The ageing of organic protective coatings depends on environmental impacts and is associated with a variety of ichemical and physical processes. The results of former thermal ageing studies indicate that evaporation and polymer degradation are the decisive processes for changes in coating properties.
For the verification of these assumptions the impact of
‐ the thermal exposure temperature TL and
‐ the length of the exposure time tL
on properties of clear lacquer coatings was determined by further studies.
The gradation of TL was aimed at creating conditions where on the one hand only evaporation processes occur, while on the other hand evaporation and polymer degradation reactions occur in parallel. The objective was to find the time tL and the temperature TL at which degradation starts to prevail.
Der Zusammenhang zwischen der Abgabe niedermolekularer Stoffe aus Beschichtungen unter dem Einfluss erhöhter Temperatur und ihren Eigenschaften wurde ermittelt. Dazu wurden Beschichtungen unterschiedlicher Lösemittelbasis und Trocknungsmechanismen wärmegelagert und die Änderungen der Beschichtungseigenschaften sowie die Abgabe flüchtiger organischer Verbindungen in Zeitabhängigkeit durch Prüfungen und Analysen erfasst.
SUMMARY:The clastic behaviour of thc rubber phase in high impact polystyrene is strongly determined by its crosslinking density. which is therefore an important parameter regulating its toughncss. Thc rubber network is formed simultaneously with the homoand graft-polymerization of the styrene monomer in a solution of rubbcr in styrene by crosslinking reactions involving the double bonds and the allylic H-atoms in the rubber. Suspension polymerization of rubber solutions in styrene, initiated with peroxides, was thoroughly invcstigated using homo-and copolymcrs of butadicnc with various chcmical structures. The experimental results lead to the following conclusions: 1.2-units in butadiene-and isoprene polymers are the preferred crosslinking sites; 1.4-and 3.4-units arc also involved in crosslinking reactions, but their reaction rate is significantly lower than for the 1.2-units. In butadiene-styrene-copolymers the 1.2-units show about the samc rcactivity as in homopolymers, in isoprene polymers however the reactivity scems to be somewhat smaller. For all investigated types of rubber the crosslinking 67 D. J. Stein, G. Fahrbach und H. Adler reaction rate increases with increasing conversion of styrene. This is most striking in the conversion range above 98 %.This phenomenon can be explained by a copolymerization of the styrene monomer with the 1.2-units of the rubber backbone.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.