The LETOXIT® Foil Technology (LF Technology) is our unique patented technology, which allows dry way of laminate production based on the impregnation of reinforcement with LETOXIT® foil resin at increased temperature and pressure.
|LF TECHNOLOGY is epoxy resin in the form of flexible foil, which softens at increased temperature and it is able to impregnate originally dry reinforcement and cure in one step.|
Prepregs are materials used for years, but they are very expensive and many prepreg types are necessary, if composite structure should be optimised well. RTM is a relatively cheap method, big parts can be manufactured. The main problem is impregnation of the reinforcement. Therefore only special types of the reinforcement have to be used and the result is relatively low reinforcement content in a final composite part. In recent years, technology called RFI – Resin Film infusion appeared. The production cycle is performed usually in the autoclave under increased temperature and pressure, where the fibre infiltration and the composite consolidation occur in a single step process. Typically, the RFI element consists of a thermoset resin film placed between one side of a metal tool and a dry textile fibre preform. Problems with conventional RFI appear if sandwich structures are manufactured; honeycombs are filled with resin and foam prevents from impregnation of the sandwich skin in opposite site of the resin layer.
Concerning these disadvantages of conventional processes and a need of universal low cost technology, 5M s.r.o. developed and patented a very efficient technique of production of sophisticated and relatively cheap composite structures, which is called Letoxit Foil Technology (LF Technology).
During manipulation, production and curing doesnt release any hazard vapours and foil is very friendly to use.
LF Technology allows the application of various types and numbers of layers at different places of the construction.
The products made by the LF Technology are comparable with products made by the prepreg technology. In comparison with prepregs has LF Technology big advantage in variability, i.e. in production can be used dry fabric as required (the same like in usual hand lay-up) and that saves money, because there is no need to store huge amount of prepregs in freezer.
|Resin LETOXIT||Basis||Curing (°C) (min)||Tg (°C)||Max. Tg (°C)||Characteristics||Techn. sheet|
|LFX 023||epoxy||120||60||95||100||universal type|
|LFX 035||epoxy||120||60||122||125||universal type for carbon
|LFX 038||halogenated epoxy||120||60||127||135||self extinguishing (FAR 23)|
|LFX 040||mod. cyanoester||150||180||190*||250||high temperature resistance
|LFX 044||mod. epoxy||120||60||95||105||high impact strength
|LFX 054||epoxy||120||60||130||155||higher temperature resistance, for carbon
|LFX 055||epoxy||120||60||130||155||higher temperature resistance, low stickiness
|LFX 056||epoxy||120||60||120||125||self extinguishing (FAR 25)|
|LFX 060||epoxy||120 (80)||20 (240)||120||125||fast curing, for carbon
|LFX 062||phenolic||120||45||80||103||self extinguishing (DIN 5510-2)|
|LFX 162||epoxy||120 (80)||20 (240)||95||100||fast curing universal type
* cured 3 h at 140°C, post - cured 4h at 200°C + 4h at 250°C
|Resin LETOXIT||Density (g/cm3)||Peak (120°C, min.)||Max. flexural stress (MPa)||Flexural modulus of elasticity (GPa)||Impact strength of pure resin (kJ/m2)|
|LFX 023||1,19||4,65||120 - 125||540**||3 - 3,1||18,9**||45 - 50|
|LFX 035||1,19||5,5||120 - 125||580**||3,2 - 3,3||17,1**||30 - 35|
|LFX 038||1,39||10,5||100||610**||3,2 - 3,3||19,5**||12|
|LFX 044||1,14||8,5||85||417**||2,2 - 2,3||12,2**||55 - 60|
|LFX 056||1,35||6||110||480***||3,3 - 3,4||15***||22|
|** 12 layers glass fabric 163 g/m2 twill + 5 layers Letoxit LFX 300 g/m2. Resin content 44%
*** 12 layers glass fabric 163 g/m2 twill + 8 layers Letoxit LFX 200 g/m2. Resin content 50%
The foil can be stored for 1 month at temperatures up to +20°C, for 3 months at +5°C and up to 1 year at -18°C without any change of its properties. Be sure not to exceed +30°C at transport and storage.
|Letoxit PFL 122||fixing agent
||fixation (temporary gluing) of dry fabrics into moulds. After curing non visible, doesnt make stains.
LF Technology is suitable for any composite structure, where balanced weight and mechanical properties ratio are required. Typical applications are tin shell structures with high reinforcement volume, locally added reinforcements and/or with different required local properties (for example reinforcement orientation) because these structures cannot be manufactured by conventional technologies without highadded cost of material and work. The conventional composite structures, originally made by RTM, VARTM, Hand-lay up, are possible, of course. but due to lower requirements on mechanical properties on parts made by these conventional technologies, economy of LF technology (RFI) must be taken into account.
Potential applications are: