Performance PP | materials
Already one of the most versatile of polymers, academics and additive suppliers are working to further enhance the performance of PP. Peter Mapleston finds out more
Lifting performance of PP compounds
Polypropylene is arguably the most versatile of all thermoplastics. Careful selection of homopolymer, random or block copolymer forms, together with appropriate compounding modification, can lead to PPs that can be either flexible or rigid, opaque or transparent, and that offer high or low melt flows. Even thermal resistance can be significantly adjusted. And all the while, PP scores over other thermoplastics with a relatively low density, high chemical resistance, and reasonable price. Given that versatility, it is no surprise that PP is so
widely used in flexible and rigid packaging, in building and construction, and by car makers (PP accounts for almost half of all of the thermoplastics used in a car by weight and that figure continues to rise). Yet still developments are ongoing to make PP an even better performer. Academics, polymer makers, additive producers and compounders all continue to work to take PP to the next level in performance terms. This article reviews some recent advances. Manchester University in the UK claims to be the home of graphene for its work a decade or so ago in extracting this new form of carbon from graphite. Now researchers led by Professor Robert Young at the university’s National Graphene Institute and School of
www.compoundingworld.com
Materials are looking at the mechanisms of reinforce- ment of polypropylene using graphene nanoplatelets (GNPs). The team has been producing nanocomposites by melt mixing and then characterising the nanostruc- ture of injection moulded test pieces. It has been found that the incorporation of GNPs increases the thermal stability of the PP and aids crystal nucleation. Graphene has the potential to impart improved
thermal conductivity, durability, thermal stability and mechanical stiffness and strength to plastics nanocom- posites, Young says, but the preparation of few and many-layer graphene materials in bulk quantities is a challenging task. GNPs consist of short stacks of graphene layers with lateral dimensions, aspect ratio, available surface area, morphology and properties that make them effective as reinforcements. “Therefore, both industry and academia are utilising materials such as GNPs that exhibit similar mechanical, thermal and electrical properties to graphene, but are significantly cheaper to produce,” he says. The addition of GNPs led to a significant increase in
the Young’s (elastic) modulus of the PP – up to around 100 GPa – coupled with a decrease in yield stress and a reduction in the elongation to failure.
August 2017 | COMPOUNDING WORLD 27 Main image:
Clariant’s soon to be launched Addworks ATR146 is a
new heat and light stabiliser aimed at high performance low VOC TPOs for automotive
s
PHOTO: CLARIANT
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