UN1500 BC Modification of Post Consumer Recycled PET Bottle

1. Experimental and Objectives

1.1. All PET materials used for compounding within this experiment is obtained from PET bottles collected in a waste treatment plant.

1.2. Place 8.0 g of PCR (post consumer recycled) PET materials into the heating chamber at 250 °C. After pre-heating for 60 seconds, the PCR PET materials were pressed with a force of 7060 gf. Every 60 seconds, a small portion of samples were removed for melting index analysis. Line graphics were prepared according to the change of melting index measured every 60 seconds. 

1.3. The objective of this investigation is to reveal the changing melting index of PCR PET with the heating time. Accordingly, the hot melt viscosity stability and material uniformity of the PCR PET bottle can be revealed (the uniformity and difference of the molecular weight).

2. Results and Discussion

2.1. Figure 1 shows the test result of PCR PET without any reagent addition with 10 replicates. The values of melting index were highly diverse among 10 replicates, reflecting the hot melting viscosity of PCR PET materials is very unstable, the uniformity of the material is very poor, and the molecular weight varies greatly. Thus, It means that the quality of PET materials recycled from waste treatment plants (garbage yard) is high diverse.

Figure. 1. The changes of melting index of post consumer recycled (PCR) PET materials obtained from PET bottles collected in a waste treatment plant with heating time.

2.2. Increasing addition of  Union 1500BC, the hot melting viscosity of the PCR PET materials has become much more consistent (Fig. 2). 

2.3. As the heating time increases, the melting index underwent a sudden increase frequently (so called “viscosity reduction”). In comparison, the test group added with 1500BC has a relative mild increase of the melting index with time. This suggests by adding Union 1500BC may largely minimise the extent of viscosity decrease (Fig. 2).

Figure. 2. The changes of melting index of post consumer recycled (PCR) PET materials after treatment with 0.2, 0.6 and 1.0% (w/w) of Union 1500BC additive with heating time.

3. Conclusion

Plastic materials whose viscosity does not change significantly with the increase in heating time are more conducive to processing. Accordingly, adding 1500BC may remarkably minimise the change of the viscosity of PCR PET materials, and improve the stability of PCR PET materials during further product processing.