{"id":7620,"date":"2026-10-27T02:37:51","date_gmt":"2026-10-27T02:37:51","guid":{"rendered":"https:\/\/uplastech.com\/pvc-foam-extrusion-process\/"},"modified":"2026-10-27T02:37:51","modified_gmt":"2026-10-27T02:37:51","slug":"pvc-foam-extrusion-process","status":"publish","type":"post","link":"https:\/\/uplastech.com\/fr\/pvc-foam-extrusion-process\/","title":{"rendered":"Cellular PVC Foam Extrusion: Process Routes, Formulation and Cooling"},"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\/pvc-foam-extrusion.jpg\" alt=\"Cellular PVC foam board emerging from an extrusion die onto a roller table in a factory\" width=\"1536\" height=\"909\"><figcaption>Cellular PVC board coming off the die. The surface skin is formed in the calibrator in the first few seconds; if the melt temperature or the line speed drifts, the skin thickness changes and the board stops being the density you ordered.<\/figcaption><\/figure>\n<div class=\"toc\"><\/div>\n<h2 id=\"what\">What cellular PVC actually is<\/h2>\n<p>Cellular PVC \u2014 foam PVC, sometimes called rigid cellular PVC \u2014 is PVC with gas dispersed through it. The gas comes from a chemical blowing agent that decomposes in the barrel, or from a physical blowing agent injected into the melt. The result is a material with a density of 0.45 \u2013 0.75 g\/cm\u00b3 instead of 1.4, which is why a foam PVC board is a third the weight of the solid board it replaces.<\/p>\n<p>The reason it matters commercially is that solid PVC is heavy and expensive. A 20 mm solid PVC board weighs 28 kg\/m\u00b2 and costs accordingly. The same board in foam at 0.55 g\/cm\u00b3 weighs 11 kg\/m\u00b2, can be nailed and screwed like timber, machines like hardwood, and takes a wood-grain surface. That combination is why foam PVC replaced timber in fascia, soffit, window surrounds and bathroom panelling.<\/p>\n<div class=\"callout\">\n<p><strong>The number that governs the whole process:<\/strong> density. Everything downstream \u2014 stiffness, screw holding, thermal insulation, surface hardness, cost \u2014 follows from it. And density is set by the balance between blowing-agent concentration and the line's ability to restrain the expansion, which means it is a <em>process<\/em> variable as much as a formulation one. The same compound run 5 % faster produces a lighter, softer board.<\/p>\n<\/div>\n<h2 id=\"types\">Three ways to make it<\/h2>\n<table>\n<thead>\n<tr>\n<th>Processus<\/th>\n<th>Density range<\/th>\n<th>Skin<\/th>\n<th>Surface<\/th>\n<th>Used for<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Celuka (internal mandrel)<\/td>\n<td>0.5 \u2013 0.7 g\/cm\u00b3<\/td>\n<td>Integral, 0.3 \u2013 0.8 mm<\/td>\n<td>Hard, glossy, smooth<\/td>\n<td>Furniture, panelling, window surrounds<\/td>\n<\/tr>\n<tr>\n<td>Free foam<\/td>\n<td>0.4 \u2013 0.6 g\/cm\u00b3<\/td>\n<td>Thin, 0.1 \u2013 0.3 mm<\/td>\n<td>Softer, visible cell texture<\/td>\n<td>Where surface is laminated or painted<\/td>\n<\/tr>\n<tr>\n<td>Co-extruded (foam core + solid skin)<\/td>\n<td>0.45 \u2013 0.65 g\/cm\u00b3<\/td>\n<td>Solid, 0.5 \u2013 1.5 mm<\/td>\n<td>Best \u2014 solid PVC surface<\/td>\n<td>Exterior, high-end<\/td>\n<\/tr>\n<tr>\n<td>Wood-plastic foam (PVC + wood flour)<\/td>\n<td>0.55 \u2013 0.9 g\/cm\u00b3<\/td>\n<td>Integral<\/td>\n<td>Wood grain, embossed<\/td>\n<td>Decking, cladding<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 1 \u2014 The four cellular PVC routes. Celuka is the volume process; co-extrusion is the quality one.<\/p>\n<p><strong>Celuka<\/strong> is the dominant process. The die has an internal mandrel or \"torpedo\" that cools the centre of the melt as it exits, so the surface freezes into a solid skin while the core stays hot and expands. The result is a board with a hard, closed surface and a uniform cellular core \u2014 the structure that makes it usable as a timber replacement.<\/p>\n<p><strong>Free foam<\/strong> lets the extrudate expand freely in air before it reaches the calibrator. It is cheaper and simpler, gives a lower density, but produces a thin skin and a surface that shows the cell structure. It is normally laminated or painted.<\/p>\n<p><strong>Co-extrusion<\/strong> puts a solid PVC skin over a foam core in a single die. It is the best surface and the best weathering, and it costs 20 \u2013 35 % more because it needs a second extruder and a more complex die.<\/p>\n<h2 id=\"formulation\">Formulation: what each part does<\/h2>\n<table>\n<thead>\n<tr>\n<th>Composant<\/th>\n<th>Typical loading (phr)<\/th>\n<th>Fonction<\/th>\n<th>If it is wrong<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>PVC resin, K-value 57 \u2013 60<\/td>\n<td>100<\/td>\n<td>Matrix<\/td>\n<td>Higher K = tougher but harder to process<\/td>\n<\/tr>\n<tr>\n<td>Calcium-zinc stabiliser<\/td>\n<td>3 \u2013 5<\/td>\n<td>Prevents dehydrochlorination<\/td>\n<td>Too little: yellowing and burning<\/td>\n<\/tr>\n<tr>\n<td>Chemical blowing agent (AC)<\/td>\n<td>0.4 \u2013 1.2<\/td>\n<td>Generates gas<\/td>\n<td>Too much: coarse cells, weak board<\/td>\n<\/tr>\n<tr>\n<td>Blowing agent activator (ZnO)<\/td>\n<td>0.1 \u2013 0.3<\/td>\n<td>Lowers decomposition temperature<\/td>\n<td>Wrong level: gas released too early or too late<\/td>\n<\/tr>\n<tr>\n<td>Acrylic processing aid<\/td>\n<td>2 \u2013 6<\/td>\n<td>Melt strength and fusion<\/td>\n<td>Too little: cells rupture, rough surface<\/td>\n<\/tr>\n<tr>\n<td>Impact modifier (CPE or acrylic)<\/td>\n<td>4 \u2013 8<\/td>\n<td>Toughness<\/td>\n<td>Too little: brittle board, cracks at fixings<\/td>\n<\/tr>\n<tr>\n<td>Calcium carbonate<\/td>\n<td>3 \u2013 10<\/td>\n<td>Cost, cell nucleation<\/td>\n<td>Too much: density up, impact down<\/td>\n<\/tr>\n<tr>\n<td>Lubricants (internal + external)<\/td>\n<td>1 \u2013 2.5<\/td>\n<td>Controls fusion and release<\/td>\n<td>Imbalance: plate-out or burning<\/td>\n<\/tr>\n<tr>\n<td>Titanium dioxide<\/td>\n<td>3 \u2013 6<\/td>\n<td>Opacity and UV<\/td>\n<td>Too little: yellowing outdoors<\/td>\n<\/tr>\n<tr>\n<td>Cell nucleating agent<\/td>\n<td>0.2 \u2013 0.6<\/td>\n<td>Uniform fine cells<\/td>\n<td>Too little: coarse, irregular cells<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 2 \u2014 A working foam PVC formulation in parts per hundred resin. The blowing agent \/ activator pair is the balance that sets density.<\/p>\n<p>The blowing agent and its activator are the two ingredients that decide whether the board is worth making. AC (azodicarbonamide) decomposes at about 200 \u00b0C on its own, which is above the PVC processing window. Adding zinc oxide drops the decomposition temperature to 170 \u2013 185 \u00b0C, inside the window. Get the ratio right and the gas is released exactly as the melt leaves the die; get it wrong and either the gas comes out in the barrel (making a low-density, coarse, weak board) or it comes out too late (making a dense board with a rough, over-expanded surface).<\/p>\n<h2 id=\"die\">Die and calibration<\/h2>\n<p>The die and the calibrator on a foam line are a single system. Unlike a solid profile, the die does not define the final dimension \u2014 it defines the melt stream, and the calibrator defines the board.<\/p>\n<table>\n<thead>\n<tr>\n<th>Element<\/th>\n<th>Design point<\/th>\n<th>Effect if wrong<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Die land length<\/td>\n<td>10 \u2013 18 \u00d7 gap<\/td>\n<td>Too short: rough surface, uneven expansion<\/td>\n<\/tr>\n<tr>\n<td>Die gap<\/td>\n<td>25 \u2013 40 % of final thickness<\/td>\n<td>Sets the expansion ratio<\/td>\n<\/tr>\n<tr>\n<td>Mandrel (Celuka)<\/td>\n<td>Cooled, 40 \u2013 60 % of die width<\/td>\n<td>Controls skin thickness and core density<\/td>\n<\/tr>\n<tr>\n<td>Mandrel temperature<\/td>\n<td>20 \u2013 60 \u00b0C below melt<\/td>\n<td>Too cold: thick skin, dense core; too hot: no skin<\/td>\n<\/tr>\n<tr>\n<td>Calibrator entry<\/td>\n<td>Close to die, 30 \u2013 100 mm<\/td>\n<td>Too far: over-expansion before restraint<\/td>\n<\/tr>\n<tr>\n<td>Calibrator taper<\/td>\n<td>3 \u2013 8\u00b0 entry<\/td>\n<td>Too steep: drag marks; too shallow: unstable<\/td>\n<\/tr>\n<tr>\n<td>Vacuum<\/td>\n<td>0.1 \u2013 0.3 bar (lower than solid)<\/td>\n<td>Too high: crushed cells at the surface<\/td>\n<\/tr>\n<tr>\n<td>Cooling length<\/td>\n<td>6 \u2013 12 m for a 20 mm board<\/td>\n<td>PVC foam insulates, so cooling is slow<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 3 \u2014 Foam die and calibration. The vacuum is lower than for solid profile, which surprises people.<\/p>\n<p>The vacuum point is worth explaining. On a solid profile, high vacuum pulls the melt hard against the calibrator and gives sharp detail. On a foam, high vacuum crushes the cells at the surface, producing a dense skin over a coarse core and a board that is heavier than specified with worse insulation. Foam lines run at 0.1 \u2013 0.3 bar, just enough to control the surface, not enough to collapse it.<\/p>\n<h2 id=\"cooling\">Cooling: the real bottleneck<\/h2>\n<p>PVC foam has a thermal conductivity of about 0.04 \u2013 0.05 W\/m\u00b7K, against 0.16 for solid PVC. It is an insulator \u2014 which is the point of the product, and also why foam lines are long.<\/p>\n<table>\n<thead>\n<tr>\n<th>Board thickness<\/th>\n<th>Cooling length at 400 kg\/h<\/th>\n<th>Line speed<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>6 mm<\/td>\n<td>3 \u2013 5 m<\/td>\n<td>1.8 \u2013 2.5 m\/min<\/td>\n<\/tr>\n<tr>\n<td>10 mm<\/td>\n<td>5 \u2013 7 m<\/td>\n<td>1.2 \u2013 1.8 m\/min<\/td>\n<\/tr>\n<tr>\n<td>15 mm<\/td>\n<td>7 \u2013 10 m<\/td>\n<td>0.9 \u2013 1.3 m\/min<\/td>\n<\/tr>\n<tr>\n<td>20 mm<\/td>\n<td>9 \u2013 13 m<\/td>\n<td>0.7 \u2013 1.0 m\/min<\/td>\n<\/tr>\n<tr>\n<td>30 mm<\/td>\n<td>13 \u2013 18 m<\/td>\n<td>0.5 \u2013 0.7 m\/min<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 4 \u2014 Cooling length for Celuka board. The thickness-squared relationship is brutal at 30 mm.<\/p>\n<p>A board that is cut before its core is cool will bow, and the bow appears hours later \u2014 often after it has been packed. The practical rule is that the core must be below 60 \u00b0C at the saw, which for a 20 mm board means a tank long enough that the line speed drops to under 1 m\/min. That is why foam lines look disproportionately long relative to their output.<\/p>\n<div class=\"myth\">\n<p><b>Myth: \"we can run faster if we cool harder.\"<\/b> On foam you cannot, because the cooling is limited by the material's own conductivity, not by the water. Adding more spray does nothing once the surface is cold; the heat has to conduct out through the foam. The only real levers are a longer tank, a lower line speed, or a thinner board.<\/p>\n<\/div>\n<h2 id=\"surface\">Surface: wood grain, lamination and painting<\/h2>\n<table>\n<thead>\n<tr>\n<th>Finition<\/th>\n<th>M\u00e9thode<\/th>\n<th>Durabilit\u00e9<\/th>\n<th>Co\u00fbt<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Smooth white<\/td>\n<td>Polished calibrator<\/td>\n<td>Bon<\/td>\n<td>Baseline<\/td>\n<\/tr>\n<tr>\n<td>Embossed wood grain<\/td>\n<td>Textured calibrator or post-embossing roller<\/td>\n<td>Good \u2014 the grain is in the surface<\/td>\n<td>+5 \u2013 10 %<\/td>\n<\/tr>\n<tr>\n<td>Co-extruded cap, wood grain<\/td>\n<td>Solid PVC cap + embossing<\/td>\n<td>Best \u2014 weathering is in the cap<\/td>\n<td>+20 \u2013 35 %<\/td>\n<\/tr>\n<tr>\n<td>Film lamination<\/td>\n<td>PVC or PET film, adhesive<\/td>\n<td>Good indoors; can delaminate outdoors<\/td>\n<td>+15 \u2013 30 %<\/td>\n<\/tr>\n<tr>\n<td>Painted<\/td>\n<td>Spray or roller<\/td>\n<td>Fair \u2014 needs re-coating<\/td>\n<td>+10 \u2013 20 %<\/td>\n<\/tr>\n<tr>\n<td>Foil wrapped (profile wrapping)<\/td>\n<td>PVC\/PET foil, hot melt<\/td>\n<td>Good indoors<\/td>\n<td>+20 \u2013 40 %<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 5 \u2014 Surface options for foam board. Co-extrusion is the only finish that is genuinely exterior-grade.<\/p>\n<p>Embossing works on foam because the surface skin is still thermoplastic when it leaves the calibrator. A textured roller or a moving belt presses the grain in at 90 \u2013 110 \u00b0C, and the skin retains it. Emboss depth is 0.3 \u2013 1.0 mm; deeper than that and the roller breaks through the skin into the cellular core, which shows as a rough patch.<\/p>\n<h2 id=\"defects\">Defects and causes<\/h2>\n<table>\n<thead>\n<tr>\n<th>D\u00e9faut<\/th>\n<th>Apparence<\/th>\n<th>Cause<\/th>\n<th>Fix<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Density too high<\/td>\n<td>Board heavier than specified<\/td>\n<td>Blowing agent too low, or melt too cold<\/td>\n<td>Increase AC; raise melt temperature 5 \u00b0C<\/td>\n<\/tr>\n<tr>\n<td>Density too low<\/td>\n<td>Board light and soft<\/td>\n<td>Too much gas, or over-expansion before the calibrator<\/td>\n<td>Reduce AC; move the calibrator closer<\/td>\n<\/tr>\n<tr>\n<td>Coarse cells<\/td>\n<td>Visible large bubbles in the core<\/td>\n<td>Poor nucleation, or gas released too early<\/td>\n<td>Add nucleating agent; check activator level<\/td>\n<\/tr>\n<tr>\n<td>Thick skin \/ dense surface<\/td>\n<td>Board heavy, core fine<\/td>\n<td>Mandrel too cold<\/td>\n<td>Raise mandrel temperature<\/td>\n<\/tr>\n<tr>\n<td>No skin<\/td>\n<td>Rough, open surface<\/td>\n<td>Mandrel too hot, or vacuum too low<\/td>\n<td>Cool the mandrel; check vacuum<\/td>\n<\/tr>\n<tr>\n<td>Surface ripples<\/td>\n<td>Wavy lines across the board<\/td>\n<td>Unstable expansion at the die exit<\/td>\n<td>Stabilise melt temperature; adjust land length<\/td>\n<\/tr>\n<tr>\n<td>Bowing after cutting<\/td>\n<td>Board curves hours later<\/td>\n<td>Core still hot at the saw<\/td>\n<td>Longer tank; slower line<\/td>\n<\/tr>\n<tr>\n<td>Yellow \/ brown streaks<\/td>\n<td>Discoloured lines<\/td>\n<td>Local overheating or a die dead spot<\/td>\n<td>Strip and clean; check for hang-up<\/td>\n<\/tr>\n<tr>\n<td>Cell collapse at edges<\/td>\n<td>Dense, glossy edges<\/td>\n<td>Vacuum too high at the calibrator entry<\/td>\n<td>Reduce vacuum; soften the entry taper<\/td>\n<\/tr>\n<tr>\n<td>Poor screw holding<\/td>\n<td>Fixings pull out<\/td>\n<td>Density too low at the surface, or skin too thin<\/td>\n<td>Raise density; thicken the skin via mandrel temperature<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 6 \u2014 Foam board defects. Six of the ten are density or skin-thickness problems, which are the same problem seen from different angles.<\/p>\n<h2 id=\"properties\">Properties and where foam PVC is used<\/h2>\n<table>\n<thead>\n<tr>\n<th>Propri\u00e9t\u00e9<\/th>\n<th>0.55 g\/cm\u00b3 board<\/th>\n<th>Solid PVC<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Densit\u00e9<\/td>\n<td>0.55 g\/cm\u00b3<\/td>\n<td>1.40 g\/cm\u00b3<\/td>\n<\/tr>\n<tr>\n<td>Flexural strength<\/td>\n<td>18 \u2013 25 MPa<\/td>\n<td>70 \u2013 80 MPa<\/td>\n<\/tr>\n<tr>\n<td>Flexural modulus<\/td>\n<td>0.7 \u2013 1.1 GPa<\/td>\n<td>2.8 \u2013 3.2 GPa<\/td>\n<\/tr>\n<tr>\n<td>Impact (Charpy, notched)<\/td>\n<td>3 \u2013 6 kJ\/m\u00b2<\/td>\n<td>4 \u2013 8 kJ\/m\u00b2<\/td>\n<\/tr>\n<tr>\n<td>Thermal conductivity<\/td>\n<td>0.04 \u2013 0.05 W\/m\u00b7K<\/td>\n<td>0.16 W\/m\u00b7K<\/td>\n<\/tr>\n<tr>\n<td>Screw pull-out, 20 mm board<\/td>\n<td>600 \u2013 1,200 N<\/td>\n<td>2,500 \u2013 3,500 N<\/td>\n<\/tr>\n<tr>\n<td>Water absorption, 24 h<\/td>\n<td>&lt; 0.5 %<\/td>\n<td>&lt; 0.1 %<\/td>\n<\/tr>\n<tr>\n<td>Service temperature<\/td>\n<td>\u221220 to 60 \u00b0C<\/td>\n<td>\u221220 to 65 \u00b0C<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 7 \u2014 Foam versus solid PVC. Stiffness drops by two-thirds but so does weight, and insulation improves fourfold.<\/p>\n<p>The stiffness loss is the design constraint. A foam board is roughly one-third the modulus of solid PVC, so a shelf or a fascia that worked in 10 mm solid needs 16 \u2013 20 mm in foam. That is fine for cladding, where stiffness is not the governing requirement, and it is why foam is not used for structural profiles.<\/p>\n<p>Screw pull-out is the second constraint. A foam board holds a screw at 600 \u2013 1,200 N, which is adequate for cladding fixings but not for anything load-bearing. Fixings should be into the skin, not the core, and should be at least 20 mm from an edge.<\/p>\n<h2 id=\"faq\">Frequently asked questions<\/h2>\n<div class=\"faq\">\n<h3>What is the difference between Celuka and free foam?<\/h3>\n<p>Celuka uses a cooled internal mandrel so the surface freezes into a solid skin while the core expands \u2014 giving a hard, smooth surface. Free foam lets the extrudate expand in air before calibration, giving a lower density but a thin skin and a visible cell texture. Celuka is the process for anything that will be seen or handled.<\/p>\n<h3>Can foam PVC be used outdoors?<\/h3>\n<p>Only with a co-extruded solid cap or a laminated\/painted finish. A plain Celuka board outdoors will chalk and yellow, and its surface will pick up dirt in the open cells. Co-extruded board with a 0.5 \u2013 1.5 mm solid cap is genuinely exterior-grade and is used for fascia and window surrounds.<\/p>\n<h3>Why is my board heavier than the specification?<\/h3>\n<p>Either the blowing agent is low, the melt is too cold so the gas does not expand fully, or the mandrel is too cold and the skin is too thick. Check the mandrel temperature first \u2014 it is the most common cause and the easiest to correct.<\/p>\n<h3>Can foam PVC be welded?<\/h3>\n<p>Yes, with hot-air or hot-wedge welding using a PVC rod. The weld is not as strong as on solid PVC because the core is cellular, so welded joints in load-bearing applications need a mechanical backing. Solvent welding works on the skin but not through the core.<\/p>\n<h3>What is the maximum thickness?<\/h3>\n<p>Practically 30 \u2013 40 mm. Beyond that the cooling length becomes uneconomic and the core density becomes hard to control. Thicker sections are usually made by lamination rather than extrusion.<\/p>\n<h3>Is foam PVC food safe?<\/h3>\n<p>Standard foam PVC is not a food-contact material. Food-contact grades exist but are uncommon; the blowing agent residues and the stabiliser system are the issues. For food display, use PET or polypropylene foam instead.<\/p>\n<h3>How much does a foam board die cost?<\/h3>\n<p>A single-cavity Celuka die for a 20 mm board runs \u20ac12,000 \u2013 \u20ac28,000 including the mandrel and the calibrator, in China. A co-extrusion version with a cap layer is \u20ac25,000 \u2013 \u20ac50,000. Add 3 \u2013 5 trials and 6 \u2013 10 weeks of lead time.<\/p>\n<h3>Why does my board bow after it is cut?<\/h3>\n<p>Because the core was still hot when the saw cut it. PVC foam conducts heat slowly, so the surface can be cold and rigid while the core is at 90 \u00b0C. As the core cools it contracts and the board curves. The fix is a longer cooling tank or a slower line \u2014 not a different formulation.<\/p>\n<\/div>\n<div class=\"cta\">\n<p class=\"cta-h\">Making or specifying cellular PVC board?<\/p>\n<p>Send the target density, thickness and finish. We will tell you which process fits, what line speed is realistic, and what the die and calibration will cost.<\/p>\n<p><a class=\"btn\" href=\"https:\/\/uplastech.com\/fr\/extrusion-de-mousse-pvc\/\">Talk to a foam PVC engineer<\/a>\n<\/div>\n<div class=\"rel\">\n<h4>Continue reading<\/h4>\n<ul>\n<li><a href=\"https:\/\/uplastech.com\/fr\/pvc-profile-extrusion\/\">PVC Profile Extrusion: Rigid, Flexible and Cellular PVC<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/fr\/pvc-window-profile-design\/\">PVC Window Profile Design: Chambers, Steel and Drainage<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/fr\/extrusion-die-design\/\">Extrusion Die Design for Profiles: Flow, Land and Die Swell<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/fr\/profile-calibration-cooling\/\">Vacuum Calibration and Cooling in Profile Extrusion<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/fr\/defauts-dextrusion-des-matieres-plastiques\/\">Plastic Extrusion Defects: 12 Problems, Causes and Fixes<\/a><\/li>\n<\/ul>\n<\/div>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>How foamed PVC is made: the three blowing routes, what each part of the formulation does, die and calibration for a low density melt, why cooling is the real bottleneck, and the defects that come from getting it wrong.<\/p>","protected":false},"author":1,"featured_media":7614,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_titles_title":"Cellular PVC Foam Extrusion: Process, Formulation, Cooling","_seopress_titles_desc":"Foamed PVC extrusion: the three blowing routes, formulation roles, die and calibration, why cooling limits line speed, and the defects that follow.","_seopress_robots_index":"1","_seopress_robots_follow":"1","_seopress_robots_imageindex":"","_seopress_robots_snippet":"","_seopress_robots_primary_cat":"36","_seopress_robots_breadcrumbs":"","_seopress_robots_freeze_modified_date":"","_seopress_robots_custom_modified_date":"","_seopress_robots_canonical":"https:\/\/uplastech.com\/pvc-foam-extrusion-process\/","_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":"pvc foam extrusion","footnotes":""},"categories":[17,36],"tags":[],"class_list":["post-7620","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-plastic-extrusion-process","category-profile-extrusion"],"meta_box":{"post-to-quiz_to":[]},"_links":{"self":[{"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/posts\/7620","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=7620"}],"version-history":[{"count":0,"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/posts\/7620\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/media\/7614"}],"wp:attachment":[{"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/media?parent=7620"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/categories?post=7620"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/uplastech.com\/fr\/wp-json\/wp\/v2\/tags?post=7620"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}