Automotive Application
The Automotive industry can be divided into several distinct parts. The two major sections are
The coatings requirements for the two parts, whilst similar, differ in more than just the different binder systems used. Different properties develop different levels of importance depending upon which side of the industry is being considered. The properties given below are those of importance to the industry that are influenced by the TiO2 pigment, but are not necessarily in order of importance.
Important properties of Automotive Finishes
Opacity
Maximizing the opacity of the coating is of importance to both sides of the automotive industry. If greater opacity can be achieved from the pigment, its potential benefits can be used in any one of several ways:
-
To reduce TiO2 content and hence lower raw material cost.
-
To run at reduced film build, giving better mileage.
-
To obtain an overall improvement in product quality at no extra cost.
The performance of a modern, high quality, superdurable pigment is tailor made for the automotive industry, offering improved opacity in the final coating with the possibility of reduced cost. Opacity is very important to both sections of the industry. Optimization of the dispersion stage guarantees that maximum opacity is obtained from the pigment, maximizing cost benefits. The advantage of having a TiO2 offering superior opacity development and obtaining the targeted opacity at lower PVC's. It can allow you to obtain significant improvements in gloss, distinctness of image and gloss haze.
Important Properties Top
Tint Strength
Tint Strength is particularly important to the refinish industry, which is now configured to make a wide range of different colors using in-store tinting systems. Variations in the tint strength of the pigment cause variability in the color of the final tinted color or problems of calibration from batch to batch in the manufacture of the white tint system products. Millennium Inorganic Chemicals pigments are all tightly controlled for tint strength and so help to guarantee the reproducibility of your tint bases. Optimization of the dispersion stage guarantees that maximum tint strength is obtained from the pigment, maximizing cost benefits.
Important Properties Top
Color Reproducibility
Color reproducibility is important to both sides of the automotive finishing industry, but more so to the refinish side. However, if the OEM colors are not reproducible, then the refinish matches will not be acceptable without individual color matching for each item. Color reproducibility depends upon the uniformity of tint strength of the pigments in use as well as their uniformity of color and undertone . Variations in the degree of pigment dispersion cause significant variations in all of these properties. Millennium Inorganic Chemicals pigments are all closely controlled with respect to color, undertone, pigment dispersibility, which is maximized, and consistent color acceptance. This control reduces variability within your tint systems and, when combined with optimized manufacturing techniques, helps to guarantee good color reproducibility. In the refinish section this control is critical.
Important Properties Top
Gloss
Maximizing gloss is important to both parts of the automotive coatings industry. The grade of pigment and its degree of dispersion are major influences on the specular gloss of all coatings systems. Modern, high-dispersibility pigments can give marked improvements in specular gloss and gloss stability. However, they need to be carefully formulated at the dispersion stage to ensure that optimum dispersion is obtained. Gloss is also impacted by the pigment content (PVC) of the coating, increased PVC can markedly reduce the gloss of an applied film.
Important Properties Top
Distinctness of Image and Gloss Haze
Similar factors influence distinctness of image (DOI) and haze as influence specular gloss. In this case the degree of dispersion may be even more important than it is with specular gloss, as any micro-roughness will show as loss of DOI or an increase in haze. The particular grade of pigment selected can have a significant influence on the DOI of the coating. In addition, the DOI and haze can be influenced by a combination of the method of application of the coating and the particular pigment used. For example it has been shown that the distinctness of image and the haze of an automotive OEM topcoat is directly and significantly influenced by pigment selection when using the electrostatic minibell spray gun. Distinctness of image and Haze are also impacted by the pigment content (PVC) of the coating. Increasing the PVC of the applied coating can significantly reduce both of these properties. This gives a significant advantage to pigments developing superior opacity at lower PVC's, allowing pigment to be removed from the coating reducing haze and increasing DOI.
Important Properties Top
Durability
The durability of the coating is important to both the OEM and the refinish industries. The grade of pigment selected and its degree of dispersion affect gloss retention which is the most important measure of the durability of an automotive coating. Chalk resistance becomes less important due to polishing of the finish by the car owner during the coating's life. For optimum gloss retention, a "superdurable" must be selected. This minimizes the degree of free radical formation within the film and so slows down weathering induced loss of gloss. The degree of dispersion influences the gloss retention of the coating, by its influence on the breakdown of pigment agglomerates. The better the pigment is dispersed; the better is its initial gloss. This in turn leads to better gloss retention. Thus it is imperative that optimized dispersion is achieved to maximize the gloss retention of the polymer/pigment system. Optimized pigment dispersion is achieved by optimizing the dispersion stage of manufacture (the millbase) for individual pigments.
Important Properties Top
Color Stability
All automotive colors must be stable over a long period of time. Within a polymer system, titanium dioxide pigments do not themselves discolor. However it is possible for them to catalyse any discoloration reaction inherent in the paint system. Thus in some susceptible polymers, discoloration can proceed at accelerated rates due to the influence of the Titanium Dioxide pigment. Changing the pigment may improve this problem, particularly by changing to the use of "superdurable" encapsulated pigments. These minimize surface reactivity of the pigment, which is the catalyst for this reaction. However, to completely overcome the problem, the polymer system itself needs to be modified.
Important Properties Top
Flow
Both sides of the automotive industry need good flow from the finishes they use and the flow of the coating can be influenced by the titanium dioxide. This is normally an effect of the pigment's oil absorption and its degree of dispersion. Pigments with low oil absorption allow the viscosity of the curing coating to be minimized. This results in improved flow, reduced orange peel etc, However, if the coating has too much flow, sharp edge coverage can be adversely affected. The use of a high oil absorption pigment can significantly reduce flow through this effect.
Important Properties Top
Paint in-can stability (shelf life)
Shelf life is particularly important for the refinish industry where coatings may be held for some time in repair shops and stockists until needed. Inventory turn in the OEM industry will reduce the importance of this property. The shelf life (viscosity stability, gloss stability, settling , cure stability etc) of coatings being stored prior to use, is influenced by the combination of all raw materials in the formulation. In some cases, such a problem may be overcome, or at least reduced by changing the titanium dioxide pigment. However, it is better to undertake an evaluation of the entire system to overcome the basic cause of the instability.
Important Properties Top
|
