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<p>Despite the solid theoretical foundation of time-cure superposition, the time-cure superposition (TCS) shift factors reported in the literature do not support the theory very well. The discrepancy stems from the <i>non</i>-<i>isocure</i> test conditions used in the tests. This study proposes a novel method to eliminate the inherent problems of existing techniques to measure the TCS shift factors, i.e., to measure them under <i>isocure</i> test conditions. The proposed method optimizes a test procedure while offering sufficient relaxation but producing no or negligible additional curing during testing. Optimization requires a complete understanding of curing behavior not only in the chemically-controlled domain but also in the diffusion-controlled domain. The method is implemented for an epoxy-based molding compound. Portions of the storage master curves are obtained at four partially-cured states <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\((p = 0.6, 0.7, 0.8, 0.9)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi>p</mi> <mo>=</mo> <mn>0.6</mn> <mo>,</mo> <mn>0.7</mn> <mo>,</mo> <mn>0.8</mn> <mo>,</mo> <mn>0.9</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>, and they are normalized by the corresponding equilibrium modulus. The normalized curves are subsequently shifted to determine the TCS shift factors using the master curve of fully-cured specimen as a reference. The results show excellent overlaps over the entire curing range after shifting, corroborating that the proposed method is accurate and effective. Validity of the time-cure superposition and applicability of the time–temperature superposition to partially-cured specimens are also confirmed using the test data used to determine the TCS shift factors as well as additional test data.</p>

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Novel test method to measure time-cure superposition shift factors of filled-thermoset under isocure testing conditions

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年2月3日

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  • Sukrut Prashant Phansalkar,
  • Bongtae Han

摘要

Despite the solid theoretical foundation of time-cure superposition, the time-cure superposition (TCS) shift factors reported in the literature do not support the theory very well. The discrepancy stems from the non-isocure test conditions used in the tests. This study proposes a novel method to eliminate the inherent problems of existing techniques to measure the TCS shift factors, i.e., to measure them under isocure test conditions. The proposed method optimizes a test procedure while offering sufficient relaxation but producing no or negligible additional curing during testing. Optimization requires a complete understanding of curing behavior not only in the chemically-controlled domain but also in the diffusion-controlled domain. The method is implemented for an epoxy-based molding compound. Portions of the storage master curves are obtained at four partially-cured states \((p = 0.6, 0.7, 0.8, 0.9)\) ( p = 0.6 , 0.7 , 0.8 , 0.9 ) , and they are normalized by the corresponding equilibrium modulus. The normalized curves are subsequently shifted to determine the TCS shift factors using the master curve of fully-cured specimen as a reference. The results show excellent overlaps over the entire curing range after shifting, corroborating that the proposed method is accurate and effective. Validity of the time-cure superposition and applicability of the time–temperature superposition to partially-cured specimens are also confirmed using the test data used to determine the TCS shift factors as well as additional test data.