Stabilization of recycled PE/PP mixed polyolefin

1, HDPE / PP plastic bottle

The recycled material composed of the HDPE bottle and the cap made of PP is a mixed polyolefin, but the ratio of HDPE and PP is uncertain. Compared with similar models of 100% HDPE, the inclusion of PP in HDPE has an effect on the processing properties, especially on the heat radiation resistance. The thermal stability of the mixture of phenolic antioxidants and phosphites is added. The improvement is very limited. The function of the stabilizer seems to be mainly due to the inhibition of a small amount of PP in the HDPE.

In this case, the stability of the mixed recycled material containing PP can be solved by adding a composite stabilizer containing an antioxidant (RS-3). The composite of antioxidants, phosphites and antioxidants is mainly to improve the thermal stability of the mixed recycled materials. The heat aging test proves that HDPE is quite stable only by adding a small amount of stabilizer, and PP is considered for long-term application only when a stabilizer is added and good stability is obtained.

The mixed material recovered from the PO bottle proved in the compounding and processing experiments that the test sample quickly deteriorated without adding sufficient stabilizer stability. However, simply adding 0.2% mixed RS-3 stabilizer will increase the aging life to 100d, which is about the same as the life of the raw materials. In particular, regardless of whether the material is extruded once or five times, this further demonstrates that the composite stabilizer prevents decomposition of the material, particularly during processing, which prevents degradation of the decomposed material.

As the proportion of PP in the PO mixed material increases, the heat stability stability gradually decreases. In addition, even if the content of PVC impurities is very low, it has a great influence on the performance of the material, and it is necessary to consider adding more stabilizers.

2, HDPE / LDPE plastic tube

A composite plastic tube consisting of LDPE (70%) and HDPE (30%) was selected and tested for performance.

If no stabilizer is added to it, the 110 °C heat aging stability test results are only 52d. If a composite stabilizer composed of a phenolic antioxidant (AO-18), a phosphite (PS-2) and a polymer HAS (HAS-3) is added, the heat aging stability at 110 ° C can be improved to 97 d. If a composite stabilizer containing an antioxidant (RS-2) is added, the aging resistance is further improved to 116d.

3, HDPE / LDPE / PP plastic board

In addition to considering the effects of impurities and different types of materials on the properties of recycled materials, the effect of the formulation of the materials on the properties of the recycled materials is also considered. For example, carbon black is commonly used to homogenize different pigments or to improve the photostability of materials, but carbon black also has an adverse effect on the thermal stability of the material, especially for the recycled mixed polyolefin. Therefore, if carbon black is used to recover materials, consideration must be given to improving the thermal stability of the material to eliminate the effects on other mechanical properties.

Adjusting stabilizer formulations for recycled materials, including polymer HAS stabilizers in complexes such as RS-3 and HA-3 complexes, RS-3 and HAS-2/HA-3 (1:1) complexes Or RS-1 can greatly improve the thermal stability of materials. Even after the carbon black content in the material is high, the tensile impact strength is exhibited after the oven aging test. The material without the stabilizer treatment completely disappears in a short period of time (serious failure), while the melt fluidity is reduced to zero due to complete crosslinking.

Increasing the amount of carbon black added to the material, the mechanical properties after the artificial aging test still maintain a fairly high level, compared with the influence of carbon black on the thermal aging properties of the material, the mechanical properties of the material are lost slowly, but continuously decreasing of.

The carbon black and light stabilizer composite can further extend the service life of the material, can reach 8000h and the mechanical properties are not lost. Moreover, light and heat stabilizers combine a small amount of carbon black as a pigment, which is superior to most materials that only add carbon black.