Page 38 - Plastics News January 2018

FeAtures

share in Food, Home Care and Personal Care (FHPC) The base geometry is selected to suit the type of product
markets traditionally dominated by HDPE (High Density involved. This is why the base of a bottle for still water
Polyethylene) and PP (Polypropylene) and is expected to looks different from that of a bottle for carbonated water.
grow by an average of 3% for all three sectors until 2020.
But why is this necessary?
The function and design of PET container bases
In the case of carbonated beverages, in contrast to still
products, the PET bottle is under internal pressure, i.e.
the base has to be able to withstand this internal pressure
without being deformed. After all, the container is
required to stand upright on the conveyor inside the line,
and not least on the supermarket shelf as well. Stabilising
ribs in the areas between the “footlets” keep the base
stable, by overall and ideally forming a hemisphere.
In the case of packages for still water, for example, or for
aseptically bottled beverages like dairy products or juices,
there will be no (or almost no) internal pressure, thanks
to a nitrogen droppler in the bottle. That’s why this base
You may perhaps have noticed that PET bottles have a looks significantly flatter.
wide variety of different bases? Some of them stand on
“footlets”, others are quite flat, and others again have a
“ribbed base”. But why exactly is this the case?
Every design is influenced by both functional and aesthetic
considerations. In some cases, the shape will be the primary
focus, while in others the purpose is paramount. The
sentence “Form follows function” coined by the American
architect Louis Sullivan is frequently cited – unfortunately,
though, this precept is often misunderstood. Actually, you
see, Sullivan was not postulating the primacy of function
over aesthetics, but stating that the appearance of objects But how do clients choose their bases?
has a function in itself. So a good designer has to decide in
each and every case which aspect is more important: the Well – often most of the clients will in fact have a more or
form or the function. When it comes to the base of a PET less specific idea of what they wish their bottle to look like.
bottle, this is not a particularly difficult decision. Since Many of them want what is called a “champagne” base,
the base is crucial to container’s technical performance, because of its upmarket character and its resemblance
and is therefore one of the most important functional
sections, it’s no accident that it looks the way it does.

Here, at least, the primary focus is definitely on
functionality. In terms of internal-pressure stability, the
most technically sophisticated base is without a doubt
the Carbo Classic Base, also known as the petaloid base.
The word “petaloid” is etymologically derived from Greek
and Neo-Latin, and in its original meaning simply signifies
“petal-shaped”. In actual fact, the Ancient Greek word
“penta”(= five) has nothing to do with the derivation of the
petaloid base, although this is often erroneously assumed, to glass bottles. Unfortunately, however, most of these
due to the five feet usually featured. bases are less than ideal for the technical requirements
the containers have to meet. They require a large amount

Plastics News Januar y 2018 38