Careers Section. Addition to our web page

Hi Everyone           Another blog from Norman – November 2019.

Just to bring to your attention that we have added another section to our web page.

At the far right end (nothing political intended) of the menu bar you will now see the new section. It is labelled “Careers”.  Click on it and you will find a copy of the job advert we have just placed on “INDEED”.

This is a new idea to us and we hope, at a later date, to add some comments/ideas from existing staff – could be interesting. Of course we will be completely unbiased and only publish the good ones.

Please keep an eye on this new part of our site (as well as all the rest) as it might change quite quickly.

Cheers for now.


Taking a closer look – SEM Pictures of FKM Crumb

After a bit of good old fashioned arm twisting, I managed to convince an old university friend to use some seriously expensive pieces of kit to peek into the fine detail of the pride of J Allcock and Son’s product line. I sent several samples of our Ambiently-ground FKM crumb, and a competitor’s Cryogenically-ground FKM Crumb to my mate Rob Hooley, studying for a PhD in Materials Science at the University of Leeds, who was kind enough to put them through a Scanning Electron Microscope (SEM) and produce some fantastic pictures.


Picture 1 (Left) & 2 (Right): Cryogenically ground FKM 30’s Mesh and Ambient Ground FKM 40’s Mesh

These two pictures above show the difference in surface structure between cryogenically and ambient ground FKM crumb. The Cryogenic material has been frozen and shattered, thus the particle morphology appears much more angular and sharp compared to the torn material, with extremely rough edges due to the physical tearing of the rubber. The coarser material should bond better into a new FKM compound, due to the much larger surface area exposed to the fresh compound, and the possible exposed polymer chains due to the tearing of the material. As cryogenic freezing causes the rubber to break along micro-fissures or micro-tears, the surface would have fewer areas available for bonding.

Picture 3 (Left) & 4 (Right): Cryogenically ground FKM 72’s Mesh and Ambient Ground FKM 72’s Mesh

The pictures above again show the two types of ground FKM, but this time the smaller 72’s Mesh size. The size of the 2 grains is very similar, which is to be expected, but again the coarseness of the ambient ground material can still be seen. The scale of the peaks and troughs are not as extreme, but as this is a smaller grain, the increase in ‘bond-able’ surface area is not to be sniffed at. We at J Allcock and Sons believe (and have done many trials that prove our belief) that our ambient ground 72’s mesh FKM binds better than our 40’s mesh FKM crumb. 72’s mesh crumb can therefore be used at higher concentrations in newly made FKM compound, therefore saving you even more on compound cost.

Picture 5 (Left) and 6 (Right).  5 Shows Ambient ground FKM 72 mesh, using ‘LU’ settings, while 6 shows the same material, at the same resolution using ‘NM’ settings.

The ‘LU’ (seen at the base of this picture) indicates a technique that focuses on showing the topography of the sample using secondary electron imaging. SE imaging (SEI) involves electrons produced by ionisation induced by the incoming electron beam. These electrons are very low energy, and as such are very sensitive to the surface structure, this allows for the surface of the sample to be resolved in great detail, even showing the 3 dimensional structure of individual crumb.

Meanwhile, the ‘NM’ (again at the base of the picture) indicates Backscattered electron imaging (BSE), where electrons hit the sample with great energy, allowing them to penetrate the surface and interact with the bulk of the material. This results in the electrons bouncing around the material before being released. The energy they leave the material with is directly proportional to the mass of the atoms they interact with, much like how sound waves are absorbed by a carpeted floor, but bounce off a marble floor. Therefore, the light specks seen in the photo are heavier parts of the rubber compound, mainly Oxides of Magnesium, Calcium and Silicon (Thanks again to some further elemental analysis by Rob Hooley) as the heavier elements reflect more electrons and thus create a brighter image.

Pictures 5 and 6 therefore show the same sample of 72’s Mesh FKM using two types of imaging technique. Picture 5 (like the previous images) shows the surface contours of the FKM crumb, again showing the coarser nature of our material, which is ideal for binding into the compound matrix. Picture 6, however, reveals some of the components of the FKM compound as well as giving a different angle on the depth of some of the troughs and the quality of the FKM compound itself (nice even spread of a moderate amount of fillers can be seen in the crumb itself).

Picture 7 (Top left) and 8 (Top right). 7 shows cryogenically ground 72 Mesh FKM Crumb using LU (SEI) Settings, while 8 shows the same material under NM (BSE) Settings. Pictures 9 (bottom left) and picture 10 (bottom right) show ambient ground 72’s mesh FKM at the limits of the SEM’s resolution, again using ‘LU’ and ‘NM’ techniques respectively

These final images push the resolution of this electron microscope to its limits, with a scale of 10 microns seen in the bottom right hand corners of the lower two images. At such a large magnification, the difference in the surfaces of the crumb is more subtle. The main difference that can be seen would be the exposure of the filler. Picture 8 shows the filler underneath the surface, while picture 10 shows the exposed filler at the surface. We believe that the exposed filler will create an increasingly jagged surface, helping bonding into the compound at a smaller scale.

I hope you’ve enjoyed the pictures, and how microscopic differences in FKM crumb can have a large effect on the resultant compound.

Thanks again for the Fantastic Pictures, and some much needed advice on some of the more technical sections of this post to Rob Hooley, Here’s to our next pint in 2016!

J. Allcock and Sons at DKT/IRC Nuremberg and Launch of the Multi-Language Website

We are happy to announce that we will be hosting a stand at the Deutsche Kautschuk-Tagung / IRC International Rubber Conference at the NuernbergMesse GmbH exhibition centre. We will be exhibiting Rubber Reclaim, Rubber Crumb and FKM Crumb, which promises to revolutionize the Fluoroelastomer Industry. With more and more compounders and moulders showing an interest and using our fine grades of FKM crumb, we would be happy to chat about the benefits of our product. Andrew Rushton, Managing Director of J. Allcock and Sons, and I will be manning the stand and hope to see you there to answer any questions our queries you may have.

In preparation for the conference, we have also had our website translated into French, German and Spanish. We hope this will make finding the correct product and information easier for our clients on the continent. If you find any grammatical or spelling errors on any page, please contact me and I will happily incorporate your suggestions to continually improve your experience of our website.

Types of Rubber – Pick-and-Mix

There are a near infinite variety of rubber compounds, with variety in mineral fillers, accelerators, curatives (and the type of cure), plasticizers, colour and of course the base rubber polymer. Rubber polymers come in two basic groups, natural and synthetic.

Natural rubber (NR), popularly known as Latex (when in the liquid form) or Natural Gum Rubber (once dried) is obtained mainly from the Hevea Brasiliensis Tree in South East Asia. Natural rubber consists of Cis-1,4-polyisoprene which can have masses as large as 1 million Daltons. Such large atomic structures, with plenty of double bonds, allows sulphur and heat to bond two double bonds of adjacent isoprene polymers with 3 or 4 sulphur atoms. This process is called vulcanisation, which was accidentally discovered by Charles Goodyear in 1839 using. Vulcanisation creates a network of bonds that changes the physical form of the Gum Rubber to the harder, elastic material that revolutionised the late 19th century world.

Initially sought by the Germans in the 1st World War, Synthetic Rubber was developed due to the Royal Navy’s Blockade causing a shortage of Natural Rubber. The first attempt at Artificial Rubber, Methyl Rubber, was of poor quality. Later attempts such as the Soviet use of Giant Dandelions to produce latex in WW2 weren’t much more successful. It wasn’t until the US Synthetic Rubber Programme developed Styrene Butadiene early in WW2 that a viable alternative to natural rubber became available, and the doorway to synthetic rubber polymers was opened.

There are now many types of rubber polymer, each tailored to the desired needs of the client. Below is a good rough outline to the characteristics of each rubber polymer, for example Acrylonitrile Butadiene Rubber is often used in oil seals and o-rings due to its excellent oil resistance:

Taken from:

We at J. Allcock and Sons are able to granulate NBR, SBR, EPDM, FKM and FFKM on site to any desired crumb mesh size, as long as the rubber is free of any textiles or metals. Crumb can be used as a filler in compounds, reduce the chance of trapped air causing lakeing during moulding or dusted onto rubber sheets to help the separation after cooling. Crumb is a great way to reduce compound cost without increasing the specific gravity of the compound (keeping volume costs down).

If you are interested in disposing of some of your cured rubber compound with us please get in touch via our website or phone us on 0161 223 7181.

Red/Brown & Green FKM Crumb Available

Red/Brown and Green FKM Crumb

Red/Brown and Green FKM Crumb

J. Allcock & Sons’ now have the ability to provide an extra 11 tonnes of Red/Brown FKM Crumb and 4 tonnes of Green FKM crumb per month.

Cured FKM scrap is sent to our facilities on a monthly basis and we granulate and “crumb” this FKM scrap to  72′s and 120′s mesh particle size. These particle sizes are not averages, so when we say 120′s Green FKM Crumb, we mean the biggest particle you will find will be 120′s mesh!

We always ask the customers we visit: What’s the cost of testing FKM Crumb in your compound? Compare that amount, to the amount you will be saving if tests came back positive and you started using it…

If you are interested in trialling some of the above crumb, please contact us at or +44 (0) 1612237181.

Alternatively, if you are unsure about using a different FKM compounded crumb in your own FKM compound, why not speak to us about “crumbing” some of your scrap and J. Allcock & Sons’ sending it back to you?