@petebedggood4
Profil
Registered: pred 1 year, 10 months
How Does UV absorber Work?
The primary function of UV absorbers is to absorb UV radiation within the presence of a chromophore (Ch) found within the polymer, the purpose is to filter out the UV light that is dangerous to the polymer earlier than chromophore free radical Ch* has had an opportunity of forming. Above all, a UV absorber should function within the 290 and 350 nm range. The effectiveness of UV absorbers is set not only by their absorption characteristics but also, above all, by the Lambert-Beer Law.
Extinction will depend on wavelength and may be thought to be a measure of the stabilizing or screening effect of the UV absorber. In other words, the higher the extinction, the higher the UV light screening and the higher the stabilizing impact – always assuming that the UV absorber is just not itself destroyed by the absorption of the light. Extinction thus is determined by the extinction coefficient, the concentration, "c", of the UV absorber within the polymer, and on the film thickness, "d", of the unpigmented polymers.
For a UV absorber to be efficient, it must soak up UV light higher and faster than the polymer it is supposed to stabilize and dissipate the absorbed energy earlier than unwelcome side reactions are triggered. This signifies that transformation of the energy absorbed within the form of UV light must take place in the singlet state. Inter-system crossing (transition S1 to T1) and therefore phosphorescence must be excluded.
Normal Guidelines to Observe When Choosing Antioxidant and UV Stabilizers
1. Stability & Extraction
Uv Stabilizers and antioxidant hydrolysis resistance are ok,it are the color stability needs to pay attention. Also, there additives shall not react with different ingredients within the system, neither corrosion equipment nor extract by the substance on the article surface.
Hindered amine light stabilizer normally shows low alkalinity, no acidic additives shall be used collectively, and ultimate article shall not apply in an acidic environment.
2. Solubility & Compatibility
Most polymers are non-polar while antioxidant, UV stabilizer are considerably polar. Solubility is a matter must concern. Antioxidant and UV stabilizers shall dissolve while not decompose in polymers processing temperature which most UV stabilizer may meet this requirement.
3. Migration
When possible, high molecule weight and comparatively high melting level antioxidants and UVA shall be selected, every dosage shall decide based on most stringent processing and finish-consumer environment.
4. Processing
When antioxidant and UV stabilizer melting range quite differ from resins’. Bias current or stick to screwing may occur. When this gap exceeds one hundred, UV stabilizer and antioxidant shall add in masterbatch form then combine with resin to process.
5. Dealing with and Safety
Antioxidant and UV stabilizer shall non or low toxic. No or low dust. Not dangerous to human during plastic process and lifetime. Not harmful to animal or plates. No pollution to air,earth and water.
For agriculture file, food packing, toys, disposable infusion set or direct food, drug, medical system, medical devices, human contact plastics. Only FDA or EU approval antioxidant and UV stabilizer observe most concentration is allowed.
Website: https://www.innospk.com/en/?list/24_3
Diskusné Fóra
Počet vytvorených tém: 0
Počet reakcií: 0
Rola: Účastník (Participant)