How to Improve the PVC Window Profile Surface ?
With the vigorous promotion and application of PVC plastic profiles in China, it has driven the vigorous development of the profile industry. At the same time, with the continuous deepening of people's understanding of PVC profiles, more users have not only limited to meet the requirements of use when choosing products, the requirements for the appearance and surface quality of products have also become higher and higher. As one of the factors affecting the appearance quality of products, the surface brightness has become an important indicator for evaluating the quality and grade of products. Especially with the development of high-speed extrusion in recent years, the surface brightness of products has increasingly become an important limiting factor for the appearance quality of products. And because the brightness of the product is affected by many aspects such as formulation, raw materials, molds, and processes in the production process, in order to obtain a better surface brightness of the product, the influence of various constraints must be integrated; through reasonable control and guarantee in all aspects In order to make the surface of the product have higher brightness.
Formula and raw materials:
Reasonable formula is the prerequisite to ensure excellent processing profile of PVC. Due to the poor performance of PVC resin, narrow processing range, and extremely harsh molding conditions, different amounts of stabilizers, modifiers, lubricants, fillers and other additives are added to the formulation to adapt its performance to the processing and use conditions. The selection and content of various additives are not only related to the processing performance and physicochemical properties of the material, but also have a very important influence on the appearance quality of the product. For example, stabilizers can improve the thermal stability of PVC processing. If the amount of stabilizer used in the formula is too small, it may cause thermal decomposition during PVC processing, resulting in the product surface appearing (light) yellow, affecting the surface brightness of the product. The processing modifier in the formula promotes the plasticization of the material and improves the processing fluidity. If its dosage is low, the processing fluidity of the material becomes poor, and the poor plasticization is easy to cause the product surface to be rough and dull, which reduces the product The brightness of the surface. The choice and proportion of lubricant in the formula, especially the amount of external lubrication, has a more obvious effect on the appearance of the product. Due to the poor compatibility with PVC, too much amount will not only produce precipitation on the surface of the product and make the surface become Roughness appears streaks or moire, and excessive precipitation adheres to the inner wall of the cavity of the mold, which will greatly affect the brightness of the surface of the product.This effect is particularly obvious during high-speed extrusion production; If the amount is not enough, the fluidity of the material becomes poor and the plasticization is poor, which will also reduce the surface brightness of the product. In addition, some manufacturers also add a small amount of fluorescent whitening agent in the formula to improve the brightness of the surface of the profile, but due to the molecular structure of the fluorescent whitening agent, it generally accelerates the aging of the profile during the later use. Therefore, the author believes that it is not suitable for promotion.
The influence of raw materials on the appearance quality of products cannot be ignored. Some defects on the surface of the product will affect the surface brightness to varying degrees, and the occurrence of these defects is often related to the quality of the raw materials. If the moisture and volatile content of PVC exceeds the standard, it often causes the material to generate too much gas during the process and cannot be completely eliminated to produce bubbles, which affects the gloss of the product surface; the surface of the filler CaCO3 is generally subjected to active treatment to Increase the affinity with the polymer, but if its particle size is too large, the degree of activation is not enough, and the dispersion on the surface of the product is uneven, it will also reduce the gloss of the product; the residual crystallization of the impact modifier CPE added in the formula When the degree exceeds 5% -10%, it may be difficult to plasticize during processing and form pits on the surface of the product, which will affect the brightness of the surface of the product to a certain extent.
Influence of PE WAX lubricant:
PE wax is a relatively common external lubricant. During the process, under the action of pressure, it is easy to squeeze out of the mixture and transfer to the surface. The PE molecules are oriented and polar groups are oriented toward the metal surface. Through physical adsorption and chemical bonding, a lubricant molecule layer is formed , It can reduce the friction between the polymer and the equipment surface, and improve the surface brightness of the profile.
Effect of PVC Processing Aid ACR dosage on surface brightness of PVC window profile
ACR as a processing aid can improve the forming performance of rigid PVC. Its addition can improve the friction coefficient between the resin and the machine, and change the rigid PVC from the sliding wall body to the sticky wall body, increase the shear stress, and the material is well plasticized, so as to have a good surface brightness.
As can be seen from Table 3, when the amount of ACR in the formula is 0.5 parts. The surface brightness of the profile is poor, and various physical performance tests are also unqualified. This is because the amount of ACR is too small to convert PVC into a sticky wall body. The material does not get enough shear stress and cannot be plasticized well. Therefore, the physical properties of the profile and the surface brightness are poor. When the amount of ACR is large, the material can obtain sufficient shear stress and good plasticization. Therefore, the physical properties of the profile and the surface brightness are improved. But the amount of ACR is not the better, because the addition of ACR can accelerate the plasticizing process of the material. If the material is plasticized too early, some materials will decompose before extruding the die, which will also reduce the surface brightness of the profile. Therefore, finding the right amount of ACR to make it work well with other additives will greatly improve the surface and internal properties of the profile.
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