\nHowever, one of the serious challenges for manufacturers in the production and use of PVC is a phenomenon called Yellowing<\/a>; an unwanted change in the color of the product that, in addition to reducing its appearance, is a sign of a decrease in the thermal and optical stability of the material.<\/p>\n
PVC yellowing<\/strong> is not accidental; rather, it is the result of the interaction of several key factors in the formulation and production conditions. In this article, we will examine from a scientific and practical perspective what factors cause yellowing, and more importantly \u2014 how to prevent it.<\/p>\n <\/p>\n Moisture is one of the main factors of degradation in the PVC production and storage process, causing PVC yellowing. The presence of water in the raw materials or production environment causes unwanted reactions during melting and shaping.<\/p>\n At high process temperatures (over 160\u00b0C), the presence of moisture can lead to the hydrolysis of lubricants and the activation of thermal degradation reactions of PVC chains. This degradation gradually releases chlorine and the polymer chain shortens.<\/p>\n The result? A color change from white to cream and ultimately a noticeable yellowness in the final product.<\/p>\n Therefore, careful drying of raw materials, control of environmental humidity and proper storage of PVC powder, additives and even final packaging are the first steps in preventing PVC yellowing.<\/p>\n Titanium dioxide (TiO\u2082) is a pigment that, in addition to providing whiteness, plays a vital role in protecting PVC from ultraviolet (UV) radiation. But not all titanium is the same.<\/p>\n There are two main types of titanium in the industry:<\/p>\n \u2022 Rutile<\/p>\n \u2022 Anatase<\/p>\n In PVC formulations, the use of rutile titanium with alumina and silica coatings is essential, as this type has higher light and heat resistance.<\/p>\n In contrast, anatase titanium accelerates oxidation in the presence of UV, resulting in faster yellowing of PVC.<\/p>\n Therefore, choosing the right type and brand of titanium according to the type of application (indoor or outdoor) plays a key role in preventing color change.<\/p>\n One of the vital components of any PVC formula is the stabilizer system. These additives prevent thermal degradation of PVC during extrusion or injection. Common stabilizers include: In rigid PVC (Rigid PVC) such as pipes or profiles, the Ca\/Zn system provides the best balance between thermal stability, environmental compatibility and color retention. If the amount of stabilizer is less than optimal or its combination with titanium and lubricant is incompatible, gradual yellowing of PVC is inevitable during the production and storage of the product.<\/p>\n Luminisers and plasticizers in PVC formulations are responsible for facilitating the flow of materials in the extruder and creating flexibility.<\/p>\n However, if these additives have low thermal stability or chemical incompatibility with PVC, they themselves become the main source of degradation.<\/p>\n For example, lubricants based on unsaturated fatty esters or containing acidic impurities decompose at high temperatures and release acid. This acid reacts with PVC and releases chlorine; a process that ultimately causes the product to turn yellow (PVC yellowing happens<\/strong>)<\/p>\n Therefore, the use of stable and refined lubricants (such as high-quality chlorinated paraffins or stable esters) along with precise adjustment of the ratio of plasticizers and resin is one of the effective solutions in preventing PVC yellowing<\/strong>.<\/p>\n Even with the best formulation, if the process temperature and shear rate are not controlled, excessive heat in the extruder or die will lead to molecular degradation and the release of HCl.<\/p>\n This chain degradation causes the PVC color to darken and ultimately the PVC yellowing<\/strong> apears.<\/p>\n In addition, oxygen in the air, especially at high temperatures, also causes the oxidation of lubricants and stabilizers.<\/p>\n Therefore, temperature control, the use of extruders with effective cooling, and reducing the contact of the melt with air are crucial steps in maintaining the white color of PVC.<\/p>\n The definitive solution to prevent PVC yellowing<\/strong> is a combination of technical knowledge in formulation and precise control of the production process.<\/p>\n Precise formulation includes: Control of production conditions includes: This intelligent combination ensures that the final PVC product is white, stable and with a lasting color.<\/p>\n Professional factories usually use the following standard tests to control PVC yellowing: The results of these tests help the manufacturer to identify and correct formulation or process weaknesses.<\/p>\n In recent years, PVC additive manufacturers have focused on developing high-temperature stabilizers and lubricants. Therefore, choosing a reliable additive supplier is as important as the PVC formulation itself.<\/p>\n Conclusion: The secret to white and durable PVC<\/p>\n PVC yellowing<\/strong> is a complex but controllable phenomenon. Ultimately, precise formulation + control of production conditions = more stable PVC with longer lasting color. <\/p>\n For any advice and price inquiries for purchasing PVC types, contact our experts<\/a> at KPPlastics- Afshin Karami Trading.<\/p>\n <\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" Introduction PVC yellowing is the result of the interaction of several hidden factors in the production process. Polyvinyl chloride, or PVC, is one of the most widely used polymers in various industries \u2014 from pipes and fittings to door and window profiles, cables, flooring, and soft films. However, one of the serious challenges for manufacturers …<\/p>\n![\"\"](\"http:\/\/irplastics.com\/en\/wp-content\/uploads\/2025\/10\/yellowed-pvc-300x182.webp\")
<\/p>\n1. Moisture; the hidden enemy of PVC stability<\/h2>\n
2. Choosing the wrong titanium; The Critical Role of TiO\u2082 in Color and Stability<\/h3>\n
3. Weak stabilizer system; a silent danger in the formulation<\/h3>\n
\nHowever, if this system is poorly selected or its amount is low, the PVC chain becomes vulnerable to heat, resulting in yellowing of the PVC.<\/p>\n
\n\u2022 Calcium-zinc stabilizers (Ca\/Zn)
\n\u2022 Tin stabilizers (Organotin)
\n\u2022 Lead stabilizers (in the past, now less used)<\/p>\n
\nHowever, in soft PVC (Soft PVC), the type and amount of stabilizer must be adjusted more precisely, since the behavior of the thermal system changes in the presence of plasticizers.<\/p>\n4. Unstable lubricant or plasticizer; gradual color change agent<\/h3>\n
5. The role of process temperature and oxygen in exacerbating PVC yellowing<\/h4>\n
6. What is the solution? Precise formulation + control of production conditions<\/h4>\n
\n1. Use of high-quality thermal stabilizers (Ca\/Zn or Organotin)
\n2. Selection of rutile titanium with appropriate coating
\n3. Use of heat-resistant lubricants without acidic impurities
\n4. Precise adjustment of the plasticizer, filler and lubricant ratio
\n5. Addition of secondary antioxidants to prevent oxidation in storage<\/p>\n
\n\u2022 Complete drying of raw materials before extrusion
\n\u2022 Adjustment of the temperature of the extruder zones within the optimal range (160\u2013180 degrees)
\n\u2022 Prevention of long-term material stops in the machine
\n\u2022 Precise control of the pressure and speed of material exit
\n\u2022 Uniform cooling of the output parts<\/p>\n7. Quality Control Tests to Measure PVC Color Stability<\/h3>\n
\n\u2022 Oven Test (thermal yellowing test) at 180 degrees
\n\u2022 Light Aging Test to evaluate light resistance
\n\u2022 Measurement of the color index (Yellowness Index) with a spectrophotometer
\n\u2022 HCl Evolution Test to check thermal stability<\/p>\n8. The role of additive manufacturers in reducing yellowing<\/h3>\n
\nModern additives based on calcium-zinc, natural epoxies (EPO), phosphites and multi-stage antioxidants help PVC to remain white for longer, even under extreme temperature and light conditions.<\/p>\n
\nAlthough factors such as humidity, incorrect titanium selection, poor stabilizer system or unstable lubricants can play a role, this problem can be minimized with scientific and careful management.<\/p>\n
\nAttention to detail, use of high-quality additives, and updating production technology is a surefire way to produce products that maintain global standards both technically and visually.<\/p>\nGet in Touch with KPPlastics-Afshin Karami Trading<\/h5>\n
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