Many of the Resins-Online casting products are supplied in innovative twinpacks that have been designed to make them much more user friendly. Robnor Resins has put together a useful guide on how to use a twinpack which we have added to the Learning Zone.
A Guide to Processing and Curing
This is the time normally in minutes that the mixed resin is ‘usable’.
This is the time normally in minutes that the mixed resin is ‘workable’.
This is the time to double the initial mixed system viscosity.
Viscosity is the resistance to flow. A high viscosity resin has high resistance to flow e.g., treacle. A low viscosity resin has low
resistance to flow e.g. water.
Curing is the process by which resins react to produce a solid infusible mass. The reaction of resin and hardener usually
involves the liberation of heat called exotherm. This is generally controlled by careful formulation and the addition of fillers and
additives that suppress excessive heat build up. It is however dependant on the ambient temperature and the mass of material used. Smaller masses and lower ambient temperature will extend cure time and larger masses and warmer ambient temperatures will reduce cure time. Hotter temperatures may be used for faster cure but will result in higher post cure shrinkage and higher cure exotherm. Experimentation and testing is suggested to avoid side effects. For maximum properties a post cure may be required - call Robnor Technical Service Department for advice.
Please consult the technical data sheet before using Resin-Online products.
In many resins the performance of the system can be enhanced by a process called post curing. This involves a secondary
cure process over and above the normal conditions to provide enhanced performance. In general post curing will improve such properties as; chemical resistance, temperature stability, dimensional stability, voltage breakdown resistance, water resistance and increase glass transition temperature. Post curing is mainly used on epoxy systems but can also be used on some high performance polyurethanes to enhance them still further. In general post curing occurs at 10 – 20.C above the maximum expected service temperature.
Typical post curing (depending on system), may involve a normal cure plus:
16 hrs at 100.C or
8 hrs at 120.C or
4 hrs at 140.C or
2 hrs at 150.C