P#5 PP – Research Ecomakery

A.K.A. Polypropylene

Polypropylene plastic is tough and lightweight, and has excellent heat-resistance qualities. It serves as a barrier against moisture, grease and chemicals. Around 70 percent of PP is estimated to be used in food contact applications. It has high melting point and can be filled with hot foods.

PP comes in many forms and has many uses:

Bags inside cereal boxes
Crystal clear plastic bags used for retail and presentation (BOPP)
Woven rice sacks and animal feed sacks
Plastic shopping bags with a woven appearance
Food containers e.g yoghurt containers – tubs for dairy products sealed with aluminum foil (both heat-resistant materials) lids can be LDPE or polystyrene
Plastic straws (before they were banned – UK)
Bottle caps (including of PET bottles)
Most plastic living hinges, such as those on flip-top bottles
Syrup bottles
Tupperware
Buckets
Some car parts
Plastic chairs
Ropes, distinctive because they are light enough to float in water
Light shades using sheets with interlocking sections
Kettles and appliances
VHS and DVD cases
Sports clothing
Disposable sanitary napkin linings

Recycling

As a packaging type, PP is increasingly collected from the home but there can be significant differences between areas and countries.

A lot of work is currently underway to increase the recycling of PP back into food grade plastic. The technology exists, but this does not currently take place at scale.

PP is commonly recycled into tubes, rigid packaging, containers, crates, disposable cutlery, pallets, hangers, and tubs.

Only about 1% of all polypropylene in the world is actually recycled.

Properties

It is tough and lightweight – stronger than PE
It is rigid and is a barrier to moisture
It keeps products dry and fresh
It does not mind heat – stable at temperatures up to 220 °F (104 °C) so is used with hot fill products
But provides poor impact resistance in cold temperatures
Excellent chemical resistance
Resistant to most solvents and glues
However, solid PP objects not subject to undue flexing can be satisfactorily joined with a two-part epoxy glue or using hot-glue guns
Can be joined by heat fusion
If you smash PP with a hammer, it will shatter

CONS:

Brittle below 0°C
High permeability to gases
Poor resistance to fuels
Poor UV resistance
Keeps burning (burns like candle wax)

How can I tell if something is made of PP? See CIWM/WasteAid guide

1. Look: Rigid PP is usually hard, opaque and coloured using pigments. Woven PP looks like cloth and is used for sacks and bags. Specially treated, PP becomes crystal clear and is used in packaging and retail for presentation. It has a high melting point (160˚C). PP often has a 5 stamped on it.

2. Feel: Woven PP feels soft, like cloth. Rigid PP feels rugged. It cannot be scratched with a fingernail.

3. Float test: PP floats in water.

4. Flame test:

Blue, yellow tipped flame
PP shrinks quickly but burns slowly
Plastic drips
Has sweet odour

WARNING

PP itself (when not burning) is not dangerous to use, however additives can be dangerous. It’s not possible to see what kind of additives are used in products.