Understanding Rubber Blooming & How to Control It

By November 18, 2020 No Comments

What the Blooming…!!!!

“Blooming” is the crystallization of compounding ingredients usually on the surface of rubber over a period of time, both in cured or uncured form. This is normally resulting in the migration of the substance from the bulk to the surface.

Most of the ingredients which are soluble in rubber have a saturation level/limit – depending on solubility parameter, molecular weight & Polarity. e.g. sulphur, accelerators, antioxidants, organic pigments, fatty acids and so on.

Blooming issue can occur in any polymer -but more predominant is elastomers which have saturated backbone e.g. EPDM or extreme polarities e.g. NBR

In unvulcanised compounds, Blooming reduces the tackiness of the stock, which causes difficulties in building up of multi-ply articles (tires, belts, etc).

EPDM is elastomer which is increasingly being used today because of its genetic properties such as -resistance to weathering and ageing. It is used most commonly in the automotive and construction industries for various seals due to its excellent resistance to environmental factors such as Ozone, UV and general weathering.

Typical applications of EPDM are window and door seals (glazing), waterproofing sheets and electrical gaskets, Underbonnet applications such as Radiator hose, Heater hoses etc.

An economically viable & effective cross-linking of EPDM with Sulphur can often only be practically achieved through complex systems with numerous combinations of ingredients consisting of vulcanization accelerators and Sulphur donors. While selecting the accelerator chemicals one must consider the very limited solubility of some of the individual nitrosamine free rubber accelerators. Exceeding the solubility levels results in to bloom on the surface of the vulcanized material.

Blooming – the downside

Blooming often depletes the aesthetical value of finished component -may not necessarily impact the functionality of product but can be a cause of rejection in production e.g. stains on black moulded component or coloured finished product.

A solution to Blooming

For over four decades D.O. G. Deutsche Oelfabrik (D. O. G.) has produced special accelerator blends that enables bloom-free EPDM cross-linking. In the range of conventional blends, D. O. G. offers a universal solution – Deovulc EG -3. If a high degree of cross-linking & faster cure rate along with excellent ageing stability is required, the right product is Deovulc EG 28.

Nitroso amine free Accelerator Blends

One of the major issues in rubber today is the formation of nitrosamines. Nitrosamines are known to have carcinogenic effects and should be avoided at all costs. In the vulcanization systems in which no secondary amines are used – no nitrosamines can be formed in vulcanization reaction.

D. O. G. has developed a Single pack accelerator blend -product line called Deovulc BG – Accelerator blends.
Deovulc BG -187 V has proven itself over the course of a number of years to be a non-staining, non-blooming, highly active accelerator based on Zinc dithiophosphate and synergic secondary accelerated combinations.
With Deovulc BG-383 D. O. G. has developed a guanadine free combination of other accelerators which do not form toxic nitrosamines. With these single pack accelerators blend systems developed by D. O. G. we can take care of your blooming problem and also offer the possibility of producing non-nitrosamine forming products.

I R Tubes Pvt. Ltd. is a leading specialty chemical supplier for the chemical industry. Contact I. R. Tubes on or Call: 9689927193 for more information.

Raju Jethmalani
IRTubes Pvt. Ltd., Pune

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