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<p>Conventional viscoelastic characterization of thermoplastic amorphous polymers employs rotational rheometer above the glass transition temperature (T<sub>g</sub>) and Dynamic Mechanical Analysis below T<sub>g</sub>. This work proposes a Single-Pellet Molding (SPM) method that enables comprehensive viscoelastic characterization across both regimes using a single rotational rheometer. The SPM procedure involves introducing a single polymer pellet into a custom mold seated on the lower plate, compressing the pellet with the upper plate, and molding a cylindrical sample between the parallel plates. This approach offers a critical advantage for thermally and oxidatively sensitive polymers, as sample preparation can be completed in air at temperatures below the trimming threshold without requiring an inert gas atmosphere. Whereas conventional preprocessing (requiring chamber opening for trimming) introduces cooling-induced artifacts to both sample and shaft geometry, that may lead to human error, the SPM method fundamentally eliminates these sources of uncertainty. SPM enables reproducible QC testing across T<sub>g</sub> for Cyclo olefin copolymer (COC), addressing recycling limitations critical to smartphone camera lens production scraps. Validation experiments comparing SPM to traditional trimming procedures, using 5&#xa0;mm diameter parallel plates, demonstrate a 69% improvement in reproducibility (relative standard deviation: 3.52% → 1.09%). By directly measuring and calibrating both the thermal expansion coefficient and torsional compliance of the measuring tool, we confirm continuous acquisition of consistent viscoelastic data from the polymer melt temperature through sub-T<sub>g</sub> region using a single instrument. The method significantly reduces measurement time, requires minimal sample mass (10–20&#xa0;mg), eliminates nitrogen gas costs, and enables low-temperature measurement without thermal degradation. We anticipate immediate industrial applicability for rapid, economical material characterization in development and quality verification workflows.</p> Graphical abstract <p></p>

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Single-pellet molding (SPM): a trimming-free rotational rheometry for wide-temperature range viscoelastic characterization of cyclo olefin copolymer

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月9日

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  • Jaehyun Kim,
  • Kyung Hyun Ahn

摘要

Conventional viscoelastic characterization of thermoplastic amorphous polymers employs rotational rheometer above the glass transition temperature (Tg) and Dynamic Mechanical Analysis below Tg. This work proposes a Single-Pellet Molding (SPM) method that enables comprehensive viscoelastic characterization across both regimes using a single rotational rheometer. The SPM procedure involves introducing a single polymer pellet into a custom mold seated on the lower plate, compressing the pellet with the upper plate, and molding a cylindrical sample between the parallel plates. This approach offers a critical advantage for thermally and oxidatively sensitive polymers, as sample preparation can be completed in air at temperatures below the trimming threshold without requiring an inert gas atmosphere. Whereas conventional preprocessing (requiring chamber opening for trimming) introduces cooling-induced artifacts to both sample and shaft geometry, that may lead to human error, the SPM method fundamentally eliminates these sources of uncertainty. SPM enables reproducible QC testing across Tg for Cyclo olefin copolymer (COC), addressing recycling limitations critical to smartphone camera lens production scraps. Validation experiments comparing SPM to traditional trimming procedures, using 5 mm diameter parallel plates, demonstrate a 69% improvement in reproducibility (relative standard deviation: 3.52% → 1.09%). By directly measuring and calibrating both the thermal expansion coefficient and torsional compliance of the measuring tool, we confirm continuous acquisition of consistent viscoelastic data from the polymer melt temperature through sub-Tg region using a single instrument. The method significantly reduces measurement time, requires minimal sample mass (10–20 mg), eliminates nitrogen gas costs, and enables low-temperature measurement without thermal degradation. We anticipate immediate industrial applicability for rapid, economical material characterization in development and quality verification workflows.

Graphical abstract