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What would cause PVC tarpaulin to discolor?

Release time:

2019-05-01 14:28

Discoloration mainly refers to the color change of the plastic PVC coated tarpaulin material fabric due to the influence of external factors. Of course, from the perspective of a PVC coated fabric canvas tarpaulin factory, the fading of PVC laminated tarpaulin fabrics is related to the light resistance, oxygen resistance, heat resistance, acid and alkali resistance of the toner, and the characteristics of the resin used. If poor-quality raw materials and additives are used, this will cause the durable coated PVC tarpaulin material to easily discolor or fade under normal use.


The following is a detailed analysis of the factors causing fading of PVC tarpaulin colorants:


Light fastness of colorants
The light fastness of the colorant directly affects the fading of the high-quality PVC tarpaulin. When applying nylon coated PVC tarpaulin exposed to strong light, the light fastness (sunfastness) grade requirement of the colorant used is an important indicator. If the light fastness grade is poor, the PVC tarpaulin will be damaged during use. Fade quickly. The light resistance level of the colorant should be no less than level six, and it is best to use levels seven or eight. For indoor PVC tarpaulin applications, level four or five can be selected.


The light resistance of PVC resin also has a great influence on the color change. After the resin is irradiated by ultraviolet rays, its molecular structure changes and it fades. Adding ultraviolet absorbers to PVC resin can improve the light resistance of PVC laminated tarpaulin fabric. ​


Weather resistance of colorants
Refers to the ability of pigments to withstand various climates. These include visible and ultraviolet light, moisture, temperature, atmospheric chlorination, and chemicals encountered during the use of PVC tarpaulin products. The most important weather resistance includes fading resistance, chalking resistance, and durability of physical properties. Organic pigments are good or bad because of their different structures. In addition, in formulations containing white pigments, the wearability of the pigments will be severely affected. The fading, darkening, or hue change of pigments is generally caused by the pigment’s reactive genes. These reactive genes can interact with moisture in the atmosphere or chemical agents – acids and alkalis.


PVC has poor thermal stability and light resistance. Hydrogen chloride begins to decompose at 150°C, and adverse reactions occur depending on the plasticizer content. In addition, the impact of pigments on PVC is reflected in whether the pigments react with PVC and other components that make up the PVC tarpaulin, as well as the migration resistance and heat resistance of the pigment itself. Certain ingredients in colorants may promote the degradation of the resin. For example, iron ions and zinc ions are catalysts for the degradation reaction of PVC resin. Therefore, the use of iron oxide (red, yellow, brown, and black) pigments or zinc oxide, zinc sulfide, and lithopone-like white pigments will reduce the thermal stability of PVC resin. Certain colorants may interact with the degradation products of PVC resin. If the pigment has poor acid resistance, it will interact with the hydrogen chloride produced by the decomposition of PVC during the PVC coloring process and lose its color. Therefore, in terms of PVC coloring, taking into account the characteristics of the resin and related additives used, combined with the characteristics of the pigment, the above-mentioned properties of the required pigments, dyes, surfactants, dispersants, carrier resins, and anti-aging additives are comprehensively evaluated.


Acid and alkali resistance of colorants
The fading of smooth PVC tarpaulin is related to the chemical resistance (acid and alkali resistance, oxidation-reduction resistance) of the colorant. For example, molybdenum chromium red is resistant to dilute acids, but is sensitive to alkali, and cadmium yellow is not acid-resistant. These two pigments and phenolic resin have a strong reducing effect on certain colorants, seriously affecting the heat resistance and weather resistance of the colorants and causing fading. 


It’s also worth taking a deeper look at each factor when using PVC tarpaulins:


Exposure to UV radiation: PVC vinyl coated polyesters are susceptible to UV degradation due to their chemical composition. PVC contains molecules called polymers that break down when exposed to ultraviolet (UV) radiation from sunlight. Over time, this causes the material to weaken, become brittle, and lose its color. We often add UV stabilizers to PVC formulations to mitigate this effect, but prolonged exposure to sunlight can still cause discoloration. Our China heavy duty PVC tarpaulin material can withstand sunlight for 15-20 years outdoors.


Chemical Exposure: PVC tarpaulins may be exposed to various chemicals during use, storage, or cleaning. Certain chemicals can react with PVC molecules, changing its structure and causing discoloration. For example, strong acids or alkalis, such as bleach or ammonia-based cleaners, can cause a chemical reaction in PVC tarps, causing the fabric material to discolor or fade. It’s important to avoid using harsh chemicals on PVC vinyl tarpaulins and follow the manufacturer’s cleaning and maintenance recommendations.


Heating: High temperatures will accelerate the degradation of PVC tarpaulin materials, causing discoloration. When exposed to heat, PVC molecules undergo chemical reactions that change their color or cause them to break down. This effect is particularly noticeable in areas with hot climates or in summer when tarpaulins are exposed to strong sunlight and high temperatures for a long time. Storing PVC tarps in a cool, dark place when not in use can help mitigate heat-related discoloration.


Poor Quality Pigments/Additives: The quality of pigments and additives used in PVC formulations can significantly affect the material’s resistance to tarnish. High-quality pigments and UV stabilizers are critical to maintaining the color and integrity of your high breaking strength PVC tarpaulin over the long term. Inferior quality or insufficient additives may not provide adequate protection against UV radiation or chemical exposure, making plastic PVC coated tarpaulins more susceptible to discoloration and degradation.

Environmental Factors: Environmental pollutants, such as airborne particles, industrial emissions, and vehicle pollutants, can settle on the surface of a high quality PVC tarpaulin and cause discoloration. These contaminants can interact with PVC molecules, causing staining, fading, or other forms of discoloration. Regular cleaning and maintenance will help remove surface contaminants and maintain the appearance of your laminated PVC tarpaulin.


Abrasion: Abrasion from friction with rough surfaces or repeated handling can wear down the outer layer of a PVC coated canvas tarpaulin, exposing it to environmental factors, and causing discoloration. Scratches, scuffs, or abrasions on the surface of the vinyl tarp can serve as entry points for UV radiation, chemicals, or contaminants, accelerating the discoloration process.


Mold and Mildew Growth: Moisture buildup on moistureproof PVC tarpaulins, especially in humid environments or during long-term storage, can create ideal conditions for mold and mildew growth. Not only can mold cause unsightly stains, but it can also cause discoloration of the PVC tarp material. Proper cleaning, drying, and ventilation are critical to preventing mold growth and maintaining the appearance of your PVC coated polyester tarpaulin.


By addressing these specific factors, you can better understand and reduce the risk of your PVC tarpaulin becoming discolored, ensuring its longevity and maintaining its appearance.