Water spray cooling of polymers

The cooling process in conventional rotomolding is relatively long due to poor thermal conductivity of plastics. The lack of internal cooling is a major limitation although rapid external cooling is possible. Various internal cooling methodologies have been studied to reduce the cycle time. These in...

Full description

Saved in:
Bibliographic Details
Published in:Polymer engineering and science 2012-05, Vol.52 (5), p.1069-1080
Main Authors: Tan, S.B., Hornsby, P.R., McAfee, M.B., Kearns, M.P., McCourt, M.P.
Format: Article
Language:English
Subjects:
Applied sciences
Cooling
Crystallization
Exact sciences and technology
Nozzles
Physicochemistry of polymers
Plastics
Polymer industry, paints, wood
Polymers
Technology of polymers
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The cooling process in conventional rotomolding is relatively long due to poor thermal conductivity of plastics. The lack of internal cooling is a major limitation although rapid external cooling is possible. Various internal cooling methodologies have been studied to reduce the cycle time. These include the use of compressed air, cryogenic liquid nitrogen, chilled water coils, and cryogenic liquid carbon dioxide, all of which have limitations. However, this article demonstrates the use of water spray cooling of polymers as a viable and effective method for internal cooling in rotomolding. To this end, hydraulic, pneumatic, and ultrasonic nozzles were applied and evaluated using a specially constructed test rig to assess their efficiency. The effects of nozzle type and different parametric settings on water droplet size, velocity, and mass flow rate were analyzed and their influence on cooling rate, surface quality, and morphology of polymer exposed to spray cooling were characterized. The pneumatic nozzle provided highest average cooling rate while the hydraulic nozzle gave lowest average cooling rate. The ultrasonic nozzle with medium droplet size traveling at low velocity produced satisfactory surface finish. Water spray cooling produced smaller spherulites compared to ambient cooling whilst increasing the cooling rate decreases the percentage crystallinity. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers
ISSN:0032-3888
1548-2634
DOI:10.1002/pen.22173