# Evidence: Couchman-Karasz equation

Parent: — · class: solid-state property · names merged here: Couchman-Karasz equation

3 papers measured or used it, 0 only mentioned it (of 207 kept papers). Papers in year order; each section heading ends with the paper's category / subcategory. Generated by tools/build_evidence.py from registry/concepts.csv and the cards; do not edit.

## 2006 Konno — Influence of Different Polymers on the Crystallization Tendency of Molecularly Dispersed Amorphous Felodipine · Solid state stability / Physical stability

[2006-konno-felodipine-polymer-crystallization-nucleation-solid-dispersions](../../../cards/2006-konno-felodipine-polymer-crystallization-nucleation-solid-dispersions/paper.html) · Solid state stability / Physical stability · used · as: Couchman-Karasz equation

| id | kind | content | locator |
|---|---|---|---|
| E4 | equation | Couchman-Karasz constant: K = ΔC_P1/ΔC_P2 (used in the form of E2) | p.2694 |
| R7 | record, derived (E2, E3, E4) | predicted Tg curves (broken line Gordon-Taylor, solid line Couchman-Karasz) — Fig. 5a-c, inputs in B1 — read at 25 and 50 wt%: PVP GT ≈54 and ≈70 °C, CK ≈55 and ≈72 °C; HPMCAS GT ≈52 and ≈63 °C, CK ≈56 and ≈70 °C; HPMC GT ≈54 and ≈68 °C, CK ≈55 and ≈72 °C (read from Fig. 5); text: HPMCAS and HPMC data below both curves, deviations most apparent at mid-range compositions; PVP data quite close to the GT curve | Fig. 5, p.2698; text p.2697 |

## 2006 Marsac — A Comparison of the Physical Stability of Amorphous Felodipine and Nifedipine Systems · Solid state stability / Physical stability

[2006-marsac-physical-stability-amorphous-felodipine-nifedipine](../../../cards/2006-marsac-physical-stability-amorphous-felodipine-nifedipine/paper.html) · Solid state stability / Physical stability · used · as: Couchman-Karasz equation

| id | kind | content | locator |
|---|---|---|---|
| R17 | record, measured | Tg versus PVP content (°C; error bars one SD), with Gordon-Taylor (solid) and Couchman-Karasz (dashed) curves — nifedipine-PVP (a) and felodipine-PVP (b) dispersions (P3, P7); fit parameters not printed — sub-table below; text: a single Tg at every composition; Tg of felodipine with 10 wt% PVP 40.5 (±0.5) °C, slightly below pure felodipine; Tgs of the two drug-PVP systems virtually identical at every concentration | Fig. 10, p.2312; text p.2311 |
| C21 | claim, conclusion, authors: "relatively ideal" | Both drug-PVP systems are relatively ideal in terms of the Gordon-Taylor and Couchman-Karasz predictions [rests on: R17] | p.2311 |

## 2009 Rumondor — Evaluation of Drug-Polymer Miscibility in Amorphous Solid Dispersion Systems · Solid state stability / Miscibility and drug-polymer interactions

[2009-rumondor-drug-polymer-miscibility-asd-dsc-ir-pxrd](../../../cards/2009-rumondor-drug-polymer-miscibility-asd-dsc-ir-pxrd/paper.html) · Solid state stability / Miscibility and drug-polymer interactions · used · as: Couchman-Karasz equation

| id | kind | content | locator |
|---|---|---|---|
| E1 | equation | Couchman-Karasz equation (Gordon-Taylor form, K from ΔCp): Tg,mix = (w1 Tg1 + K w2 Tg2)/(w1 + K w2) | p.2525 |
| E2 | equation | Couchman-Karasz constant: K = ΔCp2/ΔCp1 | p.2526 |
| R1 | record, measured (Tg columns); derived, E1 (Couchman-Karasz column) | midpoint Tg of felodipine-PAA dispersions; where two glass transition events were detected both are given as Tg1 / Tg2 (table footnote a) — felodipine-PAA bulk powders (P1); "Experiment 1" = heating to 180 °C, "Experiment 2" = heating to 146 °C with 30 s hold (P2; mapping by the 50% row, p.2526) — sub-table below | Table I, p.2526 |
| R4 | record, measured (Tg); derived, E1 (Couchman-Karasz line) | Tg,mix versus PVP content — ketoconazole-PVP (R3) — sub-table below (all values ≈, read from Fig. 2) | Fig. 2, p.2527 |