HDPE & PP-like

These materials are thermoset polyurethane resins. They are particularly recommended for prototyping applications, with the technology of vacuum casting.

Unlike thermoplastic resins, these polyurethanes can withstand high temperatures and do not melt when exposed to heat. The chemical nature of the formula shows chemical bonding between the polyol and the isocyanate called cross-linking, which leads to a strong and durable polymer.

The purpose of this range is to simulate the mechanical properties of a future extrusion thermoplastic material like PP and HDPE, in order to create a functional and strong prototype part. Although the chemistry of the 2 polymers is different (thermoset and thermoplastic), the goal of the PR777, PR740 and HPR65 is to get closer to the injection-moulding series material, to get a realistic part that will support the development of the project. These thermoset urethane resins also make a particularly good choice for small series, when investing in an aluminium tooling is not a relevant option yet.

We recommend to use these PU resins in a polyaddition silicone mould. Moreover, the materials are formulated to have a very low aggressiveness to silicone, making them gentle materials to keep your moulds in good condition, and make multiple parts.

The PR740, PR777 and HPR65 have a specific chemical formulation base, that make them very gentle to silicone-rubber. Depending on your application and the complexity of your part shape, you can expect between 30 and 50 parts.

For opaque colours, you can use Synthene pigments. Get in touch with our team to learn more about these additives. For translucent colours, we recommend to use solvent-based tints, that should not exceed 3% of the total weight of the moulded part. The pigments always have to be pre-mixed in the polyol component prior to mixing with the isocyanate.

Warning: these 3 materials can darken under the exposure to UV, without alteration of the other properties.

In order to reinforce the mechanical and thermal properties of the PR777, we can suggest the use of the Glass fiber filler SYNFILL G. Using this fiberglass filler will increase the flexural modulus and flexural strength of the material up to 64 MPa. The heat deflection temperature will be raised from 94°C to 131°C with the addition of 25% of Synfill G. The glass fiber rate can be adjusted depending on the requested properties of the project. This fiberglass filler should always be added to the isocyanate component before mixing with the polyol.

This range is composed of polyurethanes with a flexural modulus between 450 MPa and 930 MPa. They are therefore semi-rigid, or semi-flexible resins. Chemically speaking, the HPR65 is formulated as an elastomer, which is why it has no HDT. They are all good countertypes of PP or HDPE thermoplastics.

The PR777 is the most user-friendly material with a 1:1 mixing ratio and a very low viscosity. It benefits from a long pot-life and a short demoulding time, making it the winning combination.

The HPR65 also have a low viscosity. Its clear advantage is that it has a very limited exothermic reaction, and it can be used for massive parts with a curing at room temperature.

After a regular curing at 70°C, the material is not brittle and ready for using.

However, a post-curing greatly helps to speed up the chemical bonding and improve the performance of the material.

In case of big part dimensions, the HPR65 can get high mechanical properties even if it completely cures at room temperature.

The PR740 is designed for small dimensions. As the potlife is 7,5 min, sometimes it can be handy to use a differential pressure system.

The PR777 is suitable for larger parts, like car bumpers.

The HPR65 works for the fabrication of small, big or even very thick parts, with its ability to cure at room temperature without any brittleness phenomenon.

Our R&D laboratory has designed these PU resins to have a high resistance to shock. On the Charpy impact test, the PR740 and the HPR65 need to be notched, or else they do not break.

The impact resistance of these materials are respectively:

• PR740: 24 kJ · m -2 – notched
• PR777: 91 kJ · m -2 – unnotched
• HPR65: 30 kJ · m -2 – notched