The popularity of windows is due to the fact that, in addition to being strong, long-lasting and affordable, they bring countless benefits, including sound and thermal insulation. These windows are almost completely maintenance free; And this is one of the keys to their success. If you are looking to buy UPVC windows and doors, you may have come across horror stories about them discolouring over time. Unfortunately, UPVC windows in some conditions change color over time and often turn yellow.
The reason for the yellowing of some UPVC profiles
The most likely cause of yellowing is exposure to UV light. If you have used UPVC profile or low-quality laminate, you will notice that the windows that are exposed to sunlight have turned yellow, but those that did not receive sunlight or received very little sunlight; They are not yellow. UPVC is damaged over time when exposed to the sun’s UV light. UV rays break down the UPVC compound and create a chemical reaction that turns the white plastic surface yellow. Apart from sunlight, another reason for yellowing and discoloration of UPVC windows is the materials used in their construction. The fact that UPVC is recyclable has made it incredibly popular. Especially since most people try to make their lives more environmentally friendly. As you know, not all standard UPVC is made; So if the UPVC chosen contains unusual amounts of pigments and plasticizing agents, it may be at risk of yellowing in the future. In general, if we want to examine the yellowing of the profile more scientifically; We must say that thermal-photooxidation reaction occurs in the production and application of UPVC profiles. As a result of heat and pressure, polymer macromolecules are oxidized by moisture, acid, alkali, other impurities and air, and molecular weight decreases and macromolecules are oxidized. This type of chemical structural changes is called degradation, and its most obvious manifestation is the yellowing of the surface, the gradual loss of luster, and even its graying. Contact us to inquire about the price of GOLD PVC profile.
Effective factors in changing the color of UPVC window profile materials
Time and method of manufacture Older UPVC windows (those made more than ten years ago) were usually produced white or with a few millimeters of colored plastic glued to the surface. The tint of these windows fades quickly as the top layer of plastic breaks down when exposed to UV rays.
The reason for changing the color of the UPVC profile
Newer colored UPVC windows are usually made with a laminate finish or the color is infused into the UPVC profile. These methods make the color of the windows very resistant to fading and changing. However, since no color is stable forever, fading will occur but very subtly over a period of fifteen to thirty years, depending on the quality of UPVC and manufacture.
Relationship between molecular structure of UPVC and color
Since UPVC resin is a type of heat-sensitive plastic, its light stability is also poor. Under the influence of heat and light, the branched chain undergoes the reaction of de-HCI and polyene structure molecules. With the slightest color deviation, hydrogen chloride first reacts with surrounding potentially acidic reactants, and its conjugated double bond is converted to a new active position in the UPVC molecular chain. After entering UPVC by light, macromolecular free radicals, which provide the opportunity for oxidation, increase and as a result, color change occurs. There is a certain amount of low molecular weight components in UPVC resin, which reduces the thermal stability of the polymer. The decomposition mechanism of UPVC includes free radical mechanism, ion mechanism, single molecule mechanism, etc. In addition to UPVC degradation stabilizers, discoloration may be affected by the quality of the UPVC resin itself, and whether there is too much residual primer. Impurity If there are certain impurities in the polymer, such as initiators, catalysts, acids, alkaline substances added in the polymerization process, etc., which cannot be completely removed, or if water, during storage and transportation, and If the absorption profile is transferred, the stability of the polymer decreases. Since these materials can cause molecular ion destruction reactions, in PVC+CPE systems with poor stability, by increasing the amount of stabilizer, the problem of yellowing of some profiles can be solved. Weather When the UPVC profile is exposed to destructive factors in the natural environment, it is chlorinated, the original calcium carbonate component is converted into a new calcium chloride component, which causes it to disperse in the layers of the oxidative degradation product and place form potential water absorption, which is one of the reasons for the color change or yellowing of the profiles in the open air.
Solution to prevent discoloration
The following measures prevent UPVC from being decomposed to different degrees and reduce color inconsistency in profile processing: (1) By lowering the processing temperature, a whiter color is obtained. (2) Adding lead salt in composite stabilizer has no special effect on color retention. (3) It is recommended to add simple stabilizers with iodine along with the main whitening fillers or high whiteness fillers to increase the effect of titanium dioxide quickly. (4) It is better to add titanium dioxide and a moderate amount of internal lubricant to UPVC profiles. It is generally believed that low molecular weight materials have a lubricating effect on polymers. One of the mechanisms is that the interaction between macromolecules and small molecules replaces the interaction between macromolecules, which makes the movement of macromolecular parts very easy. (5) During production, the ultraviolet lamp should be used on the profile for 12 hours, and it is undoubtedly necessary to carry out the natural weather exposure test and the aging test of the product in time so that the formula becomes a product with resistance. Perfect against the weather.