Лако-красочные материалы — производство

SBS block copolymers degrade primarily via cross-linking. The thermal stability of SBS copolymers can be improved with the addition of a more effective stabilizer system. Figures 7 and 8 show gel formation and discoloration of a SBS copolymer stabilized Figure 5 Discoloration of SIS polymer: yellowness index, days at 80°C (176°F). Figure 6 Viscosity stabilization […]

A. Stabilization of Polymers (Elastomers) Typically, the polymers used in adhesive formulations have only a minimal level of stabilization to endure isolation/coagulation, drying/finishing, and warehouse storage. As an adhesive producer, it is most desirable to understand the level of performance of a stabilized polymer and determine whether additional stabilization is needed to provide the necessary […]

There are two major classes of antioxidants and they are differentiated based on their mechanism of inhibition of polymer oxidation: chain-terminating or primary antioxidants and hydroperoxide-decomposing secondary antioxidants [5]. Primary or free-radical scavenging antioxidants inhibit oxidation via very rapid chain-terminating reactions. The majority of primary antioxidants are hindered phenols or secondary aryl amines. Generally, hindered […]

The basic scheme for the autooxidation of polymers is detailed in Table 1 [2]. The scheme can be broken down into several distinct reactions: initiation, propagation, and termina­tion. The first step in the oxidation mechanism, initiation, occurs when a polymeric free radical (R*) is formed by exposure to heat, light, shear, or impurities. The propagation […]

Neal J. Earhart and Ambu Patel CIBA-GEIGY Corporation, Ardsley, New York, U. S.A. Gerrit Knobloch CIBA-GEIGY Corporation, Basel, Switzerland I. INTRODUCTION Adhesives are, in general, produced by the compounding of several different components: polymers, tackifier resins, and waxes or oils. The hydrocarbon-based components are susceptible to thermal oxidation and degradation [1]. Many adhesives are exposed […]

In the preceding discussion we dealt with BTZs and HALSs as classes of light stabilizer without much attention to structure variations within each class. As demonstrated by the numerous chapters of this book, many polymers are used for adhesive applications. Each of these materials may have unique photostability concerns. It is beyond the scope of […]

With the considerations noted above, we can now look at the performance of UV stabilizers in several illustrative examples. Table 1 shows the effectiveness of BTZ-2 and HALS-1 at preventing the degradation of a natural rubber/hydrocarbon tackifier water — based adhesive when exposed to UV light. Natural rubber undergoes chain scission upon oxidation, resulting in […]

The photostability of most hydrocarbon polymers is generally not a function of their tendency to absorb light but rather of their propensity toward oxidation (free-radical formation). Although it is well known that the inherent UV stability of an unsaturated polymer is inferior to that of a saturated analog, this effect cannot be attributed to an […]

While the most meaningful exposure testing of polymers is done under actual exposure to sunlight, accelerated aging devices are used routinely to provide predictive and reprodu­cible data in a reasonable amount of time [10,11]. The UV output of several commercial weathering devices is shown in Fig. 7. While many of these instruments are equipped to […]

As alluded to above, a second class of light stabilizers, the hindered amine light stabilizers (HALSs), provide additional stability to polymers and can function even in thin film or in sample surfaces. The chemistry of HALSs is based on the 2,2,6,6-tetramethylpiperidine derivatives (Fig. 5). Unlike UVAs, HALSs have no significant UV absorption and Figure 4 […]