Paper packaging materials: resistance to destructive factors

Abstract

Background. The dynamics of change of the complex of barrier and strength properties of moisture-resistant waterproof and moisture-resistant grease-proof paper packaging materials under the influence of temperature, humidity and mechanical factors is considered. The results of tests of the developed samples of paper packaging materials during exposure in the chamber of heat and moisture aging are given.
Materials and methods. Paper packaging materials of grades B-55 and ZhV-55 were obtained by surface treatment with compositions using polyamide­amine­pichlorohydrin, polyvinyl alcohol, urea and glycerin. To test for heat resis­tance and moisture resistance, the PPM samples were placed in a temperature-humidity aging chamber and kept for 900 days at a given temperature (–18, –1, +6, +18, + 25 °C) and relative humidity (45, 65, 85 %), periodically (every 180 days) determining the change in their mechanical strength and barrier properties. The resis­tance of barrier properties to the effects of repetitive mechanical loads was determined by measuring the corresponding index at the site of multiple double bends.
Results. During 360 days of exposure, the test samples practically do not lose resistance to the penetration of water (B-55) and fat (ZhV-55). After this exposure period, there is an intensification of degradation processes, which is more pronounced at temperatures below 0 °C. The maximum decrease (32 %) of fat permeability was recorded at a temperature of –18 °C after 900 days of ex­posure, while at temperatures above 0 °C, at this exposure, it is not more than 4 %. The strength of the packaging paper at temperatures of –1 °C and –18 °C during the test period in waterproof materials decreased by 6 % and 12 %, and in grea­seproof – 19 % and 29 %, respectively. The higher loss of strength of fat-impermeable PPM is due to the nature of the main component of the hydro­oleophobic composition – PVA, which has a higher brittleness temperature com­pared to PAAEX in the hydrophobic composition.
After 150 cycles of alternating freezing and defrosting of the samples, the destructive force of the greaseproof material ZhV-55 is reduced to 57.5 N, and the waterproof B-55 – to 63 N. The destructive force for 30 repeated cycles of tem­perature change is 70.9 N and 67.3 N, in comparison with the initial values of 72.4 and 71.8 N for waterproof (B-55) and greaseproof (ZhV-55) wrapping paper, respectively.
With 50 repeated double bends, which is close to the real conditions of use of packaging paper for its intended purpose, the water permeability of the sample B-55 is reduced by 8 %, and the fat permeability of the sample ZhV-55 – by 3 %.
Conclusion. The established dependences allow us to state that the main factors determining the barrier and strength properties of the developed materials are: physicochemical nature of the main components of hydrophobic and hydro­oleophobic compositions, which determines the nature of their interaction with cellulose fiber; resistance of the structure of the material to the penetration of moisture and fat, as well as its ability to withstand various mechanical loads.