Two decades ago, when Dow added a new building to the campus of its European headquarters in Horgen, Switzerland, the company elected to install an innovative hydronic radiant heating and cooling system based on plastic pipes made with DOWLEX™ 2344 PE-RT resin. 

The installation, an alternative to traditional oil- or gas-based heating and cooling systems, was one of the first non-residential applications of a Swiss energy conservation technology designed to heat buildings in the winter and cool them in the summer. The system works by tapping the thermal storage capacity of the concrete slabs between each storey in a multi-storey building, controlled by water-bearing pipes embedded in each concrete slab.

In all, Dow installed 40,000 meters of 16 x 2mm diameter plastic pipe in the concrete foundation (see photograph), walls and ceilings of a four-storey building. Now, as part of a refurbishment project, Dow has had an opportunity to examine and analyze a 20-year old section of the pipe system to see how it is performing after all those years of service. The results are instructive.

First, DOWLEX 2344 material from the pipe was subjected to differential scanning calorimetry (DSC) analysis, a thermo-analytical technique to measure whether any change had occurred in its melting and crystallization behaviour relative to a reference sample- in other words, to test if the material had become more brittle or is already partially degraded. As the DSC traces in Figure 1 show, this was not the case.

Figure 1 - DSC Curve for 20 Years Old DOWLEX 2344 Sample

The second test conducted on the 20-year old DOWLEX 2344 material was an oxidative induction time (OIT) measurement at 210˚ C.

This test, which is an internationally recognized means of characterizing the thermo-oxidative stabilities of polyolefins (ASTM D3895 and DIN EN 728), is used to determine if the original stabilization components are still present and capable of protecting the material against oxidation. The results of the OIT test on the DOWLEX 2344 material showed that more than 60 % of the original OIT is still available to offer long-term oxidation protection for the pipe.

"Nothing could be more convincing for our customers, and their customers, than to see a living example of DOWLEX 2344 PE-RT pipes that have stood the test of time and are still performing as well today as they were when first installed twenty years ago," said Katja Wodjereck, Market Manager for Pipes and Geomembranes at Dow Europe GmbH.