A sulfonated and nitrated polyether ether ketone/polyvinyl chloride modified atmosphere packaging delays the deterioration of grapes.

BACKGROUND

Polyether ether ketone (PEEK) was modified by a sulfuric and nitric acid mixed system to improve the solubility of the material and the gas selective permeability of the film. SN1 and SN5, synthesized from mixed acid systems (with ratios of nitric acid and sulfuric acid of 1:1 and 1:5, respectively) were chosen because they had comparable nitro groups but differing sulfonyl groups. To investigate the impact of the type and content of sulfonated and nitrated polyether ether ketone (SNPEEK) on the structure and physicochemical properties of the films, SN1/polyvinyl chloride (PVC) and SN5/polyvinyl chloride films were made by adding varying amounts of SN1 and SN5 (0.5%, 1.0%, 1.5%, 2.0% and 2.5 wt%), respectively.

RESULTS

SNPEEK (with ratios of nitric acid and sulfuric acid of 1:1-9) with high nitric acid group concentration outperformed nitrated polyether ether ketone (NPEEK) (with ratios of nitric acid and sulfuric acid of 3-9:1) with a low nitric acid concentration in terms of solubility at room temperature and expanded the application range. The inclusion of SNPEEK resulted in more micropores on the membrane microstructure, and higher contents of -SO3H and -NO2 groups enhanced the polarity, which improved permeability and selectivity for CO2 and O2 and the moisture permeability of the membranes. During grape storage (4 ± 1 °C), 1.0% SN1/PVC and 1.0% SN5/PVC membranes reached equilibrium gas concentration on day 4 (4.6-5.4% CO2, 17.6-18.1% O2; 3.5-4.1% CO2 and 18.6-19.1% O2), grapes showed lower electrolyte leakage as well as higher hardness, total soluble solid content and vitamin C content.

CONCLUSION

Because there are few studies on modified PEEK air conditioning packaging for grape preservation, SNPEEK/PVC membrane has practical value. In the present study, 1.0% SN1/PVC and 1.0% SN5/PVC membranes extended the shelf life by more than 16 and 8 days, respectively, compared to the blank group (unsealed packaging). © 2025 Society of Chemical Industry.