Mechanical and barrier properties of flexible packaging materials after the flexo printing process

In the flexo printing process, flexible food packaging materials are exposed to various effects (solvents, temperature, transport devices, etc.), that impact the quality of food packaging materials. Although, literature is available on the impact of these factors on the quality of food packaging, there are very few papers examining the impact of the flexo printing process on food packaging materials. Therefore, the aim of this paper is to examine if there are any changes occurring in tensile strength, elongation before tearing and gas permeability after the flexo-graphic printing process regarding the selected flexible packaging materials-oriented polypropylene (OPP) and coated paper/polyethylene (PAP/PE). The measurement of tensile strength and elongation before tearing was carried out according to SRPS G.S2.734, and the measurement of gas permeability according to Lussy Method - DIN 53380. The results presented in this paper show that the tensile strength and elongation in both foil samples increased after the printing process (a higher increase of strength is determined in the PAP/PE foil). The exception is the PAP/PE sample, where increased permeability of N-2 was observed. The reason for such results could be due to different surface characteristics of the tested materials since the process of ink absorption is different. Surface tension tests were conducted by applying measurements of the contact angle. The results show that the process of flexo printing did not change the functional properties of the packaging.