Formulation failures

In addition to the high costs generated by the failure in the application of a film, errors or inaccuracies of formulation also often give headaches to manufacturers. Human failures, improper cleaning of production line appliances and technical problems are the most common phenomena within the industry, and depending on the severity, they can end up spoiling an entire batch of paint with the consequent impact on the company's revenue.

However, some of these errors can be corrected with proper quality control in the processes, correct labelling of raw materials and precise instruction to the operators in charge of the mixtures.

The formulation experts consulted by INPRA LATINA agree that most manufacturing problems are solvable, although they indicated that the cost will always be high.

Jordi Calvo Carbonell, Spanish expert in the formulation of paints, with more than 40 years of experience and author of the book Paints and Coatings: Introduction to its technology, points out that the cost of a failure in the formulation depends on several factors: "There are losses for hours of work of the plant staff, hours of work of the people of the laboratory who spend time solving the problem, containers that are lost (if the packaging phase was reached), in addition to raw materials.

He points out that most of the failures are of a human type, due to lack of adequate quality control of processes and raw materials, although he assured that these are not the only ones: "Another common problem occurs due to lack of customer information. When you sell a paint you must give a technical sheet in which the details of the product are informed, the temperature to be applied, the conditions in which it must be made, among others. "

For his part, Gerardo Gurrola, of the company International Paint assures that most of the problems in the formulation are due to a lack of communication with the sales department, which does not know how to transmit the real needs of customers.

Likewise, it highlights that the introduction of new materials such as polysiloxanes, on which there is no complete information, even by the suppliers of raw materials, means that multiple tests are required before the formula works correctly.

In this regard, Calvo Carbonell said that in new developments, it is necessary for laboratory personnel to accompany the production in order to correct any failure, as there are some differences between what is done in the laboratory and in the plant, due to the volumes of material that are handled.

In the case of color contaminations they can be solved, although the cost is high. "If I manufacture five thousand liters of a product and it is contaminated with another color, I probably have to produce 15 thousand liters of the product to achieve a complete dissolution," Gerardo said.

"There are some colors more difficult to treat, such as yellows, in those cases, you can only recover between 5 and 10% of the incorrect formulation in each new production," Jordi added and added that there are other even more serious failures, as in the case of silicones "these polluting products are usually worked in separate machinery because any surface can damage an entire batch."

In the case of the granulometry of the charges and pigments, it must also be taken into account that not all components reach the expected diameter. However, the most important thing is to take care that once the dispersion has been carried out, there is no reglomeration of the pigments. This can be achieved through a proper calculation of the amount of resins. If there are failures at this point, the paint will have a low covering power and its color might not be as desired.

Our sources highlighted that for other cases such as microfoam, fungi and others, special additives have been developed that are used in small quantities and stressed that an inadequate calculation of these components could also damage the composition of the paint and generate visible defects after application.

Most common failures
To analyze the most common failures and the appropriate solutions in each case, we consutamos Carlos Giudice, researcher at the Center for Research and Development in Paintings, Cidepint and professor at the University of La Plata, in Argentina.

The most recurrent problems we were able to identify were:

Erosion: Wear of the coating until the substrate is exposed and occurs as a result of the tizing with removal by action of the environment (rain, wind) or abrasion (wind with dust or sand in suspension). Preventive measures consist of selecting a chalk-resistant, non-brittle paint with good flow properties to form a smooth and uniform film in thickness (adequate viscosity at reduced cutting speeds).

Quartered: This flaw is linked to the aging of the film. The rapid drying after application can also lead to a faster contraction on the surface than within the film, generating the cracks that characterize this failure. Drying/humidification and heating/cooling cycles contribute to the cracking of the film. It can be prevented by selecting the right components: the resin must be weatherproof and the pigments must be inert or with minimal chemical reactivity and high dimensional stability to reduce surface stresses; the plasticizer of the resin must be stable and insoluble in the medium to prevent leaching from the film to the surface during in-service exposure.

Cracked: In this case the cracks extend to the substrate, but failure is more deteriorating of the film than cracking. Cracks can occur irregularly or linearly. The preventive measures for cracking are identical to those for cracking; although in cases of intense cracking, it is common to use acicular or fibrous reinforcement pigments to reduce the aforementioned tension gradient in the film.

Wrinkled: It consists of the formation of wrinkles on the surface of the film, either in a linear or totally irregular form; wrinkles may be faint or thick. The generating cause of this failure is that on the surface of the film there is a faster expansion during drying than in the body of the film. The magnitude of the fault is proportional to the thickness of the film. In the formulation of alkyd paints, surface and internal drying agents are included to catalyze the oxygen addition reactions in the double ligatures presented by the resin, in such a way that the drying speed is similar on the surface as in the body of the film. However, an excess of surface drying agent generates rapid volumetric expansion responsible for crumpling.

Action of microorganisms: Bacteria and fungi, particularly in water-based paints, produce film softening and dark spot formation that generate a poor appearance. Microorganisms attack the biodegradable components included in the formulation, which behave as nutrients for their vital functions. This failure is reduced or completely eliminated including stable bactericides and fungicides, at adequate percentage levels.

Discoloration: This type of failure originates from a wide variety of causes and fundamentally affects the decorative aspect. Many resins used in the paint industry contain unsaturated groups, which by exposure to sunlight change color (usually a yellowing or darkening of the film is observed). The method to prevent discoloration is to select the different components of the paint with stable colors. Thus, for example, aliphatic silicone, acrylic and polyurethane resins reduce any color change to a minimum; as far as pigmentation is concerned, those of an inorganic nature should be selected for severe weather exposure conditions.

Cracked in inorganic paintings: The appearance of the fault is similar to that mentioned for organic paints; however, the root cause in this case is the excessive amount of metallic zinc powder and other pigments in the composition. Many formulations contain fibrous pigments and solvent mixtures of adequate evaporation rate to prevent cracking. The film should be applied in the recommended thickness (usually oscillating at approximately 80 μm) and should be allowed to dry under favorable conditions.