Laminate warpage


 The third problem caused by dimensional instability is warpage. Most decorative laminates consist of a two-layered aramid-formaldehyde resin impregnated paper backing with more than 5 layers of phenol-formaldehyde resin impregnated paper. The triethyleneamine-containing formaldehyde resin portion of the laminate is more than the phenol-formaldehyde-containing resin. Unstable. This indicates that the two layers of the factory laminate are subjected to different forces when there is any change in moisture content. The slab responds by deviating from its original planar form, which is called warping. Because most decorative laminate panels are ultimately attached to a flat surface, warpage makes this attachment difficult, if not impossible.
From a practical point of view, the degree of warpage is related to the amount and type of resin used for each layer, the density of the laminate, and whether or not a non-porous laminate is obtained. Controlling the volatile content of each individual prior to pressing is an effective way to adjust dimensional stability to achieve an ideal equilibrium state within the laminate.
Epstein analyzed this phenomenon and he tried to create a digital model. In his model, he assumes that the laminate is completely elastic, ie the stress is proportional to it. This seems to be a good hypothesis, because the stress-strain relationship is completely straight until the stress approaches the rupture state. He also adopted an equilibrium state, that is, the internal stress was used to estimate the warpage, and the internal stress existed after the equilibrium with the surrounding environment. To avoid the renaturation of the anisotropic structure in three directions, Epstein limited his model to one direction. According to the test, this would be equal to a warp of a narrow strip (ie, the length is much larger than the width). The Epstein model was extensively studied by others and they found that there is sometimes a good substantial consistency between the model and the experimental data. And in other respects it is not very good. A good correlation is usually obtained between the prediction at low humidity and the measured warpage, although the predicted warpage is often higher than the measured warpage. There is little correlation at high humidity.
If individual layers from the composite laminate are separately pressed and consolidated, it is shown that the individual layers are subjected to larger dimensional changes than the corresponding layers in the composite laminate. It is apparent that adjacent layers inhibit variations in their neighbors in the composite laminate. The value of the stress involved in this inhibition is completely in the straight line region of the stress-strain curve. This eliminates the possibility of stress suppression exceeding the plastic limit of the material. The conclusion is that the difference between the observed and the calculated warpage is due to the intrinsic drilling elasticity of the laminate, ie the modulus is not a constant but a value that varies with time. This will cause the stress to disappear with time. In practice, laminates are not subject to the level predicted by the elastic model but at a lower level of internal stress. The degree of warpage observed will thus be low and there is no predictive value.

  • 06/12/2018
  • Recently
Click here to view Previous or Next

Related News

Casting PA film and production technology

Casting PA film and production technology

  • 21/12/2017 09:33:12

Casting PA film and production technology 1. Casting PA film and its raw materials used: PA film has the advantages of high strength, good toughness, good transparency, good heat resistance and cold…

Read more

Cast film mechanical winding device

Cast film mechanical winding device

  • 19/12/2017 09:21:48

Cast film mechanical winding device Corona treatment device: cast film after corona treatment, can improve the surface tension of the film to improve the printing of the film and together with other…

Read more

Downstream production line auxiliaries

Downstream production line auxiliaries

  • 18/12/2017 09:42:18

Downstream production line auxiliaries Thickness measurement device: In the high-speed continuous production process, cast film thickness measurement must be non-contact automatic tracking. Most o…

Read more

Casting film production line in the cooling device

Casting film production line in the cooling device

  • 15/12/2017 10:03:16

Casting film production line in the cooling device Casting production line in the cooling device mainly by the rack, cooling roller, peel roller, refrigeration system and air knife, auxiliary device…

Read more

Hot News

Removal of excess resin

Removal of excess resin

There are two main methods for removing excess resin from the surface of the web: the doctor blade and the squeeze roller. The scraper can be as simple as a pair of angle irons arranged to contact the web. Usually they are mounted on a common rotatable su

Dipping machine

Dipping machine

Plastic laminates are manufactured industrially, and the web is impregnated in a machine called a dipper or a dipper. It includes a paper roll unwinding device, a resin tank, a facility for removing excess resin, a drying chamber for evaporating most of t

Saturated impregnation and infiltration process

Saturated impregnation and infiltration process

The analysis of the addition of the resin to the paper web in the plastic laminate is based on the assumption that the two processes that occur are simultaneous and sequential. First, the so-called saturated impregnation is the rapid absorption of the res

Laminate pore size distribution

Laminate pore size distribution

In the early 1960s, many laminates used the properties of this paper to estimate the amount of resin they absorbed. They used a thin resin solution to fill all the voids of the paper with the resin solution and scrape off the excess solution. As long as t

Laminate paper handling

Laminate paper handling

The resin and the cellulose fibers are thoroughly mixed to obtain a laminate, and the web is usually immersed in a resin solution. The surface tension causes the web to absorb the resin solution and fill the porous structure of the entire paper. The exces

Tags