JEC COMPOSITES MAGAZINE - Issue #78 - January/February 2013 - 33

prepreg adoption has been the requirement
for chilled storage and transportation. The
SparPreg™ resin will soon benefit from new
latent curing materials that provide a much
longer shelf-life at 21°C and in excess of 2
months at 35°C.

Tab. 1: Translating perceived barriers into prepreg requirements

Perceived
prepreg barrier

Prepreg requirement to eliminate barrier
Stable resin

Refrigeration

Storable at temperatures up to 35°C

A more efficient process

Robust tack control and air removal
Process window 15-35°C

Air-conditioned factory

High quality laminate
Low void content
Maximise fibre mechanical performance
Minimise quantity needed

High cost

Minimise waste & consumables
Curable at 95°C

High Tg
tooling

Peak surface exotherm < 105°C

offering superior physical and mechanical
properties, though generally at a higher price
and with higher tooling and infrastructure
costs.
To address these issues, Gurit has translated these perceived barriers into prepreg
requirements for use in wind turbine blade
component manufacture such as UD spar
caps, see Table 1.

The SparPreg™ resin has been supplied for
spar component manufacture for over 10
years, and has benefitted from continual
development and innovation to ensure the
best possible performance for out-of-autoclave processing.
The latest iteration of this well-known system provides two new key characteristics:
- Reduced exotherm: The enthalpy of an
industry-standard 120°C curing prepreg
resin has traditionally been around 200-300
J/g. Innovative curing technology has
enabled SparPreg™ to reduce the enthalpy to
just 150 J/g without altering the chemistry
or cure mechanism. Such a technology step
opens the door for standard prepreg materials to be cured using infusion grade, water
or electrically heated tooling without the
risk of excessive exotherm or lengthy curing
cycles for thick-section laminates.
- Extended shelf-life: Another key barrier to

The first key feature of this technology is
the increased air permeability between the
plies provided by the coating. This is an
extremely effective way of removing interply porosity when the vacuum is applied.
The resulting laminate has very low void
contents (<1.5%) even at production hall
temperatures in the range of 35°C on sunny
summer days. The second feature of the
product is the excellent handling characteristics provided by the low tack and high drape
it exhibits over a wide temperature range.
SparPreg™ featuring Airstream™ technology
is available with E-glass, R-glass and
carbon. n
More information:
www.gurit.com

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No78 January - February 2013 /

Feature Wind energy

By setting these prepreg requirements at the
centre of its product development strategy,
Gurit has innovated two key technology
steps:
- SparPreg™ resin technology to enable lowcost tooling, minimise cure time, eliminate
the requirement for chilled storage and
enable direct application onto complex
curvature tooling.
- Airstream™ coating technology to enable
very low void content laminates without
debulking or the requirement for air-conditioned factories.

10 years of
continuous improvement

Airstream™ is Gurit’s answer to efficiently
manufacture high-quality thick laminates
with unparalleled low void contents at
ambient production hall temperatures of
up to 35°C. In combination with unidirectional SparPreg™ materials, the Airstream™
coating technology overcomes the generally
conflicting material characteristics of low
tack (to aid inter-ply breathing) and high
drape (conformance to tooling geometry
without formation of wrinkles) avoiding
any detriment to mechanical performance
of the final laminate. The result is a very
cost-effective, user-friendly material that
eliminates the use of air-conditioned halls
using multiple debulking steps and/or the
use of high-pressure autoclaves.

jec composites magazine 33
http://www.gurit.com http://www.eastmancuts.com
JEC COMPOSITES MAGAZINE - Issue #78 - January/February 2013

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