METHODS FOR PRODUCING POLYESTER-GLASS COMPOSITES
RTM TECHNOLOGY/ LRTM (RESIN TRANSFER MOULDING)
RTM – (Resin Transfer Molding) is a method for manufacturing laminates in closed molds, which consists in forcing catalyzed resin to a tightly closed mold, filled previously when dry with reinforcing fiber or/and fill material. Counter mold is made similarly to the mold, with steel reinforcements allowing to use higher pressure of injection, and closing is performed in a mechanical way.
LRTM – (Light Resin Transfer Molding) a method for manufacturing laminates similar to RTM technology, but using a light, “transparent” counter mold, which is pressed by the use of vacuum between seals placed on the mold perimeter. Resin injection pressure is low, and the entire process is supported by vacuum pressure.
RTM / LRTM method makes possible a greater participation of reinforcing materials in the total weight of composite (over 60%) in relation to, for instance, hand laminating.
Advantages of this method:
- profitability with high volumes,
- high quality and uniform/repeatable structure of laminates,
- low emission of volatile compounds to the air,
- very good mechanical properties allowing for additional reduction in thickness of product walls,
- high glass content and highest resistance of the product in comparison with other methods,
- aesthetic and smooth surface from both sides (even without the use of gelcoat), high efficiency of the process,
- wall thickness tolerance up to 0.25 mm,
- low waste and low consumption of materials,
- low unit cost of component production – with a relatively high cost of hardware.
Limitations of this method:
- high cost of launching production, hardware, equipment,
- limited possibility of making changes in the mold,
- relatively long time for preparation of production,
- limits with manufacturing of large-size products and highly complicated products,