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Two-component polysulphide sealants consist of a base, containing the polymer, and a hardener, containing the oxidising agent.
Many components can be used as oxidising agents, the inorganic types including activated manganese dioxide which is the most commonly used oxidant for two-component polysulphide sealants.
The correct ratio and good quality of the mixture of the components are essential factors in optimal performances by the sealant (European Standard for I.G. Units, EN 1279). Fenzi has a developed a useful analysis method for assessing the quality of the material taken from manual and automatic sealing machines: via a modern analysis technique based on X-ray fluorescence (XRF), the manganese content can be determined in samples of sealant extruded from customer sealing lines.
Analysis of subsequent portions of mixed product can identify anomalous fluctuations in the mixing ratio which may be symptomatic of malfunctioning during the phases of batching, mixing and extrusion. Proper interpretation of the results obtained greatly assists the definition of possible remedial actions to be taken to solve the problems linked to mixing of the sealant.

Customers interested in this service must send to the Fenzi technical department at least 4 plastic cups containing the product mixed and properly compacted, indicating the batch number of the hardener used and numbered according to the order of extrusion.
The mixing profile relating to the customer’s sealing machine is represented by an oscillating curve which combines the values of the mixing ratios of the portions analysed in relation to a straight line indicating the mixing ratio with average volume.
Fenzi’s THIOVER polysulphide sealant achieves optimal performances:
1) for a mixing ratio with average volume of 100 : 10 ± 1
2) for fluctuations around the nominal value (100 : 10) within 20%.

In the examples shown, the most common cases of mixing profiles obtained by XRF analysis and obtained from some customers are considered.

1) Correct mixing ratio and regular trend.
2) Low mixing ratio and regular trend.
3) High mixing ratio and regular trend.
4) Correct mixing ratio and “fluctuating” irregular trend.
5) Correct mixing ratio with drop in initial batching followed by regular trend.

1) Profile 1 shows optimal extrusion with average mixing ratio close to the nominal value and minimal fluctuations. These conditions represent the prevailing factors for optimal performances (cf. graph 1 opposite).

2) Profile 2 shows a good trend in terms of fluctuations, yet the average mixing ratio is too low. The remedial action to be taken on the hardener batching system must ensure an increase in the hardener in order to restore the mixing ratio to acceptable values (cf. graph 2 opposite).

3) In profile 3 the trend is regular yet the average mixing ratio is high. The fluctuations exceed 20% in relation to the nominal value for half the extrusion. The batching system requires adjustment in order to reduce the supply of the hardener (cf. graph 3 opposite).

4) Profile 4 is an example of malfunctioning of the valves for batching the components. The customer may not detect the problem, as the mixing ratio is correct, nevertheless the analysis identifies a “fluctuating” trend which is the cause of non-optimal performances. Catalysis may be incomplete in the areas with a low mixing ratio and, in areas with a high hardener content, problems could be caused with adherence, hardness, quality of the mixture and the mechanical properties. The batching and mixing systems should be checked and repaired (cf. graph 4 opposite).

5) Profile 5 considers a case where the average mixing ratio and the trend are correct as from half of the second cup analysed. The initial part of extrusion however has a shortfall of batching of the hardener component. In this case too technical assistance is required for the batching valves (cf. graph 5 opposite).

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