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Rubber/EPDM rubber recipe

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Question
Please, I have begun to prepare a low cost recipe for construction window profiles. So, I use:
EPDM Keltan 8550  100, N550 130, Whiting 80, Paraffinic oil 75, CaO 4, ZnO 5, stearic acid 1,Deostab 1, PEG 4000 1, Deovulc EG28 3.0,MBT 1.0, S 1.0. All in phr.
  Used the up-side down technique, 6 min time mixing cycle in a two-stage mixing. Then observed porosity and bubbles. The same observations, when prepared on the lab two-roll mill mixing in thin sheets.
   Please, could you explain me this troubleshooting and how to correct it ?

   Thank you

Answer
Dear Mr. Nikos,

My suggestion is to use a normal mixing of this polymer, because it is a high viscosity EPDM and by my experience high viscosity EPDM on upside dow method do not achieve the temperature to melt the polymer properly. This fact is confirmed by your information about roll mixing, where you do not achieve good melting temperature to disperse the fillers properly.

Increase the temperature of the roll mixer or mix it with a high ethylene EPDM (crystalline), Keltan 8550 is an amorphous polymer and the blend with cristalline polymer will benefit the compound.

Luis

Rubber

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Luis Antonio Tormento

Expertise

Operational Chemical Engineer with specialization in rubber compounding and processing: - Vast knowledge on rubber molding techniques: extrusion, press and injection molding. - Marketing expertise on the development of applications of rubber chemicals, precipitated silica and specialty rubbers. - In his career he developed numerous production compounds for automotive and industrial hose, rubber mats, retread compounds, tire compounds, shoe soles and molded products. TPE/TPV/TPO applications

Experience

I have 36 years working in plant processing of hose, tire, shoes and press/injected cured rubber compounds and technical assistance for two big raw material suppliers: Chemtura and Nitriflex. Actually I have my own company

Organizations
2006-2011 - Rubber Division Director - Brazil Rubber Group 2008-2009 - Vice President - Brazil Rubber Group 2002-2007 - President - Brazil Rubber Group 2000-2001 - Technical Director - Brazil Rubber Group

Publications
Several papers published on magazines, congress and conferences about rubber processing and compounding

Education/Credentials
Chemical Engineer by FEI - Brazil (1979) Advanced Rubber Technology - Rubber Division (1992) University Expert on Plastic and Rubber - UNED (Spain) - 2002

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