Influence of organic phase change materials on the physical and mechanical properties of HDPE and PP polymers

In this work, the compatibility of four commercially available organic phase change materials, with melting points in the temperature range 44–58 _C and with engineering polymers high density polyethylene (HDPE) and polypropylene (PP), is investigated. These polymers are used for the design and manufacture of hot and cold thermal energy storage tanks or encapsulation media. The study involves interaction of polymer specimens with the four different phase change materials for a period of time up to 40 days under high temperature. The mass change, mechanical strength and properties of the polymers were tested. The wt% uptake reached 6.4 wt% for PP and 5.8 wt% for HDPE. The strength of HDPE is immediately decreased by Day 7 but at a significant level restored after Day 28. No such effect was found for PP. The surface wetting as well as thermal properties measured (DSC) on the specimens provided an insight on the interaction of the absorbed phase change materials with the polymer. An in depth distribution over time was observed with significant decrease in the mechanical strength of the polymers. An epoxybased resin was also evaluated under the same conditions and is suggested as a protective coating.