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Author: Adam Morgan , Ph.D.Fluoroelastomer rubbers (known as FKM) are widely used in sealing applications due to their excellent heat and chemical resistance. FKM grades have been in tight supply throughout 2018 and the demand for their usage in automotive, aerospace and chemical processing is increasing.1
MT carbon black (N990 in accordance with ASTM) is a common filler for FKM. In this article, we will show you how it can be beneficial to replace carbon black with TREMIN® wollastonite from HPF Quarzwerke. Switching filler allows mechanical properties to be maintained or improved at higher filler loadings. This allows for greater cost savings and extension of the polymer. It is also easy to pigment these rubbers when using wollastonite.
Let us compare the effectiveness of the aminosilane treated wollastonite (TREMIN® 283-600 AST), with an MT N990 carbon black. If you would like to view the datasheet for TREMIN® 283-600 AST then this can be found on our TREMIN® page.
Rubber compounds were made up as per the formulations shown in Table 1.
Component
Formula A (phr)
Formula B (phr)
Formula C (phr)
Formula D (phr)
Polymer Viton A-201C
100
100
100
100
Maglite - D
3
3
3
3
Rheonfit CF (Ca(OH)2)
6
6
6
6
Carbon Black MT 5990
20
-
-
-
TREMIN® 283-600 AST
-
20
40
60
Chromium Oxide Green GNM
-
5
5
5
Wax Lunacera C-44
0.5
0.5
0.5
0.5
Table 1. Starting point formulations for the rubber compounds. Notice that the wollastonite has a small quantity of green pigment added.
These compounds were then analysed with respect to their mechanical properties. Please see Table 2 below for the results.
Mechanical Test
Formula A
Formula B
Formula C
Formula D
Density (g/cm3)
2.06
1.99
2.07
2.13
Shore hardness A
71
62
73
80
Stress values 100% (MPa)
6.3
4.4
9.1
13.6
Tensile strength (MPa)
14
12.7
14.3
16.2
Elongation (%)
207
227
158
129
Tear Strength (N/mm)
3.6
3.8
3.9
3.0
Abrasion [cm3]
187
253
222
206
Table 2. Mechanical properties of the FKM compounds - formulated according to the starting point formulations shown in Table 1. All mechanical strengths were then tested in accordance with DIN 53504.2
You will see that the mechanical properties of an FKM rubber containing 40 phr wollastonite are comparable with an FKM rubber containing 20 phr carbon black. Therefore, by switching to wollastonite, you can have a greater extension of the fluoropolymer whilst still maintaining its high performance. You could attain significant cost savings and make material go further by switching to TREMIN®.
Furthermore, by changing from a black coloured carbon to the white coloured wollastonite powder, this would also allow you to have more choice over the colour of the final product. This can be useful when colour coding the products by usage or installation location.
It's worth noting that TREMIN® wollastonite also works well in other types of rubbers such as AEM, ACM and HNBR. More information on this coming soon.
Lawrence Industries is a UK supplier of wollastonite powder, in partnership with HPF Quarzwerke. Visit our TREMIN® page to request a sample and view the datasheets and brochures. You will also find the full original article from the supplier, which outlines the effect of ageing these rubbers in air and oil. Wollastonite holds up comparably well with carbon black in these situations.
Our technical team are here to help, so please don’t hesitate to get in touch with your enquiry. We are looking forward to hearing from you.
1). http://www.rubbernews.com/article/20181026/NEWS/181029959/solvay-to-increase-fluoroelastomer-production (30/10/2018).
2). https://global.ihs.com/doc_detail.cfm?document_name=DIN%2053504&item_s_key=00028732 (30/10/18).
Author: Adam Morgan , Ph.D.
Adam studied chemistry at the University of Warwick for 8 years, where he obtained a Ph.D. in the field of polymer and inorganic colloid science. He has been with Lawrence Industries since 2014 as a technical sales manager covering all industry areas. He is now responsible for marketing within the company as well.
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