Methyl methacrylate-butadiene-styrene copolymers used as modifiers for improving the impact strength of poly(viny1 chloride) have been prepared by emulsion radical graft polymerization of styrene and methyl methacrylate on a butadiene-styrene elastomer. I t is shown that efficient MBS modifiers can be synthesized from mixtures of agglomerated and non-agglomerated elastomer latexes in various ratios. The MBS copolymers obtained via a two-stage graft polymerization improve the impact strength of PVC blends t o a considerable degree compared to modifiers prepared in one stage, with simultaneous retention of transparency.
Herstellung und Untersuchung von Methylniethac~lat-Butadien-Styren-Pfropfcopolymeren und ihrer Mischungen mit PoEy (vinylchlorid)Als Modifikatoren zur Verbesserung der Schlagzahigkeit von Poly(vinylch1orid) verwendete Methylmethacrylat-Butadien-Styren-Copolymere wurden durch radikalische Emulsions-Pfropfcopolymerisation von Styren und Methylmet bacrylat auf einen Butadien-Styren-Kautschuk synthetisiert. Es wird gezeigt, da13 wirksame MBS-Modifikatoren aus unterschiedlichen Mischungen von agglomerierten und nichtagglomerierten Kautschuk-Latices hergestellt werden konnen. Die durch eine zweistufige Pfropfcopolymerisation erhaltenen MBS-Copolymere verbessern die Schlagzahigkeil von PVC-Mischungen im Vergleich zu im Einstufenvrrfahrcn liergcstellten Modofikaioren in deutlichem AusmaB, wollei die Transparenz der Proben erhalten bleibt.
ITo.ayuenue u uccJceaosanue npusumbrx m e m u n w e m a~p u u~~a m -6 y m a~u e~t -c m~p 0~~n b i x conomuepos u ux cmeceiic now us unmxaop uaom Me'roAoM 3MynbCAOHIIOfi PaAAKaJIbHOfi IIpPIBATOfi I I o J I W M e p~3 a q~1 1 CTApOJIa W MeTAJIMeTaKpAJIaTa C 6 y T a A M e H -CTWPOJIbHbIM aJIaCTOMepOM 6~~1 1 1 Ltd. (1975) 201. mol. Chemie 68/69 (1977) 95.Ltd.
Altered photosynthetic reactions in cucumber mosaic virus (CMV) inoculated leaves of virus resistant lines L113 and L57 and susceptible pepper (Capsicum annuum L.) plants cv. Albena grown in controlled environment and in the field were investigated. The CMV inoculated leaves of virus resistant lines developed different symptoms-necrotic local lesions on L113 and chlorotic spots on L57 while the same leaves of susceptible cv. Albena were symptomless. The changes in Photosystem II (PSII) and PSI electron transport were evaluated by chlorophyll fluorescence, and far-red (FR) light induced leaf absorbance A 810-860 . CMV infection caused a decrease in maximal PSII quantum yield, F v /F m , in susceptible leaves. Increased non-photochemical fluorescence quenching in CMV-inoculated leaves of both resistant lines were observed. In CMV-inoculated leaves of all tested plants FR light induced P700 oxidation was decreased. In the present study, the viral-infected pepper plants grown in controlled environment to avoid the effects of abiotic factors were used as model system that allow us to investigate the differences in leaf senescence in CMV-inoculated leaves of susceptible and resistant pepper lines expressing different symptoms. Earlier leaf falls of inoculated leaves as a result of accelerated leaf senescence is important for building successful secondary virus resistance strategy following fast responses such as hypersensitive reaction.
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