Tags: Sustainability / Natural Coatings Automotive Coatings Architectural Coatings
Sustainable paints and coatings are those that reduce harm to the environment throughout the product’s entire lifecycle without sacrificing cost or performance. This includes the use of safe and environmentally responsible materials in the paint formulation.
However, sustainability aspects have expanded well beyond just reducing volatile organic compounds (VOCs) and other environmentally harmful components. The definition of sustainability now also encompasses all aspects of the lifecycle (e.g., formulation, manufacturing, application, and disposal). One must also consider improvements in performance and durability to reduce maintenance and replacement costs.
Sustainability issues extend beyond the paint and coating producer to the suppliers of the raw material used in formulation. For example, pigments such as titanium dioxide (TiO2) can play an important role in achieving overall sustainability. This article will review how highly treated Ti-Pure™ titanium dioxide (TiO2) from Chemours can help both paint formulators and end-users provide enhanced sustainability. These pigments have been developed for high performance industrial and architectural coatings.
Sustainability and Circularity in the Paint and Coatings Industry
Sustainability efforts often make good business sense, promising to deliver revenue gains, cost savings, and other benefits that lift enterprise value. For most paint suppliers, sustainability has become an essential part of their marketing strategy. For example, sustainability certifications allow suppliers to differentiate themselves by proving that their products meet key environmental factors.
Circularity is an even more comprehensive approach. Circularity or the circular economy has been defined as a regenerative system in which resource input and waste, emission, and energy leakage are minimized by slowing, closing, and narrowing material and energy loops (Figure 1). This can be achieved through forward-looking design relative to maintenance, repair, reuse, remanufacturing, refurbishing, and recycling. In a circular economy an added emphasis is on enhancing the longevity of products.
Figure 1. The Circular Economy
In the more common linear economy, resources are turned into products which are ultimately destined to become waste because of the way they have been designed and manufactured. This linear process is often summarized by "take, make, waste”.
Some products can be manufactured from materials or designed so that they can be reused or recycled. However, in several industries (e.g., coatings and adhesives), circularity may be achieved by enhancing the longevity of the substrate by reducing replacement and maintenance costs along with developing options for paint collection, recycling, and reuse.
There are many ways of bringing sustainability to the paints and coatings industry. A simple change in one minor additive in a paint formulation can promote sustainability across the entire value chain. In this way additives are enablers of sustainability.
A pigment is a good example of this. The amount usually introduced is small however the impact on formulation and performance properties and the influence on sustainability across the entire value chain can be notable. Life Cycle Assessment (LCA) forms a solid basis for holistic or all-inclusive formulation choices, where ingredients are not judged in isolation, but in consideration of their impact on the performance throughout the life cycle of the ultimate painted article.
Function of TiO2 Pigments in Coatings
TiO
2is commercially available in two crystal structures—anatase and rutile. Rutile TiO
2 pigments are preferred because they scatter light more efficiently, are more stable and are more durable than anatase pigments. TiO
2 is commercially produced by either the chloride or the sulfate processes. In general, the chloride production process offers waste disposal and energy advantages over the sulfate process.
TiO2 is the most important white pigment used in the coatings industry. It is widely used because it efficiently scatters visible light, thereby imparting whiteness, brightness and opacity when incorporated into a coating. The
primary control of opacity and brightness in white paint films depends on the scattering (bending) of light.
For the most effective light scattering, the TiO
2 pigment diameter should be slightly less than one-half the wavelength of light to be scattered. Commercial TiO
2 pigments for coatings average 0.2–0.3 µm in diameter. Light scattering is also affected by particle spacing. As the distance between TiO
2 particles decreases, the scattering efficiency is reduced significantly resulting in a decrease in hiding power (Figure 2).
Figure 2. Relative Scattering Power as a Function of TiO2 Pigment Separation
One way to provide spacing between TiO
2 particles is to coat the pigment surface in a controlled manner. The surface coating then acts as a physical spacer, maintaining separation between adjacent TiO
2 particles and minimizing losses in diffractive light-scattering efficiency as pigment concentration is increased.
TiO
2 is also unique in that, it combines high refractive index with a high degree of transparency in the visible region of the spectrum. This combination affords the coatings formulator a route to highly opaque and bright whites or tints at minimum film thickness. Figure 3 shows a practical demonstration of the effect of refractive index on opacity. The films were formulated at constant volume percent pigment in an acrylic vehicle. The film made with rutile TiO
2 does the most complete job of hiding the substrate.
Figure 3. Effect of Refractive Index on Opacity
Chemours TiO2 Highly Treated Grades (Ti-Pure™ TS-6200 and Ti-Pure™ TS-6300)
Chemours’ technical expertise and understanding of paint applications enable the production of high-quality
Ti-Pure™ TS-6200 and
Ti-Pure™ TS-6300 TiO
2 pigments. Both are rutile pigments that are surface treated during processing to ensure (1) that particle separation is achieved to provide maximum TiO
2 efficiency and hiding power and (2) that the TiO
2 particles do not settle or clump within the paint. The properties of Ti-Pure™ TS-6200 and Ti-Pure™ TS-6300 are provided in Table 1. High quality Ti-Pure™ TS-6200 and Ti-Pure™ TS-6300 TiO
2 pigments have excellent processability and
dispersion characteristics to ensure batch consistency.
|
Property
|
Value
|
|
Ti-Pure™ TS-6200
|
Ti-Pure™ TS-6300
|
|
TiO2, wt%
|
93
|
>82
|
|
Specific gravity
|
4.0
|
3.7
|
|
Bulking value, L/kg (gal/lb)
|
0.25 (0.03)
|
0.27 (0.032)
|
|
Color CIE L*
|
99.4
|
100
|
|
pH
|
8
|
9
|
|
Carbon black undertone
|
13
|
10
|
Table 1. Analysis and Physical Properties of Ti-Pure™ Rutile TiO2 Pigments
Ti-Pure™ TS-6200 couples an advanced silica coating technology with a proprietary organic surface treatment to give optimal particle distance, superior dispersibility, with minimum photocatalytic degradation. This new technology represents a significant improvement over the traditional method of silica encapsulation found on most super-durable TO2 pigments. This product design extends the life of coatings in critical applications improving the sustainability over the product life cycle.
Ti-Pure™ TS-6200 offers:
- high hiding power,
- high initial gloss
- excellent gloss retention,
- superior durability,
- chalk resistance,
- excellent processability.
Download case study for more data about these features
It is considered a specialty pigment for
high gloss applications: automotive coatings, coil coatings, durable industrial coatings, and fluorinated polymer coatings.
Ti-Pure™ TS-6300 particle size is also optimized, and the surface oxide treatment provides physical spacing so that TiO
2 efficiency is maximized while maintaining the highest level of film integrity. It delivers exceptional brightness and maximum hiding power. It is designed primarily for high quality flat architectural coatings containing high levels of extenders and TiO
2 that are formulated near or above the critical pigment volume concentration (CPVC). The weatherability of Ti-Pure™ TS-6300 is suitable for many interior and exterior architectural coatings. The improved TiO
2 spacing results in reduced water, material, and energy usage and supports a more sustainable product design.
TiO
2 pigments in general and Ti-Pure™ TS-6300 and Ti-Pure™ TS-6200 specifically enable sustainability across the entire value chain from raw material selection to the paint formulation and manufacturing and through to the end-use. The following sections will describe how these pigments provide added value to the overall sustainability signature of paints and coatings.
Chemours talks about the three drivers for TiO2 in the industry, learn how sustainability is one of them >>>
Sustainability through Choice of Raw Material
It all begins with the selection of the right raw materials. Of course, the right raw materials must eventually produce a product that meets economic and performance specifications. However, the raw materials should also be sustainable. Materials are sustainable if they do not strain the environment during their production, use, or disposal. They also must not adversely impact health and wellbeing of individuals that come into contact with the material.
Titanium is the ninth most abundant element in the world and TiO
2 is the oxide of the metal, which occurs naturally in rocks and ores. TiO
2’s impact on overall paint costs is complex, and often cost savings can be achieved by using a higher quality TiO
2 pigment.
The chloride production process offers manufacturing and quality advantages over the sulfate process. Currently, the chloride process offers tighter product control and is less labor intensive than the sulfate process. The chloride process is also environmentally safer due mainly to the waste generated in the sulfate process.
There are no realistic alternatives to TiO
2 pigment available. No other pigment gives anywhere near the same performance, such as opacity, brightness, and
durability. You would have to apply at least three times as much paint with the nearest alternative to get the same coverage (i.e., six coats rather than two).
Health and Safety
With a legacy of around 100 years of safe production and safe commercial use across a vast number of industries, titanium dioxide has brought major benefits to society. TiO
2 pigment cannot burn or explode, neither as a dry powder nor as an aqueous slurry. Neither the dry pigment nor the slurry is corrosive or reactive.
Long-term studies have shown that the use and production of titanium dioxide do not harm human beings. It is not hazardous in the absence of the extreme inhalation conditions acknowledged in the classification. Leading European manufacturers and suppliers of titanium dioxide have formed the Titanium Dioxide Industry Consortium (TDIC) to manage REACH registration of TiO
2 and related substances. TiO
2 is not subject to any restrictions or authorizations under REACH.
The Life Cycle Approach in Selecting Raw Materials
Many formulators assess the potential environmental impacts of their products by estimating the amount of greenhouse gas emissions associated with manufacturing a liter of paint. However, the environmental impacts from the raw materials alone do not capture the overall effects from a paint’s use and beyond. Such narrow vision during formulation can lead to poor decisions with unintended consequences and costs.
The TiO
2 industry is reducing its carbon footprint. The Titanium Dioxide Manufacturers Association (TDMA) pioneered a life cycle assessment methodology to calculate an industry average carbon footprint that helps the industry monitor and measure its performance. The TDMA encourages its customers and suppliers to use this data to help them assess the product environmental footprint of their own products containing TiO
2.
Formulators should take a more holistic approach by assessing the product’s impact over its total lifecycle. By examining coatings’ “cradle-to-grave” or “cradle-to-cradle” impact, formulators can make better decisions about which materials to use based on their true lifecycle impact.
Check out Chemours’ approach for measuring Coatings’ total carbon footprint>>>
Upstream Sustainable Solutions (Formulation and Manufacturing)
Taking this holistic, systems approach, formulators and paint manufacturers may find surprising ways to achieve more sustainable products (Table 2). This approach can be used in measuring the “in-can” environmental impact.
High quality TiO
2 pigments like Ti-Pure™ TS-6200 or Ti-Pure™ TS-6300 not only enhance the formulators’ approach to sustainability, but these pigments can also reduce raw material usage, waste generation, and even reduce water use as will be shown in the next Section.
|
Value
|
Consequence
|
|
Raw material usage
|
TiO2 is by far the most suited white pigment to obtain whiteness and hiding power in coatings. The high efficiency of Ti-Pure™ TS-6200 and Ti-Pure™ TS-6300 is due to a large refractive index, optimal particle size, and surface treatment. Lower quality TiO2 has worse light scattering than its higher-quality counterpart.
|
|
Color
|
As a pigment, TiO2 has excellent light-scattering properties and is used in a variety of applications that require white opacity and brightness.
|
|
Tinting strength
|
Tinting strength describes its ability to add whiteness and brightness to the color of a tinted paint.
|
|
Reduced energy use and time savings
|
By requiring less dispersant Ti-Pure™ TS-6200 and Ti-Pure™ TS-6300 reduce grind time and possibly eliminate unneeded milling operations. These advantages can offer a very cost-effective means of increasing production capacity.
|
|
Reduced dispersant
|
By using the Ti-Pure™ TS-6300 and Ti-Pure™ TS-6300 TiO2 grades, formulators can lower the amount of dispersant needed because the dispersant binds more efficiently to the surfaces of the pigment. For example, Ti-Pure™ TS-6200 requires 50-75% less dispersant than other TiO2 pigments.
|
|
Viscosity stability during storage
|
Ti-Pure™ TiO2 particles are surface treated to ensure that they don’t settle or clump within the paint. The high degree of dispersion reduces the number of aggregates formed.
|
|
Non-hazardous
|
TiO2 is an inorganic substance that is thermally stable, non-flammable, poorly soluble, and not classified as hazardous according to the United Nations’ (UN) Globally Harmonized System of Classification and Labeling of Chemicals (GHS).
|
|
Hybridization
|
High quality TiO2 pigments provide paint formulations that can have multiple functions. This hybridization effect causes coatings to work harder in diverse applications so that there is less need for specific formulations for multiple applications.
|
Table 2. Consequent Value in Choosing TiO2 Pigments
Downstream Sustainable Solutions
Because of TiO
2’s unique properties, there are many beneficial characteristics of TiO
2 paint pigments that are passed to the end-user as shown in Table 3. Ti-Pure™ TS-6200 and Ti-Pure™ TS-6300 are high quality TiO
2 pigments that produce paints to protect and preserve the substrates they are applied to, thus conserving energy and material resources.
|
Property
|
Value
|
|
Hiding power
|
The hiding power of a paint is a measure of its ability to obscure a background of contrasting color, and results from interactions between incident light and the pigments present in the paint film.
|
|
Spread rate
|
Higher hiding power results in higher spread rate (less paint use).
|
|
Weatherability (retention of color, retention of gloss, chalking, adhesion and film integrity, corrosion protection)
|
Weatherability is a term applied to the various changes in appearance and functional value during service. These properties are controlled principally by formulation (e.g., choice of vehicle, extender, pigment volume concentration, etc., which are relatively independent of the grade of TiO2 used). However, chalk resistance, retention of color (tinted paints) and gloss, and resistance to discoloration by mildew and dirt collection can be influenced by TiO2 grade selection.
|
|
UV protection
|
TiO2 absorbs UV light. When TiO2 pigment is incorporated in a polymer, it can protect against fading, cracking, and weakening. Surface treating of the TiO2 can further improve this property.
|
|
Longevity
|
When used in a paint or coating system, TiO2 helps maintain the longevity of the paint and the continued protection of the painted surface.
|
|
Energy savings
|
The brightness TiO2 can confer to light colored paints can, when compared to darker colors, reduce the energy needed to light the interiors of buildings. In exterior applications the coolness conferred by TiO2 colored surfaces can lead to considerable energy savings in warm and tropical area by light reflectance that can reduce the need for air-conditioning.
|
Table 3. Characteristics of TiO2 Afforded to the End-User
The greater light scattering efficiency of Ti-Pure™ TS-6200 and Ti-Pure™ TS-6300 results in a higher hiding power and spread rate. Coatings with higher spread rate reduce the total amount of paint required to cover surfaces, and therefore reduce the carbon footprint per square meter covered. Long lasting paint that requires just one coat is better for the environment. The cradle to grave carbon footprint of Ti-Pure™ paints are 22% smaller than that of other paints.
The resulting value to the end-user includes:
- One coat coverage and the possible elimination of a primer reduces the amount of formulated product and ingredients used.
- Fewer coats can lead to less time required by painters.
- Reduction in the quantity of waste generated (e.g., steel cans, plastic containers, masking film, etc.) that eventually will enter landfills.
- Reduction in the use of water, a critical resource. Water is used in the formulation of waterborne paints and in cleaning accessory equipment such as brushes, rollers, and sprayers.
TiO
2 pigments can help to promote a more sustainable environment by helping to maintain the longevity of the paint and the continued protection of the painted surface. This conserves energy and material resources over the life cycle of the painted product. There are additional performance benefits to using less dispersant that affect the quality of the paint. For example, paints that use less dispersant tend to produce films with less water sensitivity, stronger adhesion to substrates, lower hardness, and greater resistance to humidity.
TiO
2 also enhances a coating’s UV resistance because the pigment absorbs UV light-forming free radicals (photocatalysis). Surface treating of the TiO
2 can further improve this property. The specific surface treatment on a grade of TiO
2 will influence the coating’s outdoor durability. Durable and super-durable TiO
2 grades include a layer of silica that is applied during pigment production to prevent radical formation.
Ti-Pure™ TS-6200 is a highly surface treated TiO
2 pigment to reduce photocatalysis and provide UV resistance. This innovative technology combines an advanced silica coating with a proprietary surface treatment. It represents a significant improvement over the silica encapsulation found on most super-durable TiO
2 pigments. The weatherability of paints formulated with Ti-Pure™ pigments also leaves a durable, washable surface that resists color fading, gloss retention, and chalking over time.
Ti-Pure™ TS-6200 provides the highest degree of durability and is used
in demanding indoor and outdoor applications such as automotive coatings and weatherable industrial coatings. The weatherability of Ti-Pure™ TS-6300 is adequate for many exterior coatings. It is specifically designed for mid-to-high quality flat architectural coatings.
TiO
2 pigments also enhance the sustainability of painted structures by reducing the structure’s energy costs in several ways.
- The brightness that TiO2 confers to light colored paints can reduce the energy needed to light the interiors of buildings.
- TiO2 pigments possess the property to reflect the heat generated by the infrared rays of the sun.
TiO
2 pigments used in paint applied to the external surfaces of buildings can help to reduce heat build-up. ‘Cool roofs’, those painted with white or light-colored coatings, can significantly reduce heat build-up in buildings and other structures (e.g., school buses, handrails, protective coverings). This helps to reduce the energy that would otherwise be consumed by cooling devices like air conditioning.
Explore the new methodologies and tools that demonstrate how TiO2 selection can lower the environmental impact of a coating. Join the webinar from the team of experts from Chemours.
Conclusion: Why Chemours Ti-Pure™ TiO2
TiO
2 pigments are enablers for innovation and sustainability. Paint formulators, by taking a holistic approach to selecting materials, can enhance resource efficiency and environmental wellness across the entire value chain.
Highly treated TiO
2 pigments such as Chemours’ Ti-Pure™ TS-6200 and Ti-Pure™ TS-6300 can not only increase hiding power and optimize energy saving, but also improve processability and paint endurance for greater longevity and reduced maintenance costs.
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