Polydicyclopentadiene

The reacting system is formulated in such a way that for the reaction to complete at maximum speed, two components need to be mixed at equal volume (1:1 ratio). Both components contain mainly DCPD with some additional additives. The catalyst system is divided into two parts, each part going into a separate component. When both components are mixed, the complete catalyst system is recombined and becomes active. This is an important difference from other reaction injection moulding (RIM) systems like polyurethane, since the reaction is not stoichiometric. The 1:1 ratio for DCPD molding is not critical since this is not a combination of two different chemical elements to form a specific matrix. Significant changes in ratio will slow down the system's reactivity because fewer active reaction nuclei are being formed.

DCPD resins are transformed using high pressure RIM equipment as used in the polyurethane industry, with some small changes to be considered. The most important change is that the resin can never be in contact with air or moisture, which requires a nitrogen blanket in the tanks. The tools or molds are closed tools and are being clamped using a hydraulic press. Because the resins shrink about 6% in volume during reaction, these presses (also called clamping units) don't have to handle high pressures such as for sheet moulding compound (SMC) or expanding polyurethane.

Most tooling for PDCPD is made from aluminium. Flat parts can be made from machined aluminum while deeper 3D-shaped parts are often made in cast aluminium tools. It is important to take volumetric shrinkage into account, and gaskets must be used around all cavities.

The liquid resin has a density of 0.97 and reacts into a solid with a density of 1.03 which constitutes a volumetric shrinkage of 6%. Since most parts are panels, most of the shrinkage will happen in the Z-axis (thickness). This makes the parts self-demoulding as they do not have a good contact with the core side(which is the back side) of the tool.

A reacting system is always governed by temperature - in any form. This means that the temperature of the liquid components has a strong influence on the reactivity. To ensure that one side has the required surface finish, the temperature on that side needs to be higher than on the core side. Both tool-halves are therefore tempered at a different temperature with typical values of 60°C and 80°C.

Typical cycle times for moulding parts range between 4 and 6 minutes.

PDCPD has a combination of properties:

• high impact resistance
• high chemical corrosion resistance
• high heat deflection temperature (HDT).[1]

PDCPD does not contain any fiber reinforcement although a fiber reinforced version has been in development. PDCPD allows the thickness to vary throughout a part, to incorporate ribs and to overmould inserts for an easy assembly of the parts. PDCPD cannot be painted in mass and needs to be painted after moulding.

Since PDCPD is still a new material, the number of applications is quite limited. The major applications is in the field of body panels, mainly for tractors, construction equipment, trucks and buses. In the industrial applications, the main usage is components for chlor-alkali production (e.g. cell covers for electrolyzers). Other applications is used where impact resistance in combination with rigidity, 3D design and/or corrosion resistance is required.

PDCPD is not recyclable. In July 2020 researchers reported the development of a technique to produce a degradable version of the tough thermoset plastic which may also be applicable to other plastics, that aren't part of the 75% of plastics that are recyclable.[2][3]

• Book: "An Introduction to PDCPD", Dirk Vervacke, 2008, ISBN 978-90-79480-01-2, 129p
• The polymerization of dicyclopentadiene: an investigation of mechanism - Journal of Molecular Catalysis A
• Polydicyclopentadiene - Polymer Science Learning Center
• Properties of Polydicyclopentadiene (PDCPD) - MatWeb database