The Dutch arm of the petrochemical giant (2011 turnover: $50.64bn) said that the new grade was principally targeted at bottles for UHT (ultra-high temperature) and sterilised milk produced on high-speed extrusion blow-moulding lines, especially in Southern European countries.
The material - SABIC HDPE B5260ULS – can be either coloured on the blow moulder or by using compounding equipment.
A spokeswoman for SABIC told DairyReporter.com that geographical and historical factors have led to a consumer preference in countries including France, Spain, Italy and Greece for UHT or sterilized milk in plastic milk bottles made out of this type of HDPE.
Shelf life required
“This is partly indeed to do with the climate, where improved shelf life is required. Due to the warm climate, fresh milk (which is for example the main type milk in the UK) would have a very short shelf life,” said the spokeswoman.
“However, UHT milk is also being consumed in large quantities in other countries such as Germany. There it is being packaged in cartons instead of HDPE bottles. Although cartons in general have a more negative impact on carbon footprint due to the limited recyclability, an industry can’t change overnight from packaging milk in cartons to packaging milk in HDPE bottles.”
The spokeswoman added that the SABIC HDPE B5260ULS is one of only a few materials that has the necessary processing properties required by converters to run on equipment typically used for UHT and sterilised milk.
A melt-flow rate (MFR at 2.16kg) of 2g/10 minutes* and a broad molecular weight distribution ensured good performance during extrusion and blowing, with the grade suitable for mono- and multi-layer constructions.
“The HDPE bottles in the South of Europe are typically being made on one type of extrusion blow molding machinery, which requires a certain set of processing properties from the material,” she added.
“In the past 20 years, this market has been dominated by one single supplier. This one machine manufacturer and one material supplier fine-tuned their assets to one another, making it difficult for other materials to be processed.”
In-bottle sterilisation
Gerrit-Jan Bekink, technical marketing engineer (HDPE) for SABIC, based in Sittard, The Netherlands, said: “HDPE B5260ULS – ULS stands for ultra-long shelf life – is a high purity grade that features good organoleptic properties [relating to potential transfer of packaging taste, odors to foods or beverages].
"[These] are especially important when using in-bottle sterilisation, where the packaging as well as the product are subjected to tough thermal and mechanical conditions," he added.
The new grade’s balanced mechanical properties – stiffness, impact and environmental stress crack resistance (ESCR) – were also well-suited for a demanding segment, Bekink added.
*Melt flow index (MFI) measures the ease of flow of a thermoplastic polymer, defined as the mass thereof in grams flowing through a capillary over 10 minutes, driven by gravimetric weights.
Processors require a polymer with an MFR high enough for it to be easily formed in a molten state, but not so high that this jeopardises the finished product’s mechanical strength.