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A powder gelcoat process

News International-French

27 Nov 2015

The Ecogel Cronos project aims to the development of an ecological and innovative coating for composite parts which may be able to eliminate the styrene emissions from the workplace. 

Composites begin to demonstrate their worth in the equally demanding consumer, infrastructure, automotive, transport and sporting goods industries. However, the transition to many of these mass-production sectors is slow, primarily due to low productivity rates for cost-efficient manufacturing.

The transport industry is facing increasingly stringent environmental regulations which lead to increase the power-to-weight ratio of the cars, reducing the overall weight and thereby reducing vehicle emissions. To achieve this goal, composites are a key technology but they must meet weight, cost and production rate requirements. While traditional composites used in the automotive industry have typically utilised high cost aerospace-derived prepreg technology for autoclave curing or Sheet Moulding Compound (SMC). The Ecogel Cronos project is focusing on Resin Transfer Moulding (RTM) to provide unparalleled efficiency in terms of cost and production rate with the same performance and quality.

The main aim of the Ecogel Cronos project is to develop an innovative and high productivity Resin transfer Moulding (RTM) process by means of the use of:

  • fast curing "zero VOCs emissions" powder gel coats (with and without electrically conductive properties)
  • electrically conductive hot skin mould technologies based on laminates made of carbon-fiber- plastics (CFP laminates) to mass production parts for automotive and goods transport sector.

The first step in the development of the powder gel coat has been the formulation of a powder resin system.

Different systems have been developed within the project and combined with the suitable additives in order to obtain highly reactive, stable, cost-effective and suitable for case studies requirements powder gel coat formulations.

Modelling tasks have been employed to determine the electrical conductivity threshold in the formulations of electrically conductive powder gel coat.

Promising results have been obtained with good results regarding gel time, storage stability, electrical conductivity and temperature to film formation. Additionally, different resin modifications are being formulated to improve the powder gel-coat adhesion to different resins such as epoxy or vinylester.

The use of innovative powder gel coat in the RTM production is only possible if new moulding technologies are developed. The proposed RTM process implements the introduction of reusable electrically conductive, temperature controlled skins that can be prepared off-line. This allows the release agent, gel coat and fibre to be applied to the skin whilst another one is being injected. In this way it is possible to increase production for a relatively small additional investment compared to RTM tooling. The skin design includes an electrically conductive surface and heated systems to fully optimise production allowing the introduction of powder gel coat in the RTM production as it is shown below.

A pilot plant mould has been built and tested at pilot plant level. The production method for the manufacturing of RTM moulds with electrically heated skins has been defined and, currently, work is being undertaken to manufacture a prototype mould with an electrically heated skin. This skin includes an electrically conductive surface (developed within the project) and heated systems to fully optimise production allowing the introduction of powder gel coat in the RTM production.

Simulations of mechanical tests and thermo-mechanical tests were performed to determine the optimum skin layup.

Two products, representatives of the advantages of this new production line, have been selected as demonstrators: a fully finished truck side skirt and an automotive door skin part ready for E-coating bath painting treatment. The door skin is an example of a metal replacement product, while the truck side skirts is an example of a current RTM technology component that is being upgraded through the new process developed within the project.

The main requirements of these case studies are also defined and are being used as a baseline to measure project progress.

Environmental, health and economic factors are taken into account throught the duration of the project; an LCA of the powder gel coat will be completed, specifying the safety criteria for the new processes based on standards and legislation in force and defining the methodology for estimating the price of the chosen demonstrators while making an estimation of cost savings.

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