Energetica India nº91 July August 2020

CASE STUDY 51 energetica INDIA- July-Aug_2020 ethylene and polypropylene, as well as compounds based on these polymers with add-on functional stabilization such as light and heat resistance, depending on the local climate conditions which are well suited for use in production of the vital pontoons that sit on the water under the blazing sun to support the panels over many years in use. These materials demonstrated high resistance to corrosion and weathering in the lab tests carried out according to interna- tional standards in various countries such as India, Japan and China, where their resistance to environmental stress cracking (ESCR) extended beyond 3000 hours, which outperformed the industry standard thatspecifies an ESCR require - ment of 1000 hours. Furthermore, creep resistance is also very high: this means that parts will not stretch under constant stress, and so the pontoons will retain their integrity. FPV systems installed to date typical- ly make use of primary and second- ary floats, which range in volume from around 50 liters to 300 liters. These floats are produced using very large ex - trusion-blow molding (EBM) machines. Processors require resins with the right flow properties (MFR) to run on their ma - chines, with consistency across batches. End-user specifications may call for the floats to be resistant to ambient tempera - tures ranging from as low as -60° all the way up to +80°C. Apart from resistance to continuous exposure to the sun, they also obviously have to withstand con- stant contact with water, they need to be airtight, plus, they should not affect wa- ter quality (leaching). Choosing the right materials A grade of high-density polyethylene (HDPE) developed by SABIC specifical - ly for FPV floats, SABIC® B5308 resins, is capable of meeting these processing and performance-in-use requirements. This grade has already been approved by several companies specializing in FPV systems. HDPE B5308 is a high mo- lecular weight material with a so-called multi-modal molecular weight distribu- tion that provides particular processing and performance characteristics. It has outstanding ESCR, excellent mechani- cal properties, a very good balance of toughness and stiffness (something not always easy to achieve in plastics), a long lifetime and easy blow molding pro- cess ability. SABIC HDPE B5308 has a Melt Flow Rate (MFR, 21.6kg load) of around 8g/10 min. This is high enough to enable the molten polymer to be easily formed during blow molding, but low enough so that the melt strength of the parison (the tube of mate- rial extruded vertically before it is blown) is sufficient to stop it distorting during production. SABIC B5308 has a melting temperature of 132°C and a Vicat Soft- ening Point (under 10N load) of 126°C. It has excellent ESCR properties: over 3000 hours according to ASTM 1693B. Rigidity is very good: tensile modulus is 1050 MPa (ISO527). A bright future SABIC fully expects that we will see many more FPV systems deployed as society grapples with increased pres- sures to create energy without harming the environment. SABIC has already worked on floating solar farm projects in India, Japan, and China. The company believes that its polymer solutions can be key to help further unlocking the po- tential of FPV technology.