubbles and a permanent strength loss.<\/p>\n<h3>Why does my soft part tear when it is ejected?<\/h3>\n<p>Because the tool is using ejector pins designed for a rigid plastic. A soft TPE stretches over the pin instead of being pushed off. Use a stripper plate, a sleeve, or air assist, and increase the draft to at least 2\u00b0.<\/p>\n<h3>What is the softest hardness that can be moulded reliably?<\/h3>\n<p>Around 20 \u2013 25 Shore A, and only with air assist or stripper ejection. Below 20A the material behaves like a gel and the parts are usually cast or 3D printed rather than injection moulded.<\/p>\n<h3>Can TPE be painted?<\/h3>\n<p>Poorly. TPEs have low surface energy and high elongation, so paint films crack when the part flexes. If colour is needed, mould it in colour \u2014 TPE masterbatches are widely available. For markings, pad printing with a flexible ink works better than paint.<\/p>\n<\/div>\n<div class=\"cta\">\n<p class=\"cta-h\">Overmoulding a soft grip or a seal? Send us the substrate and the pull-test requirement<\/p>\n<p>We will tell you which TPE family bonds to your substrate, what hardness will pass the feel and the seal, and how the tool needs to eject it without tearing.<\/p>\n<p><a class=\"btn\" href=\"https:\/\/uplastech.com\/tr\/tpe-tpu-injection-molding\/\">Talk to a TPE moulding engineer<\/a>\n<\/div>\n<div class=\"rel\">\n<h4>Continue reading<\/h4>\n<ul>\n<li><a href=\"https:\/\/uplastech.com\/tr\/overmolding-insert-molding\/\">Overmolding and Insert Molding: The Complete Design Guide<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/tr\/abs-injection-molding-guide\/\">ABS Injection Molding: Grades, Processing and Finishing<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/tr\/pc-injection-molding-guide\/\">PC Injection Molding: Drying, Melt Temperature and Stress Cracking<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/tr\/injection-molding-design-guidelines\/\">Injection Molding Design Guidelines: 12 Rules That Cut Part Cost<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/tr\/injection-molding-material-selection\/\">Injection Molding Material Selection: 14 Plastics Compared<\/a><\/li>\n<\/ul>\n<\/div>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>Soft-part moulding: TPE families and what each bonds to, Shore hardness, ejection and draft, overmould bond strength, compression set and two-shot versus insert moulding.<\/p>","protected":false},"author":1,"featured_media":7604,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_titles_title":"TPE & TPU Injection Molding: Hardness, Bonding, Overmolding","_seopress_titles_desc":"Soft-part moulding: TPE families and what each bonds to, Shore hardness, ejection, overmould bond strength, compression set and two-shot versus insert moulding.","_seopress_robots_index":"1","_seopress_robots_follow":"1","_seopress_robots_imageindex":"","_seopress_robots_snippet":"","_seopress_robots_primary_cat":"35","_seopress_robots_breadcrumbs":"","_seopress_robots_freeze_modified_date":"","_seopress_robots_custom_modified_date":"","_seopress_robots_canonical":"https:\/\/uplastech.com\/tpe-tpu-injection-molding-guide\/","_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":"tpe tpu injection molding","footnotes":""},"categories":[35],"tags":[],"class_list":["post-7612","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-injection-molding"],"meta_box":{"post-to-quiz_to":[]},"_links":{"self":[{"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/posts\/7612","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/comments?post=7612"}],"version-history":[{"count":0,"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/posts\/7612\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/media\/7604"}],"wp:attachment":[{"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/media?parent=7612"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/categories?post=7612"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/tags?post=7612"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}