materials feature | PEX
crosslinking of XHDPE was developed based on the tetrafunctional network containing the dangling chains. The normalised gel fraction-crosslink density relation- ship of the de-crosslinked XHDPE was simulated. This relationship was strongly affected by the weight ratio between the network strands and dangling chains of XHDPE, the researchers concluded.
Patent win Earlier this year, Uponor won a long-running patent infringement case against two Canadian companies. It has since come to a licensing agreement with them. The company first filed a suit against Heatlink and
Isayev: “Ultrasonic extrusion can be used to recycle crosslinked HDPE and LDPE”
– and higher ultrasonic power consumption during de-crosslinking of XLDPE. There was higher de- crosslinking efficiency for the XHDPE. Under some processing conditions, mechanical
properties of the de-crosslinked XHDPE were found to be close to – or higher than – those of XHDPE. The melting temperature and crystallinity of the de- crosslinked XLDPE increased with the ultrasonic amplitude, with their values being lower than those of the virgin LDPE. The tensile stress-strain behaviour of the de-crosslinked XLDPE was that of a typical branched PE. The tensile properties of the de- crosslinked XLDPE showed a clear dependence on the ultrasonic amplitude. In particular, the Young’s modulus, stress at break and strain at break increased with the ultrasonic amplitude and levelled off at the high amplitudes.
The simulation of ultrasonic decrosslinking of XHDPE was carried out by modifying a model that the researchers had earlier developed by ultrasonic devulcanization of rubber vulcanizates. In the earlier model, the effects of residence time on evolution of the gel fraction and crosslink density and the bulk rheology of the polymer on the ultrasonic power consumption were not considered. So, an ultrasonic decrosslinking model that included these two effects was modified to simulate the gel fraction and crosslink density of the decrosslinked XHDPE – providing the correct prediction of their dependence on the ultrasonic amplitude. Using one set of material parameters, the model
correctly predicted the decrease of the measured gel fraction and crosslink density at high ultrasonic ampli- tude with some deviation at low ultrasonic amplitude. To improve the predictive capability of the model, the non-isothermal flow simulation was carried out. A simulation program to calculate the ratio between the crosslink and main chain breakage during de-
32 PIPE & PROFILE EXTRUSION | November/December 2016
PexCor in 2011 – in both the US and Canada – alleging they had infringed claims in a patent relating to the manufacture of PEX pipe. In January 2016, the suit went to trial in Calgary, Alberta and on March 16, 2016, the judge ruled in Uponor’s favour. The action in the US was previously stayed pending
the outcome of the Canadian litigation, said Uponor. Heatlink and PexCor are affiliated companies based in Calgary, Alberta that make and sell PEX pipe. As a result of the ruling, Heatlink, PexCor and
associated companies were ordered to stop production and sales of infringing PEX products, and were ordered to pay damages and costs. The judge’s ruling found that: five claims of Uponor’s
patent are valid, and infringed by PexCor and Heatlink; and, Uponor is entitled to damages as a result of the patent infringement, as well as post-judgment interest and costs. “We’re pleased that the Federal Court of Canada deemed these claims to be valid and appreciate the considerable amount of time and effort it expended to arrive at its ruling,” said Bill Gray, president of Uponor North America. However, Uponor has now come to an agreement
with the companies – which can now “resume business under a licence agreement with Uponor”. “It’s a fair outcome for all involved and allows us to
focus on our respective markets and customers,” said Gray.
Back in Europe, Uponor is to close its PEX pipe
production site in Mostoles, Spain and transfer production to its facilities in Virsbo, Sweden. The Mostoles plant manufactures PEX pipe for the
south European markets. As part of a restructuring programme, which began in autumn 2015, the company now plans to transfer the production to rationalise manufacturing and reduce cost in supply chain and production operations. “Our main PEX pipe markets are in the Nordic
countries and Germany, so the manufacturing location
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