STORMS - Key Processing Points For Dow PU Systems

STORMS - Key Processing Points For Dow PU Systems

Andrew Davies

Introduction The aim of this presentation is to help achieve better success at trials and hence faster

customer approval. We will highlight the importance of correct material handling and conditioning.

Mercury is a very forgiving and versatile catalyst in terms of:• Delayed action cure profile with fast demould capability.• Versatile amongst DIPRANE™ and HYPERLAST™ product groups (spray, cold-cure)• More forgiving than other catalyst groups in variety of environments• More forgiving to a variety of ‘handling’ methods The Dow mercury alternatives address the majority of the above characteristics

however the non mercury alternatives• require better, more efficient mixing of polyol components• require better control of temperatures for both components and moulds.• tend to be more moisture sensitive Hence the importance for following the principals of STORMS

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WHAT IS STORMS?

STORMS - The Definition

Stir PolyolTemperature ControlOperator EngagementRatio ControlMoisture ToleranceStir Components Together

Stir Polyol Non-mercury catalysed products require better mixing than mercury catalysed

products because: lower catalyst levels need better dispersion to gain different effects desiccants need to be thoroughly mixed to enhance moisture control homogeneous mixing is needed to realise full range of properties this will help ensure the additives package within polyol is full effective

Drums and kegs must be handled as follows; Melted and conditioned to correct temperatures as indicated on the Technical

Data Sheet (TDS) Rolled/tumbled or mixed with collapsible/helicoidal stirrer for minimum 30

mins. ensuring minimum air entrapment (see next slide) The machine tank handling the polyol will require degassing and then constant

agitation by either or both: recirculation at rate so as not to introduce air keeping the agitator on, again so not to introduce air

Types of Drum Mixing

Drum Roller Drum Tumbler Drum Attach Mixer

Bung Mixer/transfer pump

Temperature Check Proper temperature control is more critical for non-mercury based systems due

the use of more temperature sensitive catalysts Polyol, prepolymer and mould temperatures must be adhered to – generally the non-

mercury catalysed systems require increase in either or both the liquid temperatures or mould temperatures

Check and familiarise yourselves with the most up to date technical datasheet Systems processed at temperatures lower than datasheet recommendation can

lead to some of the following effects: Longer pot-life Slower demould In-complete cure Sticky surface effects – most critical for open casting that requires flaming Reduced physical properties Duller surface finish Shrinkage effects

Temperature Contd. Systems processed at temperatures higher than datasheet recommendations can result

in:• Faster gel times so restricting casting size• Inability to fill the mould• Air entrapment/bubbles• Difficulties when hand casting

Typical properties – not to be construed as specifications ®TM Trademark of The Dow Chemical Crompany (“Dow”) or an affiliated company of Dow

System HYPERLAST™200

HYPERLAST™201

HYPERLAST™ 100

HYPERLAST™101

DIPRANE™ 53 DIPRANE™ 530

Polyol Temperature*

20-30 20-30 35-40 35-40 35-40 50 – 55

Prepolymer Temperature*

20-30 20-30 25-40 25-40 35-40 50 – 55

Mould Temperature*

70 - 80 80 - 90 70-90 80 - 95 70 - 90 80-100

Demould Time* Temperature °C

15-20 15-25 20 - 30 20 - 30 30 - 40 15 - 40

Pot-life Comparisons Mercury Catalysed Grades vs. DIPRANE™ C530/85

®TM Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow

0 1 2 3 4 5 6 7 8 9 100

20000

40000

60000

80000

100000

120000

140000

160000

180000

200000

DIPRANE™ 53/85DIPRANE™ 530/85DIPRANE™ 54/85

time (mins)

Visc

osity

(Poi

se)

Three Component Requirement for Catalysed Extender

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 560.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

Time at 10 second intervals (+100)

Exotherm Temperature

Some users currently taking Three Component DIPRANE™ with CX may need to use the DIPRANE CA in order to ensure efficient demould at higher hardness.

-------- DIPRANE™ 53/85 CX

-------- DIPRANE™ 530/65A + CA

Operator Engagement

New products will have some differences. It is imperative that the Operators and production personnel are made fully aware of the requirements and understand the differences between the traditional mercury containing and the new non-mercury systems

Attention should be given to the product documentation and drum labelling Material Safety Data Sheet (MSDS) should be available and read by production

operators and supervisors Data sheet information on material conditioning, handling should be understood Data sheet information on temperature for materials and moulds must be adhered to Data sheet information for ratio of components must be adhered to

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Ratio Check

The ratio must be worked out to ensure the correct proportion of –OH groups versus –NCO groups to achieve full cure and property realisation.

The materials should be mixed together to a ratio tolerance no greater than 1% by weight Engineering Elastomer datasheets quote ratios as ‘parts’ polyol to 1 part prepolymer. DO NOT ASSUME THE MIX RATIOS ARE THE SAME AS BEFORE. The development of the mercury alternatives has led in some circumstances to a slight

difference in mix ratio versus its predecessor, for example DIPRANE™ 530/85 is 0.92: 1 by weight versus 1:1 for the mercury catalysed grade ALWAYS CONSULT THE TECHNICAL DATASHEET – NEVER ASSUME. Ensure your customer has the correct and current Technical Datasheet

Polyol rich castings can lead to soft product with reduction in physical properties and poor output. Isocyanate rich castings can lead the product to be more susceptible to moisture effects, slow

demould, increased post hardening and poor physicals.

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Moisture

Non-mercury catalysed systems are usually more susceptible to moisture leading to bubbles or foaming in the casting and so care needs to be taken as follows:

Polyols must be kept sealed until required Replace lids on part filled drums – especially in regions where atmospheric humidity is high The elevated temperatures that non-mercury catalysed systems require are more susceptible to moisture

ingress Containers for mixing must be clean and dry before use when mixing plugs or decanting

samples. Samples sent back to Dow at Birch Vale, UK for analysis must also be clean, dry, sealed

and fully filled – It is mandatory that these are labelled correctly and accompanied by MSDS

Polyols contain a moisture scavenger – this must be totally mixed prior to decanting to keep it efficient

Machine polyol (and prepolymer) tanks MUST have a dry air supply and also be sealed.

Moisture Contamination

IsocyanateGroup

(R” NCO)Unstable

intermediate product

Substitute UreaR” HN - C(O) - NH – R

Water(H - O - H)

Carbon Dioxide

(O - C - O

Stir components together

The polyol and isocyanate must be thoroughly mixed together to achieve a homogeneous material at the correct ratio to realise full physical properties.

Stir the material either: By hand – depending on pot-life and size of casting using following guidelines:

Condition as per datasheet temperatures Weigh out appropriate amounts of polyol and prepolymer Mix between 30 seconds to 1 minute depending on casting size with stirrer/spatula Transfer mix to another container Vacuum degas to remove air (minus 1 bar for 30 sec to 1 minute depending on gel

time) Pour into suitable mould at preconditioned temperature as indicated on TDS.

By machine Conditioned and vacuumed in accordance to TDS and machine specification.

To enable fast and efficient success at trials always remember:

STORMS