Resin theory

Starting to picking up a Resin in one of our previous articles, we ended up engaged in a discussion with a local Resin supplier – Acme Composite Supplies. You can see their reviews on a Google below and I have to agree. In a situation where guys coming in with an idea of building a new Hindenburg – they’ve been very open to help – from very beginning.

Unfortunately their experience with high-temperature curing was limited, so their preference was to use resin with curing cycle temperature up to 70C. Unfortunately that would potentially come with some manufacturing issues on a horizon such, where we were counting on our Aluminium tube/mold expansion at 150C to assist us with decoupling. That tube expansion is also there to counteract external forces (tape) to serve us on behalf of missing autoclave processing.

So the option left in their offer was to use PRIME^TM 37 RESIN & PRIME™ HIGH TG HARDENER from Gurit.

Mechanical properties

Hoping that, when everything going well, we should get mechanical properties somehow close to following values (using two-plies of uni-directional Carbon Fiber instead of 4 plies of XE600 biaxial e-glass):

Comparing it with other resin / hardeners combination, this one provides roughly 5-10% better values across all properties see PRIME^TM 37 RESIN & AMPREG 3X FAST HARDENER below.

Curing time

While the mold handling (Aluminium tube decoupling process due to temperature change) is the important one, pretty much same importance comes with the curing time, which is with our selection shortened from 10+ hours to a single hour. That should potentially allow us to streamline pipe production.

Viscosity

The last bit to solve here was the initial system viscosity. There were some concerns that HTC solution will have very low viscosity so it won’t stick on our CF tape. Comparing a mixture viscosity for PRIMETM 37 RESIN & AMPREG 3X FAST HARDENER – 375 at 30C – with our selection – 210-230 at 30C, indicates that it will be really more “running” than what guys at Acme Composite Supplies are used to.

Just to understand what we’ll be facing here, I did a tiny excursion to Wikipedia to check how that compares. Apparently viscosity of water at 20C equals 1, while our expectation of 210 – 230 throws us probably to the “Sour cream” region. For others see the table below.