Whether the color stability of a coating affected by mixing household-based bio-based polyols with water-based pigments depends on the chemical compatibility of the two and the subsequent application environment. While this is not absolute, there are several potential influencing factors that warrant consideration. Bio-based polyols are derived from natural raw materials, and their molecular structure differs from that of traditional petrochemical-based polyols. The color stability of water-based pigments depends on their own chemical structure and the balance of the dispersion system. The interaction between the two when mixed directly affects the color durability of the final coating.
The molecular structure of bio-based polyols is a crucial factor influencing color stability. These polyols are often derived from plant oils, starches, or sugars, and often contain hydroxyl and ester groups, and some also have unsaturated carbon-carbon bonds. To maintain color stability, pigment particles in water-based pigments must avoid chemical degradation. If unsaturated bonds in bio-based polyols undergo oxidation during storage or use, the resulting peroxides and other substances may interact with the pigment molecules in the water-based pigment, disrupting the pigment's conjugated structure and causing the coating to appear lighter, yellower, or have a color shift. This reaction is particularly pronounced when the polyol contains a high proportion of unsaturated components.
The dispersion of the two after mixing also directly affects the color uniformity and stability of the coating. Water-based pigments cannot be evenly dispersed directly in the binder and require a dispersant to form a stable dispersion system. However, the surface tension and viscosity of bio-based polyols differ significantly from those of traditional petrochemical-based polyols. If the surface tension of the polyol is not well-matched with the water-based pigment dispersion system, the dispersant's adsorption state in the polyol will change, preventing it from effectively encapsulating the pigment particles and causing pigment particle agglomeration. Agglomerated pigment particles not only cause coatings to exhibit appearance issues such as color spots and blooming, but also reduce the pigment's light reflection and absorption stability. Over long-term use, particle sedimentation or surface wear can lead to localized color shifts in the coating, disrupting overall color consistency.
pH compatibility also plays a key role in color stability. Bio-based polyols from different sources can have varying pH levels due to varying raw material processing techniques and levels of purification, with some systems being acidic, others neutral, or slightly alkaline. Most water-based pigments are sensitive to pH. For example, azo-based water-based pigments are prone to hydrolysis in acidic environments, causing color fading. Phthalocyanine pigments can experience molecular structural breakdown in strongly alkaline conditions, causing the coating's original vibrant color to gradually fade. If the pH of a bio-based polyol exceeds the optimal stability range for water-based pigments, even if the color appears normal during initial mixing, subtle pH fluctuations during drying or subsequent use can exacerbate the pigment's structural damage, affecting color durability.
External conditions in the home environment can further exacerbate or exacerbate color stability issues. Household coatings are often exposed to sunlight, temperature, and humidity fluctuations. The weatherability of bio-based polyols can indirectly affect the color stability of water-based pigments. Compared to some petrochemical-based polyols with stronger weather resistance, some bio-based polyols, due to the presence of natural groups in their molecules, have weaker resistance to UV rays. These bio-based polyols are susceptible to molecular chain degradation under prolonged sunlight, resulting in small molecules that may interact with pigment particles and disrupt their stable structure. Furthermore, repeated fluctuations in temperature and humidity can cause stress within the coating. If the binding strength between the bio-based polyol and the pigment is insufficient, this can exacerbate pigment particle shedding and gradually fade the coating color. This change is particularly noticeable in environments such as balconies and kitchens.
The storage stability of the mixed system can also affect the color of subsequent coatings. Household base materials often need to be stored for a period of time before use. The natural ingredients in bio-based polyols may foster microbial growth. If the storage environment's temperature and humidity are improperly controlled, microbial growth can decompose some of the polyol components, producing acidic or alkaline metabolites. These metabolites can alter the system's pH and, in turn, affect pigment stability. Furthermore, if the system is not properly sealed during storage, moisture evaporation or air ingress can cause the polyol to oxidize or pigment particles to settle. Even with subsequent stirring, the polyol may not be evenly dispersed, resulting in noticeable color variations after application and a lack of color consistency.
However, this effect is not uncontrollable. Appropriate selection and combination can improve color stability. For example, choose a bio-based polyol with a stable molecular structure and low unsaturated content, paired with a water-based pigment that matches the polyol's pH. Additionally, add an appropriate amount of dispersant to enhance pigment dispersion, and antioxidants and UV absorbers to improve weather resistance. Maintain proper temperature and humidity control and ensure a sealed seal during storage. This not only leverages the environmental advantages of bio-based polyol, but also ensures that after mixing with water-based pigments, the coating color remains long-lasting and stable in home use scenarios, meeting appearance and performance requirements.
