Processing of polymer resins (UP)up).pdf · Base training UP-processing 1 Processing of polymer...

DSM Composite ResinsBase training UP-processing

1

Processing of polymer resins (UP)

Mouldmaking

Gel coat and top coat

HLU/SU application

Properties


2Mould making

Important:• Highest gloss surface• No print through• Durability


3Mould making: Critical issues

• Design of product• Plug construction• Tooling gelcoat application• Laminate build up, construction• First release from the new mould


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.


5Plug making: Materials

• Wood or plaster, coated with PU paint.

• Wood or plaster, GRP or epoxy coated.

• GRP.

• Foam, GRP or Epoxy coated.

• Combinations


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


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.


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


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


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.


11Mould release categories

• PVA (poly-vinyl alcohol)• Waxes• Polymeric mould release• Internal mould release • silicones


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.


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.


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


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)


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.


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


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


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


20Application procedures

• Spray and brush• Procedures for gelcoat application• Important issues to control• Trouble shooting


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


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.


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


25Low film thickness

• Apply more gelcoat• Pay extra attention to areas difficult to reach

Alligatoring Fish eyes Fibre print through


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


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


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


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


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)


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


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

Date post:	18-Mar-2018
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Processing of polymer resins (UP)up).pdf · Base training UP-processing 1 Processing of polymer...

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