Interactions between hot melt and paperboard
Järvenpää, Joel (2021)
2021
Materiaalitekniikan DI-ohjelma - Master's Programme in Materials Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2021-09-09
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202108196654
https://urn.fi/URN:NBN:fi:tuni-202108196654
Tiivistelmä
This thesis focuses on behavior of hot melt adhesive on different carboard substrates under deep freeze conditions. It is important to understand how bonds form and break in order to improve packages. Aim of the thesis is to clarify the role of different adhesion modes between folding boxboard (FBB) and hot melt adhesive and how the interactions between FBB and hot melt affect to the adhesion formation.
Exact formation mechanism of adhesion between paperboard and hot melt adhesive can’t be unambiguously explained since many mechanisms contribute to the total adhesion. Prop erties of the FBB that contribute to the adhesion are surface energy of the substrate, surface roughness and presence of functional groups. Hot melt properties such as polarity, glass transition temperature, and rheological properties affect to the interaction between FBB. Ad hesion between FBB and hot melt can be improved by matching polarity of the hot melt close to that of the FBB. Adhesion can be promoted by modifying either FBB’s or hot melt’s prop erties. Corona treatment is known to increase paperboards total surface energy and is widely used. Hot melts composition can be modified to promote adhesion to different materials.
Temperature of either hot melt or FBB is an important factor when discussing adhesion. Cold FBB substrate can cause premature solidifying of the hot melt because hot melt viscosity is strongly temperature dependent Moisture content together with temperature have an influ ence on the elastic modulus of the paperboard. Condensed water could potentially break the hydrogen bonds formed between the FBB and hot melt. Hot melt is a widely used adhesive in packaging industry. It has advantageous properties for high speed converting applications such as hot tack and short set time. Deep freeze hot melt adhesives are subcategory of hot melt adhesives that are especially meant to work under deep freeze conditions by retaining their flexibility. Hot melt consists of three main components which are polymer, wax and tackifying resin. These components can be varied, and their ratio adjusted to acquire the desired properties.
Folding boxboard’s typical structure is a sandwich structure where mechanical pulp layer is in the middle and with chemical pulp layers on both sides. Surface characteristics, such as surface strength and roughness have a strong influence on the strength of the adhesive joint. Thermal properties of FBB are strongly dependent on moisture content of the board, its den sity and amount and type of fillers used. Internal sizing of FBB is done at the wet end of paper machine often using Rosin, Alkyl-ketene-dimer or Alkenyl-succinic-anhydride. Surface sizing is carried out at the dry end, usually using cationic starch. Rosin are most effective in the acidic region whereas AKD and ASA are in the alkaline to neutral region. Main function of the internal sizing is to slow down the rate of water absorption. Surface sizing’s main function is to improve surface strength, reduce water absorption through capillary action and improve printability.
In the experimental part FBB’s properties were studied using water absorption, coefficient of friction, air permeability, roughness, surface topography, surface energy, surface strength and gluing tests. Earlier Metsä Boards’ studies were used as research material. The hot melts’ thermic properties were studied using differential scanning calorimetry.
Exact formation mechanism of adhesion between paperboard and hot melt adhesive can’t be unambiguously explained since many mechanisms contribute to the total adhesion. Prop erties of the FBB that contribute to the adhesion are surface energy of the substrate, surface roughness and presence of functional groups. Hot melt properties such as polarity, glass transition temperature, and rheological properties affect to the interaction between FBB. Ad hesion between FBB and hot melt can be improved by matching polarity of the hot melt close to that of the FBB. Adhesion can be promoted by modifying either FBB’s or hot melt’s prop erties. Corona treatment is known to increase paperboards total surface energy and is widely used. Hot melts composition can be modified to promote adhesion to different materials.
Temperature of either hot melt or FBB is an important factor when discussing adhesion. Cold FBB substrate can cause premature solidifying of the hot melt because hot melt viscosity is strongly temperature dependent Moisture content together with temperature have an influ ence on the elastic modulus of the paperboard. Condensed water could potentially break the hydrogen bonds formed between the FBB and hot melt. Hot melt is a widely used adhesive in packaging industry. It has advantageous properties for high speed converting applications such as hot tack and short set time. Deep freeze hot melt adhesives are subcategory of hot melt adhesives that are especially meant to work under deep freeze conditions by retaining their flexibility. Hot melt consists of three main components which are polymer, wax and tackifying resin. These components can be varied, and their ratio adjusted to acquire the desired properties.
Folding boxboard’s typical structure is a sandwich structure where mechanical pulp layer is in the middle and with chemical pulp layers on both sides. Surface characteristics, such as surface strength and roughness have a strong influence on the strength of the adhesive joint. Thermal properties of FBB are strongly dependent on moisture content of the board, its den sity and amount and type of fillers used. Internal sizing of FBB is done at the wet end of paper machine often using Rosin, Alkyl-ketene-dimer or Alkenyl-succinic-anhydride. Surface sizing is carried out at the dry end, usually using cationic starch. Rosin are most effective in the acidic region whereas AKD and ASA are in the alkaline to neutral region. Main function of the internal sizing is to slow down the rate of water absorption. Surface sizing’s main function is to improve surface strength, reduce water absorption through capillary action and improve printability.
In the experimental part FBB’s properties were studied using water absorption, coefficient of friction, air permeability, roughness, surface topography, surface energy, surface strength and gluing tests. Earlier Metsä Boards’ studies were used as research material. The hot melts’ thermic properties were studied using differential scanning calorimetry.