Resine strutturali trasparenti
Attività di studio scientifico e ricerca e sviluppo di laboratorio permettono di aggiornare quotidianamente le nostre formulazioni.
Fomulazioni speciali di resine epossidiche
È possibile preparare speciali formulati a base di resine epossidiche bicomponente caratterizzati da una eccezionale trasparenza, adatti a riempire cavità ed imperfezioni in materiali di varia natura, utili per eseguire inglobamenti a scopo decorativo e come collanti per impasti di sassi, graniglie e polveri. Formulati a base di resina epossidica possono essere colorati e utilizzati anche come materiale trasparente strutturale per realizzare oggettistica, manufatti artistici, tavoli e componenti plastici.
Il sistema epossidico Borma Glass presenta proprietà eccezionali:
1. nessuna emissione di sottoprodotti nella reazione di polimerizzazione e bassissima contrazione durante la polimerizzazione
2. altissima adesione su una varietà di superfici
3. bassa viscosità e molto semplice da miscelare e colare
4. flessibilità applicativa per cui è possibile realizzare oggetti di dimensione piccola e grande, con la tecnica di applicazione a strati successivi.
5. ritiro lineare molto ridotto, pressoché nullo in caso di inglobamenti
6. ottima durezza e bagnabilità superficiale: è quindi possibile effettuare operazioni di calibrazione, levigatura, lucidatura con abrasivi ed utilizzare vernici antigraffio base acqua per la finitura lucida.
7. elevata compatibilità con coloranti trasparenti, fluorescenti, iridescenti o con altre caratteristiche speciali
Epoxy Resins – Component A
Basic epoxy resin is very viscous and unsuitable for easy handling use in laboratory except as a thick glue for specialized applications. A casting resin is a low viscosity clear modified epoxy resin. Modifications include additives to promote leveling, air detrainment, resiliency, toughness, high impact resistance, and recoatability, without removing amine blush or sanding between coats. Shelf life is unlimited in closed containers stored below 32 °C. Haziness and crystallization will occur if stored at cold temperatures (below 10 °C) for prolonged periods. Immersing the closed container in hot tap water and heating to 50 °C or above will bring the resin back to a clear state. Neither crystallization nor heating will adversely affect the product. Crystallization will reoccur if the material is not totally brought back to a clear bright state after heating. Simply warming cold material to room temperature will not melt the crystals.
Hardeners – Component B
Linear or crosslinked epoxy polymers are obtained by reaction of the epoxy monomers with co-monomers (“hardeners”) and/or initiators. Epoxy polymers can be produced by step or chain polymerizations or, eventually, by a combination of both mechanisms. Amines are the most commonly used room temperature curing agents/hardeners for epoxides. Epoxy-amine step- growth polymerization proceeds via a step-by-step succession of elementary reactions between reactive sites. The number of reactive sites per monomer (functionality) and the molar ratio between co-reactive sites are the main parameters that control the polymer structure. To obtain linear polymers, the reactants must be bifunctional; monofunctional reactants interrupt the polymer growth. A condition to obtain crosslinked polymers is that at least one of the monomers has a functionality higher than 2.
The ratio of epoxy-polyamine, taking into account the various molecular weights and densities involved, determines the final properties of the resin. Varying the recommended ratio will leave unreacted sites, the resultant cured resin will have lower strength as it is not as completely crosslinked.
Epoxy hardeners are not catalysts. Catalysts promote reactions but do not chemically become a part of the finished product. Epoxy hardeners mate with the epoxy resin, greatly contributing to the ultimate properties of the cured system.
Curing time of an epoxy system is dependent upon the reactivity of the amine hydrogen atoms. Cure time can be altered only by selecting a different hardener, adding an accelerator in systems that can accommodate one, or by changing the temperature and mass of the resin/hardener mix.
The epoxy curing reaction is exothermic. This means that it gives off heat as it cures. The rate at which the epoxy resin cures is dependent upon the curing temperature. For example, if an epoxy system takes 3 hours to become tack free at 20 °C, it will be tack free in 1.5 hours at 30°C or tack free in 6 hours at 10 °C. Pot life and working time are greatly influenced by the initial temperature of the mixed resin and hardener.
The working time of the resin depends also by the quantity of the mixture and heat exchanges. If the heat generated is immediately dissipated to the environment (as occurs in thin films) the reaction speed proceeds uniform. If the mixture is confined (as in bulk containers) the the temperature raises, accelerating the reaction speed. Experienced users either mix batches that will be applied almost immediately or increase the surface area to slow the reaction.
After gelation the reaction speed slows down as hardness increases. Chemical reactions proceed more slowly in the solid state. From the soft sticky gel the system gets harder, slowly losing its stickiness. It becomes tack free and continues to become harder and stronger as time passes.
At room temperatures, generally speaking, a polyamine-epoxy system will reach about 60% to 80% of ultimate strength after 24 hours. Curing then proceeds slowly over the next several weeks, finally reaching a point where no further curing will occur without a significant increase in temperature.