Description:
M-Cure® EP resins are blends
of liquid epoxy resin and acrylate ester functional reactive
diluents and modifiers. They are developed specifically for
two-component, ambient temperature, epoxy-amine cure markets
such as protective coatings, rapid set adhesives, and chemically
resistant sealants. These epoxy-acrylate ester resins can be
used alone or blended further with a conventional liquid Bisphenol
A epoxy resin for systems requiring low to zero VOC and fast
cure at lower temperatures.
Physical properties
of the M-Cure EP resins are shown below in Table 1. They are
used in the resin component of a typical epoxy resin-amine hardener
two-component system. The epoxy-acrylate equivalent weights
are reported to assist in the calculation of formula stoichiometry
and mix ratio.
The acrylate ester
portion of the blend reacts rapidly with polyamines containing
primary amine hydrogens by addition across the acrylate ester
double bond to form an amine –acrylate adduct as shown in Figure
1. This is commonly referred to as Michael Addition polymerization.
The amine hydrogen of the amine-acrylate adduct can then add
to the oxirane ring of the epoxy and ultimately form a highly
crosslinked thermoset material.
To compare performance
properties of the M-Cure EP resins to a neat liquid epoxy resin,
each M-Cure EP resin was evaluated as a direct replacement and
also blended with liquid epoxy resin as described in the model
formulations shown in Table 2.
Figures 2 & 3
illustrate the increased reactivity of the M-Cure EP products
versus a conventional Bisphenol A epoxy resin. A 80/20 blend
of cycloaliphatic and aliphatic amine curing agents is used
as the hardener. The M-Cure EP products exhibit much faster
gel times and tack-free cure times than conventional liquid
Bisphenol A epoxy resin. The increased reactivity of the M Cure-EP
modifying resins is even more pronounced at lower temperature
compared to the liquid Bisphenol A epoxy, which never cures
in 24 hours (Figure 2). The reactivity of the M-Cure EP resins
increases with decreasing equivalent weight of the resin.
Table 3 shows the
cured film performance properties of the M-Cure EP products
versus liquid Bisphenol A epoxy. In general, all of the M-Cure
EP resin-modified formulations maintain comparable physical
properties to those of the neat liquid Bisphenol A epoxy. Formulation
hardness and abrasion resistance are shown to be a function
of epoxy-acrylate ester equivalent weight. The lower equivalent
weight results in higher crosslink density and therefore higher
hardness and better abrasion resistance. Similarly, all of the
M-Cure EP resin-modified formulations exhibit a higher tensile
modulus than neat liquid Bisphenol A epoxy due to increased
crosslink density. M-Cure EP400 exhibits the lowest tensile
strength and modulus, but still provides good hardness and abrasion
resistance.
Summary:
The new M-Cure EP resins provide
formulators the ability to modify conventional two-component
liquid epoxy-polyamine-cure systems for reduced formula viscosity
and faster cure at lower temperatures without the use of a mercaptan
curing agent. In addition, these new resins impart enhanced
cure performance, while maintaining hardness, physical properties,
and adhesion.
