Degradation and stabilization of PVC in blends

Abstract

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)).

Principles of Thermal Degradation

“…333 Authors, following studies on PVC/NBR blends, suggest that increased degradation rate is caused by formation of CN...HCl complex which accelerates dehydrochlorination. 278 The dehydrochlorination rate increases more for blend with SAN 28 (28% acrylonitrile) than for blend with SAN 19 (19% acrylonitrile). 278 The dehydrochlorination rate increases more for blend with SAN 28 (28% acrylonitrile) than for blend with SAN 19 (19% acrylonitrile).…”

“…47,274 Its equimolar blend with PVC gives plasticizer-free low-fogging film which can be used in tarpaulins, roofing sheets, and pond liners. It is regarded as miscible, 275 miscible in a narrow range of vinyl acetate content (65-70%), 274 and its miscibility increases with CO content increasing in EVA-CO. 278 There is an agreement regarding thermal stabilities of polymers and blends but details depend on chemical composition. It is regarded as miscible, 275 miscible in a narrow range of vinyl acetate content (65-70%), 274 and its miscibility increases with CO content increasing in EVA-CO. 278 There is an agreement regarding thermal stabilities of polymers and blends but details depend on chemical composition.…”

“…PVC forms a miscible blend with NBR as evidenced from a single glass transition temperature, which is intermediate between that of the pure components. 278 UV degradation is prevented by coating products with PVC/NBR blend with poly(vinyl alcohol) containing nanoparticles of titanium dioxide. It is usually explained by interaction between unsaturated bonds and HCl.…”

“…If information on morphological features of both polymers is not available, it is thus difficult to assess why some blends are miscible or immiscible. 278,308,315,316 Figure 4.54 shows that the weight loss is proportional to PVC concentration. Reactive processed blends had single phase morphology and single glass transition temperature.…”

Analytical Methods

“…• degree of gelation and fusion, [69][70][71] • melting point of stearates and consequently effect on their properties, 72 • melting point determination of stabilizers, 73 • effect of plasticizer addition and loss on glass transition temperature, [74][75] • stabilizer distribution in polymer blend, 76 • decomposition and concentration of azodicarbonamide and performance of kickers, 77,78 • decomposition of epoxidized soybean oil, 79 • crystallinity of PVC, 80,81 • glass transition temperature of PVC, 82,83 • gauging the mechanically induced stress in PVC when oriented below glass transition temperature, 84 • cis/trans isomerization, 85 • activation energy of thermooxidative degradation, 86 • oxidative induction time. 87 …”