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Understanding the different
formulations used in resin
bonded anchors
Written by Matthew Cleaver, 2K polymer systems ltd
For the Construction Fixings Association
It is often difficult for someone new to Unsaturated polyester resins can offer negligible health hazard.
resin anchors to understand the difference This was the first available polymer type This type of resin gives a reasonable strength
between the array of resins available. For and has been available for many years with performance for the majority of applications
those who specify anchors it is also styrene monomer. Although styrene is still and is best suited to fixings into hollow blocks
important to understand this difference to widely used for injection anchors and in many or masonry.
ensure any specification changes are to other industries, concerns over its safety both Styrenated (styrene-containing) resins have
truly equivalent products. In this article for transport (it is flammable) and for health been around for many years and have
Matthew Cleaver gives an overview of the (it is classified as harmful) have led to the become well known for glass reinforced
types available and the applications for introduction of “styrene-free” variants, the plastic manufacture and their use in
which they are best suited. difference being the liquid monomer used in automotive body filler. They are used because
of their low cost and fast cure.
Introduction Styrene-free resins are a
The resins used for anchoring pur- relatively new development (since
poses are usually composed of sev- the late 1990s) and they use
eral ingredients; the main ones are acrylic or vinyl monomers.
listed below with the primary reason These are more expensive than
for their incorporation: styrene, but as they can be
selected from a greater range of
• A polymer, which gives the basic different monomers they can give
properties of the resin and binds it an improved performance over the
together – like cement in concrete. styrenated resins.
Polyester resins cure by what is
• One or more monomers, these known as a “free radical” curing
liquids are used to give a workable mechanism in which the resin is
product. catalysed by a peroxide. This
mechanism is characterised by a
• Mineral additives, to give extra fast reaction and good low
strength to the cured resin – like temperature cure, which means
aggregates in concrete. that the product can give short
loading times, even under low
• A curing agent or hardener, mixing temperature conditions.
this in starts the chemical reaction
to harden the resin. Epoxy acrylate
Also known as vinyl ester, these
• Other additives, added to give the resins (which should not be
correct consistency, colour, etc. confused with pure epoxy – see
below) offer improved properties
It should be noted that there are compared to polyesters although
variations in the composition of the they cure in the same way, and
resin and additives used. These variations give the manufacture of the resin. The use of therefore show the same fast cure and good
rise to the differences in performance of the alternative monomers enables lower health low temperature performance. Due to the
products available on the market. and transport classifications but increases the different polymer they generally exhibit
All of the resin types which will be cost of the resin. improved strength and importantly better
described are available as injection anchors for It should be noted that when installed in chemical resistance.
cartridge based delivery. The information is valid accordance with the manufacturer’s Styrenated and styrene-free versions of
for all delivery systems but each resin type may recommendations, including precautions for epoxy-acrylates are available and again, the
not be available in all delivery formats. health and site protection, styrene based styrene-free products have the
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