Chemistry Reference
In-Depth Information
White pigments, such as TiO
2
and ZnO [63] are used with the purpose of ultra-violet
rays absorption and for dulling of PA-fibres and films. Titanium oxide begins to reflect light
only at the wave-length more than 340 nm. However, TiO
2
action at irradiation of filled
polymers is not always identical it may behave as sensibilizer at photooxidation and this
requires additional stabilization [64]. For example, processing TiO
2
by small quantities of
aluminium, silicon and zinc decreases negative action of pigment.
Zinc oxide is one of more effective and economic white inorganic stabilizers, especially
for ultra-violet region from 240 to 380 nm [65], however, its use is limited because of
corrosion activity in respect of applied equipment for polymer processing.
Ultra-violet absorbers on the basis of derivatives of 2 - oxybenzophenol: specifically
Benzon OA, where R
1
=H and R
2
=C
7
H
15
-C
9
H
19
,
Benzon OM, where R=H and R
2
=CH
3
; 2 - oxyphenylbenzotriazoles:
specifically Benazole II (Tinuvine II) at
R
1
R
1
and R
2
=H; Benazole PXB (Tinuvine 326)
at R=H, R
1
=C, R
2
=C(CH
3
) and others; aryl ethers of benzoic, salicylic, tetraphthalic and
isophthalic acids [21, 66] are of interest. Mechanism of shielding effect of such stabilizers is
in absorption and transformation of short-wave light energy and also in suppression of triplet
and singlet excited states of polymers.
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