{"id":14363,"date":"2022-11-16T09:23:25","date_gmt":"2022-11-16T14:23:25","guid":{"rendered":"https:\/\/www.alpha-technologies.com\/?p=14363"},"modified":"2023-10-02T16:18:30","modified_gmt":"2023-10-02T20:18:30","slug":"how-to-predict-die-swell-in-rubber-compounds-using-a-premier-rpa","status":"publish","type":"post","link":"https:\/\/www.alphatechnologies.cn\/en\/blog\/how-to-predict-die-swell-in-rubber-compounds-using-a-premier-rpa\/","title":{"rendered":"How To Predict Die Swell in Rubber Compounds using a Premier\u00ae RPA\u00a0"},"content":{"rendered":"\t\t
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Author <\/p>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Li Wan<\/p>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Application Engineer, China<\/p>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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Does This Die Make Me Look Bloated? <\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Rubber compounds are viscoelastic materials that are subject to die swell (also called the <\/span>Barus<\/span> Effect) and dimensional stability <\/span>issues<\/span> when <\/span>processed by <\/span>extruding or <\/span>calendaring<\/span> in the factory. Die swell is a phenomenon that occurs when the extruded rubber compound leaves the extruder die with a greater dimensional diameter than the diameter of the extruder die orifice itself. This effect is demonstrated In Figure 1 below.<\/span><\/span>\u00a0<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Figure 1 Extruding rubber through a die orifice<\/span><\/em><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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For many years, efforts have been made to predict compound <\/span>die swell<\/span> in extrusion. <\/span>The most common method for measuring die swell and other rheologic behavior is by using a c<\/span>apillary rheometer. <\/span>A capillary rheometer such as the ARC 2020 can provide accurate data<\/span>, however <\/span>the <\/span>complicated testing process <\/span>it requires <\/span>limits its wide use. <\/span>Fortunately, t<\/span>he Premier RPA is unique in its ability to perform test<\/span>s<\/span> under a range of large strain\/ frequency combinations<\/span>. M<\/span>ore importantly, it has the great advantage of being easy to operate <\/span>while delivering<\/span> excellent repeatability. <\/span>In short, the Premier RPA is <\/span>a more <\/span>convenient<\/span> <\/span>way<\/span><\/span> to predict the die swell.\u00a0<\/span><\/span>\u00a0<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Figure 2. The Premier RPA and ARC2020 Capillary Rheometer<\/em><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Your results may vary. Well\u2026 actually no, they won\u2019t. <\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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To demonstrate the ability of the Premier RPA to predict die swell, we compared testing results between the <\/span>RPA and <\/span>an <\/span>ARC 2020. As can be seen in Figure 3<\/span> below<\/span>, RPA uncured tan \u03b4 inversely correlates to the capillary rheometer running <\/span>a<\/span>die<\/span> s<\/span>well<\/span> test<\/span>. Using simple correlation <\/span>methodology<\/span>, RPA Tan \u03b4 at appropriate (usually high) strain correlated well with <\/span>the <\/span>die swell <\/span>data from the<\/span> capillary rheometer<\/span>. <\/span>Specifically,\u00a0<\/span> the<\/span> trend is increasing Tan \u03b4 when die swell is reduced (lower intrinsic elasticity).<\/span><\/span>\u00a0<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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F<\/span>igure 3 Die Swell from capillary rheometer, RPA Tan Delta vs. phr Silica<\/span><\/span>\u00a0<\/span><\/em><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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One minor issue is that to achieve the best prediction of die swell with the RPA requires adjustments in the applied strain during frequency sweeps to simulate more effectively the destruction of the filler network which is also happening in the factory during an extrusion operation, especially for fully reinforcing fillers. When you setup the test, the specific strain amplitude applied during the performance of the RPA frequency sweep is very important, and actual process conditions, screw speed and temperature, head temperature etc, can also be considered as important reference parameters.\u00a0<\/span>\u00a0<\/span><\/p>

This is covered more completely in Part 2 of this blog.<\/span>\u00a0<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Figure <\/span>4<\/span> R<\/span>esults of <\/span>i<\/span>ncreasing <\/span>c<\/span>oncentration of <\/span>f<\/span>iller on <\/span>u<\/span>ncured Tan Delta at 1.0%<\/span> and 50%<\/span><\/span>\u00a0<\/span><\/em><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Faster. Easier. More Repeatable. What's Not to Like?<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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While a capillary rheometer, such as the ARC 2020 is the most common and accurate way to predict die swell, it can be difficult to use. This complexity can result in unintentional variability of data, if not managed by a skilled operator.<\/span>\u00a0<\/span><\/p>

On the other hand, the Premier RPA provides these advantages:<\/span>\u00a0<\/span><\/p>