Effect of Operating Parameters and Particle Size of Calcium Carbonate on the Physical Properties of Latex Paint

Effect of Operating Parameters and Particle Size of Calcium Carbonate on the Physical Properties of Latex Paint. The purpose of this study is to measure the effect of operating parameters and particle size of paint filler calcium carbonate having particle size 400 mesh. Trials were done with Nano Mill and Conventional Agitator to measure effect of operating parameters. Two calcium carbonate slurries were manufactured through nano mill and conventional agitator independently having same composition. Nano mill showed exceptionally good results than conventional agitator. The slurry processed through Nano Mill reduced the particle size of calcium carbonate from 37.5 microns to 2.63 microns while the slurry processed through conventional agitator reduced the particle size of calcium carbonate from 37.5 microns to 18.05 microns. Furthermore, the paint manufactured through Nano Mill slurry showed better Whiteness, wet hiding, dry hiding, adhesion and gloss than conventional agitator.


Introduction
Paint is a liquid which spreads over a substrate in the form of thin layer and it is transformed into a solid adherent film [1].
There are two major functions of paint. One protection and other is decoration. The earliest known use of paints dates back more Table 2: Differences between step-growth and chain-growth polymerization.
Step-growth Polymerization Chain-growth Polymerization Common to all three coating systems are the resin and additive.
Clear coats are optically inactive; therefore pigments and fillers are not present. Powder coatings are not in a liquid medium; therefore a solvent is not present. Paints are liquid materials that are optically opaque coatings that form when applied by brushing, rolling or spraying [2,3]. The technical definition of a binder is the non-volatile part of a paint excluding the pigments and filler, which includes the non-volatile additives [2]. Binder forms the film of the paint. Binder is a polymer which has impact on important properties of the paint like adhesion to the substrate, sheen, application properties, color acceptance, durability and flexibility. There are different types of binders like synthetic binders and natural binders. Water based paints binders include poly vinyl acetates, poly vinyl acrylic, styrene acrylic, pure acrylics, etc. Oil-based paints include alkyd resins, polyurethane resins, melamine resins, etc. Natural oils or fatty oils were important film forming agents which were able to convert a low viscosity liquid into a solid [3]. Synthetic resins came about in the 1920s with the advancements in polymer chemistry.
The primary benefits of synthetic resins are that products can be tailored with specific properties with nearly unlimited availability.
The different resin systems are mentioned above, all of which are either step-growth or chain-growth polymerization [6]. Chain-growth reactions typically have three reactions -initiation, propagation, and termination.
Step-growth polymerizations are reactions between functional or multifunctional monomers without an initiation or termination step. Characteristics common in pigments include extreme optical characteristics, particles smaller than 10 μm, being insoluble in water and most organic solvents, and being chemically inert or chemically stable [7]. A comparison between the organic and inorganic pigments is presented in (Table 3) [2]. Colored inorganic pigments are typically variants of iron oxides [3]. The dispersion process involves 3 steps -wetting, separation, and stabilization [6]. The refractive index can be described as the degree of bending of light as it passes through a material. This value is a dimensionless value and is typically referenced to light traveling in a vacuum. Larger refractive indexes reflect a greater degree of bending of light. The refractive index of pigments and film formers are presented in (Table 4). TiO2 is not used as a biocide, but has some antimicrobial properties due to the photo catalytic reaction mentioned earlier [8,9]. Filler or extender particles such

Materials and Methods
The following Instruments and Analyzers Were used to Analyze Various Properties of Paint Samples

Determination of Dispersant Demand
The first step in sample preparation was to determine

Calcium Carbonate Slurries Preparation
The composition of calcium carbonate slurry was prepared as shown in (Table 6) (Table 6) was prepared using laboratory mixer.
Dispersion of calcium carbonate slurry found on hegman guage was 50 micron.     were offered with each of the Crypto meter products to cover a range of film thickness.

Gloss Measurements
Gloss was tested through Tri-Gloss master following the standard ASTM D2457. i.e. "Standard Test Method for Specular Gloss of Plastic Films and Solid Plastics".

Dry Hiding and Whiteness
Dry Opacity was checked through Spectrophotometer data color 110.

Drying Time
Drying time was measured through stop watch at ambient temperature.

Discussion and Results
Paint in which calcium carbonate slurry processed from Nano mill showed brilliant results in terms of wet opacity, dry opacity, gloss, smoothness and drying time compared to the paint in which calcium carbonate slurry processed through laboratory mixer as shown in (Figure 4). All quality parameters were significantly increased in the paint in which calcium carbonate slurry processed from Nano mill.

Conclusion
It is observed that with the reduction of particle size of calcium carbonate, latex paint showed better results in terms of better hiding, better whiteness, higher gloss, more adhesion.
Calcium carbonate slurry processed through Nano mill showed exceptionally good compared to conventional agitator. The slurry processed through Nano Mill reduced the particle size of calcium carbonate from 37.5 microns to 2.63 microns while the slurry processed through conventional agitator reduced the particle size of calcium carbonate from 37.5 microns to 18.05 microns.
Furthermore, the paint manufactured with Nano mill slurry showed better Whiteness, wet hiding, dry hiding, adhesion and gloss than the paint manufactured with conventional agitator.