Accelerated weathering of pectin/poly(vinyl alcohol) blends studied by spectroscopic methods

Abstract

The blends of pectin (PEC) and poly(vinyl alcohol) (PVA) at different components ratios were prepared by mixing in water. Thin polymeric films of PEC/ PVA blends and pure polymers were obtained by casting method. All samples were then artificially aged using Suntest apparatus (Atlas) up to 780 h. The changes in chemical structure during sample ageing have been monitored by infrared and ultraviolet-visible absorption spectroscopies. The first stage of weathering (up to $ 300 h) was very slow and alteration of chemical structure was negligible in all samples. Prolonged ageing (>300 h) caused more significant degradation processes. FTIR spectra exhibited the highest changes in hydroxyl and carbonyl band ranges indicating the efficient photooxidation of macromolecules. The mechanisms of the observed processes have been discussed. It was found that PVA undergoes faster photoxidative degradation than pectin aged at the same conditions. The PEC/PVA blends exhibited the improved resistance to weathering comparing with both polymers aged individually. Mutual stabilization effect can be explained by intermolecular interactions between PEC and PVA confirmed by spectroscopic methods.

Rheological properties of pectin, poly(vinyl alcohol) and their blends in aqueous solutions

“…The deviations of log η a decrease with the increase of the temperature and with the increase of shear rate. Such behaviour suggests that PEC with PVA is poor or immiscible, which was also suggested in the previous works concerning these blends [11,12]. in the experiment carried out up and down [9].…”

“…The amount of methyl esterified groups in pectin, equal to 27.8%, was estimated by FTIR spectroscopy [12] as the ratio of integral intensity of band attributed to methyl esterified carboxylic groups (A 1739 ) and the sum of areas of ester and carboxyl bands (A1739+A1612).…”

“…The photoaging studies performed in laboratory conditions using weatherometer showed that PEC/PVA blends are more stable compared to both polymers aged individually. It was explained by intermolecular interactions between PEC and PVA, which was additionally confirmed by spectroscopic methods [12]. There is still lack of work describing the relationship between chemical structure/blend composition and processing properties in such biodegradable plastics.…”

“…Recently, the surface properties and resistance to weathering of PEC/PVA blends have been investigated [11,12]. It was found that their surface properties can be modified by air plasma and UV-irradiation during a very short time.…”

Natural weather ageing of starch/polyvinyl alcohol blend: effect of glycerol content

“…They reported that ageing causes an increase in the transparency and converts these blends to small fragments after 30 days. The accelerated weathering of the pectin/PVA blend was studied by exposing the samples for 780 h [18] . Changes in the hydroxyl and carbonyl peaks of the blends in the Fourier transfer infrared spectroscopy (FTIR) spectra indicate the photo-oxidation of the polymer chains.…”