Improved properties of blends of ultrasonically treated unfilled polyurethane rubber

Abstract

The aim of this investigation is to improve the properties of the polyurethane rubber that has been devulcanized using the coaxial ultrasonic reactor. After devulcanization of the cured rubber under varying gap sizes and amplitudes, blends of the devulcanized and virgin rubber at different ratios are prepared. Rheological and mechanical properties, hardness as well as gel fraction and crosslink density of the vulcanized blends have been investigated. Results show that compared to the vulcanizates of the devulcanized samples, the vulcanizates of the blends show a remarkable improvement in properties, which are sometimes comparable to or even better than the virgin vulcanizate. Blends have also prepared using different proportions of ground samples and virgin rubber, and a comparison of properties between these blends and the blends of the devulcanized rubber has been carried out. The results show that compared to the ground samples, the blends of the devulcanized samples are easier to mix and exhibit enhanced and more uniform properties. Polym. Eng. Sci. 44:794–804, 2004. © 2004 Society of Plastics Engineers.

Continuous Process for Recycling of Polyurethane Foam

“…Typically during blending, the final torque of the samples increases as the added material (ground or decrosslinked) imparts some reinforcing properties to the samples. Similar results have been seen for blends of devulcanized and virgin PUR [21]. Again, the minimum torque value is an indication of the viscosity of the samples, and from the cure curves, it shows that the PUR containing decrosslinked PU foam possess a higher viscosity compared to the virgin PUR due to the Time, min presence of gel in the treated samples.…”

Ultrasonic Devulcanization of Carbon Black Filled Polyurethane Rubber

“…Hence it was not possible to obtain revulcanized samples from the grooved barrel reactor and samples with poor mechanical properties were obtained from the coaxial reactor. However, ultrasonic treatment causes better bonding of the devulcanized rubber with the virgin and this has been observed in our experiments with the unfilled system [28]. So even though the samples show degradation, when compounded with the virgin, they can blend effectively thereby causing a marked improvement in the properties.…”

“…Since it was not possible to cure 100% devulcanized filled PUR obtained from the grooved barrel reactor and the coaxial reactor gave samples of inferior mechanical properties, the next plausible approach was to blend the devulcanized sample with the virgin. This approach has been successful for unfilled PUR [28] and for other filled rubbers like NR [29] and EPDM [11]. The homogenized devulcanized rubber (15 and 30 phr) was mixed with the virgin in three proportions À 25, 50, and 75%.…”

Recycling of thermoset polyurethane foams

“…They also established that the final PVC/PU blend could be reused as an effective polymer plasticizer for PVC resin and as a modifier for plasticized PVC. PU devulcanization can be also improved by using ultrasounds [8] even if the effect of ultrasound is less pronounced in PUs than rubbers such as SBR, PDMS, and BR owing to its low degree of unsaturation [9].…”