Two component spray foam systems, for sprayed in place or spray on polyurethane foam insulation blends, are primarily packaged in steel 55 gallon barrels and distributed by their weight in volume as a paired set. A Paired Set is two barrels consisting of one “A” side (Activator/Isocyanate) and one “R” side (Resin/Polyol) ranging in a combined liquid weight from 970 lbs. to 1050 lbs. It should be noted that in many instances the components are referred to as “A” and “B”, respectively. In general the spray foam systems are produced having at minimum six months shelf-life within the original unopened barrel. Stored between 60 and 75 degree F (15 – 24C), do not require additives, B sides may require mixing and/or continual agitation.
The barrel colors vary between blenders. As a result of the highly reactive nature of the two components, cross contamination of the barrels must be avoided. A standard procedure in spray foam rigs to identify each side component by color is often used where red identifies the “A” side and blue identifies the “B” side.
An emphasis must be placed on keeping the two components free of moisture contamination. Unfortunately, exposure to the smallest amounts of moisture (even the moisture from the air) causes a reactionary affect hindering the ability of the spray foam equipment to function properly and/or achieve the desired density and related physical properties of a quality insulating product. Isocyanates are notoriously known for their ability to absorb moisture. When isocyanates are exposed to moisture, solids will develop either as small hard crystals or as a hard skin over the surface of the liquid (like paint in an open bucket). Once these solids form, reversal to liquid becomes cost prohibitive and remaining liquids are likely to require extensive filtering prior to use. Resin sides are affected by exposure to small amounts of moisture absorption as well. Additional moisture in resins alter the chemical reaction and physical properties of the insulation.
Once the barrels are in your possession, prevention of moisture contamination and other conditions which render the products unusable becomes the SOLE responsibility of the handler. Processing equipment and barrels are generally kept in designated rigs such as enclosed trailers, box trucks or even set up in a factory environment. Often referred to as the “spray rig” or “foam rig” the enclosed features of the rig provide an initial degree of protection from environmental conditions. Excess material storage on construction sites often involves the utilization of storage containers or can be as minimal as an outdoor staging area where the drums are left exposed to the elements.
Contamination from moisture and particulates is minimized or prevented in the following ways:
- Don’t allow for the storage of open barrels in the presence of water or conditions that may result in contaminants entering the barrel. Utilize tarps and barrel covers designated to protect the materials from inclement conditions.
- Don’t leave barrel lids and caps open for an extended period of time without the use of a dry-nitrogen shield or one-way descant air dryers.
- Learn ways of handling residual materials for reuse and manage inventory flows effectively.
Another critical factor relating to barrel storage is temperature. The “A” and “B” side components become increasingly viscous (i.e., thickness or resistance to flow increases) as temperatures decrease. As a result, if the barrel temperatures are not intentionally controlled, the liquids inside will become too thick to flow easily enough to be transferred from the barrel to the main spray foam machine (also referred to as a proportioner); even when positive pressure is achieved. The lack of flow to the proportioner pump would result in an off-ratio mix.
Two major factors are in play once cold liquids reach the proportioner. First, what is the maximum centipoise (measurement used in determining viscosity, water being 1 centipoise) the equipment can process and secondly, what is the delta t (max heating capacity) of the heating system. Request the material temperature curve for the each of the component blends from your material supplier. You will also want to know the maximum centipoise the spray foam equipment can process which can be obtained from the foam machine manufacture. These bits of information will allow you to process spray foam insulations to achieve their maximum yield and efficiency.
However, it doesn’t stop there with cold temperatures. The majority of liquids freeze around 32 f however many isocyanate blends will freeze once the temperature drops below 40F (4C). Frozen isocyanate looks much like water contamination in which it forms tiny crystals. To determine if the “A” side has been frozen simply rub the crystals between your fingers. If the crystals dissolve the product has been frozen. Reverting the crystals as a result of freezing temperatures to its previous liquid state will involve reheating the materials to temperatures in access of 90 f. Consult with the material compounder to determine best practices.
Closed cell resin blends with their extremely reactive blowing agents will expand when the temperatures are above boiling point (as low as 90 f). Open resin barrels under elevated temperatures is the number one promoter of loss of blowing agent. Loss of blowing agents creates increased insulation density and poor yield results.
Protections from excessive environmental temperatures are achieved through the following means:
- Mechanical measures to condition the air temperature during storage and use.
- Barrel heating devices are proven to be the most effective way to control barrel temperatures.
- Keeping drums out of direct sunlight when conditions are too hot.
With dedicated effort you can develop controls and handling procedures to carry out in a manner in which the contamination or exposure doesn’t result in inferior product or render the equipment unable to perform satisfactory. Prevention is carried out by protecting the liquids in the barrels from excessive environmental conditions that promote contamination and waste of otherwise good product.