Ultrasonic decrosslinking of crosslinked high‐density polyethylene: Effect of screw design

Huang, Keyuan; Isayev, A. I.; Zhong, Jing

doi:10.1002/app.40680

Cited by 15 publications

(23 citation statements)

References 39 publications

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“…The decrease of barrel pressure in SSE with the amplitude is due to the decrease of viscosity caused by thixotropic effect and permanent decrease of the gel fraction and crosslink density introduced by ultrasonic treatment [14]. The decrease of die pressure in TSE with the amplitude is due to the permanent decrease of viscosity caused by reduction of the gel fraction and crosslink density [16]. It is seen from Figure 5a that the barrel pressure in SSE during extrusion of XHDPE is slightly higher than that of XLDPE.…”

Section: Resultsmentioning

confidence: 98%

“…However, a severe thermal degradation occurred due to significant ultrasonic energy dissipation in the ultrasonic treatment zone leading to inferior tensile properties of decrosslinked XHDPE. To overcome this problem, two novel ultrasonically aided extrusion systems with better controlled cooling of ultrasonic treatment zone are developed [13] and used to perform ultrasonic decrosslinking of XHDPE [14][15][16][17]. The effects of ultrasonic amplitude [14][15][16][17], flow rate [14,15], extruder type [15], screw design [16] and degree of crosslinking [17] on ultrasonic decrosslinking of XHDPE are studied.…”

Section: Introductionmentioning

confidence: 99%

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Comparison between decrosslinking of crosslinked high and low density polyethylenes via ultrasonically aided extrusion

Huang

Isayev

2015

Polymer

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Please cite this article as: Huang K, Isayev AI, Comparison between decrosslinking of crosslinked high and low density polyethylenes via ultrasonically aided extrusion, Polymer (2015), AbstractAmong various polymer wastes, management of crosslinked plastics is a major environmental problem requiring a solution. Among various crosslinked plastics, recycling of crosslinked polyethylenes is of a great importance due to the presence of a three-dimensional network. To solve this problem, novel environmentally friendly technologies for decrosslinking of the crosslinked polymers are developed based on ultrasonically assisted single (SSE) and twin screw (TSE) extruders. In particular, decrosslinking of peroxide crosslinked high-density polyethylene (XHDPE) and low-density polyethylene (XLDPE) by means of an ultrasonic SSE and TSE is investigated. Barrel pressure, die pressure and ultrasonic power consumption during extrusion are recorded. Swelling, rheological, thermal analysis and tensile tests are used to elucidate the structure-property relationships of decrosslinked XHDPE and XLDPE. The frequency dependencies of the storage and loss moduli, complex viscosity and tangent loss of XHDPE, XLDPE and their decrosslinked networks are described by the post critical gel model with its parameters correlated with gel fraction and crosslink density. The dynamic, thermal and tensile properties of the decrosslinked XHDPE and XLDPE are greatly affected by the type of preferential bond breakage. It was found that the decrosslinking of XLDPE is more difficult than that of XHDPE. An analysis based on the Horikx function reveals a highly preferential breakage of crosslinks during decrosslinking of XHDPE. In contrast to decrosslinking of XHDPE, the presence of long-chain branching in XLDPE is found to lead to the breakage of its main chains during decrosslinking. An improvement and a reduction in mechanical properties of decrosslinked XHDPE and XLDPE are, respectively, observed in comparison with those of virgin XHDPE and XLDPE. Such differences in behavior are due to the occurrence of a highly preferential breakage of crosslinks in XHDPE and the breakage of main chains in XLDPE during ultrasonic decrosslinking. Graphic AbstractStress-strain curves of HDPE, LDPE, XHDPE and XLDPE (a) and decrosslinked XHDPE (b) and XLDPE (c) by SSE and TSE with and without ultrasonic treatment.

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Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Comparison between decrosslinking of crosslinked high and low density polyethylenes via ultrasonically aided extrusion

Huang

Isayev

2015

Polymer

Self Cite

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show abstract

“…The decrease of barrel pressure in SSE with the amplitude is due to the decrease of viscosity caused by thixotropic effect and permanent decrease of the gel fraction and crosslink density introduced by ultrasonic trreatment [9]. The decrease of die pressure in TSE with the amplitude is due to the permanent decrease of viscosity caused by reduction of the gel fraction and crosslink density [11]. It is seen from Figure 1a that the barrel pressure in SSE during extrusion of XHDPE is slightly higher than that of XLDPE.…”

Section: Resultsmentioning

confidence: 98%

“…The ultrasonically aided extrusion of XHDPE is studied including the effects of flow rate [8,9], extruder type [10], screw design [11] and degree of crosslinking [12]. It is found that the ultrasonically aided extrusion is a promising technology to obtain a decrosslinked XHDPE exhibiting good processibility and superior mechanical performance.…”

Section: Introductionmentioning

confidence: 99%

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Comparison between decrosslinking of crosslinked high and low density polyethylenes via ultrasonically aided extrusion

Isayev¹,

Huang²

2016

AIP Conference Proceedings

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Stress growth and relaxation of dendritically branched macromolecules in shear and uniaxial extension Journal of Rheology 61, 35 (2017) Abstract. Among various crosslinked plastics, recycling of crosslinked polyethylenes is of a great importance due to the presence of a three-dimensional network. To solve this problem, novel environmentally friendly technologies for decrosslinking of the crosslinked polymers are developed based on ultrasonically assisted single (SSE) and twin screw (TSE) extruders. In particular, decrosslinking of peroxide crosslinked high-density polyethylene (XHDPE) and low-density polyethylene (XLDPE) by means of an ultrasonic SSE and TSE is investigated. Barrel pressure, die pressure and ultrasonic power consumption during extrusion are recorded. Swelling, rheological, thermal analysis and tensile tests are used to elucidate the structure-property relationships of decrosslinked XHDPE and XLDPE. The frequency dependencies of the storage and loss moduli, complex viscosity and tangent loss of XHDPE, XLDPE and their decrosslinked networks are described by the post critical gel model with its parameters correlated with gel fraction and crosslink density. The dynamic, thermal and tensile properties of the decrosslinked XHDPE and XLDPE are greatly affected by the type of preferential bond breakage. It was found that the decrosslinking of XLDPE is more difficult than that of XHDPE. An analysis based on the Horikx function reveals a highly preferential breakage of crosslinks during decrosslinking of XHDPE. In contrast to decrosslinking of XHDPE, the presence of long-chain branching in XLDPE is found to lead to the breakage of its main chains during decrosslinking. An improvement and a reduction in mechanical properties of decrosslinked XHDPE and XLDPE are, respectively, observed in comparison with those of virgin XHDPE and XLDPE.

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Recycling of crosslinked high‐density polyethylene through compression molding

Santos

Jayaraman

2019

J of Applied Polymer Sci

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Crosslinkable high‐density polyethylene (XHDPE) is used to manufacture large and rigid products such as fuel tanks using rotomolding. Currently, defective and postconsumer parts are not recycled and sent to landfills. Hence, recycling of this material through compression molding is the objective of this study. Thermal analysis revealed that the extent of crosslinking varied across the thickness of the rotomolded part due to the role played by oxygen in air. Despite the crosslinking, the recycled XHDPE (RXHDPE) could be remelted with higher viscosity than the virgin XHDPE (VXHDPE). Consolidation studies indicated that both the RXHDPE and the VXHDPE could be compression molded to a density of 0.952 g cm−3. However, higher consolidation stress is required for the RXHDPE when compared to the VXHDPE to realize the same density. The RXHDPE, compression molded at 1.6 MPa and 230 °C, had properties similar to those of the VXHDPE molded at 0.32 MPa. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48145.

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Ultrasonic decrosslinking of crosslinked high‐density polyethylene: Effect of screw design

Cited by 15 publications

References 39 publications

Comparison between decrosslinking of crosslinked high and low density polyethylenes via ultrasonically aided extrusion

Comparison between decrosslinking of crosslinked high and low density polyethylenes via ultrasonically aided extrusion

Comparison between decrosslinking of crosslinked high and low density polyethylenes via ultrasonically aided extrusion

Recycling of crosslinked high‐density polyethylene through compression molding

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