Clamshell Blog

Photodegradation refers to sunlight, the light absorption of UV radiation degradable plastics induced by light after the role, so that keys can be weakened, long-chain split into fragments of lower molecular weight polymer damage the integrity of the physical performance. Low molecular weight fragments in the air, further oxidation occurs, resulting in free radical chain scission reaction, can be degraded into low molecular weight compounds of biological decomposition of the final was completely oxidized to C02 and H20. Throughout the degradation process is initiated by photo-degradation and oxidation of free radical chain-breaking combination of Norrish reaction.

Photo-degradation factors

Impact plastic optical degradation of the main factors include:

1. Plastic molecular structure. Light degradable plastics is the photodegradation of the molecular structure of the main factors.

2. Photosensitizer. Add a photosensitizer can promote the photodegradation. Photosensitizer that can be sustained at the initial stage of its photochemical reaction. The induction period, was light-induced excited-state energy can be transferred to the polymer (plastic), to accelerate its photochemical reaction, so that the degradation and oxidation of plastics. Commonly used photosensitizer with acetylacetone metal compounds, dithiocarbamate metal compounds, ferrocene, stearic acid salts and fatty salt.

3. Optical wavelength. According to quantum theory of light, the shorter the wavelength, the light quantum has the energy of the larger, in the range of 290μm ~ 400μm by UV light energy is generally higher than with the plastic polymer chain caused by a variety of energy needed to break chemical bonds. However, a variety of polymer structure on the sensitivity of different wavelength. If the wavelength is not absorbed by a polymer sensitive to the wavelength, its photodegradation very small. Therefore, the UV wavelengths to be sensitive to fracture and plastic polymer to match the wavelength.

4. Atmospheric conditions. The atmosphere of oxygen, heat and humidity will accelerate photodegradation. If the increase of temperature, thermal motion of polymer increased, increased number of collisions between molecules are conducive to contact with oxygen photo-oxidation.