The use of experimental design to study the responses of continuous devulcanization processes

Abstract

This paper presents the use of statistical analysis for studying the responses of two continuous devulcanization processes (of the EPDM roofing sheet and the EPDM profile) in the extruder. The response is represented by the reaction conversion, which is denoted as the relative decrease in crosslink density. Experimental design is considered as a useful tool when the kinetic data for the physical modeling are not available. The models derived show similar tendency of both processes with respect to the temperature and the screw speed. A difference is observed in their responses to the feed rate, which might be the consequence of their different devulcanization rates.

Devulcanization of waste tires using a twin‐screw extruder: The effects of processing conditions

“…The cross‐link density of rubber network decreases during devulcanization and the amount of decrement is accepted as a criterion for assessing the process by many researchers [17–19]. Combination of shear stress applied by screws and temperature causes selective breakage of cross‐links in the cross‐linked rubber devulcanization, while in the absence of shear stress (just heating), only the polysulfide and disulfide bonds convert into monosulfide bonds [17, 20].…”

“…Continuity, high speed and higher efficiency are the advantages of this approach compared to other devulcanization methods. The quality of devulcanized rubber which is obtained through this method is affected by processing conditions such as temperature profile, screw rotation speed and screw configuration [4–9].…”

Devulcanization of Natural Rubber in Composites with Distinct Crosslink Densities by Twin-Screw Extruder

“…In this study, the accelerators concentration was fixed, resulting in mechanical properties very proportional to the sulphur amount variation. In the literature, a wide range of mechanical properties values can be found, being extremely influenced by rubber compounding formulation 9,10,11 . Were also determined the percent devulcanization, considered the ratio of the crosslink density difference before (v eb ) and after (v ea ) extrusion, and the crosslink density before extrusion (v eb ), as represented in equation 4.…”

“…These processes are rarely finding sufficient results to compete with the methods of re-use as co-processing, granulation and rolling, which in turn does not reutilize much of the energy potential in NR from tires 2,3 . Among the main devulcanization methods currently searched, highlights processing by ultrasound 4,5 , microwave 6,7 , chemical method 8 , biological treatment 9 and thermomechanical 10,11 . Currently, two relevant theories attempt to explain the mechanisms of crosslink selective breaking.…”

Product engineering and sustainability

“…It is particularly attractive if the possibility to purify the recycle stream is limited like in food packaging. A rather recent new technique is the use of devulcanized tire rubber to reinforce bitumen roof coverings [8]. This technique can also be used instead of back to feed stock.…”