What is PP?
PP, also known as polypropylene
, is a widely used semi-crystalline thermoplastic polymer. It is translucent or opaque, rigid or semi-rigid, water-repellent, and very scratch-resistant.
How is it used?
In the food processing industry, polypropylene is used for food packaging due to its resistance to grease (for butter containers, for example) and gloss finish. It is also used for prepared dishes ready to be reheated in the microwave.
Can PP be used on Arcil FFS machines?
PP is not as flexible as PS. On an FFS machine, PP is more complicated to configure, and stricter parameters must be adhered to when heating the plastic than for PS (must be accurate to within 2-3°). Heating times and, consequently, cooling times for PP are long, which could impact production rates. Furthermore, its thermoforming temperature range is very narrow. It is therefore more difficult to use on FFS machines, especially when a machine needs to be restarted following a problem upstream or downstream.
Expanded polypropylene is the most suitable PP for thermoforming applications since the compact outer layers are thin, allowing for faster heat transfer. The addition of mineral fillers also helps maintain the plastic's shape after thermoforming and allows it to be scored, resulting in properties very similar to PS.
"The peak of scientific knowledge about PP has not yet been reached," explains Pierre Dupont, Equipment Qualification Manager at Synerlink. "The material is currently not being used to its full potential."
Arcil A7 machines are able to work with PP after some minor alterations, such as the addition of a cooling system. An A7 machine that has been modified to work with PP will also work with PS. Switching from one material to the other takes less than 30 minutes.
"We were confident in our machine's ability to accommodate both PS and PP, but we are still amazed at how fast and easy it is to switch materials," said Daniel Pereira, Equipment & Material Qualification Engineer at Synerlink.
Is PP the material of the future?
PP has a better water vapor transmission rate than PS, and is therefore better for long-term storage. Since it is compatible with a wide variety of foods, it can be used for packaging almost every type of food, and can also be heated in the microwave.
Last but not least, the price of PP does not fluctuate as much as PS because the market is substantially bigger. Recycling of PP is also becoming an alternative source.