In the manufacturing of power electronics, high-voltage transformers and current transformers, as well as semiconductor power devices, epoxy resin potting materials serve as core electrical insulation and protective materials, directly determining the lifespan limit of electrical equipment under high and low temperature shocks and strong electric field operations.

Evaluating the initial thermal decomposition temperature, the fastest rate of thermal weight loss, and the high-temperature carbon residue rate above 800℃ of cured epoxy resin through thermogravimetric analysis (TGA) is a key quality inspection method for assessing the temperature resistance grade (such as Class B, Class F, Class H) and flame retardant properties of formulations.

However, if the polymer sample is improperly prepared, has excessive particle size, or the crucible is overfilled, it is prone to internal heat transfer lag, local thermal expansion and overflow, and even explosion, which can damage the sensor. Based on the technical specifications of the Baoding Huazheng Electric HZ2329 thermogravimetric analyzer, we have developed a set of standard testing and sample preparation essentials for epoxy potting materials:

I. Selection of reference material and crucible: An empty ceramic crucible serves as the benchmark

Reference material configuration: In polymer and electrical insulation material testing, a clean empty ceramic crucible is selected as the reference end tray;

Material Stability: The standard high-quality ceramic crucible boasts advantages such as high temperature resistance (capable of withstanding 1150°C), strong chemical inertness, and non-reactivity with conventional polymers, ensuring stable thermogravimetric benchmarks throughout the entire testing cycle.

II. Core Techniques for Sample Preparation and Volume Control

According to the specification requirements for cured epoxy samples in the HZ2329 instruction manual:

Shape preparation: For solidified and molded block-shaped samples such as high-melting-point epoxy potting materials and polyurethane elastomers, it is recommended to use a sharp knife or a dedicated micro-slicing tool to cut them into regular small cubes or thin slices. Avoid using irregular long strips or thick blocks, so as to maximize the contact area between the sample bottom and the flat bottom of the crucible and reduce the thermal contact resistance;

Strict volume control (no more than 1/2): Place the prepared small sample block into the dedicated ceramic crucible on the right side. The total volume of the sample must not exceed one-half (1/2) of the crucible's capacity. Because polymer materials often undergo volume expansion and intense gas evolution during the initial stages of rapid glass transition and thermal decomposition, leaving a space margin of more than 50% can effectively prevent sample overflow or foaming and adhesion to the furnace chamber walls.

III. Standardize the operation of double-layer covered stove

After firmly placing the sample crucible and the reference crucible on the balance pan:

The furnace body sealing adopts a "double-layer protective structure" - the internal ceramic heat insulation cover must be covered first, followed by the tightly sealed external metal furnace cover;

The double-layer furnace cover structure not only effectively reduces the loss of high-temperature radiation to the environment and enhances the axial temperature uniformity in the center of the furnace chamber, but also prevents weak mechanical disturbances to the microbalance tray caused by air convection.

From neat sample preparation, strict quantity control to double-layered cover, the standardized sample pretreatment, coupled with the sensitive mass capture capability of HZ2329, can truly reproduce the entire process of thermal degradation of epoxy insulation materials.