What are the influencing factors of glass transition temperature testing?

What are the influencing factors of glass transition temperature testing?

Key Factors Affecting Glass Transition Temperature (Tg) Testing‌

The primary factors influencing glass transition temperature (Tg) measurements are summarized below based on testing experiences with diverse materials:

‌Material Intrinsic Properties‌

‌Crystallinity‌:

Each 10% increase in crystallinity may raise Tg by 2–3°C (e.g., PET requires drying pretreatment).
‌Molecular Weight & Structure‌:

High-molecular-weight materials (e.g., PMMA) typically exhibit higher Tg; chain structure variations can cause data fluctuations.
‌Modification Treatments‌:

Adding glass fibers may elevate PET's Tg to 85–100°C;

Copolymer modification could reduce Tg below 60°C.

‌Testing Methodology Variations‌

‌Instrument Selection‌:

Results from DSC and DMA methods may differ.
‌Heating Rate‌:

Excessive rates (>20°C/min) may overestimate Tg;

Too slow rates (<5°C/min) prolong experiments (recommended: 10°C/min).
‌Atmosphere Control‌:

Nitrogen flow (50 mL/min) minimizes oxidation interference.

‌Sample Preparation & Operational Factors‌

‌Pretreatment‌:

PET must be dried at 120°C for >4 hours to remove moisture;

Sample mass: 10–20 mg for uniformity.
‌Baseline Calibration‌:

Blank experiments are essential to correct thermal flow and avoid systematic errors.
‌Thermal History‌:

Initial heating tests may show deviations (e.g., PMMA); verification via second heating is advised.

‌Environmental & Instrumental Factors‌

‌Temperature Range‌:

Should cover expected Tg range (e.g., –50 to 200°C).
‌Data Interpretation‌:

Midpoint, inflection, or extrapolation methods significantly impact results.

The ST146 Crystalline Thermal Analyzer is designed and manufactured in accordance with the new version of the 2020 Chinese Pharmacopoeia General Rules 0981 Crystalline Inspection Method and 0661 Differential Scanning Calorimetry Method. It is a touch screen type and can perform tests such as glass transition temperature, phase transition, melting and enthalpy values, product stability, curing, specific heat, and oxidation induction period.