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PP is the most preferred material
for houseware products, as it provides all the desired properties
at the most economic value. However, this consumer-oriented market
is increasingly becoming competitive, with returns on the houseware
business dipping very low.
Processors have driven the developments of newer
grades with better flow, better impact-rigidity balance and enhanced
clarity without sacrificing clarity to a great extent. Higher flow
materials provide saving in production cycle due to saving in cooling
time. The newer PP grades, having MFR as high as 100, could help
the converters to save enough money to generate profits instead
of loss. These high flow materials can be processed at lower temperatures
and hence save significantly in cooling times.
The last decade has seen significant changes in
the flow behaviour of PP. While a maximum MFR of 25-50 was typical
in the early 90s, grades with about 100MFR are now commonly used
for manufacture of injection moulded housewares. All the major PP
producers have put up the newer grades with such high flow characteristics.
These grades not only include impact copolymer with low rubber contents
but also copolymers that have higher rubber contents. The "impact
rigidity balance" has been achieved with catalyst modifications.
Some impact copolymer grades with 100MFR have been designed to give
about 1000 Mpa . In fact, many newer grades with about 70-100 MFR
have similar properties as that of earlier 30-50 MFR. The new impact
copolymers with better haze values compared to the conventional
impact copolymers also have been developed for this market. These
grades can produce parts showing about 25% haze compared to 95%
earlier. To provide aesthetics through clarity, random copolymers
of about 30-40MFR have been introduced with excellent clarity.
All the major PP suppliers like Atofina, Basell,
Borealis, DSM(Sabic) and Dow have these newer grades with enhanced
fluidity and properties.
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