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Polydicyclopentadiene (pDCPD) is used in Reaction Injection Moulding (RIM) technology to produce large parts. Among other key features, designers are praising the ability to mould three-dimensional parts and the possibility of varying the thickness and integrating ribs or inserts.
(Published on July-August 2008 – JEC Magazine #43)
FRÉDÉRIC DÉMOUTIEZ INTERNATIONAL BUSINESS DEVELOPMENT ENGINEER TELENE SAS
Polydicyclopentadiene (pDCPD) is a high-performance thermoset polymer obtained by Ring Opening Metathesis Polymerization (ROMP) of highly purified dicyclopentadiene (DCPD). PDCPD shows an exceptional track record of impact and corrosion resistance, even at extreme temperatures (from -40°C to +160°C). Over the past twenty years, it has been used successfully in sectors such as agricultural and construction equipment, trucks and buses (body panels mainly), the chlor-alkali industry (electrolyser cell covers or butterfly valves) and other fields of applications, e.g. for various types of containers such as individual wastewater systems, waste containers, military boxes, and more. Telene® is the registered trade name for DCPD resins distributed and developed by Telene S.A.S, Drocourt, France, a company that belongs to Rimtec Co., Japan, a world-leader in the formulation of DCPD resin systems.
New benefits using the R-RIM process
Reinforced Telene® now widens the performance range for DCPD grades and makes it possible for designers and engineers to benefit from twice as much rigidity and an improved dimensional stability, by reducing the coefficient of linear thermal expansion (CLTE).
Thanks to the R-RIM process, the new reinforced material has been qualified in truck applications and in the construction market. The very first breakthrough application of this material in Europe enabled an innovative new concept for the construction of swimming pools.
It actually took less than a year of joint efforts between the engineers of the OEM, Terinjec (Aubagne, France), Rimtec and Telene S.A.S. to develop the whole project, which grew out of a two-fold technological advance:
This formulation was adapted for use with In-Mould Coating (IMC) technology, an environment-friendly and cost-effective painting process for reaction-injection-moulded parts.
Extra R&D input, including finite elements analysis (FEA), was a key element in fine-tuning the panel design; for instance, with the simulation of the effect of the back-filling.
The pool panels can be produced rapidly and easily using reinforced Telene® with R-RIM technology. The reinforced DCPD systems comprise three formulated, ready-to-use components, A, B and F, which are low-viscosity liquids (300 to 500 Cps). These contain a cocatalyst, a catalyst, and the fibrefilled component, respectively. The three components are fed into a high-pressure RIM machine at a 1:1:1 ratio and are then injected into a closed mould, where polymerization starts.
Given the moderate pressures at stake (usually less than 2 bars), moulders generally try to choose a low-cost tooling option that will still provide the surface appearance and tool thermal properties they expect from the most expensive tools. Reinforced Telene® is no exception to that rule.
In this project, a machined aluminium billet was used for the highly polished cavity side, while the core side was made from low-cost machine aluminium casting. The button-to-button cycle time is around 4’30” for the pool panels. Four to five minute cycle times are actually quite typical for almost all the moulded parts, regardless of their size, weight and developed surface. This is possible because the formulation can be tailored to fine-tune its reactivity and viscosity build-up rate.
The resulting panels facilitate pool construction: with only five different panels (flat, 90°-in and 90°-out panels), modularity is almost endless, and because the shape flexibility makes it easier to adapt the pool to the building site, there are no longer terrain limitations. Transporting the lightweight modular panels (density 1.23 g/cm3) to the installation site is much easier than for one-piece pools, so accessibility is no longer a problem, either.
The high surface quality of the panels is another key element in the material’s success for this particular application, as it eliminates the need for wall liners. The new panel concept also offers the possibility for pool decoration, until now limited to concrete pools. For instance, ceramic tiles can be glued to the panels to decorate the water line.
As far as installation is concerned, the panels are fastened to a concrete screed with dowels. Water tightness is guaranteed by an initial sealing strip applied on the edge of the panel before assembly
and backed up by a second one at the panel joints. This doesn’t affect the assembly’s aesthetics. The lining on the pool bottom is made perfectly continuous by means of a co-laminated sheet fastened to the bottom of the panel, to which a reinforced PVC sheet is welded. Once earthwork is completed, it takes two workers only a day to install a 10 m x 5 m swimming pool. This development has led to the submission of 17 patent applications.