cols, an acrylic resin system was thus selected for further
initial evaluations of DeGreez.
STEP 5: ASSESS REACTIVITY IN POLYMER SYSTEMS
Polymer matrices provide a very different environment for a
biocompound when compared with traditional solution-based systems. Therefore, it is necessary to determine if the
biomolecule will exhibit the desired reactivity when blended
with a resin. More specifically, when hydrolysis in solution is
performed, the enzyme is solvated at the molecular level
resulting in homogeneous biocatalysis. In a polymer system
or coating, however, the biocompound is not dissolved but
rather suspended in the polymer matrix, creating a heterogeneous system, and there is no way to easily predict if the
desired functionality will be achieved. In this case, diffusion-al constraints derived from substrate accessibility to the
bioactive become crucial. As a result, reactivity can be a function of total surface area or bulk volume, and it is necessary
to understand which mechanism is operating (see,
“Formulating with Bioengineered Additives: Enhancing the
Performance and Functionality of Paints and Coatings,”
Coatings World, March 2010).
We have observed each mechanism operating for different
products developed at Reactive Surfaces. Lipases investigat-
ed for our DeGreez additive have been shown to exhibit an
increasing catalytic rate for hydrolysis with increasing sur-
face area when blended with Avanse MV-100 emulsion and
applied to polypropylene sheets. Activity was independent of
bulk volume, however. In comparison, coatings containing our
OPDtox enzyme additive for decontamination of organophos-
phorous compounds including chemical warfare agents and
pesticides have been shown to exhibit catalytic activity that
is directly related to bulk volume. Clearly, the property and
performance optimization of the selected polymer type must
match the sorption characteristics of the reactants.
STEP 6: ANALYSIS OF REACTIVE COATINGS
The final step in the development of reactive coatings must
include assessment of activity by application specific property testing. This phase of the development process includes
evaluation of both the performance of the bioactive and the
conventional properties of the coating. It is imperative that
the biobased additive exhibit long-term stability and activity without having any impact on desirable coating characteristics such as gloss, hardness, adhesion and impact resistance. In addition to employing specialized testing methods
for determining the activity profile of the new bioadditive,
typical chemical resistance, hydrolysis, thermal, scrub testing and other tests must be completed on representative
coating formulations.
In the case of our Degreez lipase additive, the addition of
lipase had no discernable effect on coating performance at an
enzyme addition level of three percent. All properties of the
enzyme modified coating were equal to that of the un-modi-fied standard. At an enzyme level of 14.3%, film softening
and blistering were observed in the coatings, possibly as a
result of the carrier solvent. The enzyme formulation is currently being investigated to minimize these impacts on coating performance.
With respect to bioadditive performance, the biocatalytic
clearing of a heavy oil incident was demonstrated by contaminating prepared surfaces with a thick layer of vegetable oil (2
Figures 5a & 5b
Scrub test results for a DeGreez enhanced acrylic-styrene crosslinked topcoat over a modified acrylic emulsion
sealant undercoat system applied on Leneta plastic scrub panels. (A) Visual scrub results showing the control com-
pared to panels with coatings containing DeGreez; (B) Hydrolysis activity retention after scrubbing of panels with the
control and DeGreez-containing coatings. Enzyme activity was measured using a UV/Vis spectrophotometer set to
detect p-nitrophenyl acetate hydrolysis at 405 nm. Measurements were taken every 30 minutes from a 0 time point to
40 minutes. "Buffer normalized" refers to the rate of uncatalyzed conversion of p-nitrophenyl acetate.
