1. Pvc stabilizer. 

Ca/Zn stabilizer get more and more used because of its eco-friendly and better cost-performance. But if it can't used well, it may lead different problems. Use more or less both are not good. 

It lead yellow, buring, frigial , low-strength, and low foaming. 

If we use too much stabilzier, it can make foaming agent disolved and gas will overflow from the feeding and vacumm hole, there will be cracks or shrink marks in the cavity structure. 

2. Outer lubricant

A lot of foaming producer may choose PE wax not paraffin because paraffind is easy to wipe out. Or if you dont consider cost, you can try TL-74 ( equivalent grade Loxiol G-74)

For foaming products, it usually use PE wax or paraffin 

The 4th or 5th Zone Temp is hard to control which it cause big,string bulles. 

The surface of board is also not smooth and yellow. And even it can lead material burning. 

Outer Lub more. 

It may bad plasticization and mold cavity scaling and end-products wipe out. 

3. Inner Lub. 

Stearic acid, G-60, GMS and 316 is ususal inner lubricants. 

Less inner Lub for bad performance : 

Poor dispersion, un-plasticization, 

The middle of foaming board is thick and both sides is thin. 

Much inner Lub. 

Foaming board is frigial and heat-resistance reducing ,it can change to out lub losing balance for the whole formulation. 

Inner and outer Lub are both less. 

Viscosity and torque become large, meltiing wall sticking is serous

the surface smoothness is poor, and the mechanical properties of the product are reduced;

Inner and outer Lub are both more. 

plasticizing torque is small, and the melt plasticization is obviously insufficient.

The point adhesion is poor, which seriously affects the mechanical properties.

Less internal Lub, more external Lub. 

Time of plasticizing become longer and torque is reduced. Products is hard to form and become frigile.

More internal lubrication, less external lubrication, the plasticizing time is significantly shortened, there is more serious wall sticking phenomenon, the thermal stability time is shortened, and the surface of the product has decomposition yellow lines;

4.Caco3 

Foaming products usually choose light calcium with a particile size 1200 mesh. Calcium powder is easy to absorb moisture and form bubbles and silver streaks on the surface of the product, which affects the appearance and physical properties.

When the particle size of calcium carbonate is too large, it is easy to mix unevenly, the plasticizing time of the mixture is delayed, and the screw torque is low;

When the particle size of calcium carbonate is too small, agglomeration easily occurs, from small particles to large particles, similar to the consequences of too large particles;

When the dose of calcium carbonate is too small, the cells lack a core, the number of cells decreases, and the foaming rate decreases;

When the amount of calcium carbonate is too much, the relative content of resin in the components decreases, the melt strength decreases, and the board section is prone to bubble breaking;

5.Pvc processinga aid. 

Its mooney viscoisty had better be above 10. ( TF-100,TF-200.TF-530)

Wood-plastic foam products such as medium ecological wood and wallboards generally use fast plasticization PA. Foaming boards, especially cabinet boards, generally use slow plasticizing slow-melt foaming regulators.

Insufficient foaming regulator, poor melt strength, uneven cells, cells appear on the cross-section, and the density increases;

Too much foaming regulator, the melt strength is too great, the bubbles in the melt cann't expand, the product density is high, and the board surface is easy to come out wavy patterns, distortions, etc.

6. Foaming agent

  The largest amount of blowing agent is AC yellow blowing agent and NC white blowing agent, AC will be released during the decomposition process

  A large amount of heat causes the product to yellow, and decomposition will have a small amount of ammonia; NC will absorb heat during the decomposition process,

  And the decomposition is odorless, so two kinds of foam products are generally used in coordination.

  Insufficient amount of foaming agent, low foaming ratio, less foam cells, and higher density;If the amount of foaming agent is too much, the melt strength will be low, the product is difficult to form, and the foam board is prone to foam cells;

  Yellow foaming agent is more, white foaming agent is less, and large and round cells are easy to appear on the cross section.

Therefore, we should give full play to the coordination effect of various raw materials, find the best balance point, fully improve the melt strength and foaming efficiency, and extend the startup time.

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