PVC foam products-imbalance between various types of additives

PVC foam products-symptoms of imbalance between various additives

1. Stabilizer

       The stabilizers used in PVC foam products are lead salt stabilizers and calcium zinc stabilizers. As environmental protection requirements become more stringent and calcium zinc stabilizers become more cost-effective, 

      the application of calcium zinc stabilizers begins to become more and more important. increasingly widespread.

       Insufficient stabilizer results in yellowing of the board surface, paste, high brittleness of the product, reduced strength, and low foaming rate;

       If there is too much stabilizer, the foaming agent will decompose in advance, and the gas will overflow from the feeding hole and vacuum hole. 

       If there is a cavity structure, there will be cracks or shrinkage marks;

2. External lubricant

       The external lubrication applied to foam products generally includes paraffin wax and PE wax. Paraffin wax is easy to precipitate, so PE wax is generally used.

       Insufficient external slip, the temperature in zones 4 and 5 of the extruder is difficult to control, and it is easy to over-temperature. Large bubbles, bubbles, 

       and yellowing appear on the board surface, and the surface of the board is rough; the friction and shear heat is large, causing the material to decompose and the board surface to turn yellow. paste;

       Excessive external slippage and poor plasticization will lead to scaling in the inner cavity of the mold and precipitation on the surface of the product, which is prone to leucorrhea, uneven wall thickness, and some symptoms that move back and forth on the surface irregularly;

3. Internal lubricant

       Commonly used internal lubricants include stearic acid, 60, monoglyceride, 316, etc.

       Insufficient internal lubrication, poor material dispersion, uneven plasticization, difficult to control the thickness of the product, the foam board is thick in the middle and thin on both sides, and phenomena such as white banding, adhesion to the mold cavity, and local overheating may occur;

       If there is too much internal lubrication, the foamed product will become brittle, the heat resistance will decrease, and it will transform into external lubrication under a certain temperature and melt pressure, resulting in lubrication imbalance;

       Internal and external lubrication is insufficient, the melt viscosity is large, the plasticizing torque is large, the melt wall sticking phenomenon is serious, there are yellow decomposition lines on the surface of the material, the surface smoothness is poor, and the mechanical properties of the product are reduced;

       Both internal and external lubrication are excessive, the plasticizing torque is small, and the melt plasticization is obviously insufficient. Although the product has good smoothness, the pressure point adhesion is poor, which seriously affects the mechanical properties of the product;

       With less internal lubrication and more external lubrication, the plasticizing time is significantly extended, the plasticizing torque is reduced, and the product is difficult to form and becomes brittle;

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

4. Calcium powder

       Foaming products generally use light calcium with a particle size of about 1,200 mesh. Calcium powder easily absorbs moisture and forms bubbles, silver streaks, etc. 

       on the surface of the product, which affects the appearance and physical properties, so pay attention to storage during the rainy season.

       When the particle size of calcium carbonate is too large, uneven mixing is likely to occur, the plasticization time of the mixture is delayed, and the screw torque is low;

       When the particle size of calcium carbonate is too small, it is easy to agglomerate and change from small particles to large particles, similar to the consequences of excessively large particles;

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

       When the dosage of calcium carbonate is too much, the relative content of resin in the component decreases, the melt strength decreases, and the board section is prone to foam breakage;

5. Foaming regulator

       Foaming regulators generally refer to acrylic processing aids with a viscosity of more than 10. Among them, wood-plastic foam products such as ecological wood and wall panels generally use the type that plasticizes quickly. Foam boards, especially cabinet boards, are generally used. Foaming regulator with strong plasticizing slow melt strength.

       Insufficient foaming regulator, poor melt strength, uneven cells, cells appearing in the cross section, and high density;

       There are too many foaming regulators, the melt strength is too high, the bubbles in the melt cannot expand, the product density is high, and the board surface is prone to wavy lines, distortion, etc.;

6. Foaming agent

        The foaming agents that use the most amount are AC yellow foaming agent and NC white foaming agent. 

        AC will release a lot of heat during the decomposition process, causing the product to turn yellow, 

        and there will be a small amount of ammonia smell during decomposition; NC will emit a lot of heat during the decomposition process. It absorbs heat, decomposes and is odorless, so the two are generally used in coordination in foaming products.

        The dosage of foaming agent is insufficient, the foaming ratio is low, the product has few cells and the density is too high;

        If the amount of foaming agent is too much, the melt strength will become lower, the product will be difficult to form, and the cross section of the foam board will easily produce bubbles; if it exceeds a certain range, the density of the product will increase;

        There is more yellow foaming agent and less white foaming agent, and large and round cells are prone to appear in the cross section.

        Therefore, the dosage of various additives has a certain degree and a mutually restrictive relationship. Less is not enough, and too much is not bad. In production practice, repeated trials must be carried out to give full play to the coordination effect of various raw materials and find a balance point. , fully improve melt strength and foaming efficiency, and extend startup time

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  We have a modern standard factory. Adhering to R&D and innovation to achieve stable quality, all products have passed EU SGS certification, 

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