Cellulose
Fig. 1 Plants growing in the bio-degradable paper pots ( a ), laboratory manufactured prototype pots made of waste pulp with addition of cereal bran ( b ), commercially available pots made of pulp with addition of peat ( c )
• Breaking length (PN-ISO 1924-1 1998) on the Schopper apparatus. • Extensibility (PN-EN ISO 1924-2 2009) on the Schopper apparatus. • Tearing resistance (PN-EN ISO 1974:2012P 2012) on the Elmendorf apparatus. • Burst test (PN-EN ISO 2758 2005) on the Mullen’s apparatus. • Air permeability according to Gurley (PN-ISO 11004 1995) on the Gurley apparatus. • Rate of absorbency according to Cobb (PN-EN 20535 1996) on the Cobb apparatus. In addition, crushing strength was tested on paper pots on the Zwick/Roell Z005 (Zwick Roell AG, Ulm, Germany) mechanical testing machine in compression mode according to TAPPI T804 standard (2006). All the samples were conditioned to 7 ± 1% moisture content before characterization. It was impossible to perform all tests on some samples following degrada- tion due to excessive disintegration.
Coniferous forest soil is usually enriched with cones and needles, but is rather poor in nutrients. It was the most acid soil studied and had pH of * 3.5 to4.0. Agricultural soil, which consisted of highly decom- posed matter deeply mixed with mineral soil had pH of * 5.0 and carbon to nitrogen ratio of * 10. The laboratory experiment was conducted in plastic boxes containing soils. Experimental samples (paper sheets) were fully covered by the soil. Paper pots were placed in the containers to the depth corresponding to * of the pot height. All the samples were exposed to the soil for 2 months and the degradation progress was mon- itored at the 2nd, 4th and 8th week of the experiment. The moisture of the soil during the whole campaign was kept constant in the range of around 55%. The water capacity of the soil and the ambient temperature was continuously monitored during the tests in order to provide amount of water required to achieve an adequate level of humidity. Containers with samples after installation were kept in climatic chamber (20 C, 60% RH). Once a month small amount of water was added to the constant weight of the containers.
Polymerization degree
Evaluation of paper properties
The degree of cellulose polymerization (PD) for paper products was determined on samples before and after soil degradation. During the test, the intrinsic viscosity
The following tests were performed before degrada- tion in soil (according to corresponding standards) in order to characterize the produced paper sheets:
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