Interactions of HALS

Still other mechanisms have been postulated, e.g., the interaction of HALS with a,P,-unsaturated carbonyl compounds and the formation of charge-transfer complex between HALS and peroxy radicals. However, despite extensive publications in the field, a complete knowledge of the process occurring in polymer photooxidation in the presence of HALS is still not available. 

Goldstein S. Interaction of HALS and colorants. ANTEC 2007, conference proceedings. Society of Plastics Engineers 2007. 

As shown in Fig. 1.3, MIFs account not only for intramolecular effects, but also for intermolecular interactions, allowing macroscopic properhes to emerge. The interactions of a chemical with a solvent reveal such pharmacologically essen-hal properties as solubility (Chapters 10 and 11) and partihoning/lipophilicity (Chapters 12-16). The interactions between a large number of idenhcal molecules... 

Moreover, it was shown that the presence of Hal Hal interactions between the partially oxidized molecules also contribute to the electronic delocalization. Indeed, the presence of non-zero atomic coefficients on the halogen atoms in the HOMO of EDT-TTF-Br2 or EDT-TTF-I2 [66], together with the short Hal Hal contacts, leads to a sizeable increase of the band dispersion and stabilizes a rare (V structure through the side-by-side arrangement of the inversion-centred dyads connected by Hal- Hal interactions. Both 13 salts are semiconductors with room temperature conductivities around... 

The next step was therefore to study the interaction of TMP derivatives with peroxides and with the products arising from them during photooxidation. A direct hydroperoxide decomposing effect of the HALS derivatives studied was not observed. 

Since the reactions occur under oxygen saturation, the principal stabilizing steps are the interactions of the HALS derivatives with the alkoxy and peroxy radicals and with the hydroperoxides. 

Jljig electrophoretic results on the interaction of Zn, Cd and Pb with humic acid (HAL sample) in different dilutions of sea-... 

In many stabilizer formulations, different types of stabilizers are used. As processing stabilizer phenolic antioxidants and phosphites are applied, for long-term heat stability phenolic antioxidants and thioethers are used and for UV stability, combinations of HALS with other types of UV stabilizers can be applied. HALS stabilizers show interactions with these types of stabilizers that can lead to synergisms as well as antagonisms. 

Interactions Between HALS and Acids Stabilized polymers can be exposed to acids from pollution or from degradation products of halogen containing compounds. Due to their chemical structure HALS can be basic (see Table 17.2) and form ammonium salts with acids. 

E.N. Step, J. Turro, M.E. Gande, andP.P. Klemchuck, Mechanism of polymer stabilization by hindered-amine light stabilizers (HALS). Model investigations of the interaction of peroxy radicals with HALS amines and amino ethers, Macromolecules 1994, 27, 2529-2539. 

N.S. Allen, A. Hamid, F.L. Loffelman, P. Macdonald, M. Rauhut, and P.V. Sushi, Interactions of antioxidants with HALS in the thermal and photochemical oxidation of PP film, Plast. Rubber Process. Appl. 1985, 5, 259-265. 

The cross-linkages found in collagen and elastin arise from the non-enzymatic interaction of a-amino adipic acid 8-semialdehyde (AL) and 8-hydroxy a-amino adipic acid 8-semialdehyde (HAL) with another residue of the aldehyde or with lysine, hydroxylysine, or histidine residues located at specific positions in the collagen polypeptide chains. Possible relationships among the different compounds in Table II are shown in Figures 4 and 5 for collagen and elastin. 

---