{"id":7623,"date":"2026-10-27T02:37:59","date_gmt":"2026-10-27T02:37:59","guid":{"rendered":"https:\/\/uplastech.com\/pvc-conduit-trunking-extrusion\/"},"modified":"2026-10-27T02:37:59","modified_gmt":"2026-10-27T02:37:59","slug":"pvc-conduit-trunking-extrusion","status":"publish","type":"post","link":"https:\/\/uplastech.com\/de\/pvc-conduit-trunking-extrusion\/","title":{"rendered":"PVC Conduit and Trunking Extrusion: Impact Strength and Fusion"},"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-conduit.jpg\" alt=\"Bundles of white PVC electrical conduit and rectangular trunking stacked on a factory floor\" width=\"1536\" height=\"909\"><figcaption>Conduit and trunking bundles after cut-off. These profiles are thin-walled, run at high output and are judged almost entirely by whether they survive being hit with a hammer at \u22125 \u00b0C \u2014 which is a formulation and fusion question, not a dimensional one.<\/figcaption><\/figure>\n<div class=\"toc\"><\/div>\n<h2 id=\"why\">The most under-designed profiles in the plant<\/h2>\n<p>Conduit, trunking, cable duct and skirting duct are the highest-volume PVC profiles made and the ones that get the least design attention. They are thin-walled, run fast, and are sold on price per metre. That combination produces a category of product where the difference between a good and a bad profile is invisible at the point of sale and obvious two winters later when a length shatters under a hammer blow.<\/p>\n<p>The governing requirement is not dimensional tolerance \u2014 conduit tolerances are loose. It is <strong>impact strength at low temperature<\/strong>, and that is set almost entirely by formulation and fusion, not by the extrusion line settings.<\/p>\n<div class=\"callout\">\n<p><strong>The number that decides whether a conduit passes:<\/strong> impact energy at <strong>\u22125 \u00b0C or \u221215 \u00b0C<\/strong>, tested to EN 61386-1 or the equivalent. A 20 mm conduit must survive a specified impact without cracking. A profile that passes at 20 \u00b0C and fails at \u22125 \u00b0C was made with too little impact modifier, or with poor fusion \u2014 and no dimensional inspection will reveal it.<\/p>\n<\/div>\n<h2 id=\"product\">The product family<\/h2>\n<table>\n<thead>\n<tr>\n<th>Product<\/th>\n<th>Typical wall<\/th>\n<th>Key requirement<\/th>\n<th>Standard<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Rigid conduit, round<\/td>\n<td>1.5 \u2013 3.0 mm<\/td>\n<td>Impact at low temperature, bending<\/td>\n<td>EN 61386-21<\/td>\n<\/tr>\n<tr>\n<td>Corrugated conduit<\/td>\n<td>0.4 \u2013 0.8 mm<\/td>\n<td>Flexibility, crush resistance<\/td>\n<td>EN 61386-22<\/td>\n<\/tr>\n<tr>\n<td>Trunking, rectangular<\/td>\n<td>1.0 \u2013 2.0 mm<\/td>\n<td>Impact, lid retention, straightness<\/td>\n<td>EN 50085-2-1<\/td>\n<\/tr>\n<tr>\n<td>Skirting duct<\/td>\n<td>1.2 \u2013 2.2 mm<\/td>\n<td>Impact, appearance, lid fit<\/td>\n<td>EN 50085<\/td>\n<\/tr>\n<tr>\n<td>Cable duct \/ raceway<\/td>\n<td>1.0 \u2013 2.5 mm<\/td>\n<td>Crush resistance, flame<\/td>\n<td>EN 50085 \/ UL 94<\/td>\n<\/tr>\n<tr>\n<td>Junction box<\/td>\n<td>2.0 \u2013 3.5 mm<\/td>\n<td>Impact, dimensional, lid threads<\/td>\n<td>EN 60670<\/td>\n<\/tr>\n<tr>\n<td>Profile for luminaires<\/td>\n<td>1.0 \u2013 2.0 mm<\/td>\n<td>Straightness, glow-wire<\/td>\n<td>EN 60598<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 1 \u2014 The electrical PVC profile family. Impact at low temperature is the common thread.<\/p>\n<p>All of these are made from the same base \u2014 rigid PVC, calcium-zinc stabilised, with an impact modifier \u2014 but the modifier loading varies enormously. A conduit for indoor use might carry 4 phr of CPE; a conduit for outdoor or cold-store use might carry 8 \u2013 10 phr. The difference is invisible and it doubles the cost of the additive.<\/p>\n<h2 id=\"impact\">Impact: the property that decides everything<\/h2>\n<p>PVC is notch-sensitive and its impact strength falls sharply as temperature drops. The glass transition of rigid PVC is around 78 \u00b0C, so at room temperature the material is well below Tg and behaves in a brittle manner under impact. Impact modifiers \u2014 chlorinated polyethylene (CPE), acrylic (ACR) or MBS \u2014 work by dispersing rubber particles that cavitate and absorb energy.<\/p>\n<table>\n<thead>\n<tr>\n<th>Impact modifier<\/th>\n<th>Loading (phr)<\/th>\n<th>Impact at 23 \u00b0C<\/th>\n<th>Impact at \u221210 \u00b0C<\/th>\n<th>Weathering<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>None<\/td>\n<td>0<\/td>\n<td>Low \u2014 brittle<\/td>\n<td>Very low<\/td>\n<td>\u2014<\/td>\n<\/tr>\n<tr>\n<td>CPE<\/td>\n<td>4 \u2013 6<\/td>\n<td>Gut<\/td>\n<td>M\u00e4\u00dfig<\/td>\n<td>Gut<\/td>\n<\/tr>\n<tr>\n<td>CPE<\/td>\n<td>8 \u2013 12<\/td>\n<td>Very good<\/td>\n<td>Gut<\/td>\n<td>Gut<\/td>\n<\/tr>\n<tr>\n<td>ACR<\/td>\n<td>4 \u2013 8<\/td>\n<td>Very good<\/td>\n<td>Gut<\/td>\n<td>Ausgezeichnet<\/td>\n<\/tr>\n<tr>\n<td>MBS<\/td>\n<td>5 \u2013 10<\/td>\n<td>Ausgezeichnet<\/td>\n<td>Very good<\/td>\n<td>Poor outdoors<\/td>\n<\/tr>\n<tr>\n<td>ACR + CPE blend<\/td>\n<td>8 \u2013 12<\/td>\n<td>Ausgezeichnet<\/td>\n<td>Very good<\/td>\n<td>Very good<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 2 \u2014 Impact modifiers. MBS is the best performer and the worst for outdoor use.<\/p>\n<p>MBS gives the best impact per phr of any modifier, which is why it dominates indoor applications. It is also a butadiene-styrene copolymer, and the butadiene double bonds oxidise in UV \u2014 so an MBS-modified profile used outdoors will embrittle within a few years and start failing the very test it was formulated to pass. For anything that sees sunlight, ACR or a CPE\/ACR blend is the correct choice.<\/p>\n<p>The second factor in impact strength is <strong>fusion<\/strong>. PVC is not a true melt in the extruder \u2014 it is a particulate gel, and the quality of that gel determines the mechanical properties. Under-fused PVC has visible particle boundaries, and those boundaries are where an impact crack starts. A profile with 10 phr of impact modifier and poor fusion will fail a low-temperature impact test that a profile with 5 phr and good fusion passes.<\/p>\n<h2 id=\"fusion\">Fusion: how to measure it and how to control it<\/h2>\n<table>\n<thead>\n<tr>\n<th>Methode<\/th>\n<th>What it shows<\/th>\n<th>Good result<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Dichloromethane (DCM) immersion<\/td>\n<td>Degree of gelation \u2014 unfused particles swell and show white<\/td>\n<td>No white core after 30 min<\/td>\n<\/tr>\n<tr>\n<td>Acetone soak<\/td>\n<td>Similar, faster, less discriminating<\/td>\n<td>Uniform surface<\/td>\n<\/tr>\n<tr>\n<td>Microtome section<\/td>\n<td>Particle boundaries under a microscope<\/td>\n<td>No visible boundaries<\/td>\n<\/tr>\n<tr>\n<td>Capillary rheometry<\/td>\n<td>Melt viscosity as a proxy<\/td>\n<td>Within the specified band<\/td>\n<\/tr>\n<tr>\n<td>Impact test<\/td>\n<td>The consequence, not the cause<\/td>\n<td>Pass at the specified temperature<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 3 \u2014 Fusion tests. The DCM test is the standard shop-floor method and takes 30 minutes.<\/p>\n<p>Fusion is controlled by three things: melt temperature, residence time and the lubricant balance. A higher melt temperature fuses better but risks degradation; a longer residence time fuses better but limits output. The lubricant balance is where most formulations are tuned \u2014 external lubricants delay fusion, internal lubricants promote it, and the ratio determines where in the screw the gel forms.<\/p>\n<p>The practical consequence for a high-output conduit line is a real tension: you want to run fast (short residence time, less fusion) and you want to pass the impact test (needs fusion). The resolution is usually a higher melt temperature with a very well-balanced stabiliser, plus a screw designed for PVC \u2014 which is why conduit lines often run 195 \u2013 205 \u00b0C melt rather than the 185 \u2013 190 \u00b0C used for window profiles.<\/p>\n<h2 id=\"processing\">Processing a thin-walled electrical profile<\/h2>\n<table>\n<thead>\n<tr>\n<th>Parameter<\/th>\n<th>Conduit<\/th>\n<th>Trunking<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Schmelztemperatur<\/td>\n<td>190 \u2013 205 \u00b0C<\/td>\n<td>185 \u2013 200 \u00b0C<\/td>\n<\/tr>\n<tr>\n<td>Mould \/ calibrator temperature<\/td>\n<td>20 \u2013 40 \u00b0C<\/td>\n<td>25 \u2013 45 \u00b0C<\/td>\n<\/tr>\n<tr>\n<td>Output, 20 mm conduit<\/td>\n<td>250 \u2013 450 kg\/h<\/td>\n<td>\u2014<\/td>\n<\/tr>\n<tr>\n<td>Line speed<\/td>\n<td>8 \u2013 20 m\/min<\/td>\n<td>2 \u2013 6 m\/min<\/td>\n<\/tr>\n<tr>\n<td>Draw-down<\/td>\n<td>1.05 \u2013 1.20<\/td>\n<td>1.05 \u2013 1.15<\/td>\n<\/tr>\n<tr>\n<td>Vacuum<\/td>\n<td>0.2 \u2013 0.5 bar<\/td>\n<td>0.3 \u2013 0.6 bar<\/td>\n<\/tr>\n<tr>\n<td>K\u00fchlung<\/td>\n<td>Spray tank, 3 \u2013 6 m<\/td>\n<td>Spray tank, 4 \u2013 8 m<\/td>\n<\/tr>\n<tr>\n<td>Cut-off<\/td>\n<td>Planetary or saw<\/td>\n<td>Saw<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 4 \u2014 Processing windows. Conduit runs at speeds that window profiles never see.<\/p>\n<p>The draw-down on conduit is modest but important. The die is cut oversize and the profile is pulled down to size, which orients the polymer along the axis. Some axial orientation is beneficial \u2014 it raises the hoop strength and the impact resistance \u2014 but too much makes the profile split longitudinally when it is bent. A draw-down of 1.05 \u2013 1.20 is the usual band.<\/p>\n<p>Cooling is the constraint on speed. A 2 mm conduit wall cools quickly, but at 15 m\/min the profile is in the tank for only 12 \u2013 20 seconds. That is enough for a 2 mm wall but not for a 3 mm one, which is why heavy-wall conduit runs slower and why the tank length is matched to the product range rather than to the fastest item.<\/p>\n<h2 id=\"flame\">Flame, glow wire and smoke<\/h2>\n<table>\n<thead>\n<tr>\n<th>Requirement<\/th>\n<th>Test<\/th>\n<th>What it means<\/th>\n<th>Formulation impact<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Glow wire, 960 \u00b0C<\/td>\n<td>EN 60695-2-11<\/td>\n<td>Does not ignite under a hot wire<\/td>\n<td>Requires a flame-retardant package<\/td>\n<\/tr>\n<tr>\n<td>Glow wire, 850 \u00b0C<\/td>\n<td>EN 60695-2-11<\/td>\n<td>Lower severity, common for trunking<\/td>\n<td>Standard FR package<\/td>\n<\/tr>\n<tr>\n<td>UL94 V-0<\/td>\n<td>UL 94<\/td>\n<td>Self-extinguishing<\/td>\n<td>FR package plus wall thickness<\/td>\n<\/tr>\n<tr>\n<td>Oxygen index<\/td>\n<td>ISO 4589<\/td>\n<td>&gt; 32 % for many electrical applications<\/td>\n<td>Phosphate or brominated FR<\/td>\n<\/tr>\n<tr>\n<td>Smoke density<\/td>\n<td>IEC 61034<\/td>\n<td>Light transmission in smoke<\/td>\n<td>Low-smoke FR system, higher cost<\/td>\n<\/tr>\n<tr>\n<td>Halogen-free<\/td>\n<td>IEC 60754<\/td>\n<td>No corrosive gases<\/td>\n<td>Significant reformulation; usually a different polymer<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 5 \u2014 Flame requirements. Halogen-free is the one that usually forces a change of base material.<\/p>\n<p>Standard rigid PVC is inherently self-extinguishing because of its 57 % chlorine content \u2014 it has an oxygen index of about 45 %, which is why it does not need much help. That is one of the reasons PVC dominates conduit. But \"self-extinguishing\" is not the same as \"passes glow wire at 960 \u00b0C\", and the FR package needed for the higher ratings costs 8 \u2013 20 % more and usually reduces impact strength, which brings you back to the impact modifier balance.<\/p>\n<h2 id=\"defects\">Defects and causes<\/h2>\n<table>\n<thead>\n<tr>\n<th>Defekt<\/th>\n<th>Erscheinungsbild<\/th>\n<th>Ursache<\/th>\n<th>Fix<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Low-temperature impact failure<\/td>\n<td>Splits or shatters when hit cold<\/td>\n<td>Insufficient impact modifier, or poor fusion<\/td>\n<td>Increase modifier; raise melt temperature; check DCM<\/td>\n<\/tr>\n<tr>\n<td>Longitudinal splitting on bending<\/td>\n<td>Split along the axis<\/td>\n<td>Excessive draw-down \/ axial orientation<\/td>\n<td>Reduce draw-down; adjust die and haul-off<\/td>\n<\/tr>\n<tr>\n<td>Ovality<\/td>\n<td>Round conduit is not round<\/td>\n<td>Uneven vacuum, or uneven cooling<\/td>\n<td>Balance the vacuum slots; check spray<\/td>\n<\/tr>\n<tr>\n<td>Internal die lines<\/td>\n<td>Lines along the bore<\/td>\n<td>Mandrel damage or build-up<\/td>\n<td>Polish or replace the mandrel<\/td>\n<\/tr>\n<tr>\n<td>Wall thickness variation<\/td>\n<td>Thin on one side<\/td>\n<td>Mandrel off-centre<\/td>\n<td>Re-centre the mandrel; check the die alignment<\/td>\n<\/tr>\n<tr>\n<td>Rough surface<\/td>\n<td>Matte or drag marks<\/td>\n<td>Cold die, or lubricant imbalance<\/td>\n<td>Raise die temperature; adjust lubricant<\/td>\n<\/tr>\n<tr>\n<td>Yellow \/ brown streaks<\/td>\n<td>Discolouration<\/td>\n<td>Degradation from over-heating or a dead spot<\/td>\n<td>Lower melt; strip and clean the die<\/td>\n<\/tr>\n<tr>\n<td>Plate-out<\/td>\n<td>White deposit on the die and calibrator<\/td>\n<td>Lubricant or stabiliser migrating<\/td>\n<td>Rebalance the lubricant package<\/td>\n<\/tr>\n<tr>\n<td>Brittle after storage<\/td>\n<td>Fails impact months later<\/td>\n<td>MBS modifier degrading, or plasticiser migration<\/td>\n<td>Switch to ACR; check for contact with other plastics<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 6 \u2014 Electrical profile defects. \"Brittle after storage\" is the MBS weathering failure in slow motion.<\/p>\n<h2 id=\"quality\">What to actually inspect<\/h2>\n<table>\n<thead>\n<tr>\n<th>Check<\/th>\n<th>Methode<\/th>\n<th>Frequency<\/th>\n<th>Acceptance<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Abmessungen<\/td>\n<td>Gauge or laser<\/td>\n<td>Kontinuierlich<\/td>\n<td>Per standard<\/td>\n<\/tr>\n<tr>\n<td>Wall thickness<\/td>\n<td>Micrometer, 4 points<\/td>\n<td>Hourly<\/td>\n<td>Minimum per standard<\/td>\n<\/tr>\n<tr>\n<td>Impact at \u22125 \u00b0C<\/td>\n<td>Falling weight or hammer<\/td>\n<td>Per batch<\/td>\n<td>No crack or split<\/td>\n<\/tr>\n<tr>\n<td>Fusion (DCM)<\/td>\n<td>30 min immersion<\/td>\n<td>Per shift<\/td>\n<td>No white core<\/td>\n<\/tr>\n<tr>\n<td>Ovality<\/td>\n<td>Gauge, two axes<\/td>\n<td>Hourly<\/td>\n<td>Within the specified band<\/td>\n<\/tr>\n<tr>\n<td>Glow wire<\/td>\n<td>EN 60695-2-11<\/td>\n<td>Type test \/ per batch<\/td>\n<td>Per rating<\/td>\n<\/tr>\n<tr>\n<td>Bending \/ flexibility<\/td>\n<td>Mandrel bend<\/td>\n<td>Per batch<\/td>\n<td>No cracking<\/td>\n<\/tr>\n<tr>\n<td>Colour<\/td>\n<td>Visual against a master<\/td>\n<td>Start of run<\/td>\n<td>Spiel<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 7 \u2014 Inspection plan. The impact and fusion tests are the two that predict field failure.<\/p>\n<p>The impact test is the one worth insisting on, and it is cheap: a length of conduit conditioned at \u22125 \u00b0C for two hours and struck with a specified weight. It takes a freezer, a weight and ten minutes. Suppliers who do not do it are relying on the formulation being right, which is exactly the assumption that fails when a modifier supplier changes a grade.<\/p>\n<h2 id=\"faq\">Frequently asked questions<\/h2>\n<div class=\"faq\">\n<h3>Why does my conduit crack when it is installed in winter?<\/h3>\n<p>Because the impact strength of rigid PVC falls steeply below about 5 \u00b0C, and the profile was formulated for indoor use. A conduit for cold installation needs 8 \u2013 12 phr of CPE or ACR, and it needs good fusion. The same profile that survives a hammer at 20 \u00b0C can shatter at \u22125 \u00b0C.<\/p>\n<h3>What is the difference between conduit and trunking formulation?<\/h3>\n<p>Mostly the impact modifier loading and the flame package. Trunking usually needs a higher glow-wire rating and better surface appearance; conduit needs higher impact and better dimensional consistency. Both are rigid PVC with calcium-zinc stabiliser.<\/p>\n<h3>Can PVC conduit be bent on site?<\/h3>\n<p>Yes, with a bending spring for small sizes or a hot-box for larger ones. The profile must be warm (60 \u2013 80 \u00b0C) and bent slowly. Cold bending cracks it \u2014 and the crack may not appear until the conduit is under load.<\/p>\n<h3>Why is my conduit oval instead of round?<\/h3>\n<p>Uneven vacuum around the calibrator, or uneven cooling. Check that all the vacuum slots are clear and that the spray is symmetric. A mandrel that is off-centre also produces ovality, but that usually shows as a wall thickness variation as well.<\/p>\n<h3>What does the DCM test actually measure?<\/h3>\n<p>The degree of gelation \u2014 how completely the PVC particles have fused into a continuous matrix. Unfused particles swell in dichloromethane and show as white; well-fused material stays clear. It is the best cheap predictor of impact strength, because cracks start at particle boundaries.<\/p>\n<h3>Is halogen-free conduit available in PVC?<\/h3>\n<p>Not really \u2014 PVC contains 57 % chlorine by weight, so it is inherently halogenated. Halogen-free conduit is made from other materials, usually polypropylene or a halogen-free flame-retardant compound. If the specification says halogen-free, the material is not PVC.<\/p>\n<h3>How fast can a conduit line run?<\/h3>\n<p>20 mm conduit at 8 \u2013 20 m\/min is typical, with output of 250 \u2013 450 kg\/h. The limit is cooling, not the extruder \u2014 a longer tank or a larger spray volume is what buys speed.<\/p>\n<h3>Why does my profile go brittle after a few months in the warehouse?<\/h3>\n<p>If it is MBS-modified and stored where light reaches it, the butadiene phase is oxidising. MBS should not be used for anything that will be stored or used where UV is present. ACR costs more and does not have this failure mode.<\/p>\n<\/div>\n<div class=\"cta\">\n<p class=\"cta-h\">Making conduit, trunking or electrical profiles?<\/p>\n<p>Send the standard, the impact class and the service temperature. We will tell you the impact modifier loading, the fusion target and the line speed that meets both.<\/p>\n<p><a class=\"btn\" href=\"https:\/\/uplastech.com\/de\/pvc-profile\/\">Talk to a PVC electrical profile engineer<\/a>\n<\/div>\n<div class=\"rel\">\n<h4>Continue reading<\/h4>\n<ul>\n<li><a href=\"https:\/\/uplastech.com\/de\/pvc-profile-extrusion\/\">PVC Profile Extrusion: Rigid, Flexible and Cellular PVC<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/de\/pvc-profile-weathering-colour\/\">PVC Profile Weathering and Colour: TiO2, Stabilisers and Lamination<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/de\/pvc-window-profile-design\/\">PVC Window Profile Design: Chambers, Steel and Drainage<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/de\/fehler-in-der-kunststoffextrusion\/\">Plastic Extrusion Defects: 12 Problems, Causes and Fixes<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/de\/extrusion-quality-control\/\">Extrusion Quality Control: Inspection, SPC and Acceptance<\/a><\/li>\n<\/ul>\n<\/div>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>The highest-volume PVC profiles are the least designed: low temperature impact decides whether a conduit passes, fusion degree is what controls it, plus thin-wall processing, flame ratings and what to actually inspect.<\/p>","protected":false},"author":1,"featured_media":7617,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_titles_title":"PVC Conduit & Trunking Extrusion: Impact and Fusion","_seopress_titles_desc":"PVC conduit and trunking extrusion: low temperature impact, how to measure and control fusion, thin-wall processing, flame ratings and inspection criteria.","_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-conduit-trunking-extrusion\/","_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 conduit extrusion","footnotes":""},"categories":[17,36],"tags":[],"class_list":["post-7623","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\/de\/wp-json\/wp\/v2\/posts\/7623","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/uplastech.com\/de\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/uplastech.com\/de\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/uplastech.com\/de\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/uplastech.com\/de\/wp-json\/wp\/v2\/comments?post=7623"}],"version-history":[{"count":0,"href":"https:\/\/uplastech.com\/de\/wp-json\/wp\/v2\/posts\/7623\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/uplastech.com\/de\/wp-json\/wp\/v2\/media\/7617"}],"wp:attachment":[{"href":"https:\/\/uplastech.com\/de\/wp-json\/wp\/v2\/media?parent=7623"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/uplastech.com\/de\/wp-json\/wp\/v2\/categories?post=7623"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/uplastech.com\/de\/wp-json\/wp\/v2\/tags?post=7623"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}