The main reason for the yellowing of PVC pipes is that the amount of stabilizer is not enough or the grade is not good, and there should be redness. It is possible that a stabilizer of particularly poor quality was used
But in most cases, it is the problem caused by unbalanced lubrication. Too little lubrication, especially too little external sliding, and too much plasticization cause the pipe to change color and become brittle
You can add a little Titanium Dioxide to see if it can be covered. If not, try adding a stabilizer or replace it. If it is a calcium zinc stabilizer, you should pay more attention to the adjustment of the lubricant.
In addition, lubricants affect plasticization, calcium carbonate is added with brightener, and PVC Resin. Under the same conditions, poorly used PVC will also become more yellow and need more stabilizers.
In general, you will think of the problem of stabilizer. In fact, lubrication is also a very important factor when the stability is sufficient. In addition, if calcium powder is damp, it will also affect plasticization.
Stabilizer is generally the first consideration, but the solution to the problem can generally start with the appropriate adjustment of the lubrication system. If the problem of stabilizer is eliminated, the sliding agent and dynamic balance shall be emphasized. Stabilizers mentioned in the industry generally do not contain antioxidants. However, calcium zinc stabilizers generally contain antioxidants.
The ground color of rutile type is reddish, while that of anatase type is blue. Rutile is better, but more expensive.
Both rutile and anatase titanium dioxide have high reflectivity to light in the visible wavelength range (400-700nm), so they all have good whiteness. However, in the ultraviolet wavelength range smaller than the visible light range, such as 300-400 nm, the performance of two different crystal forms of titanium dioxide is very different.
For Rutile Titanium Dioxide (red line), in the UV-A band (350-400nm) with strong lethality, its reflectivity to ultraviolet light is much lower than that of blue anatase titanium dioxide. In other words, its absorption rate to ultraviolet light is much higher than that of blue anatase titanium dioxide.
In this case, the UV light shared by the surrounding film-forming organic resin is much less, so the service life of these organic substances will be longer. This is the reason why the weather resistance of rutile titanium self powder is much better than that of anatase. These characteristics are innate.
During extrusion, the base color of titanium dioxide type affects the color of the product. In later use, the different absorption of titanium dioxide to ultraviolet rays affects the weather resistance of the product, thus affecting its color. In fact, rutile titanium dioxide is only slightly yellow than anatase, but it will not turn yellow. The problem lies in the greater possibility of stabilizers, and it may also be the use of composite stabilizers. At present, some domestic manufacturers of composite stabilizers have added a large amount of lubricants to reduce the cost and reduce the amount of effective ingredients, and the stability is slightly insufficient under the same amount
The temperature is too high, the mold compression ratio is too large, the stabilizer addition is not enough, there is a problem with the lubrication system, the stability of the resin itself is not enough, calcium powder is damp, there are problems in the gap between the screw and the barrel, and the shear is too large. There are many reasons, which must be investigated according to the actual situation!!
Problem solving:
Adding 0.1 more stearic acid to promote plasticization and 0.3 parts of titanium dioxide is mainly to cover up the problem of background color. The appearance of the pipe is white and light is red
