Puncture resistance of papers used in packaging
do Carmo Tinoco, Lucas (2020)
do Carmo Tinoco, Lucas
2020
Master's Programme in Materials Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2020-12-03
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202011097881
https://urn.fi/URN:NBN:fi:tuni-202011097881
Tiivistelmä
Puncture resistance (PR) is a key material property in order to evaluate how a component can withstand external or internal piercing loads without being damaged by those. A package material must have high PR to be effective as a packaging.
This thesis focused on the puncture resistance of papers used in packaging. It had different objectives: to design and manufacture the testing equipment; to analyze how different parameters affect the puncture resistance; to determine which mechanical properties correlates better with PR; and to evaluate possible causes for the differences in PR of the papers tested.
First, all the tool necessary for the testing were manufactured – probe holder, sample holder and penetration probes. These probes were produced in order to emulate different damages a package can suffer in real conditions.
In total, it was used five different probes: one flat probe; and four hemispherical probes. They all had the same base dimensions, but their tip radius varied. Only one probe had a soft tip -to emulate the impact of a chocolate bar into its package-, the others were hard tip probes.
It was determined that stress concentration is the main factor which justifies the difference in a paper puncture resistance when using different probes. A probe that causes higher stress con-centration to a paper will pierce it easier.
The flat probe caused less stress concentration than the hemispherical ones, thus provided higher PR. Also, it was evaluated that probes with the same tip geometry will affect a paper’ puncture resistance in a direct proportion to its tip dimension. Finally, it was concluded that the tip’s material does not have more influence than its shape.
The tensile properties of the samples were calculated to check their correlation with PR. Ten-sile Energy Absorption (TEA) proved to be the property with higher correlation. This correlation was used to determinate which are the driving factors that justifies the PR differences between the tested papers, taking in consideration that the driving factor for TEA would be similar to PR. Those are the pulp used, the quantity of filler added, and the refining process. In order to produce a paper with high puncture resistance it is necessary to reduce the amount of filler and to wisely select the pulp and its refining process.
The papers selected for this thesis had different characteristics, such as grammage and pres-ence of coating/glazed side in order to analyze if those effect its puncture resistance value. It was analyzed that a particular paper will have its puncture resistance directly proportional to its gram-mage. Also, for the papers tested the presence of coating/glazed side did not show influence on PR.
Furthermore, different papers’ types were used to check the influence of moisture content in PR. It was concluded that higher moisture content increases a paper’s puncture resistance, but this relation is not directly proportional. Finally, it was concluded that in overall unbleached paper tends to provide higher PR than bleached paper, and that the material used (pulp), or even a combination of it, will influence on the paper’s puncture resistance.
This thesis focused on the puncture resistance of papers used in packaging. It had different objectives: to design and manufacture the testing equipment; to analyze how different parameters affect the puncture resistance; to determine which mechanical properties correlates better with PR; and to evaluate possible causes for the differences in PR of the papers tested.
First, all the tool necessary for the testing were manufactured – probe holder, sample holder and penetration probes. These probes were produced in order to emulate different damages a package can suffer in real conditions.
In total, it was used five different probes: one flat probe; and four hemispherical probes. They all had the same base dimensions, but their tip radius varied. Only one probe had a soft tip -to emulate the impact of a chocolate bar into its package-, the others were hard tip probes.
It was determined that stress concentration is the main factor which justifies the difference in a paper puncture resistance when using different probes. A probe that causes higher stress con-centration to a paper will pierce it easier.
The flat probe caused less stress concentration than the hemispherical ones, thus provided higher PR. Also, it was evaluated that probes with the same tip geometry will affect a paper’ puncture resistance in a direct proportion to its tip dimension. Finally, it was concluded that the tip’s material does not have more influence than its shape.
The tensile properties of the samples were calculated to check their correlation with PR. Ten-sile Energy Absorption (TEA) proved to be the property with higher correlation. This correlation was used to determinate which are the driving factors that justifies the PR differences between the tested papers, taking in consideration that the driving factor for TEA would be similar to PR. Those are the pulp used, the quantity of filler added, and the refining process. In order to produce a paper with high puncture resistance it is necessary to reduce the amount of filler and to wisely select the pulp and its refining process.
The papers selected for this thesis had different characteristics, such as grammage and pres-ence of coating/glazed side in order to analyze if those effect its puncture resistance value. It was analyzed that a particular paper will have its puncture resistance directly proportional to its gram-mage. Also, for the papers tested the presence of coating/glazed side did not show influence on PR.
Furthermore, different papers’ types were used to check the influence of moisture content in PR. It was concluded that higher moisture content increases a paper’s puncture resistance, but this relation is not directly proportional. Finally, it was concluded that in overall unbleached paper tends to provide higher PR than bleached paper, and that the material used (pulp), or even a combination of it, will influence on the paper’s puncture resistance.