processing of polymer resins (up)up).pdf · base training up-processing 1 processing of polymer...
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DSM Composite ResinsBase training UP-processing
1
Processing of polymer resins (UP)
Mouldmaking
Gel coat and top coat
HLU/SU application
Properties
DSM Composite ResinsBase training UP-processing
2Mould making
Important:• Highest gloss surface• No print through• Durability
DSM Composite ResinsBase training UP-processing
3Mould making: Critical issues
• Design of product• Plug construction• Tooling gelcoat application• Laminate build up, construction• First release from the new mould
DSM Composite ResinsBase training UP-processing
4Plug making: Design
• Release angle > 3°• Avoid narrow and high ribs• No sharp edges (min. radius 5 mm.)• Build in a 5 cm rim around the plug • For Infusion and LRTM moulds a flange of 15 cm is
required.
DSM Composite ResinsBase training UP-processing
5Plug making: Materials
• Wood or plaster, coated with PU paint.
• Wood or plaster, GRP or epoxy coated.
• GRP.
• Foam, GRP or Epoxy coated.
• Combinations
DSM Composite ResinsBase training UP-processing
6Plug making: Steps to obtain gloss
• Fill imperfections with putty• After cure, dry sanding with P180• Apply one coat (1-1.5 mm) of spray filler (car spray putty)• After cure, dry sanding with P180• Apply one coat of gel coat with paraffin solution• After 24 hours wet sanding with P600, P800 and P1000• Polish the surface using compound and machine
DSM Composite ResinsBase training UP-processing
7Mould making
• Apply gel coat • Let it cure for at least 4 hours, but not longer than 16 hours
• Laminate first layer: • 225 + 300 gr CSM wet in wet • Leave overnight to cure
• Continue lamination with max. 2 x 450g CSM / day • Exotherm must be minimised.• Typical 6-10 days per mould.
DSM Composite ResinsBase training UP-processing
8First release from a new mould
• Always very critical• Post curing the mould on the plug helps• Release agent (Carnauba): Minimum 6 layers• PVA release, only for first product
DSM Composite ResinsBase training UP-processing
9Effective mould releaseshould have the following
• Chemical inertness to both mould surfaces. This is essential to counter the adhesion that commonly occurs between two surfaces. It is influenced by factors like chemical reaction and compatibility,penetration, surface tension, surface configuration and polarity between two surfaces
• Low surface tension (it wets out the moulding to form a continuous film)
• Insolubility• Heat resistance to avoid being melted
DSM Composite ResinsBase training UP-processing
10Facts related to release problems
Delayed cure at the interface• A good mould release agent must have some resistance to
styrene, the fact is that the longer the contact before gel the higher the risk that the styrene affects the mould release agent.
• During change of seasons (summer to winter or reverse) experience more sticking to the mould,
• this could be caused by an inadequate (amount of) catalyst that results in a slower reaction, that means a longer gel time in winter.
• or, the exact opposite can occur in summer when a too quick reaction raises the exothermic temperature. A fast, hot cure can melt the wax release film if it has a low temperature tolerance.
DSM Composite ResinsBase training UP-processing
11Mould release categories
• PVA (poly-vinyl alcohol)• Waxes• Polymeric mould release• Internal mould release • silicones
DSM Composite ResinsBase training UP-processing
12PVA
• Film forming release agent• The safest, most reliable for new green moulds• Does not dissolve in styrene• Clean mould after demoulding with warm water to remove
PVA.(When the PVA sticks to the mould, the PVA film was too
thin.) Apply two layers.
DSM Composite ResinsBase training UP-processing
13Waxes
• The first mould release agents• Available in paste and liquid forms• Some will have low temperature resistance other can be
used for high temperature applications• Waxes can contain silicones, the reason for fish eyes and
pre-release of the gel coat.
DSM Composite ResinsBase training UP-processing
14Polymeric mould release
• Are based on fluorocarbon chemistry, include PTFE• Strong adhesion to the mould• Multiple releases • Parts moulded with polymeric release agents release the
easiest• Can be painted without adhesion problems
DSM Composite ResinsBase training UP-processing
15Internal mould release
• Based on vegetable oils or refined type of polymer chemistry
• Incompatible with the resin• Mostly used in hot press moulding (SMC and BMC)
DSM Composite ResinsBase training UP-processing
16Trouble shooting
• Sticking and hanging• Inadequate mold design or fabrication• No draft on vertical surfaces• Porosity in the mould surface• Dirty moulds (poly-styrene)• Product cured not well• Release agent not enough or not enough polished
• Fish eyes• Traces of silicone or oil, can occur in the plant air tubes (oiltraps)• Dust or residu of sanding.
DSM Composite ResinsBase training UP-processing
17Trouble shooting
• Pre-release
• Shrinkage of resin/gelcoat• Excess of gel coat • Excess of release agent• Walkig in the mould after applying the gel coat• Too much shrinkage in the structural resin• Difference in shrinkage between gel coat and resin
DSM Composite ResinsBase training UP-processing
18What is a gelcoat exactly ?
• Special polyester resin• Applied first in the mould• Appearance, colour• Protection against weather, abrasion, chemical attack• Applied by spraying or brushing
DSM Composite ResinsBase training UP-processing
19What is a topcoat exactly ?
• Applied not in the mould but on the back of the laminate)• Topcoat = Gelcoat + Paraffin wax solution• Appearance not glossy but dull• Protection of glass fibres
DSM Composite ResinsBase training UP-processing
20Application procedures
• Spray and brush• Procedures for gelcoat application• Important issues to control• Trouble shooting
DSM Composite ResinsBase training UP-processing
21Spray and brush application
Viscosity Brush application: High
Spray application: Low
• Thixotropy:Brush application: Slow
recovery Spray application: Fast recovery
• Spray application: fast curing
Each gelcoat is formulated for a specific application
DSM Composite ResinsBase training UP-processing
22Airless spray
• External mixing • Internal mixing
Application procedures
• Temperature of gelcoat andmould between 16°C-30°C.
• Humidity below 80 %.• Stir gelcoat before use.• Catalyse with MEK-peroxyde
at a level of 1-2 %.• Apply an even layer at
thickness 400-600 microns.• When spraying, build
thickness in 3 or 4 passes.• Correct distance to mould:
± 60 cm, at right angle• Do not dilute gelcoat with
solvents other than styrene.
DSM Composite ResinsBase training UP-processing
24Trouble shooting
• Constant layer thickness, between 400 and 600 micron wet• Temperature between 16 and 30 °C (Workshop, gel coat
and mould)• Use correct catalyst and correct amount• For airless spray: Correct machine settings (nozzle 19/40
or 21/40, pressure settings)• Ventilate deeper mould areas
Most important parameters to check
DSM Composite ResinsBase training UP-processing
25Low film thickness
• Apply more gelcoat• Pay extra attention to areas difficult to reach
Alligatoring Fish eyes Fibre print through
DSM Composite ResinsBase training UP-processing
26High film thickness
• Use gelcoat wet thickness gauge during application• Adjust spray equipment: reduce output with smaller nozzle• Adjust spray technique: move gun faster or more distance
Parallel crack Spider crack Yellowing
DSM Composite ResinsBase training UP-processing
27Low temperature / high humidity
• Increase peroxide addition to max. 2.5 %• Addition of extra accelerator, max. 1.5 % (Cobalt solution 1%)• Spray: Use in-line heater or add 3 – 5 % extra styrene
Alligatoring Orange peel Pinholes
DSM Composite ResinsBase training UP-processing
28High Temperature
• Lower amount peroxyde to minimum 1 %• Use inhibitor for longer gel time• Store gelcoat in cooler area
Pre-release Sags and runsFibre print through
DSM Composite ResinsBase training UP-processing
29Influence of external conditions on curing
• Temperature of resin and mould• 1 degree difference causes ± 10% difference in gel time• 1 degree difference cuses ± 5-10% difference in viscosity• Humidity in workshop and in compressed air
• Insufficient polishing of release wax• Influence of realease wax on gel time
DSM Composite ResinsBase training UP-processing
Processing techniques
• Hand lay up• Spray up• Wet press moulding• Resin transfer moulding• Light resin transfer moulding• Liquid resin infusion• Hot (wet) press moulding• Hot press moulding SMC and BMC)
DSM Composite ResinsBase training UP-processing
Required equipment (1)
• Hand lay up: simple mould, brush, roller
• Spray up: simple mould, glass/resin spray, roller
• Wet press moulding: double mould, hydraulic press
• RTM: double (metal) mould, hydraulic press, injection machine, optional vacuum pump
DSM Composite ResinsBase training UP-processing
Required equipment (2)
• Light RTM: rigid bottom mould with flange, semi rigid top mould with special flange for closing and resin injection valves, injection machine or pressed air, vacuum pump.
• Resin infusion: rigid bottom mould with flange, tacky tape, air-tight cover foil, vacuum pump
• Hot press moulding: Metal top and bottom mould with heating facilities, hydraulic press