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An important functional property of paper products which affects evaluation and quality of the products, is their resistance to ageing. The article deals with the tests of the impact of selected fibrous pulps on paper ageing. Results of the strength tests of four pulps subjected to artificial accelerated ageing were described. Slight changes of the examined parameters were found in the comparison before and after agening. The greatest decrease was found in the dynamic strength property: tearing resistance.
The effect of air humidity on the mechanical properties of selected paper products. Paper products belong to the materials that can strongly sorb water from both liquid and gas phase. Chemical properties of cellulose and a structure of cellulose fibres cause that the amount of absorbed water affects significantly paper utility. From the point of view of both producers and consumers it is very important to know this effect, because despite proper production technology such quality changes may occur as a result of improper conditioning, storage or transport of paper products that will disqualify them. Investigations of the effect of ambient air humidity on changes of the equilibrium water content in selected types of paper and resulting changes of basic mechanical properties are presented in this study.
Taking into account economic and environmental aspects, it can be assumed that the majority of packagings will be made of paper products in the future. Packaging paper grades require good strength properties. This can be obtained by paper production from primary material, to be precise from unbleached kraft pulp, most often based on softwood. To provide desired strength level to sack paper, some chemicals were used. Tests proved that addition of chemical agents in the production of sack paper brings satisfactory results enhancing its strength properties in this way. Synthetic agents showed better effectiveness then natural agents.
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