Optimisation of multi-layer rotationally moulded foamed structures

Research output: Contribution to conferencePaper

Abstract

Multi-layer skin-foam and skin-foam-skin sandwich constructions are of increasing interest in the rotational moulding process for two reasons. Firstly, multi-layer constructions can improve the thermal insulation properties of a part. Secondly, foamed polyethylene sandwiched between solid polyethylene skins can increase the mechanical properties of rotationally moulded structural components, in particular increasing flexural properties and impact strength (IS). The processing of multiple layers of polyethylene and polyethylene foam presents unique challenges such as the control of chemical blowing agent decomposition temperature, and the optimisation of cooling rates to prevent destruction of the foam core; therefore, precise temperature control is paramount to success. Long cooling cycle times are associated with the creation of multi-layer foam parts due to their insulative nature; consequently, often making the costs of production prohibitive. Devices such as Rotocooler®, a rapid internal mould water spray cooling system, have been shown to have the potential to significantly decrease cooling times in rotational moulding. It is essential to monitor and control such devices to minimise the warpage associated with the rapid cooling of a moulding from only one side. The work presented here demonstrates the use of threaded thermocouples to monitor the polymer melt in multi-layer sandwich constructions, in order to analyse the cooling cycle of multi-layer foamed structures. A series of polyethylene skin-foam test mouldings were produced, and the effect of cooling medium on foam characteristics, mechanical properties, and process cycle time were investigated. Cooling cycle time reductions of 45%, 26%, and 29% were found for increasing (1%, 2%, and 3%) chemical blowing agent (CBA) amount when using internal water cooling technology from ∼123°C compared with forced air cooling (FAC). Subsequently, a reduction of IS for the same skin-foam parts was found to be 1%, 4%, and 16% compared with FAC.
Original languageEnglish
DOIs
Publication statusPublished - May 2018
Event21st International ESAFORM Conference on Material Forming, ESAFORM 2018 - Palermo, Italy
Duration: 23 Apr 201825 Apr 2018

Conference

Conference21st International ESAFORM Conference on Material Forming, ESAFORM 2018
CountryItaly
CityPalermo
Period23/04/201825/04/2018

Fingerprint

Foams
Cooling
Skin
Polyethylenes
Rotational molding
Blowing agents
Impact strength
Molding
Mechanical properties
Polymer melts
Thermal insulation
Cooling water
Thermocouples
Air
Cooling systems
Temperature control
Decomposition
Processing
Costs
Water

Cite this

Pritchard, A., McCourt, M., Kearns, M., Martin, P., & Cunningham, E. (2018). Optimisation of multi-layer rotationally moulded foamed structures. Paper presented at 21st International ESAFORM Conference on Material Forming, ESAFORM 2018, Palermo, Italy. https://doi.org/10.1063/1.5034979
Pritchard, Alex ; McCourt, Mark ; Kearns, Mark ; Martin, Peter ; Cunningham, Eoin. / Optimisation of multi-layer rotationally moulded foamed structures. Paper presented at 21st International ESAFORM Conference on Material Forming, ESAFORM 2018, Palermo, Italy.
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Pritchard, A, McCourt, M, Kearns, M, Martin, P & Cunningham, E 2018, 'Optimisation of multi-layer rotationally moulded foamed structures', Paper presented at 21st International ESAFORM Conference on Material Forming, ESAFORM 2018, Palermo, Italy, 23/04/2018 - 25/04/2018. https://doi.org/10.1063/1.5034979

Optimisation of multi-layer rotationally moulded foamed structures. / Pritchard, Alex; McCourt, Mark; Kearns, Mark; Martin, Peter; Cunningham, Eoin.

2018. Paper presented at 21st International ESAFORM Conference on Material Forming, ESAFORM 2018, Palermo, Italy.

Research output: Contribution to conferencePaper

TY - CONF

T1 - Optimisation of multi-layer rotationally moulded foamed structures

AU - Pritchard, Alex

AU - McCourt, Mark

AU - Kearns, Mark

AU - Martin, Peter

AU - Cunningham, Eoin

PY - 2018/5

Y1 - 2018/5

N2 - Multi-layer skin-foam and skin-foam-skin sandwich constructions are of increasing interest in the rotational moulding process for two reasons. Firstly, multi-layer constructions can improve the thermal insulation properties of a part. Secondly, foamed polyethylene sandwiched between solid polyethylene skins can increase the mechanical properties of rotationally moulded structural components, in particular increasing flexural properties and impact strength (IS). The processing of multiple layers of polyethylene and polyethylene foam presents unique challenges such as the control of chemical blowing agent decomposition temperature, and the optimisation of cooling rates to prevent destruction of the foam core; therefore, precise temperature control is paramount to success. Long cooling cycle times are associated with the creation of multi-layer foam parts due to their insulative nature; consequently, often making the costs of production prohibitive. Devices such as Rotocooler®, a rapid internal mould water spray cooling system, have been shown to have the potential to significantly decrease cooling times in rotational moulding. It is essential to monitor and control such devices to minimise the warpage associated with the rapid cooling of a moulding from only one side. The work presented here demonstrates the use of threaded thermocouples to monitor the polymer melt in multi-layer sandwich constructions, in order to analyse the cooling cycle of multi-layer foamed structures. A series of polyethylene skin-foam test mouldings were produced, and the effect of cooling medium on foam characteristics, mechanical properties, and process cycle time were investigated. Cooling cycle time reductions of 45%, 26%, and 29% were found for increasing (1%, 2%, and 3%) chemical blowing agent (CBA) amount when using internal water cooling technology from ∼123°C compared with forced air cooling (FAC). Subsequently, a reduction of IS for the same skin-foam parts was found to be 1%, 4%, and 16% compared with FAC.

AB - Multi-layer skin-foam and skin-foam-skin sandwich constructions are of increasing interest in the rotational moulding process for two reasons. Firstly, multi-layer constructions can improve the thermal insulation properties of a part. Secondly, foamed polyethylene sandwiched between solid polyethylene skins can increase the mechanical properties of rotationally moulded structural components, in particular increasing flexural properties and impact strength (IS). The processing of multiple layers of polyethylene and polyethylene foam presents unique challenges such as the control of chemical blowing agent decomposition temperature, and the optimisation of cooling rates to prevent destruction of the foam core; therefore, precise temperature control is paramount to success. Long cooling cycle times are associated with the creation of multi-layer foam parts due to their insulative nature; consequently, often making the costs of production prohibitive. Devices such as Rotocooler®, a rapid internal mould water spray cooling system, have been shown to have the potential to significantly decrease cooling times in rotational moulding. It is essential to monitor and control such devices to minimise the warpage associated with the rapid cooling of a moulding from only one side. The work presented here demonstrates the use of threaded thermocouples to monitor the polymer melt in multi-layer sandwich constructions, in order to analyse the cooling cycle of multi-layer foamed structures. A series of polyethylene skin-foam test mouldings were produced, and the effect of cooling medium on foam characteristics, mechanical properties, and process cycle time were investigated. Cooling cycle time reductions of 45%, 26%, and 29% were found for increasing (1%, 2%, and 3%) chemical blowing agent (CBA) amount when using internal water cooling technology from ∼123°C compared with forced air cooling (FAC). Subsequently, a reduction of IS for the same skin-foam parts was found to be 1%, 4%, and 16% compared with FAC.

U2 - 10.1063/1.5034979

DO - 10.1063/1.5034979

M3 - Paper

ER -

Pritchard A, McCourt M, Kearns M, Martin P, Cunningham E. Optimisation of multi-layer rotationally moulded foamed structures. 2018. Paper presented at 21st International ESAFORM Conference on Material Forming, ESAFORM 2018, Palermo, Italy. https://doi.org/10.1063/1.5034979