A B S TRA C T:Poly(vinylch1oride) (PVC)was mixed with various poly(methacry1ate)s. poly(carb0nate)s and polymers containing nitrile groups (poly(acrylonitrile), poly(styreneco-acrylonit r i l e ) , nitrile rubber, hydrogenated nitrile rubber) a n d / o r C -C double bonds ( n i t r i l e rubber, high-impact poly(styrene)). The thermal stability was measured a t 180 OC in nitrogen, and the evolved HC1 was d e t e c t e d by conductometry.I t is shown that t h e n a t u r e of the e s t e r group and the content of nitrile groups and C-C double bonds a r e t h e dominating f a c t o r s for the thermal stability of poly(vinylchloride) in these blends. An influence of t h e miscibility of PVC with the various blend components on t h e t h e r m a l stability can not b e c l e a r l y detected.Differential scanning calorimetry (DSC) was used a s a powerful method to study the stabilizer distribution of heterogeneous PVC/poly(styrene-co-acrylonitrile) and PVC/poly(methylacrylate) blends. It is shown that the stabilizer can be solubilized either in t h e PVC phase (PVC/poly(methylacrylate)) or in both phases of t h e blends PVC/poly(styrene-co-acrylonitrile)).

The thermal degradation of poly(viny1 chloride) (PVC) has been studied by differential scanning calorimetry (DSC). Due to crosslinking, the glass transition temperature (Tg) of PVC raises during the degradation. The thermal degradation of PVC has also been studied for heterogeneous 1: 1 (w/w) blends of PVC with polystyrene (PS), poly(styrene-co-acrylonitrile) (SAN), high-impact PS (poly(styrene-g-butadiene)) (HIPS) and poly(SAN-g-butadiene) (ABS). Tg of the PVC phase raises slower during degradation in the PVC/PS-blend, whereas in the other blends the crosslinking is accelerated, due to a negative influence of the double bonds and/or the nitrile groups on the thermal stability of PVC. Since most methods use the determination of eliminated HCI to study the degradation of PVC, the DSC method is very useful in investigations on PVC-containing polymer blends, if there might be a reaction of HCI with one of the blend components. ZUSAMMENFASSUNG:Der thermische Abbau von PVC wurde mittels DSC untersucht. Durch die Vernetzung des PVC steigt die Glastemperatur mit zunehmender Abbaudauer an. Abbauversuche wurden auch an mehrphasigen 1 : 1-Mischungen (w/w) von PVC mit PS, HIPS, SAN und ABS durchgefiihrt. Wahrend der Abbau von PVC/PS-Mischungen einen langsameren Abstieg der Glastemperatur des PVC zur Folge hat, steigt sie bei den anderen Mischungen starker an als beim reinen PVC. Dies bestatigt den negativen EinfluB von Doppelbindungen und/oder Nitrilgruppen auf die thermische Stabilitat des PVC. Wahrend die Mehrzahl der Methoden zur Untersuchung der Dehydrochlorierung auf der Detektion des abgespaltenen HCI beruht, eignet sich die DSC-Methode insbesondere zur Untersuchung des thermischen Abbaus von PVC in Mischungen, bei denen mit einer Reaktion des Mischungspartners mit dem entstehenden HC1 gerechnet werden mu& 0

The distribution of a liquid organotin stabilizer between the phases of heterogeneous poly(viny1 chloride) (PVC) blends has been studied by differential scanning calorimetry (DSC). This method can be used even at low stabilizer concentrations. At concentrations > 1 wt.4'0 the stabilizer can be detected in both phases of a PVCISAN (poly(viny1 chloride)/poly(styrene-co-acrylonitrile)) blend. At lower concentrations no stabilizer could be found in the SAN phase. Determination of the induction period of thermal degradation at 180°C under nitrogen atmosphere showed no loss of thermal stability for blends containing the stabilizer partly in the SAN phase. Kinetic measurements with the DSC indicate a migration of the stabilizer out of the SAN phase. PVC/PMA (poly(viny1 chloride)/poly(methyl acrylate)) blends showed no solubility of the stabilizer in the soft PMA phase. ZUSAMMENFASSUNG:Es wurde die Verteilung eines flussigen Organozinnstabilisators zwischen den Phasen zweiphasiger Blends aus PVC/SAN sowie PVC/PMA mittels DSC untersucht. Die angewandte Methode erwies sich als geeignet, die Verteilung auch in niedrigen Konzentrationsbereichen zu messen. In PVC/SAN-Blends befindet sich der Stabilisator bei Konzentrationen > 1 Gew.-qo in beiden Phasen, bei niedrigeren Konzentrationen nur im PVC. Messungen der Induktionszeiten des thermischen Abbaus bei 180 "C unter Stickstoff zeigen keine Verschlechterung der stabilisierenden Eigenschaften fur die Blends, bei denen ein Teil des Stabilisators in der SAN-Phase vorlag. Kinetische Messungen mit der DSC-Methode sprechen fur eine Migration des Stabilisators aus dem SAN. In PVC/PMA-Blends wurde dagegen eine vollstandige Unlaslichkeit des Stabilisators in der weichen Polyacrylatphase nachgewiesen.

The photooxygenation of the 1,4‐disubstituted 2,3‐dimethyl‐2‐butenes 1–4 [1,4‐dichloro, ‐dibromo, ‐dimethoxy, and ‐bis(trimethylsilyl), respectively afforded the corresponding allylic hydroperoxides 1a–4a via regioselective ene reaction exclusively of the methyl hydrogens. The dichloro derivative 1 gave on photooxygenation in the presence of titanium tetraisopropoxide the desired epoxy alcohol 1b in fair yield (42%), along with the allylic alcohol 1c. The epoxy‐hydroxylation of the dibromo derivative 2 turned out to be problematic. Photooxygenation in the presence of Ti(OiPr)4 („one‐pot”︁ procedure) led to a complex product mixture, from which the allylic alcohol 2c, the dioxolane 2d, and the rearranged epoxy alcohol 5b were isolated. The structure of the latter was rigorously confirmed by an X‐ray analysis. Separate treatment of the allylic hydroperoxide 2a with Ti(OiPr)4 gave a similar complex product mixture.