Different methods of polypropylene recycled particles

Different methods of polypropylene recycled particles

The difference between recycled PP and new material PP is the comparison of particle appearance and physical properties.

The easiest way to distinguish from appearance is to distinguish by color. The new material PP is transparent milky white, most of the recycled PP is dark silver or gray. The reason is that the recycled PP is produced by crushing, washing, drying, and compressing PP SCRAP of various colors, so it will not produce transparent milky white . [1]

Secondly, the appearance of the new material PP is round, and there are no bubbles or no bubbles in the particles. Recycled PP has a rectangular cross-section with right-angled particles and bubbles inside.

The reason is the difference in the production methods of recycled PP and new PP. The new material PP is made in accordance with the Under Water Cutting method in which the compressed PP is taken out of the water and directly cut (Cutting) in mass production. Recycled PP is produced by cutting compressed PP in water after cooling. As the new material PP is cut in water before cooling and then cooled, the particles aggregate together to form a round shape, while the recycled PP is cut into a rectangular shape after cooling. In addition, during the production of recycled PP, when it is cooled in water, scrap contains a lot of water when it melts in the compressor, so the particles will have many bubbles. When the new material pp cools in the water, the particles shrink and generate bubbles, but at this time, the bubbles generate uniform shapes inside the particles, and there are many cases that are invisible to the naked eye.

When the difference in appearance is difficult, the physical properties will be different.

The density of new material PP is 0.90 (g/cm3) uniform, and the recycled PP is composed of scrap so the density will exceed 0.90 (g/cm3).

There is a difference in bending strength. The bending strength of new material PP is about 1,600 ~ 1,700 Mpa, while recycled PP is lower than it. (Same product 980 ~ 1,050 MPa)

The taste of the particles is different. Recycled PP has peculiar smell in many cases, while new material PP is almost odorless or faint candle smell.

And if the particles are burned, the new PP will have smoke and the smell of candle burning will completely burn, and the recycled PP will have smoke or residue after burning.