Hydrolytic stability of unsaturated polyester networks with controlled chain ends

Investigation of Degradation of Composites Based on Unsaturated Polyester Resin and Vinyl Ester Resin

This study compares the degradation process of unsaturated polyester resin (UPR) and vinyl ester resin (VER) and their biocomposites with kraft lignin. In order to study their degradation, accelerated aging, immersion in different solvents, microwave radiation and high temperature were applied. The results show that, depending on the conditions, the degradation assumes a different course. The VER resin is more chemically resistant than the UPR resin. In the case of the composites immersed in an aggressive solvent (acetone), it can be observed that the polymer matrix is degraded, whereas in water only a small increase of weight takes place. Immersion in NaOH initiates the degradation process consisting in the hydrolysis of ester bonds, which are especially observed for pure resins. Under the influence of UV radiation and microwaves, the resins are additionally cross-linked. Thermogravimetric analysis shows that in the case of composites heated to 1000 °C, a residual mass remains, which is carbonized with lignin. In turn, composites treated with microwaves lost weight.

Effect of Eco-Friendly Peanut Shell Powder on the Chemical Resistance, Physical, Thermal, and Thermomechanical Properties of Unsaturated Polyester Resin Composites

The paper investigates the synthesis of eco-friendly composites and their properties before and after immersion in solvents of different chemical natures. For their preparation, unsaturated polyester resin (UPR) based on recycled poly (ethylene terephthalate) (PET) and peanut shell powder (PSP) were used. Polymerization was carried out in the presence of environmentally friendly polymeric cobalt. Distilled water, acetone, 10% hydrochloric acid, 40% sodium hydroxide, toluene, and 2% sodium carbonate were used as solvents in the chemical resistance test. Changes in the structure, properties, and appearance (morphology) of composites after 140 days of immersion in solvents were investigated. The results show that both the resin and its composites show resistance towards 10% HCl and toluene. The immersion in water has no significant effect on the resin, but for PSP composites, the plasticizing effect of water was observed. In acetone, after only one day, the resin and its composite with 10% PSP shrink and fall into pieces. However, the most destructive is an alkaline environment. After the immersion test, a huge increase in mass and a deterioration of gloss and thermomechanical properties were observed. The destructive influence of the 40% NaOH environment mainly concerned the resin.

Hydrolytic degradation of polyglyconate B: the relationship between degradation time, strength and molecular weight

Bioresorbable polymers have found a wide range of uses in medical implants, from sutures to scaffolds for tissue engineering applications. Increasingly they are being used in internal orthopaedic fixation devices, in which the strength retention profile is important. Polyglyconate B, a block co-polymer of glycolic acid and trimethylene carbonate, is one polymer used in these applications. In this study, the hydrolytic degradation of polyglyconate B has been studied in vitro. Specimens were prepared with two initial molecular weights and aged in PBS solution at 37 degrees C for up to 31 days. The polymers were characterised by gel permeation chromatography. for molecular weight, tensile testing and mass change, as a function of degradation time. A further aim of the work was to determine whether the measured changes in tensile strength over time could be fitted to a simple model. The results showed that the observed relationship between strength and molecular weight was more complex than that used in our model. However, the data could be modelled using an empirically derived relationship between tensile strength and number average molecular weight (Mn). Changes in other mechanical properties, such as strain at break, were also found to be strongly dependent on changes in the single parameter of Mn.