Devulcanisation experiment

A team of workers in India [52] have described the use of tetramethyl thiuram disulfide (TMTD) in the presence of Spindle oil for the devulcanisation of ground tyre rubber at near ambient temperatures. Small-scale (-100 g batches) devulcanisation experiments were carried out on a two-roll mill and the products produced characterised using a variety of analytical techniques (e.g., dielectric analysis and TGA). The amounts of TMTD and Spindle oil were 2.75 and 10%, respectively. The DR was mixed with virgin, uncompounded NR and a cure system, with the DR content varying from 0 to 60%. Vulcanisates were produced, which were characterised by both physical (e.g., tensile strength and swelling) and analytical (e.g., SEM and DMA) tests. The tensile strengths that resulted were found to vary from 7.7 MPa (60% DR) to 14 MPa (0% DR). 

A group of workers at Twente and Groningen Universities in the Netherlands [53] have carried out devulcanisation experiments... 

A group of Chinese workers [58] have carried out work to devulcanise a NR compound using snpercritical CO2 in conjunction with the chemical devnlcanising agent diphenyl disulfide. During the study they investigated the effects of a number of parameters, such as CO2 density, temperatnre, pressnre and reaction time. They also used two analytical techniqnes, GPC and NMR, to study the products of the various devulcanisation experiments. 

Verbruggen and co-workers [13] prepared a model NR gumstock (i.e., cure system only, no fillers or other additives) compound and subjected a thin film (300 pm thick) of it to DPDS at 200 "C. Solvent extraction (with acetone and tetrahydrofuran), swelling experiments (in toluene) and chemical analysis by GPC and nuclear magnetic resonance (NMR) spectroscopy were used to assess the degree of devulcanisation and to characterise the samples produced. It was found that complete network breakdown was obtained with 2.4% w/w of DPDS after 2 h of heating, but that both crosslink scission and main-chain scission had occurred. 

The use of the amine hexadecylamine (HDA) to devulcanise sulfur-cured EPDM rubbers has been described by Dijkuis and co-workers [50]. Conventionally and efficiently vnlcanised (EV) EPDM rubbers were devulcanised in a Brabender Plasticorder with HDA under various conditions. The effects of temperature, time, shear and amonnt of reclaiming agent on devnlcanisation were examined nsing a design of experiments approach, and the devulcanisates were characterised by Mooney viscosity measnrements, solvent extraction, crosslink density determinations and light microscopy. 

These accelerators (ratio MBTS 0.65, CBS 0.48 and DPG 0.15) had also been used to vulcanise the original SBR rubber compound (along with 2 phr sulfur, 5 phr zinc oxide and 1 phr stearic acid) that was being devulcanised in these experiments ... 

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