Epoxy resin

epoxy resin (abbreviation EP) is in the hardened condition a duroplastischer plastic of high firmness and chemical stability. For production epoxy resin and hardeners are carefully mixed. Depending upon composition and temperature takes place within few minutes to several weeks the hardening by precipitation of the originally liquid mixture from epoxy and hardener. The polymerization reactions consist of the polycondensation and the polyaddition.

Epoxy resins were manufactured 1966 of the CIBA as pouring and lacquer resin. Particularly adjusted epoxy resins find as metal bonding agent application.

Table of contents

use

Because of the small expenditure for the production in the hand laminating procedure of necessary equipment need and the high firmness with small weight and the nearly arbitrary shaping possibilities this is also in the private model construction range likes.

Due to its innocuousness epoxy resin is also very often used for the Terrarienbau. Since it is liquid impermeable, one can use it just as well in Feuchtterrarien.

In the building of yachts it does not differ from polyester resin thereby that it comes to no osmose damage, also if sea water by a damaged Gelcoat - layer penetrates and with the material in contact comes. Therefore epoxy resin is used also for the repair by osmose damage to polyester resin bottom structures.

Epoxy resin is not recyclingable with the current state of the art and the materials to its production from oil is predominantly won.

characteristics

the following characteristics apply to the pure, non-strengthened resin without aggregates.

  • Modulus of elasticity: <math> E \ approx3000-4500 \ frac {\ rm {N}} {\ rm {mm} ^2}< /math>
  • Tensile strength: <math> R \ approx 80 \ frac {\ rm {N}} {\ rm {mm} ^2}< /math>
  • Density: <math> \ rho \ approx1 {,} 2 \ frac {\ rm {g}} {\ rm {cm} ^3}< /math>

Depending upon attitude of the resin system the temperature resistance can amount to with hot-hardening systems more than 250°C. The glass transition temperature of cold-hardening systems is with for instance 80°C. Epoxy resin pours like the thermoplastics under moisture absorption.

Due to the good dielectric characteristics epoxy resin finds, e.g. as sealing compound, in the electrical industry application.

processing

differently than with polyester resin must be normally kept when mixing epoxy resin the stoichiometric resin/hardener relationship. Otherwise remain parts of resin or hardeners without reaction partners, which entails sticky surfaces and decreased firmness of the final product. Some epoxy systems are however expressly suitable for a variation of the mixing proportion within close borders. Thus can be affected hardness, elasticity and other characteristics.

An inhomogenous mixture of the components has just as negative effects as a wrong relationship of the components, since the polymerization runs off only incompletely.

The polyaddition is strongly exothermic. Therefore no of any size quantities of resin and hardener may be mixed in particular with highly reactive systems. The developing heat of reaction can become so large that it comes to the fire. For construction units with large wall thickness therefore only lowreactive resins should be used.

The processing duration of reaction resins is called pot life. It depends on the processing temperature and the attitude of the resin. Slow-reactive epoxy resins need long bakeout periods and a high Härtetemperatur. If necessary accelerators can be added, which shorten the response time. Epoxy resins can be submitted to an annealing process to the complete Ausreaktion after the hardening by precipitation.

Epoxy resin can with reactive solvents (e.g. Aliphate) to be mixed, in order to degrade the viscosity of the resin. Thus a better soaking of fabrics or the workability is ensured in the RTM procedure.

Epoxy resins can with aggregates (e.g. to adjust pyrogene silicic acid) to be provided around it thixotrop. This thickened resin can be used as insulating material or adhesive. Other aggregates serve than filling or propellants around the density of the resin to reduce, in order to improve or increase by the maximum continuous operation temperature the pavement grip the surface. Aggregates can positively affect the behaviour in case of fire of epoxy resin. This is particularly important with the employment in means of transport.

The chemical shrink with the polymerization lies with 1-5% clearly smaller than with the ungestättigten polyester resins, it can with suitable aggregates even still well under 1% be brought.

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