When it comes to packaging finished lubricants for consumers, theres no substitute for the lightweight durability of plastic containers. Plastics cost less than other packaging materials, last forever, and are recyclable in most cases.
But as barriers, polymers are no match for organic mixtures. Basically any solvent is trying to migrate in and out through plastic walls – it can vaporize through, or it can eventually soak in to the plastic and leak through, said Steve Banko of Inhance Technologies at the Petroleum Packaging Councils spring meeting in Tucson, Ariz.
Diverse chemicals – base oils, finished lubricants, greases, solvents, additives – can permeate a plastic container, potentially degrading the formulation and thwarting the performance of the product. Escaping chemicals can produce emissions and render the container noncompliant with air quality regulations. Furthermore, solvents that leak out can warp bottles (an effect called paneling), create a sticky residue on the containers surface, and stain or destroy labels.
Thats where Inhances surface fluorination solution comes in. The Houston-based companys Fluoro-Seal process imparts hydrocarbon barrier properties to plastics, Banko said, but not by adding anything to the surface of the container.
Fluorination is not something that is spray-based, Banko pointed out. The process does not create an artificial skin, does not make the product thicker in any way, and does not wash off with water. It actually transforms the surface permanently and creates a new polymer surface.
This is done by manipulating typical surface polymers and substituting carbon-fluorine (C-F) bonds to a surface depth of mere nanometers. Elemental fluorine reacts with a polymer, Banko explained, substituting fluorine atoms for hydrogen atoms and forming permanent covalent bonds. This helps to avoid undesired plastic degradation and decomposition reactions. The depth of the treatment is controlled precisely in a gas-phase operation, in a post-mold stage after the container is formed.
The level of fluorine substitution on any particular surface is determined by a number of considerations: the plastic material composition, additives and other materials present, the container or tank characteristics, the expected storage conditions, and the composition of the liquid to be contained.
Careful maintenance and control of the relative gas mixture, the reaction temperature, and the exposure time enables the formations of C-F bonds, Banko said, emphasizing that C-F is the strongest type of bond in organic chemistry.
Fluorination substitution actually manipulates surface energy, he went on. With fluorination, the packagings surface energy increases significantly due to an increase in polarity, which results in reduced solubility of low-polarity organic liquids.
Most of the molecules used in the petroleum industry are nonpolar hydrocarbons, and nonpolar chemicals are just like nonpolar plastics, Banko explained. In a nutshell, like substances dissolve in like substances. Fluorination flips it, and creates a positive surface which then acts as a repellent to the chemicals inside, keeping them from escaping out.
As if it werent enough to just protect the inside surface of the container, the process involves a double layer of protection – changing the surface of both the inside and outside of the container.
The fluorination process creates a barrier in several other ways, Banko continued. It actually increases the density of the surface. As the amount of free volume or void space between the polymer molecules is decreased, solvent permeability is reduced.
Fluorine substitution also generates radicals through the high-energy process, which creates a slight degree of polymer crosslinking on the surface. This creates a permanent bond which further fortifies the structure, minimizing swelling and plasticization effects, and suppressing permeability.
Theres a lot of confusion in the marketplace about exactly what fluorination does, Banko noted, so he uses a simple metaphor to describe its effect: Its like waxing your car. Wax on the surface of the car makes rain bead up. By changing a plastics surface and imparting a fluorinated barrier, essentially whats happening is that fluorination is allowing barrier chemicals to repel solvents.
The process can be performed on all plastics, Banko stressed. Although one of the main applications for Inhances barrier technology is commodity plastics such as polypropylene and high-density polyethylene, it can be used on other hydrocarbon-based polymers. The Fluoro-Seal process is suitable for use on virtually all plastics, he noted. Virtually all organic polymers can be modified.
We treat [packaging] for basically anything that can go into a container – anything from foodstuffs to poisons, Banko said. That includes corrosive chemicals, flammable liquids, grease, hazardous waste, industrial chemicals, lubricants and other refined petroleum products, solvents, water treatment chemicals and more.
The process isnt limited to the container walls. Inhance can treat three-dimensional and complex parts of any shape or size, which is important, Banko said, because every square inch of a containers surface area can be susceptible to permeability, chemical attack or chemical stress fracturing. That includes bottles, pails, drums, sprayers, nozzles, closures and more. By treating every single component, youve now created protection to get the lifecycle barrier you need.
How do packagers know it works? Its simple, Banko responded. We test for loss of weight, weighing a package before and after the process to measure whats migrated out. The loss of motor oil in a container subjected to a steady temperature of 50 degrees C after 28 days was only 0.06 percent.
Fluorination also addresses another important issue: Industrial shippers are increasingly switching from all-steel to lightweight HDPE intermediate bulk containers to save packaging and shipping costs. These often are fitted into a sturdy steel cage. However, as with any plastic container, plastic-bottle IBCs are susceptible to certain chemicals absorbing into the plastic walls or permeating through.
As with smaller containers, leakage of lubricants through plastic IBCs can result in significant waste, container discoloration and distortion, and substantial loss of performance. It also can cause label blistering and flagging, which can infringe on compliance with Occupational Safety and Health Administration regulations.
Here again, Banko said the solution is fluorination. Inhance can treat monolayer HDPE containers to produce a fluorinated layer on all surfaces: the inside and outside of the container, caps, fittings, valves – everything but the steel cage. For multi-layer plastic IBCs, between five and seven layers can be extruded together and blow molded into the final shape.
Fluorinating both the inside and outside of the IBC makes it easier to clean and rinse the container, as it drastically reduces absorption into the inside walls. Fluorination also increases the wet out surface energy, for more effective draining, Banko noted, and it reduces the unsightly staining that fatty oils can leave on the visible surface of the container.
Banko said that fluorination is strides ahead of other barrier technology options such as coextrusion and lamellar methods. Coextrusion – using more than one type of plastic – impacts recyclability, for example, and increases costs. The material costs for clay additive and Selar RB lamellar barriers are high, and neither is as effective, he stated. A benefit of fluorination is that the barrier protection can be verified at any time, even in the field.
Carbon-fluorine is the strongest bond in organic chemistry – its not affected by ultraviolet rays, so your outdoor stability is not affected nor destroyed by heat, Banko added.
The only way to break that bond is by altering its physical cohesiveness, he continued. In other words, the barrier is only altered if the polymer underneath the layer is removed or broken or physically damaged – say, if it were cut with a box cutter.
The Fluoro-Seal process can be done at a packagers location, or at one of Inhance Technologies manufacturing facilities, but the treatment does require strict environmental and safety controls, as hydrogen fluoride is an extremely toxic gas that causes severe burns and can be fatal upon exposure. All processes are carried out in closed systems that are operated with a high degree of process automation, Banko told LubesnGreases, and the company has developed proprietary process controls and operational measures that ensure safety.
He added that Inhance participates in the American Chemistry Councils Responsible Care program, and has locations throughout the United States and in Australia and Mexico.