Studies of photooxidative degradation of poly(vinyl chloride)/poly(ethylene oxide) blends

Abstract

The photooxidative degradation of blends (in a full range of compositions) of amorphous poly(vinyl chloride) (PVC) with semicrystalline poly(ethylene oxide) (PEO) in the form of thin films is investigated using absorption spectroscopy (UVvisible and Fourier transform infrared) and atomic force microscopy (AFM). The amount of insoluble gel formed as a result of photocrosslinking is estimated gravimetrically. It is found that the PVC/PEO blendsí susceptibility to photooxidative degradation differs from that pure of the components and depends on the blend composition and morphology. Photoreactions such as degradation and oxidation are accelerated whereas dehydrochlorination is retarded in blends. The photocrosslinking efficiency in PVC/ PEO blends is higher than in PVC; moreover, PEO is also involved in this process. AFM images showing the lamellar structure of semicrystalline PEO in the blend lead to the conclusion that the presence of PVC does not disturb the crystallization process of PEO. The changes induced by UV irradiation allow the observation of more of the distinct PEO crystallites. This is probably caused by recrystallization of short, more mobile chains in degraded PEO or by partial removal of the less stable amorphous phase from the film surface. These results confirm previous information on the miscibility of PVC with PEO. The mechanism of the interactions between the components and the blend photodegradation are discussed.

Estudo do efeito do tipo de polipropileno na fotodegradação da blenda polipropileno/poliestireno de alto impacto

“…Alguns tipos de polímeros, como o polietileno, polipropileno, poliestireno e poli(tereftalato de etileno), foram extensivamente estudados ao longo dos anos, e os mecanismos de fotodegradação e fotoestabilização, bem como os fatores que controlam a cinética do processo e mudanças nas propriedades do produto estão razoavelmente bem estabelecidos [7][8][9][10][11][12][13][14] . Enquanto isso, no caso de blendas poliméricas, poucos estudos na área de fotodegradação podem ser encontrados na literatura [15][16][17][18] . Polipropileno (PP) e o poliestireno de alto impacto (HIPS) são usados em larga variedade de produtos.…”

Miscibility of Poly(Vinyl Chloride) with Poly(Ethylene Oxide) of Different Molecular Weights

“…The miscibility of the PVC/PEO blend was explained as a result of donor-acceptor interactions between the chlorine atoms of PVC, as a weak acceptor species, and oxygen atoms of the PEO, as a donor species. Kaczmarek et al 19 had a similar conclusion with the exception that interactions are possible because PEO is a proton-accepting agent (due to the ether atom in each unit) and PVC is a proton-donating polymer (because of α-hydrogen atoms). On the other hand, by differential scanning calorimetry and viscosimetric analyses, Ramesh et al 2 showed that the PVC/PEO blends are fully miscible.…”

“…7 Miscibility, mechanical, optical, morphological, and thermal properties of PVC/PEO blends have already been studied in the literature. [2][3][4][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] However, data on the miscibility of PVC and PEO are contradictory. Margaritis and Kalfoglou 10 found that PVC and PEO were miscible for PVC-rich blends according to results obtained by dynamic mechanical analysis, differential scanning calorimetry, and optical microscopy.…”

“…PVC/PEO blends were usually prepared by solution casting. 2,4,8,11,13,14,18,19,21 Because the polymer miscibility is often due to strong intermolecular interactions like hydrogen bonding, studies of miscibility carried out in solution may produce a system, which would be much closer to equilibrium in comparison to the system obtained by other techniques, e.g. extrusion.…”

Surface properties of ionomers based on styrene-b-acrylic acid copolymers obtained by copolymerization in emulsion

“…In the presence of oxygen UV-irradiation causes photooxidation of polymeric films [22][23][24]. Chain scission and cleavage of chemical bonds lead to the formation of free radicals, which can react with oxygen from air and produce peroxide radicals and then they can react with polymer.…”