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 ID: 465998
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Slide1
STORMS - Key Processing Points For Dow PU Systems
Andrew DaviesSlide2
IntroductionThe 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 environmentsMore forgiving to a variety of ‘handling’ methodsThe Dow mercury alternatives address the majority of the above characteristics however the non mercury alternativesrequire better, more efficient mixing of polyol componentsrequire better control of temperatures for both components and moulds.tend to be more moisture sensitive Hence the importance for following the principals of STORMS
®TM Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow Slide3
WHAT IS STORMS?Slide4
STORMS - The Definition
Stir Polyol
T
emperature Control
Operator EngagementRatio ControlMoisture ToleranceStir Components TogetherSlide5
Stir Polyol
Non-mercury catalysed products require better mixing than mercury catalysed products because
:
lower catalyst levels need better dispersion to gain different effectsdesiccants need to be thoroughly mixed to enhance moisture controlhomogeneous mixing is needed to realise full range of propertiesthis will help ensure the additives package within polyol is full effectiveDrums 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 airkeeping the agitator on, again so not to introduce airSlide6
Types of Drum Mixing
Drum Roller
Drum Tumbler
Drum Attach Mixer
Bung Mixer/transfer pumpSlide7
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-lifeSlower demould In-complete cureSticky surface effects – most critical for open casting that requires flamingReduced physical propertiesDuller surface finishShrinkage effectsSlide8
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/bubblesDifficulties when hand castingTypical 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 - 40Slide9
Pot-life Comparisons Mercury Catalysed Grades vs. DIPRANE™ C530/85
®TM Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow Slide10
Three Component Requirement for Catalysed Extender
®TM Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow Slide11
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 supervisorsData sheet information on material conditioning, handling should be understoodData sheet information on temperature for materials and moulds must be adhered toData sheet information for ratio of components must be adhered to ®TM Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow Slide12
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 weightEngineering 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 exampleDIPRANE™ 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 DatasheetPolyol 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.
®TM Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow Slide13
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 efficientMachine polyol (and prepolymer) tanks MUST have a dry air supply and also be sealed.Slide14
Moisture Contamination
Isocyanate
Group
(R” NCO)
Unstable intermediate productSubstitute UreaR” HN - C(O) - NH – RWater(H - O - H)Carbon Dioxide
(O - C - OSlide15
Stir components togetherThe 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 temperaturesWeigh out appropriate amounts of polyol and prepolymerMix between 30 seconds to 1 minute depending on casting size with stirrer/spatulaTransfer mix to another containerVacuum 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 machineConditioned and vacuumed in accordance to TDS and machine specification.Slide16
To enable fast and efficient success at trials always remember:
STORMS