Usage Method of NC AC Foaming Agent

I. Performance

1. AC Foaming Agent (Yellow Foaming Agent): Gas evolution is about 220, and decomposition temperature is around 180℃-210℃. Contact with lead salts will sharply reduce the decomposition temperature; for example, statically, adding 10g of lead salt to 1kg of AC foaming agent lowers the decomposition temperature from 210℃ to about 147℃.

2. NC White Foaming Agent (commonly known as Soda): Both gas evolution and decomposition temperature are much lower than those of the yellow foaming agent, with gas evolution around 110 and decomposition temperature between 130℃-150℃.

3. Universal Foaming Agent (chemical name: sulfonylhydrazide): Decomposition temperature is 110℃-190℃, and gas evolution varies with physical conditions. Its main advantage is fine foaming cells (more cells with smaller pores in the same volume). It is widely used in high-grade sole plastics, aviation equipment products and high-end civil foamed products.

II. Application

1. When producing PVC foam boards with only AC foaming agent, thick boards are prone to wall breaking and cell problems. This is because the high decomposition temperature leads to little volatilization in the early stage of the barrel and sudden outburst when exiting the mold in the later stage, resulting in easy cracking.

2. When using only NC white foaming agent for PVC foam boards, low-density boards cannot be produced due to its low decomposition temperature, small gas evolution and early decomposition (a large amount volatilizes when exiting the mold). Excessive NC dosage will cause more gas volatilization in the early stage, hindering material flow in the barrel and possibly over-plasticization, leading to yellowing of the board.

3. Mediation Solution: To delay the decomposition of NC white foaming agent, lubricants are mixed with it in a mixer for coating to improve fluidity and extend decomposition time.

4. Reasonable ratio of AC and NC foaming agents should be adjusted according to the desired density. However, excessive total dosage will cause a large amount of gas to be generated in the barrel in advance, affecting fluidity. Proper dosage is crucial—too little or too much will fail to meet the required density, as foam boards require fast flow rate to impact the mold mouth and sufficient gas evolution.

III. Interfering Factors

1. If the fluidity of the formula system is too good, the dosage of foaming agent (especially external lubricant) and foaming regulator must be accurately calculated to avoid waste or affecting the force when exiting the mold.

2. Different stabilizers (lead salt, calcium-zinc, organotin, rare earth, etc.) lead to different foaming agent ratio parameters.

3. Screw Impact: Poor plasticizing screws require less foaming agent, while over-plasticizing screws need an appropriate increase. The screw is also closely related to the regulator.

4. Mold Relationship: The discharge speed and back pressure of the mold are critical for stable product quality, which are directly related to the dosage of foaming agent and regulator. A high-quality screw and mold can reduce the usage of regulators.

Due to many uncertain factors in foam board production (including calcium powder fineness, mixing temperature, startup settings, etc.), this article only provides basic references. The purpose of this sharing is to exchange and discuss with everyone for mutual development and progress!