Suomella ei ole varaa keskinkertaiseen Teknilliseen korkeakouluun

Keskustelua

Aikasarjoja alkoholista

Keskustelua

Nokia, Pohjola ja Ericsson : keskustelua

Kommentti kirja-arvosteluun: Nokian pääkonttorin historia / Jari Ojala // Historiallinen aikakauskirja. 100 (2002) : 1

Determination of compression behaviour of coating layer

The strength properties of paper coating layer are very important in converting and printing operations. Too great or low strength of the coating can affect several problems in printing. One of the problems caused by the strength of coating is the cracking at the fold. After printing the paper is folded to final form and the pages are stapled together. In folding the paper coating can crack causing aesthetic damage over printed image or in the worst case the centre sheet can fall off in stapling. When folding the paper other side undergoes tensile stresses and the other side compressive stresses. If the difference between these stresses is too high, the coating can crack on the folding. To better predict and prevent cracking at the fold it is good to know the strength properties of coating layer. It has measured earlier the tensile strength of coating layer but not the compressive strength. In this study it was tried to find some way to measure the compressive strength of the coating layer and investigate how different coatings behave in compression. It was used the short span crush test, which is used to measure the in-plane compressive strength of paperboards, to measure the compressive strength of the coating layer. In this method the free span of the specimen is very small which prevent buckling. It was measured the compressive strength of free coating films as well as coated paper. It was also measured the tensile strength and the Bendtsen air permeance of the coating film. The results showed that the shape of pigment has a great effect to the strength of coating. Platy pigment gave much better strength than round or needle-like pigment. On the other hand calcined kaolin, which is also platy but the particles are aggregated, decreased the strength substantially. The difference in the strength can be explained with packing of the particles which is affecting to the porosity and thus to the strength. The platy kaolin packs up much better than others and creates less porous structure. The results also showed that the binder properties have a great effect to the compressive strength of coating layer. The amount of latex and the glass transition temperature, Tg, affect to the strength. As the amount of latex is increasing, the strength of coating is increasing also. Larger amount of latex is binding the pigment particles better together and decreasing the porosity. Compressive strength was increasing when the Tg was increasing because the hard latex gives a stiffer and less elastic film than soft latex.

Lakeus 1-5

Digitoitu 15. 8. 2008.

Hoffmannin kertomukset

Esityskieli: suomi.

Sinfonia g-molli

Digitoitu 15. 7. 2008.

Jazz : Sibelius-Akatemian Jazzstudio

Digitoitu 15. 10 2008.

[Don Juan]

Digitoitu 8. 9. 2008.

Avointen ammattikorkeakoulujen sähköinen asiointijärjestelmä opetusministeriön tietohallintostrategian näkökulmasta

Virtuaaliammattikorkeakoulu, VirtuaaliAMK

Rautkalliolle ja Häikiölle : keskustelua

Keskustelua. Vastaus Hannu Rautkalliolle ja Martti Häikiölle // Historiallinen aikakauskirja. 99 (2001) : 1, s. 89-91.