DCPD Polyesters: Borne of Necessity, Perfected by Design
The once unknown open molding low profile resins have become the leading marine composite systems
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By Margie Krantz
Marine Product Leader
AOC, LLC
Collierville, Tennessee, USA
When the crude oil crises of the 1970s affected the supply of some petrochemicals more than others, unsaturated polyester resin manufacturers were left looking for technologies that used less styrene. From such necessity emerged new dicyclopentadiene (DCPD)-containing polyesters. These resins had cost and performance advantages but had marginal processability issue which plagued some of the earlier formulations.
Workable DCPD-based polyesters were elusive to some resin manufacturers. But these resins were especially well-received by boat manufacturers who came to appreciate the technology’s distinct cosmetic benefits. Because of lower styrene levels and a unique polymer structure, DCPD polyester resins shrink less than typical orthophthalic resins. Less resin shrinkage results in a smoother surface with very minimal or no visual print-through from reinforcing fibers.
The improved surface profile with DCPD-content polyesters is also attributed to its higher heat distortion temperature and a more complete cure during the molding when compared to conventional orthophthalic polyesters.
How DCPD Resins are Better
|
Resin Type
|
Traditional Ortho
|
Altek® H834-R Series
|
|
Styrene content
|
42-44%
|
<35%
|
|
Emissions (wt. of resin)
|
4-8%
|
2-4%
|
|
Gel-to-peak exotherm
|
45 minutes
|
15 minutes
|
|
Peak exotherm temperature
|
284-354°F
(140-175°C)
|
300°F
(149°C)
|
|
Heat distortion temperature
|
153°F
(67°C)
|
176-203°F
(80-95°C)
|
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Reduced Styrene Emissions
DCPD resins have considerably lower styrene content than standard orthophthalic resin systems. As a result, DCPD technologies were well-positioned when European and North American governments started mandated significantly lower emissions of volatile organic compounds and hazardous air pollutants in the workplace and Environment. As noted in the accompanying table, a DCPD-based resin applied under similar conditions as an ortho can help reduce the amount of emissions realized versus the ortho resins.
The Technology Continues to Evolve
Over the years chemists for AOC have led the development of new and better DCPD resin technologies. Each new generation surpasses the previous in processing characteristics and end-use performance. For example, after years of success with Altek® DCPD polyesters for open contact molding, AOC scientists have fine-tuned the technology for Resin Transfer Molding (RTM), RTM Light and Vacuum Infusion. Ongoing research continues to bring the benefits of DCPD to the growing number of manufacturers who look to AOC for the latest technology.
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The Leading Marine System: DCPD Performance & Optimum Osmotic Protection
AOC H834-R Series DCPD polyester resins are approved by Lloyd’s Register, which conforms to International Quality Standards, and meets the mechanical, water absorption and finish requirements of major builders. 
For optimum protection from osmosis, major yacht builders combine a Hydropel® Vinyl Ester product in the skin coat with an Altek DCPD resin system in the bulk of the laminate. AOC’s Hydropel high performance vinyl esters offer superior performance for naval architects, designers and boat and yacht builders throughout the world.
The use of a Hydropel vinyl ester resin skin coat creates hulls with exceptional blister resistance. Hydropel technology can combine the superior osmotic blister resistance and physical properties of a vinyl ester with the handling and cure properties of a general purpose polyester resin. Toughness, mechanical strength and crack resistance can also be improved.
About AOC
AOC is a leading global supplier of resin and gel coats. AOC products are manufactured in facilities strategically located in North America, Europe and Asia. AOC-owned manufacturing plants are ISO 9001:2000-certified, use proprietary technology to ensure resin batch-to-batch consistency, and follow Six Sigma-Lean principles for improved efficiency and quality. For more information, phone Stephen Olle +44 1473 288997, e-mail solle@aoc-resins.com .