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Once unheard of, open-moulding low-profile resins have become the leading marine composite systems.
(Published on January - February 2008 – JEC Magazine #38)
MARGIE KRANTZ MARINE PRODUCT LEADER AOC
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, although marginal processability plagued some of the earlier formulations.
Workable DCPD-based polyesters were elusive to some resin manufacturers. But these resins were received especially well 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 fibres. The improved surface profile with DCPD-content polyesters is also attributed to its higher heat distortion temperature and a more complete cure during the moulding, compared to conventional orthophthalic polyesters.
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 mandating 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 generate lower emissions than the ortho resins.
The technology continues to evolve
Over the years, AOC chemists 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 moulding, scientists have fine-tuned the technology for Resin Transfer Moulding (RTM), RTM Light and vacuum infusion technologies. Ongoing research continues to bring the benefits of DCPD to the growing numbers of manufacturers who look for the latest technology.
DCPD performance and optimum osmotic protection
AOC H834-R Series DCPD polyester resins meet the mechanical, water absorption and finish requirements of major builders and are approved by Lloyd’s Register, which conforms to international quality standards. For optimum protection from osmosis, major yacht builders combine a Hydropel® vinylester product in the skin coat with an Altek DCPD resin system in the bulk of the laminate. AOC’s Hydropel high-performance vinylesters offer superior performance for naval architects, designers, and boat and yacht builders throughout the world.
The use of a Hydropel vinylester resin skin coat creates hulls with exceptional blister resistance. This technology can combine the superior osmotic blister resistance and physical properties of a vinylester with the handling and cure properties of a generalpurpose polyester resin. Toughness, mechanical strength, and crack resistance can also be improved.