HAND LAY-UP (METHOD OF CONTACT)
Hand lay-up method, however is one of the oldest ways of production of moulds and composites, is still the most popular one. A mould (or, while the process of production, a mould’s model) after positioning on it a separator (a classifier, wax), is covered with gelcoat. We use different kinds of gelcoats depending on the kind of surface we want to achieve. Gelcoat is sprayed or positioned manually in the mould (the layer does not extend 10 mm). It guarantees the satisfying visual effect and the resistance to any outdoor conditions (water, air, chemical substances). When gelcoat hardens a little (when touched it does not stick to a finger, but there is a visible fingerprint on a gelcoat’s surface), it is covered with resin (that is beforehand mixed with a hardener). Then, a moulder makes the sandwich structure by putting reinforcements, between which the resin is positioned by a brush or a roller. It is important to remove air bubbles and the excess of the resin, thanks to which the laminate will be more durable.
Laminate is hardened in the room temperature, however the process might be hastened if the level of warmth is higher. High temperature also results in the bigger warmth resistance of the laminate. Thanks to its infinite possibilities the hand lay-up technology is used worldwide; it is applied in the production of big and small, complicated and uncomplicated, so as in some complex shapes products that are made in a low and an average amount. Due to the possibility of production of the small number of products, it is often applied while making prototypes.
Reinforcement: fiberglass, carbon, aramid or any other synthetic or natural fibers.
Resins: most frequently epoxy or polyester. The kind of a resin, initiator or hardener should be chosen in regard to the estimated time of the production, and while taking into consideration requirements concerning durability characteristics, warmth and chemical resistance, or other special requirements (low flammability etc.). All of these should be adapted to properties and an application of a final product.
Gelcoats are worth mentioning because they remain in a constant relation with resins and the production of moulds. For a better understanding of the definition we will first explain what the gelcoat is and what kinds of it we can encounter.
The general definition is quite complicated and not fully understandable for everyone that is why we will simplify it a little. Gelcoat, in other words, is a gel resin created on the basis of polyesters or epoxes, which give ready products the required resistance, durability and moreover: a color and gloss. Depending on a kind of surface a moulder wants to gain, different kinds of gelcoats are used. On the one hand, in the production of moulds one uses hard, and chemical/attrition resistant gelcoats. On the other hand, in the production of gelcoat top coatings in composite elements the most important features are: UV resistance, polishability and weather conditions resistance.
Other kinds of gelcoats are silicone ones which are good for the production of irregular-shaped elements such as: figurines, sculptures and wherever we have negative angles and the dividing lines should not be visible.
- Injection moulds,
- Moulds for products made of integral foam,
- Open moulds,
- Composite moulds and laminate products.