Paper-based flexible laminates tendency to curl
(2018) In MTTM01 20181 MTTM01 20181Packaging Logistics
- Abstract
- The main purpose of this study is to assess the impact of environmental conditions on paper-based flexible laminates tendency to curl. Any deviation in flatness may indeed affect materials processability. Two different paper-based flexible laminates are considered: a widely processed heat-sealable yogurt lid (paper / metallized polyethylene terephthalate / heat-sealing lacquer) and a prototype laminate (aluminium / paper / polyethylene). Packaging materials sheets (54*36 cm) are namely sampled from packaging materials rolls. Their tendency to curl is assessed by implementing the cross-cut method described in the German DIN 55403 standard (Deutsches Institut für Normung (DIN), 2014). Fifteen climates are tested i.e. five different relative... (More)
- The main purpose of this study is to assess the impact of environmental conditions on paper-based flexible laminates tendency to curl. Any deviation in flatness may indeed affect materials processability. Two different paper-based flexible laminates are considered: a widely processed heat-sealable yogurt lid (paper / metallized polyethylene terephthalate / heat-sealing lacquer) and a prototype laminate (aluminium / paper / polyethylene). Packaging materials sheets (54*36 cm) are namely sampled from packaging materials rolls. Their tendency to curl is assessed by implementing the cross-cut method described in the German DIN 55403 standard (Deutsches Institut für Normung (DIN), 2014). Fifteen climates are tested i.e. five different relative humidity values (30%, 40%, 50%, 60% and 70%) and three different temperature values (20°C, 25°C and 30°C). The effect of a polyethylene wrapping is also evaluated as a potential solution to prevent or reduce curl. For the yogurt lid which is shown to be sensitive to climate conditions, deformation occurs in both machine and cross-machine directions: average curl values respectively reach 13 millimetres and 37 millimetres. An equation to predict curl parameters as a function of climate and room conditions is furthermore suggested (r² = 72%). For the prototype laminate which appears not to be sensitive to climate conditions, deformation happens to be much lower than for the first material and only occurs in the machine direction. Average curl values reach 3 millimetres in the machine direction and zero millimetres in the cross-machine direction. Finally, considering the material-specific results obtained for the two laminates, no general conclusion can be drawn as regard to the polyethylene wrapping effect. (Less)
- Popular Abstract
- Water (and temperature) can also make packaging curl
What does usually happen, at the beginning of a greyish rainy day, after you spent so much time trying to style your hair in order to avoid looking like a scarecrow? Curl, of course... If moisture can be "hair-unfriendly", it can also be harmful to paper-based flexible multilayer packaging materials (= paper-based flexible laminates).
There is certainly one problem which is commonly encountered by paper-based packaging suppliers (and namely paper-based flexible laminates suppliers): curl. What is it about? Paper fibres ability to absorb and release water from the surrounding environment. What kind of consequences? Negative impact on materials processability: a decrease in the packed... (More) - Water (and temperature) can also make packaging curl
What does usually happen, at the beginning of a greyish rainy day, after you spent so much time trying to style your hair in order to avoid looking like a scarecrow? Curl, of course... If moisture can be "hair-unfriendly", it can also be harmful to paper-based flexible multilayer packaging materials (= paper-based flexible laminates).
There is certainly one problem which is commonly encountered by paper-based packaging suppliers (and namely paper-based flexible laminates suppliers): curl. What is it about? Paper fibres ability to absorb and release water from the surrounding environment. What kind of consequences? Negative impact on materials processability: a decrease in the packed products quality or even machines stop. What to do then? Describe and assess the effect of climate conditions on packaging materials tendency to curl, try to understand to what extent environmental conditions can affect their processability beforehand.
Aren’t there any recommendations made from the paper industry to avoid or solve this curl issue?
Well, after having studied two different laminates, it seems that recommendations to avoid paper-based packaging materials curl phenomenon aren’t applicable to paper-based multilayer packaging materials. Materials behaviour would differ depending on if they are free to move on their own or if they are bound and have to adapt to each other. Need for deeper technical data concerning the tendency to curl of a laminate of interest? You have better conduct a study yourself…
Is there any multilayer packaging structure which would be better than others?
“Sandwiching” paper may help. Let’s consider a yogurt lid. The paper layer is in direct contact with the atmosphere (printed face). Results? The material is sensitive to climate conditions: curl significantly varies as function of moisture and temperature. Let’s take a second example, an aluminium/paper/polyethylene structure. Paper is sandwiched between an aluminium and a plastic layer. Results? The material tendency to curl is lower and not sensitive to climate conditions. Therefore, depending on the multilayer structure, climate-related risk can be quite low or high. But don’t be afraid, perfectly flat packaging materials aren’t always required. It is all about the demanding nature of the filling process your material has to undergo. For some applications, you may not face any problem even if the material is climate-sensitive. The picture is a bit more complex.
What if I want to assess packaging films tendency to curl? Easily manageable?
Go for the cross-cut method which is described in the German standard DIN 55403. It is relatively simple, quick and affordable. You just need basic materials: a weather station, a cutting mat, a specific cutting pattern, a cutter, a ruler and tape. Cut crosses, measure specific distances and you are almost done. Both low and high tendency to curl can be characterized. Curl is morever described in two directions, in the machine direction and in the cross-machine direction. It is quite informative. On the whole, a good quality control method but also a useful test method to help select multilayer packaging materials for demanding applications. Packaging suppliers, developers and researchers could all implement it. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/8947134
- author
- Muller, Clémentine LU
- supervisor
- organization
- course
- MTTM01 20181
- year
- 2018
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- flexible laminates, paper, curl, relative humidity, temperature
- publication/series
- MTTM01 20181
- ISBN
- 978-91-7753-753-3
- language
- English
- id
- 8947134
- date added to LUP
- 2018-06-18 08:58:46
- date last changed
- 2018-06-18 08:58:46
@misc{8947134,
abstract = {{The main purpose of this study is to assess the impact of environmental conditions on paper-based flexible laminates tendency to curl. Any deviation in flatness may indeed affect materials processability. Two different paper-based flexible laminates are considered: a widely processed heat-sealable yogurt lid (paper / metallized polyethylene terephthalate / heat-sealing lacquer) and a prototype laminate (aluminium / paper / polyethylene). Packaging materials sheets (54*36 cm) are namely sampled from packaging materials rolls. Their tendency to curl is assessed by implementing the cross-cut method described in the German DIN 55403 standard (Deutsches Institut für Normung (DIN), 2014). Fifteen climates are tested i.e. five different relative humidity values (30%, 40%, 50%, 60% and 70%) and three different temperature values (20°C, 25°C and 30°C). The effect of a polyethylene wrapping is also evaluated as a potential solution to prevent or reduce curl. For the yogurt lid which is shown to be sensitive to climate conditions, deformation occurs in both machine and cross-machine directions: average curl values respectively reach 13 millimetres and 37 millimetres. An equation to predict curl parameters as a function of climate and room conditions is furthermore suggested (r² = 72%). For the prototype laminate which appears not to be sensitive to climate conditions, deformation happens to be much lower than for the first material and only occurs in the machine direction. Average curl values reach 3 millimetres in the machine direction and zero millimetres in the cross-machine direction. Finally, considering the material-specific results obtained for the two laminates, no general conclusion can be drawn as regard to the polyethylene wrapping effect.}},
author = {{Muller, Clémentine}},
isbn = {{978-91-7753-753-3}},
language = {{eng}},
note = {{Student Paper}},
series = {{MTTM01 20181}},
title = {{Paper-based flexible laminates tendency to curl}},
year = {{2018}},
}