Mineral fi llers | materials feature
Natural born fi llers
Mineral fi llers, such as talc, have always been sold on the basis that they cut the cost of the fi nal part – by replacing a certain portion of the (more expensive) resin. But fi llers are also starting to take on a green tinge.
Many new types of fi ller are derived from sustainable sources. This gives rise to a new sales pitch: fi llers that can reduce the use of non-renewable content (in the shape of the plastic resin). An example is Seppa, which is derived largely from sea shell waste. It can be used as a fi ller in a range of plastics, helping to reduce the amount of polymer used for a variety of applications (especially fi lm and sheet). “It has no claims to biodegradability, but simply
reduces use of a non-renewable source,” said Colin Farrant of CFM Machinery, the UK agent for Seppa. Seppa contains three core ingredients: chitin, calcite
and aragonite. Chitin is contained in the outer layer of sea shells. Calcite is calcium carbonate – as is found in rocks like chalk and limestone. It is already widely used as a fi ller for plastics, but this version is from a renewable source. Aragonite is a special form of calcium carbonate with a different crystalline structure. Seppa contains more aragonite than calcite. The three ingredients are processed into a micro-
fi ne powder and compounded into a pellet of LLDPE, ready to add to batches of synthetic resin. Each element has a different role to play. The
aragonite promotes even distribution of in fl exible and
www.fi lmandsheet.com
Fillers from renewable resources – including sea shells, grain and paper – are becoming more commonplace. Lou Reade reports
rigid plastics. Product performance can be retained at far higher loading levels than ordinary calcium carbon- ate. Chitin provides strength and durability. The benefi ts of using calcite as a fi ller are already well known. Seppa does not contain any oxo-degradable technol- ogy such as metal salts – and, unlike bioplastics based on corn-starch, does not contain a food stock. Seppa distributes evenly in HDPE and LDPE fi lms. A
loading level of 27.5% can easily be run in 13-15 micron fi lms, to give around 25% bio-renewable content. In thicker fi lms, a loading of 40% or more is possible. It can be used in products ranging from lightweight carrier bags and reusable shopping bags, to plastic sacks and sheeting. For thermoformed products, it can replace up to 45% of the synthetic polymer normally required to make the item – without affecting product performance. Finished goods are recyclable using standard processes. “It comes from a renewable and sustainable source
January/February 2014 | FILM & SHEET EXTRUSION 29 Waste paper
can be ground to a fi ne
powder and used as a fi ller for PP and other resins
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