How to choose foaming agent during PVC product processing?

About how to use foaming agent

1. Performance

1. AC foaming agent (yellow foaming agent) has a gas generation capacity of about 220 and a decomposition temperature of 

180℃-210; contact with lead salt will cause the decomposition temperature to plummet. 

For example, under static conditions, if 10 grams of lead salt is added to 1Kg of AC foaming agent, 

the decomposition temperature will drop directly from 210°C to about 147°C.

2. NC white foaming agent is also called alkali (commonly known as soda). Its gas generation volume and 

decomposition temperature are much lower than that of yellow foaming agent. The gas generation volume is 

about 110 and the decomposition temperature is about 130-150℃. The main production area of alkali: 

Jiaodong Peninsula, Shandong Province. The price is around 2,500-3,000 yuan/ton. 

the white foaming agent used by everyone is a prepared formula based on soda ash.

3. Universal foaming agent, chemical name sulfonyl hydrazide, decomposition temperature 110-190°C, 

gas generation volume changes with changes in physical conditions, the main advantage is fine foaming holes, 

for example, within the same volume range, there are many foaming holes. 

The pore size is small. It is widely used in high-end shoe sole plastics and aviation equipment products, 

as well as high-end civilian foam products. Origin: Mainly imported, current price is 45,000-80,000 yuan/ton.

2. Application

1. When producing PVC foam boards, if only one yellow foaming agent is used, 

wall breaks and holes are likely to occur when making thick boards. 

The reason is that due to the high decomposition temperature, there is less volatilization in the early stage of the barrel 

and the mold is released in the later stage. It breaks out instantly, so it is easy to crack.

1. When producing PVC foam boards, if only one NC white foaming agent is used, 

it will decompose in advance due to its low decomposition temperature and low gas generation, 

and it will volatilize a lot when it comes out of the mold, so it is impossible to make boards with low density. ; 

If the foaming dose is added too much, more gas will evaporate in the early stage, causing obstacles to the flow of the fabric

in the barrel, which may lead to excessive plasticization, so the color of the board that comes out is easy to turn yellow.

2. Blending solution: When processing NC white foaming agent, the delay time is taken into consideration, 

so lubricant is used to mix the foaming agent through the mixer, coat it, increase fluidity, etc., 

to increase the decomposition time.

3. According to different production densities, the proportion of AC and NC foaming agents should be reasonably matched to 

achieve a balance. However, if the total amount of the two is too large, it will also cause a large amount of gas to be 

generated in the barrel in advance, thus affecting the fluidity. 

Since making foam boards requires fast flow speed to impact the die opening, 

and sufficient gas generation volume to meet the needs, too little or too much foaming agent dosage will affect the density and fail to achieve the purpose.

3. Mutual influencing factors

1. If the fluidity of the formula system is too good, the amount of foaming agent must be calculated appropriately for 

changes in the amount of foaming agent, especially when there is more or less external lubrication. 

Furthermore, the amount of foaming regulator and foaming agent must be calculated appropriately, 

otherwise it will cause waste or affect the force exerted when exiting the die.

2. When using different stabilizers such as lead salt, calcium zinc, organic tin or rare earth, the ratio parameters of the foaming 

agent are not consistent.

3. The influence of screw on foaming agent:

Whether a pair of screws plasticizes well or not, other costs will of course vary greatly, 

let’s not mention these for now. Regarding the foaming agent, a screw with poor plasticization will use less foaming agent; 

a screw with good plasticization will require more foaming agent. Also, the screw and the regulator are also closely related.

1. The relationship between mold and foaming agent:

To produce stable and high-quality products, the discharging speed and back pressure of the mold are very critical, 

and this is also closely related to the amount of foaming agent, and is also directly related to the amount of regulator.

Therefore, with a good screw and a good mold, you can use less regulator.

Since there are too many uncertain factors in the production of foam boards 

(including the selection of calcium powder thickness, mixing temperature, startup setting data, etc.), 

it cannot be fully explained here and can only provide a basic reference.

Here is a simple sharing, the purpose is to communicate and discuss with everyone, 

and develop and progress together through mutual communication!

If you encounter any problems, you can contact me for communication.