1. STORMS - Key Processing Points For Dow PU Systems
Andrew Davies

2. 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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3. WHAT IS STORMS?

4. STORMS - The Definition
Stir Polyol
Temperature Control
Operator Engagement
Ratio Control
Moisture Tolerance
Stir Components Together
Processing Polyurethanes
It is essential that the process procedures be kept in order to obtain the desired properties from the polyurethane. The following mnemonic covers the critical points for processing polyurethane:
S tir polymer
T emperature check
O perator training
R atio check
M oisture ingress
S tir polyol and isocyanate components together

5. 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
Stir Polyol
The polyol components will have a tendency to separate when left standing, in a similar way to paint. Thus, for the reaction to work correctly, it is important that the polyol be thoroughly stirred before mixing with the isocyanate.
Failure to do so may result in an incomplete reaction.

6. Types of Drum Mixing Drum Roller Drum Tumbler Drum Attach Mixer
Bung Mixer/transfer pump

7. 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 Check
Check that the materials being used are at the correct temperature for processing.
Temperature too low
- initial materials are not correctly melted
- may cause problems pouring materials from their drums
- slows down reaction
- may result in an incomplete reaction
Temperature too high
- speeds up gel time
- storage at a high temperature may affect the material’s reactivity and may cause damage to the material

8. 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
System
HYPERLAST™
200
201
HYPERLAST™ 100
101
DIPRANE™ 53
DIPRANE™ 530
Polyol Temperature*
20-30
35-40
50 – 55
Prepolymer Temperature*
25-40
Mould Temperature*
70-90
80-100
Demould Time
* Temperature °C
15-20
15-25
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9. Pot-life Comparisons Mercury Catalysed Grades vs. DIPRANE™ C530/85
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10. Three Component Requirement for Catalysed Extender
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11. 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
Operator Training
The operator should be properly trained in:
- the processing methods for the particular materials
- the correct use of machinery
- health & safety
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12. 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.
Ratio Check
It is important to make sure that there is the same number of polyol OH groups as isocyanate NCO groups to ensure a complete reaction.
An incorrect ratio will mean that there is unreacted material. In such a case, the system is:
- polyol rich or
- isocyanate rich
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13. 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.

14. Moisture Contamination
Isocyanate
Group
(R” NCO)
Unstable intermediate product
Substitute Urea
R” HN - C(O) - NH – R
Water
(H - O - H)
Carbon
Dioxide
(O - C - O

15. 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.

16. To enable fast and efficient success at trials always remember:
STORMS