{"id":14348,"date":"2022-10-25T10:59:36","date_gmt":"2022-10-25T14:59:36","guid":{"rendered":"https:\/\/www.alpha-technologies.com\/?p=14348"},"modified":"2023-10-02T16:18:22","modified_gmt":"2023-10-02T20:18:22","slug":"how-to-control-die-swell-in-rubber-compounds-using-a-premier-rpa","status":"publish","type":"post","link":"https:\/\/www.alphatechnologies.cn\/en\/blog\/how-to-control-die-swell-in-rubber-compounds-using-a-premier-rpa\/","title":{"rendered":"How To Control 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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Well, That's Just Swell<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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As we covered in Part 1<\/span> of this blog, die swell (also called the Barus Effect) occurs during extruding or calendaring in the factory.<\/span> It\u2019s when the extruded rubber compound leaves the extruder die with a greater dimensional diameter than the diameter of the extruder die orifice itself. Die swell is a viscoelastic effect relate<\/span>d<\/span> to the compound\u2019s uncured elasticity or \u201cnerviness\u201d. This effect is demonstrated In Figure 1<\/span> below.<\/span>\u00a0<\/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 office<\/span>\u00a0<\/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>And i<\/span>t is well known that the capillary rheometer is an effective instrument for measuring die swell.<\/span> In fact, the c<\/span>apillary<\/span> rheometer is the most common way to measure the die swell and other rheological behavior.<\/span> H<\/span>owever<\/span> the <\/span>complicated testing process<\/span> required by an instrument such as the ARC 2020 <\/span>limits its wide use. <\/span>Fortunately, t<\/span>he <\/span>Premier\u2122<\/span><\/a><\/span>\u00a0RPA is unique in its ability to perform test<\/span>s<\/span> under a range of large strain\/ frequency combinations<\/span>.\u00a0<\/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 a more <\/span>convenient<\/span> <\/span>way<\/span><\/span> to <\/span>control<\/span> die swell.<\/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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Ways to Control Die Swell Using a Premier RPA<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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For this article, c<\/span>omparisons were made between Premier RPA and ARC 2020. As can be seen in Figure 3 below, RPA uncured tan \u03b4 inversely correlates<\/span> to the capillary rheometer die. In other words, increasing Tan \u03b4 when die swell is reduced (lower intrinsic elasticity), Tan \u03b4 is the key parameter for controlling the die swell. However, <\/span>the key question is <\/span>how to get a<\/span>pposite<\/span> Tan \u03b4<\/span> values<\/span>?<\/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 vs RPA Tan Delta<\/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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Figure <\/span>4<\/span> shows the results of <\/span>increasing <\/span>the <\/span>concentration of filler on uncured Tan Delta<\/span> at 1% <\/span>and 50% <\/span>strain.<\/span> As can be seen<\/span> in <\/span>the result<\/span> at 1%<\/span> strain<\/span>, <\/span>75 phr N234 carbon black shows the lowest tan \u03b4 values even at the higher frequencies<\/span>, which is inconsistent with the above model<\/span>.<\/span> This is <\/span>because<\/span> filler network is not disturbed greatly by applying only <\/span>1<\/span>% strain during this RPA <\/span>frequency sweep<\/span>. However, by rerunning this frequency sweep at 50% strain<\/span> instead of 1%, <\/span>you<\/span> can see that this higher strain is beginning to break up the filler network and is causing a crossover in the tan \u03b4 data points<\/span> – <\/span>where an<\/span> inversion in the ordinal relationships occurs<\/span> \u2013 which <\/span>shows the correct data relationship<\/span>. <\/span>This means 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<\/span>,<\/span> which is also happening in the factory during an extrusion operation. <\/span>This tuning of strain is probably more critical for fully reinforcing <\/span>fillers.<\/span>\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 <\/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>