May 1, 2012 – Capsules – One and the Same?
QUESTION:
What is the difference between a product that is labeled "capsule suspension" and one that is "micro-encapsulated"? Are they both less repellant than EC's and WP's?
ANSWER:
I believe that these two designations refer to essentially the same technology. Microencapsulated is the original way in that these formulations were described, while Capsule Suspension may describe it a little better. In either case the formulation is created by adding chemicals such as amine and isocyanate, as in one of BASF's products, to a solution of the active ingredient. The chemicals react by forming a solid layer around the micro-droplets of the active ingredient, essentially forming a round ball with the a.i. trapped inside. Then, when that material is applied and it dries the active ingredient is able to slowly make its way out of the capsule and onto the surface or onto an arthropod that the capsule may have adhered to. The walls of the capsule are slightly porous, allowing the a.i. to escape, but in a slow and controlled fashion.
View past Ask Mr. Pest Control questions.
What is the difference between a product that is labeled "capsule suspension" and one that is "micro-encapsulated"? Are they both less repellant than EC's and WP's?
ANSWER:
I believe that these two designations refer to essentially the same technology. Microencapsulated is the original way in that these formulations were described, while Capsule Suspension may describe it a little better. In either case the formulation is created by adding chemicals such as amine and isocyanate, as in one of BASF's products, to a solution of the active ingredient. The chemicals react by forming a solid layer around the micro-droplets of the active ingredient, essentially forming a round ball with the a.i. trapped inside. Then, when that material is applied and it dries the active ingredient is able to slowly make its way out of the capsule and onto the surface or onto an arthropod that the capsule may have adhered to. The walls of the capsule are slightly porous, allowing the a.i. to escape, but in a slow and controlled fashion.
The formulator may even be able to tweek the capsules in various ways to regulate the speed at which the active ingredient is released, such as modifying the size of the capsule or the thickness of the capsule walls. A very attractive aspect of these formulations is that many of them are water-based as the diluent, eliminating the use of solvents and oil diluents that added to the cost, odor, and toxicity. Within the enclosed capsule the active ingredient is not in contact with the water, preventing hydrolysis and degradation. Once the material is diluted with water for use and applied to a surface, the a.i. still within the capsule also is protected from UV light a pH, again extending the residual effect. A product like Demand CS, for example, will place more than 14,600 microscopic capsules on each square inch of the surface once applied according to the label, offering a tremendous opportunity for insect pests to contact them and have them adhere to their exoskeleton.
Containing the active ingredient within the capsule does also greatly reduce the repellency of the a.i., as we saw with perhaps the first microencapsulated product to enter our structural market. This was Knox-Out 2FM, containing diazinon, and while diazinon EC and WP formulations tended to be repellant to ants the Knox-Out worked fairly well on them. It was the same old diazinon, but the level of the a.i. on a surface from a microencapsulated formulation was just that much less than from EC and WP applications.
Another apparent advantage of microencapsulation is the tremendous reduction in relative toxicity to mammals. The LD-50 may be hundreds of times higher for the microencapsulated version than for the EC or WP. The capsules also tend to rest on the surface they are applied to, so for porous surfaces like wood or concrete they may be more effective and available to the pest insect.
View past Ask Mr. Pest Control questions.
