{"id":7634,"date":"2026-10-27T06:50:13","date_gmt":"2026-10-27T06:50:13","guid":{"rendered":"https:\/\/uplastech.com\/packaging-tube-barrier-coextrusion\/"},"modified":"2026-10-27T07:19:57","modified_gmt":"2026-10-27T07:19:57","slug":"packaging-tube-barrier-coextrusion","status":"publish","type":"post","link":"https:\/\/uplastech.com\/tr\/packaging-tube-barrier-coextrusion\/","title":{"rendered":"Barrier Co-Extrusion for Packaging Tubes: EVOH, Tie Layers and Layer Control"},"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\/pkg-tube-barrier-v2.jpg\" alt=\"Cut sections of a co-extruded plastic tube showing fine concentric barrier layers in the wall\" width=\"1536\" height=\"909\"><figcaption>Sectioned co-extruded tube bodies. The thin amber ring in the middle is the barrier; the two grey rings either side of it are the tie layers. At 0.5 mm total wall, each of those layers is thinner than a sheet of paper \u2014 which is why layer control, not resin choice, is what usually decides whether the tube works.<\/figcaption><\/figure>\n<div class=\"toc\"><\/div>\n<h2 id=\"why\">Why a barrier tube is a layer-thickness problem<\/h2>\n<p>Everyone who specifies a barrier tube starts with the resin. They compare EVOH grades, they read the oxygen transmission tables, they choose the one with the best number. Then the tube fails its shelf-life test anyway, and the reason is almost never the resin \u2014 it is that the 20 \u00b5m barrier layer ended up at 9 \u00b5m on one side of the circumference and 26 \u00b5m on the other.<\/p>\n<p>Barrier is additive across layers but it is <em>not<\/em> linear with thickness in a thin film. A barrier layer that is halved does not halve the transmission \u2014 it multiplies it by a factor of two to five, because pinholes, incomplete coverage and edge effects start to dominate. This is why layer uniformity matters more than nominal layer thickness, and why a 15 \u00b5m layer held to \u00b1 5 % outperforms a 25 \u00b5m layer held to \u00b1 40 %.<\/p>\n<div class=\"callout\">\n<p><strong>The rule that governs everything below:<\/strong> on a 0.5 mm tube wall, a 20 \u00b5m barrier layer is 4 % of the wall. A 10 % variation in total wall thickness is a 50 % variation in the barrier layer. Total wall control and barrier control are the same problem, and you cannot solve one without the other.<\/p>\n<\/div>\n<h2 id=\"structures\">The layer structures in use<\/h2>\n<table>\n<thead>\n<tr>\n<th>Layers<\/th>\n<th>Structure (outside \u2192 inside)<\/th>\n<th>Barrier<\/th>\n<th>Used for<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>3<\/td>\n<td>PE \/ tie \/ EVOH<\/td>\n<td>Good, but the EVOH is exposed to product<\/td>\n<td>Rare; the inner layer must be product-safe<\/td>\n<\/tr>\n<tr>\n<td>5<\/td>\n<td>PE \/ tie \/ EVOH \/ tie \/ PE<\/td>\n<td>\u0130yi<\/td>\n<td>The standard barrier tube<\/td>\n<\/tr>\n<tr>\n<td>6<\/td>\n<td>PE \/ tie \/ EVOH \/ tie \/ regrind \/ PE<\/td>\n<td>\u0130yi<\/td>\n<td>Where trim recycling is required<\/td>\n<\/tr>\n<tr>\n<td>7<\/td>\n<td>PE \/ tie \/ EVOH \/ tie \/ EVOH \/ tie \/ PE<\/td>\n<td>Very good<\/td>\n<td>Long shelf life, high humidity<\/td>\n<\/tr>\n<tr>\n<td>5 + foil<\/td>\n<td>PE \/ foil \/ adhesive \/ PE (ABL)<\/td>\n<td>Absolute<\/td>\n<td>Not co-extruded \u2014 a laminate<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 1 \u2014 Layer structures. The five-layer version dominates because it protects the EVOH from moisture on both faces.<\/p>\n<p>The reason a five-layer structure exists rather than a three-layer one is entirely about moisture. EVOH is hygroscopic; its oxygen barrier degrades as it absorbs water, and the degradation is severe \u2014 a 32 mol% EVOH can lose 60 \u2013 80 % of its dry barrier at 90 % relative humidity. The PE on the inside keeps product moisture away from the barrier, and the PE on the outside keeps ambient humidity away. Both are barrier-protection layers, not just structural ones.<\/p>\n<p>That has a direct design consequence: the inner PE layer has to be thick enough to act as a moisture buffer, not just thick enough to seal. In practice 40 \u2013 80 \u00b5m, and the lower end only for products with low water activity.<\/p>\n<h2 id=\"evoh\">Choosing the EVOH grade<\/h2>\n<p>EVOH is a copolymer of ethylene and vinyl alcohol, and the ethylene content sets the trade-off.<\/p>\n<table>\n<thead>\n<tr>\n<th>Ethylene content<\/th>\n<th>Dry OTR<\/th>\n<th>Humidity sensitivity<\/th>\n<th>\u0130\u015fleme<\/th>\n<th>Typical use<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>27 mol%<\/td>\n<td>Very low<\/td>\n<td>Y\u00fcksek<\/td>\n<td>Narrow window, needs a hot screw<\/td>\n<td>Dry products, maximum barrier<\/td>\n<\/tr>\n<tr>\n<td>32 mol%<\/td>\n<td>D\u00fc\u015f\u00fck<\/td>\n<td>Orta d\u00fczeyde<\/td>\n<td>Standard<\/td>\n<td>The default for tubes<\/td>\n<\/tr>\n<tr>\n<td>38 mol%<\/td>\n<td>Orta d\u00fczeyde<\/td>\n<td>Daha d\u00fc\u015f\u00fck<\/td>\n<td>Easy<\/td>\n<td>Humid conditions, retort<\/td>\n<\/tr>\n<tr>\n<td>44 mol%<\/td>\n<td>Daha y\u00fcksek<\/td>\n<td>D\u00fc\u015f\u00fck<\/td>\n<td>Very easy<\/td>\n<td>Structural, not barrier<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 2 \u2014 EVOH grades. Higher ethylene means easier processing and better humidity tolerance, at the cost of barrier.<\/p>\n<p>Most tube work uses 32 mol%, because it is the point where the barrier is still good and the processing window is wide enough for a co-extrusion line that also runs PE. Moving to 27 mol% buys maybe 30 % more dry barrier and costs a much narrower temperature window and a dedicated screw \u2014 a bad trade unless the product genuinely needs it.<\/p>\n<p>The counter-intuitive part is that for a humid product, a 38 mol% grade can outperform a 27 mol% grade. At 90 % RH the high-ethylene grade retains more of its barrier, and the crossover happens around 80 % RH. If your product is a water-based cream in a tropical market, the \"better\" grade is the one with the worse dry number.<\/p>\n<h2 id=\"tie\">Tie layers: the part that gets ignored until it delaminates<\/h2>\n<p>EVOH will not bond to PE. Nothing bonds to EVOH except a polymer with both polar and non-polar character, which is what a tie layer is: usually a maleic anhydride grafted polyethylene or an EVA\/EMA-based adhesive.<\/p>\n<table>\n<thead>\n<tr>\n<th>Tie type<\/th>\n<th>Bond strength<\/th>\n<th>\u0130\u015fleme<\/th>\n<th>Maliyet<\/th>\n<th>When to use<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Maleic anhydride grafted PE<\/td>\n<td>Y\u00fcksek<\/td>\n<td>Standard<\/td>\n<td>Y\u00fcksek<\/td>\n<td>Default for PE\/EVOH<\/td>\n<\/tr>\n<tr>\n<td>EVA-based<\/td>\n<td>Orta<\/td>\n<td>Easy, low temperature<\/td>\n<td>Orta<\/td>\n<td>Lower temperature processes<\/td>\n<\/tr>\n<tr>\n<td>EMA-based<\/td>\n<td>Medium-high<\/td>\n<td>Easy<\/td>\n<td>Medium-high<\/td>\n<td>Where EVOH is sensitive to heat<\/td>\n<\/tr>\n<tr>\n<td>Ionomer<\/td>\n<td>Y\u00fcksek<\/td>\n<td>Needs high shear<\/td>\n<td>Very high<\/td>\n<td>Demanding, high-value applications<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 3 \u2014 Tie layer options. The tie is 20 \u2013 30 % of the material cost on a five-layer tube and it is where delamination starts.<\/p>\n<p>Two things go wrong with tie layers. The first is thickness: below about 8 \u00b5m the layer becomes discontinuous and the bond fails in patches, which shows up as local delamination after the tube is squeezed. The second is temperature \u2014 tie resins have their own processing window and it is often narrower than the PE around them. Running the whole die at PE temperatures can leave the tie under-fused, and an under-fused tie has almost no bond strength even though it looks fine on the section.<\/p>\n<p>The test that matters is peel strength on a strip cut from the tube, pulled at 90\u00b0 or 180\u00b0. Below 2 N\/15 mm is a marginal bond; 4 N\/15 mm or more is a tube that will survive handling. Anything that fails by peeling cleanly at the interface \u2014 rather than by tearing one of the layers \u2014 is an adhesion failure and will get worse with time.<\/p>\n<h2 id=\"control\">Layer thickness control<\/h2>\n<p>On a co-extrusion line each layer comes from its own extruder, and the ratio of the extruder outputs sets the ratio of the layer thicknesses. That sounds simple and it is not, for three reasons.<\/p>\n<p><strong>First, output is not linear with screw speed.<\/strong> Each extruder's output curve flattens at high speed, so a 10 % speed change on two different extruders does not produce a 10 % change in the layer ratio. <strong>Second, melt viscosity differences cause interface distortion.<\/strong> If the barrier layer is much less viscous than the skin layers, it can migrate toward the wall of the flow channel and end up thinner at the die lip than it was at the feed block. <strong>Third, the die itself distributes unevenly<\/strong> around the circumference, so the barrier layer is thinner where the flow path is longer.<\/p>\n<table>\n<thead>\n<tr>\n<th>Control point<\/th>\n<th>Y\u00f6ntem<\/th>\n<th>Typical capability<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Extruder output<\/td>\n<td>Gravimetric feeder on each unit<\/td>\n<td>\u00b1 1 \u2013 2 %<\/td>\n<\/tr>\n<tr>\n<td>Melt metering<\/td>\n<td>Gear pump per layer<\/td>\n<td>\u00b1 0.5 %<\/td>\n<\/tr>\n<tr>\n<td>Layer ratio<\/td>\n<td>Speed ratio, calibrated per material<\/td>\n<td>\u00b1 5 \u2013 8 %<\/td>\n<\/tr>\n<tr>\n<td>Circumferential uniformity<\/td>\n<td>Die flow balance, spider or crosshead design<\/td>\n<td>\u00b1 10 %<\/td>\n<\/tr>\n<tr>\n<td>Total wall<\/td>\n<td>Vacuum plus haul-off, laser gauge<\/td>\n<td>\u00b1 8 \u2013 10 %<\/td>\n<\/tr>\n<tr>\n<td>Barrier layer thickness<\/td>\n<td>Section and microscope, or IR gauge<\/td>\n<td>\u00b1 10 \u2013 15 %<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 4 \u2014 Where layer thickness variation comes from. Circumferential uniformity is the largest single contributor and the hardest to fix.<\/p>\n<p>The gear pump is the single biggest improvement available. A metering pump between the extruder and the die removes the screw's inherent pulsation and makes the layer ratio independent of screw speed drift. On a five-layer line with three gear pumps, layer thickness repeatability goes from about \u00b1 15 % to \u00b1 5 %, which is the difference between passing and failing a shelf-life test.<\/p>\n<h2 id=\"measure\">Measuring a 20 \u00b5m layer inside a 500 \u00b5m wall<\/h2>\n<p>This is the practical difficulty that stops most plants from controlling the barrier properly. You cannot see a 20 \u00b5m layer with a caliper, and you cannot infer it from total wall thickness.<\/p>\n<table>\n<thead>\n<tr>\n<th>Y\u00f6ntem<\/th>\n<th>What it gives<\/th>\n<th>Destructive<\/th>\n<th>H\u0131z<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Microtome section + optical microscope<\/td>\n<td>Exact layer geometry, all layers<\/td>\n<td>Evet<\/td>\n<td>Hours<\/td>\n<\/tr>\n<tr>\n<td>Section + measuring magnifier<\/td>\n<td>Layer thickness to \u00b1 2 \u00b5m<\/td>\n<td>Evet<\/td>\n<td>Minutes<\/td>\n<\/tr>\n<tr>\n<td>Confocal Raman \/ FTIR mapping<\/td>\n<td>Layer identification and thickness<\/td>\n<td>Evet<\/td>\n<td>Hours, external lab<\/td>\n<\/tr>\n<tr>\n<td>IR gauge (in-line, multi-wavelength)<\/td>\n<td>Layer thickness, continuous<\/td>\n<td>Hay\u0131r<\/td>\n<td>Real time<\/td>\n<\/tr>\n<tr>\n<td>Oxygen transmission on the finished tube<\/td>\n<td>The actual performance<\/td>\n<td>Hay\u0131r<\/td>\n<td>Days<\/td>\n<\/tr>\n<tr>\n<td>Peel test<\/td>\n<td>Adhesion, not thickness<\/td>\n<td>Evet<\/td>\n<td>Minutes<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 5 \u2014 Layer measurement. Only the in-line IR gauge gives continuous data; everything else is a sample.<\/p>\n<p>For most tube plants the practical combination is a microtome section at start-up and every four hours, plus an OTR test on the first and last tube of each batch. The section catches geometry drift; the OTR catches everything the section cannot see, including pinholes and incomplete coverage.<\/p>\n<p>The section has to be taken correctly to mean anything. Cut a short length, embed it in epoxy or clamp it in a sectioning jig, and cut perpendicular to the axis with a fresh blade. A hand-cut section smeared with a knife leaves the layers distorted and reads 30 \u2013 50 % wrong. This is worth doing properly \u2014 a bad section is worse than no section, because it produces confident wrong numbers.<\/p>\n<h2 id=\"delam\">Delamination and the interface problems<\/h2>\n<table>\n<thead>\n<tr>\n<th>Symptom<\/th>\n<th>Neden<\/th>\n<th>Check<\/th>\n<th>Fix<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Clean peel at the tie\/EVOH interface<\/td>\n<td>Tie too thin, or under-fused<\/td>\n<td>Peel test, layer thickness<\/td>\n<td>Thicken the tie, raise its temperature<\/td>\n<\/tr>\n<tr>\n<td>Peel at the PE\/tie interface<\/td>\n<td>Tie incompatible with the skin resin<\/td>\n<td>Check the tie grade against the PE grade<\/td>\n<td>Change tie grade<\/td>\n<\/tr>\n<tr>\n<td>Blistering between layers<\/td>\n<td>Moisture in the EVOH or the tie<\/td>\n<td>Dry the resin, check the dryer<\/td>\n<td>Dry to specification, purge the hopper<\/td>\n<\/tr>\n<tr>\n<td>Local delamination in patches<\/td>\n<td>Layer discontinuity, contamination<\/td>\n<td>Section at several points around the circumference<\/td>\n<td>Thicken the layer, filter the melt<\/td>\n<\/tr>\n<tr>\n<td>Delamination after ageing<\/td>\n<td>Stress relaxation, differential shrinkage<\/td>\n<td>Peel test at 0, 7 and 30 days<\/td>\n<td>Balance layer thicknesses, slow the cooling<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 6 \u2014 Interface failures. A bond that passes on day one and fails on day thirty is a shrinkage mismatch, not an adhesion problem.<\/p>\n<p>The ageing failure is the one that catches good plants. A tube that peels cleanly at 4 N\/15 mm when new can drop to 1.5 N\/15 mm after a month, because the layers shrink at different rates as the residual stress relaxes. PE shrinks more than EVOH, so the interface is under shear, and a marginal bond gives way. Testing only at production is testing the best case.<\/p>\n<h2 id=\"trim\">Trim and regrind in a co-extruded tube<\/h2>\n<p>Co-extrusion produces trim \u2014 the start-up tube, the cut-off ends, the rejected sections. That trim contains EVOH and tie resin, and putting it back into the skin layer is standard practice up to a limit.<\/p>\n<p>The limit is set by the barrier, not by the mechanics. Regrind containing 4 % EVOH blended into a skin layer at 30 % loading puts roughly 1.2 % EVOH into the skin, which is enough to create discontinuities and nucleation sites but not enough to help the barrier. In practice regrind is capped at 20 \u2013 30 % and is kept out of the product-contact layer entirely, which is why six-layer structures with a dedicated regrind core exist.<\/p>\n<div class=\"myth\">\n<p><strong>Common assumption:<\/strong> \"if the barrier layer is thick enough, the tube will pass the shelf-life test.\"<\/p>\n<p>Only if the layer is continuous and uniform. A 40 \u00b5m barrier layer with a 3 \u00b5m thin patch fails where a uniform 18 \u00b5m layer passes, because transmission is dominated by the thinnest point, not the average. This is why layer uniformity is specified separately from layer thickness on any serious tube drawing.<\/p>\n<\/div>\n<h2 id=\"spec\">Writing a co-extrusion specification that can be met<\/h2>\n<p>A barrier tube specification needs more than a layer list. These are the items that decide whether the tube can be made repeatably:<\/p>\n<ul>\n<li>Layer structure with each layer as a percentage of total wall, not as an absolute thickness \u2014 absolute thicknesses change when the total wall is adjusted<\/li>\n<li>Minimum barrier layer thickness, not just nominal<\/li>\n<li>Layer thickness tolerance, per layer, with the measurement method<\/li>\n<li>Tie layer type and minimum thickness<\/li>\n<li>Peel strength requirement, and the ageing point at which it is measured<\/li>\n<li>OTR and WVTR targets with the test conditions (temperature and RH matter more than the number)<\/li>\n<li>Regrind policy \u2014 permitted layers, maximum ratio<\/li>\n<li>Resin grades named by manufacturer and grade, because \"EVOH\" is not a specification<\/li>\n<\/ul>\n<p>The two that are most often missing are the peel strength at age and the regrind policy. Both of them decide whether the tube that passed the first-article test still works after a month in a warehouse.<\/p>\n<div class=\"faq\">\n<h3>How thick should the EVOH layer be?<\/h3>\n<p>Twelve to thirty micrometres in a packaging tube. Below 12 \u00b5m the layer becomes discontinuous and the barrier collapses; above 30 \u00b5m the gain is small relative to the cost. Most tubes run 18 \u2013 25 \u00b5m, and the tolerance on that layer matters more than the nominal value.<\/p>\n<h3>Why does my barrier tube fail in a humid climate?<\/h3>\n<p>Because EVOH absorbs moisture and loses barrier as it does. A 32 mol% grade can lose 60 \u2013 80 % of its dry-state barrier at 90 % RH. The fix is a thicker inner PE layer to buffer product moisture, or a higher-ethylene EVOH grade that tolerates humidity better even though its dry number is worse.<\/p>\n<h3>Can I use a three-layer structure instead of five?<\/h3>\n<p>Only if the EVOH is not exposed to the product, which is unusual. In a three-layer PE\/tie\/EVOH tube the barrier is the product-contact layer, and most products will attack or plasticise it. Five layers put PE on both faces of the EVOH, which is why it is the standard.<\/p>\n<h3>What causes delamination between the tie and the EVOH?<\/h3>\n<p>Usually an under-fused or too-thin tie layer. Below about 8 \u00b5m the tie becomes discontinuous. Below its processing temperature it does not develop bond strength even though it looks intact. Both show up as a clean peel at the interface rather than a tear within a layer.<\/p>\n<h3>How do I measure a 20 \u00b5m layer inside a 500 \u00b5m wall?<\/h3>\n<p>Section it. Cut perpendicular to the axis with a fresh blade, ideally in a jig, and measure under a microscope or a measuring magnifier. A hand-cut smeared section reads 30 \u2013 50 % wrong. For continuous data you need an in-line multi-wavelength IR gauge.<\/p>\n<h3>Is a co-extruded barrier tube as good as an ABL tube?<\/h3>\n<p>No. Nine micrometres of aluminium foil is an absolute barrier; a 25 \u00b5m EVOH layer is a very good one that depends on humidity. For most cosmetic and personal care products EVOH is sufficient. For oxygen-sensitive pharma, foil remains the only option.<\/p>\n<h3>Can co-extruded tubes be recycled?<\/h3>\n<p>Yes, in the HDPE stream, provided the EVOH and tie layers stay below roughly 5 % of the total. That is why the barrier is kept thin and why regrind is capped. An ABL tube, by contrast, is a metal-plastic composite with no mainstream recycling route.<\/p>\n<h3>Why does the barrier layer end up thinner on one side?<\/h3>\n<p>Because the die does not distribute flow evenly around the circumference, and because a low-viscosity barrier layer migrates toward the channel wall. The result is a barrier that is thick on the short flow path and thin on the long one. Flow balancing in the die is the fix; nothing downstream can correct it.<\/p>\n<\/div>\n<div class=\"cta\">\n<p class=\"cta-h\">Specifying a barrier tube and not sure of the layer structure?<\/p>\n<p>Send us the product, the target shelf life and the storage conditions. We will propose the layer stack, the barrier grade and the tolerances that make it repeatable.<\/p>\n<p><a class=\"btn\" href=\"https:\/\/uplastech.com\/tr\/boru-ve-tup-ekstruzyonlari\/\">Talk to a co-extrusion engineer<\/a>\n<\/div>\n<div class=\"rel\">\n<h4>Continue reading<\/h4>\n<ul>\n<li><a href=\"https:\/\/uplastech.com\/tr\/abl-pbl-pe-packaging-tube-materials\/\">ABL, PBL or PE: Choosing the Tube Body Material<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/tr\/plastic-packaging-tube-extrusion\/\">Plastic Packaging Tube Extrusion: From Die to Finished Tube<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/tr\/co-extrusion-profiles\/\">Co-Extrusion Profiles: Bonding, Layer Control and Dies<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/tr\/packaging-tube-extrusion-defects\/\">Tube Extrusion Defects: Gels, Die Lines and Weld Lines<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/tr\/packaging-tube-tolerances-wall-thickness\/\">Packaging Tube Tolerances: Diameter, Wall and Ovality<\/a><\/li>\n<\/ul>\n<\/div>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>Why a barrier tube is a layer-thickness problem rather than a resin problem: EVOH grade selection, what tie layers do and how they fail, controlling a 20 micron layer inside a 500 micron wall, and how to write a specification that can be met.<\/p>","protected":false},"author":1,"featured_media":7640,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_titles_title":"Barrier Co-Extrusion for Tubes: EVOH and Tie Layers","_seopress_titles_desc":"Barrier co-extruded packaging tubes: five-layer structures, EVOH grade choice, tie layer adhesion, layer thickness control, measurement methods and delamination causes.","_seopress_robots_index":"1","_seopress_robots_follow":"1","_seopress_robots_imageindex":"","_seopress_robots_snippet":"","_seopress_robots_primary_cat":"17","_seopress_robots_breadcrumbs":"","_seopress_robots_freeze_modified_date":"","_seopress_robots_custom_modified_date":"","_seopress_robots_canonical":"https:\/\/uplastech.com\/packaging-tube-barrier-coextrusion\/","_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":"barrier co-extrusion tube","footnotes":""},"categories":[17],"tags":[],"class_list":["post-7634","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-plastic-extrusion-process"],"meta_box":{"post-to-quiz_to":[]},"_links":{"self":[{"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/posts\/7634","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=7634"}],"version-history":[{"count":1,"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/posts\/7634\/revisions"}],"predecessor-version":[{"id":7641,"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/posts\/7634\/revisions\/7641"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/media\/7640"}],"wp:attachment":[{"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/media?parent=7634"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/categories?post=7634"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/uplastech.com\/tr\/wp-json\/wp\/v2\/tags?post=7634"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}