Plastic greenhouse film is an important construction material in agricultural production. Since the plastic greenhouse directly contacts the natural light source, the problems of thermal oxidation aging and photoaging need to be considered. Therefore, the plastic used in the greenhouse film needs to be added with anti-aging additives to improve its resistance to light and oxygen. stability. This article will introduce the readers to the selection of anti-aging system of PE greenhouse film.
The mechanical strength of PE greenhouse film is relatively high. Generally, LDPE resin with a melt flow rate of less than 1g/10min, or a blend of LDPE and 25%~50% LLDPE is selected. Due to the high degree of branching of the LDPE molecular chain, the molecules are easily photo-oxidative aging. In addition, the use environment of the greenhouse film is relatively harsh, and it is exposed to the sun for a long time. Therefore, its anti-aging system should mainly focus on the stability of light and oxygen.
For light stabilizers, UV-531, UV-327, UV-326, HALS, BAD and salicylates are commonly used in PE. In the anti-aging formula of PE greenhouse film, HALS light stabilizers are usually better than UV absorbers and UV quenchers, and HALS light stabilizers can also avoid the use of UV quenchers containing heavy metal ions. adverse effects. Therefore, the HALS-based light-stabilizing system is mainly used in the formulation. Usually, the polymeric hindered amine light stabilizer BW-10LD is mostly used. It has excellent light and thermal stability, and has good water extraction resistance, which is more targeted.
Antioxidants commonly used in PE mainly include antioxidant CA, antioxidant 1010, antioxidant 168, antioxidant 1076, etc.
The combination system of Antioxidant 1010/Antioxidant 168 or Antioxidant 1076/Antioxidant 168 has a good synergistic effect and is a highly efficient antioxidant system commonly used in polyolefin plastics.
For example, when a company uses the blend of LDPE and LLDPE to produce greenhouse film, its anti-aging system uses antioxidant 1076, antioxidant 168, GW-480, UV-531, and the dosage is 0.2 parts. After the greenhouse film is covered by a greenhouse for 10 months, the retention rate of the longitudinal and transverse tensile strength of the film is over 70%, and the retention rate of the elongation at break is over 80%.
