Are all MEKP curing effects the same? What you don't know about methyl ethyl ketone peroxide
Methyl Ethyl Ketone Peroxide: MEKP, the English abbreviation of Methyl Ethyl Ketone Peroxide,
Many people mistakenly believe that as long as it is MEKP, its curing effect is the same, but experience tells us that the same MEKP has different curing effects from different manufacturers and different series. In fact, this is because the MEKP curing agent solution is not purely a single-component MEKP, but a multi-component one, and there is a synergistic effect between the components.
MEKP solution has three active ingredients:
①Hydrogen peroxide only affects the gel process of the resin;
②MEKP monomer form affects the gel process to a small extent, but affects the initial curing speed to a large extent;
③The dimer form of MEKP affects the gel process to a relatively small extent, but to a great extent affects the entire curing and post-curing process.
In actual use, it will be found that after adding methyl ethyl ketone peroxide to the pre-accelerated vinyl ester resin, a lot of foam will be generated. This is the result of the massive decomposition of excess hydrogen peroxide in methyl ethyl ketone peroxide. Some MEKP curing agents with low hydrogen peroxide (hydrogen peroxide) content will greatly reduce the probability of bubbles in the resin.
When the free radicals are decomposed faster than the double bonds of the vinyl ester resin are absorbed, a large number of excess free radicals will combine and lose activity, which will lead to the serious consequences of poor curing of the resin due to insufficient free radicals. This is the essential reason why the resin does not solidify if too much methyl ethyl ketone peroxide is added.
Mixing these three components in different proportions can change the normal temperature gel and curing properties of vinyl ester resin. But its limitation is that, by law, peroxide manufacturers must control the maximum content of MEKP active ingredients within the allowable formulation range. Its inactive ingredients, such as diluents [containing dimethyl phthalate (DMP) and pentylene glycol bisisobutyrate (TXIB), water, methyl ethyl ketone, ethylene glycol, etc.], will affect the performance of the MEKP curing agent, such as solubility, density, stability, filterable substances or trace residues, so the inactive ingredients also need to be integrated and controlled. What needs to be pointed out here is that DMP is widely used by MEKP manufacturers as a diluent, and DMP is a typical plasticizer that is potentially harmful to the human body. It has been included in the controlled list in Europe and the United States. Many curing agent manufacturers have begun to use other solvents to replace DMP, such as benzyl benzoate, but benzyl benzoate has a certain smell.
As a three-component system, MEKP has the following advantages:
①Flexibility, there are many different options available according to different performance parameter requirements;
② Broadness, within a limited range, acceptable products can be obtained by using an appropriate amount or excessive use;
③Can be used in both gel coat and resin;
④It rarely causes discoloration of the finished product.
Of course, standard MEKP also has disadvantages:
① Hazard level III, refer to Fire Department Standard 432 (this level is set according to the danger of organic peroxides, from high level I to low level V);
② Toxicity, classified as a moderate health hazard, requires protective equipment;
③Leakage must be removed immediately to prevent fire or explosion.
