Tooling gelcoat MGS F 300

Transcription

1 3-15 Tooling gelcoat MGS Hardener MGS page Characteristics 15 Application 16 Specifications 20 Processing details 20 Mixing ratios 20 DMA 21 Content Application tooling Characteristics Operational temperature up to 150 C (302 F) Processing mixing and application by hand or by machine Features provides hard, scratch resistant surface long open time high heat resistance Special modifications on request Storage shelf life of 24 month in originally sealed container s

2 3-16 is a tooling gelcoat, which has been modified with special fillers. Tooling produced with this resin system result in sratch resistant surfaces in combination with a high heat resistance after a suitable post cure. The very hard surface is worked best with diamond tools. The tooling gelcoat features high stability and good heat conductibility. Application Special care should be taken for a good preparation of the plug, as finishing of the surface might be difficult due to its high hardness. As the material shows a very high potential heat stability, the material properties after an initial cure at room temperature are too poor to be sufficient for demoulding. Therefore, a heat treatment of minimum 10 hours at minimum 50 C is required before further processing. The material can then slowly be brought to its final thermal properties by using post cure techniques at elevated temperatures. It is good workshop practice to ramp up to a post cure temperature that exceeds the planned operational temperature. Important All work for the manufacturing of epoxy resin moulds (and parts) must be performed "wet-in-wet" in order to achieve good chemical bonding of the layers. Application of further layers to partially hardened (dust-dry) surfaces inevitably results in insufficient bonding, and even a small amount of stress will cause the layers to separate. Always use slowly reacting laminating resin systems to produce thicker laminates or backfills. Highly reactive systems may heat up considerably due to reaction heat and cause thermal stresses. The moulds or parts are then possibly distorted and unusable. Overheating may also have further consequences such as destruction of the master, melting of the parting wax (preventing removal from the mould), "freezing" of high shrinkage stresses which may cause the formation of cracks in the mould resin. Consumption The general recommendation is to apply 1-2 layers. The following quantities are required (for 2 layers): with hardener : 2,0-3kg/m² Processing The optimal processing temperature is in the range between 20 and 25 C. Higher processing temperatures are possible, but will shorten pot life. A 10 C temperature increase will halve the pot life. Water (for example, very high humidity of the ambient air) causes an acceleration of the resin-hardener reaction. Different temperatures and humidities during processing have no significant effect on the strength of the cured product. The specified mixing ratios must be observed as precisely as possible. Adding more

3 3-17 or less hardener will not effect a faster or slower reaction - only an incomplete curing of the material which cannot be corrected by reworking. Since the tooling gelcoat contains heavy fillers (metal powder), the contents of the container must be stirred thoroughly before using the resin. Use a spatula or metal bar to check whether or not all filler sediment has been stirred up. If you detect deposits on the container bottom, we recommend the following procedure: Transfer the entire contents of the container to an appropriate empty container. Then remove the filler sediment (solid deposit) from the bottom with a spatula and add to the resin while stirring. Stir until the filler is uniformly distributed in the resin (e.g., using a power drill with an agitator attachment). When mixing resin and hardener, particular attention should be paid to the walls and bottom of the mixing tank due to the different viscosities of the components. Since mould resin not thoroughly mixed and processed makes the entire mould unusable, the following procedure is recommended: Evacuation: Weigh the resin and hardener as accurately as possible and mix thoroughly - preferably using a power drill with an agitator blade. Transfer the resin-hardener mixture to a large, new mixing tank and mix thoroughly once more. Then remove the air entrapped by stirring by means of evacuation since the air bubbles cannot rise after application due to the toughness of the product and the short gelling time. Use a glass desiccator with a suitable vacuum pump, e.g., a water suction pump, sliding-vane rotary pump, etc. (available at a reasonable price in laboratory equipment stores). The mixing tank used for evacuation must have at least three times the volume of the resinhardener mixture. When the vacuum is applied, the air bubbles expand, thereby increasing the volume of the mixture 2- or 3-fold, before the air bubbles burst and the mass "collapses". This process can be observed very well in a glass desiccator. The vacuum pump's power must be sufficient to complete the evacuation within a maximum of 5 minutes due to the short pot life of the resin-hardener systems. The appropriate industrial safety regulations must be observed when processing epoxy resins and hardeners. Also refer to the instruction sheet for safe processing of epoxy and polyester resins, issued by BG Chemie. Building negative moulds Typically 2 layers of a suitable mould resin system are applied to the master which has been carefully treated with the parting agent. Allow the last layer to gel for a short period and then apply the so-called "bonding layer". This layer must assure the bonding between the mould resin layers and the backfill. Generally, the best solution is to use the same slowly reacting laminating resin system used in the backfill. To make sure that a thin layer is present even on vertical surfaces, add a thixotroping agent (e.g., Aerosil ) to the mixture. Ready-made thixotropic laminating resins are also available (e.g., laminating resin L 160 T).

4 3-18 The entire surface of the model is carefully painted with the thixotropic laminating resin mixture after a brief gelling period (consumption approx g/m 2 ). Then the mould resin layers must cure for additional approx. 2-3 hours, depending on the temperature - to prevent fibers or backfill material from penetrating into the soft mould resin layer. The backfill is then applied to the bonding layer. Use a glass or carbon fiber laminate or a backfill mass containing aluminum powder or quartz sand depending on the requirements. If low mould weight is required, a sandwich structure may be an efficiant solution. Satisfactory results can also be obtained with spacer fabrics. If the moulds are used at different temperatures, it is essential for the mould to be of symmetrical construction. Asymmetrical moulds will distort during warming up due to the different materials' coefficients of thermal expansion, just as bimetal parts do. Built-in metal parts such as copper pipes for heating or cooling, steel bars for bracing, etc., must be thoroughly treated with a parting agent before installation. The coefficients of thermal expansion of the synthetic resin materials and of the metals differ widely, causing considerable stress build-up during warming which may destroy the mould. Storage Although our resin systems are very unlikely to crystallize at low temperatures, storage conditions of C and low humidity are recommended. After dispensing material, the containers must again be closed carefully, to avoid contamination or absorption of water. All amine hardeners show a chemial reaction when exposed to air, known as blushing. This reaction is visible as white carbamide crystals, which could make the materials unusable.

5 3-19 Backfill masses Rugged and inexpensive moulds can be built with backfill masses. A disadvantage of these masses is their heavy weight. Recommended formula for an easily workable backfill mass: Parts by weight Laminating resin-hardener mixture 20 Quartz powder, e. g., W 8 20 Fine quartz sand ( mm) 30 Coarse quartz sand (2-3.5 mm) 30 Laminating resin systems for mould building Always use slowly reacting laminating resin systems to produce thicker laminates or backfills. Highly reactive systems may heat up considerably due to reaction heat and cause thermal shrinking by a factor of between 4 and 5 %. The moulds or parts are then distorted and unusable.

6 3-20 Tooling gelcoat Hardener Specifications V iscosity [ mpas] pastous Epoxy equivalent Epoxy value Amine value Mixed viscosity Refractory index [ g/equivalent] [equivalent/ 100g] 0,17 [ g/equivalent] 53 [ mpas] ,4900-1,5000 Tooling gelcoat / Hardener Processing details Potlife Geltime Curing Heat treatment 100 g / 25 C (77 F) film of 1 mm at 25 C (77 F) app. 4 h app h initial curing C Tooling gelcoat : Hardener Mixing ratios Parts by weight 100 : 9 ± 0, 5

7 3-21 [N/mm 2 ] Storage Modulus Storage Modulus Onset: 117,3 C 243,14 F Peak: 133,6 C 272,48 F 0,70 0,60 0,50 DMA Curing: 10 h / 95 C (203 F) 0,40 0,30 0, [ C] [ F] ,10 0,00 Temperature [N/mm 2 ] Storage Modulus Storage Modulus Curing: 10 h / 150 C (302 F) Peak: 161,3 C 322,34 F Onset:145,1 C 293,18 F 0,70 0,60 0,50 0,40 0, , [ C] [ F] ,10 0,00 Temperature Test: DMA, 3-Point bending Parameter: Frequenzy 1 Hz Heat rate 2 K/min Coupon thickness 2 mm