Analysis of Common Quality Defects of Melamine Decorated Panel
Melamine MDF and plywood QC inspection checklist and grading rules
1. Physical and chemical performance defects
The physical and chemical properties of melamine veneer panels can generally refer to the physical and chemical properties of the board surface, such as water vapor resistance, crack resistance, cigarette burning resistance, formaldehyde emission resistance and so on.
1.1 Poor surface water vapor resistance index
The surface moisture resistance index is the surface moisture and heat resistance of the decorative panel. GBIT 15102-1994 “Impregnated Plastic Film Paper Decorated Wood-based Panels” requires that the surface of decorative panels should be fumigated by steam for 1 hour without bulging, bubbling and discoloration; the surface of decorative panels is not qualified, usually the surface becomes white or bulging after fumigation. Observed under a magnifying glass, it is found that the surface resin has been broken by steam and the steam has been immersed in the surface paper. The unqualified water vapor resistance of the surface indicates that the resin has not been able to seal the surface, there are still some holes left, or the resin has not yet fully cured, and is not resistant to water vapor. Through the inspection of the following items, the solution to this problem can be found:
(1) Whether the resin content of surface paper is too low;
(2) Whether the volatile content of the film paper is too low to cause the poor resin fluidity;
(3) Whether the pressure is too low when pressing, resulting in poor resin flow;
(4) Whether the parameters of curing speed, amount of curing agent, hot pressing temperature and hot pressing time of the resin meet the technological requirements.
1.2 The poor burning resistance of cigarette surface is mainly due to the low resin content, which can properly increase the amount of impregnation.
1.3 is the poor surface pollution resistance, because the surface of the base material is too rough, resin content is low, can be made up by increasing the amount of dipping film paper.
1.4 is poor surface crack resistance.
Generally speaking, the reasons for poor surface physical and chemical properties of decorative panels are as follows: first, low hot pressing temperature or short hot pressing time lead to incomplete resin curing; second, excessive hot pressing temperature, uneven template surface temperature, long storage period of film paper, excessive pre-curing degree of film paper, resulting in poor resin flow; only the low dipping amount of film paper or uneven distribution of dipping amount affect the physical and chemical properties of decorative panels. Chemical properties.
2. Appearance quality defects
The common appearance quality defects of melamine decorative panels are dry flowers, wet flowers, stratified bubbling, and the phenomenon of sticking template often occurs in the process of pressing.
2.1 Dry flower on board, also known as white flower, is an opaque white spot on the surface of the product. The main reasons for this defect are poor resin flow ability or insufficient resin impregnation. There are many reasons for this:
(1) Inspection of base material for veneer is not strict and the surface is uneven;
(2) The local pre-curing layer on the surface of the base material is not Sandy and the resin flow on the surface of the board is poor.
(3) The impregnation of the laminated paper is uneven during the impregnation process.
(4) The hot pressing temperature is too high, the hot pressing pressure is too low, and there are pollutants on the surface of the hot pressing template.
(5) Local damage of cushion pad;
(6) Due to the long storage period and high pre-curing degree of film paper;
(7) The impregnation amount of Shanyu film paper is too large.
2.2 Wet flower on board is also called water mark, which is foggy mark on product surface. Causes of wet flowers:
(1) Because of the high volatile content of the film paper, it can not be excreted and accumulated on the surface of the sheet or the film paper is subjected to pressure.
(2) The pre-curing degree of film paper is too low, the hot pressing temperature is too low or the hot pressing time is too short.
(3) Because of the high moisture content of the base material, excessive water vapor is produced during pressing.
2.3 The main reasons for stratified bubbles of products are as follows:
(1) The hot pressing temperature is too high and the hot pressing time is too long.
(2) If the moisture content of the base material is too high or the thickness of the base material is too thin, the steam pressure in the core layer of the middle plate will be larger.
(3) The density of the base material is low, the compressive performance of the plate is poor or the hot pressing pressure is too high.
2.4 Formwork bonding refers to the partial or total adherence of sheets to the formwork during the pressing process. The main reasons are as follows: (1) short hot pressing time, low hot pressing temperature or partial low, which makes the curing of resin incomplete;
(2) The moisture content of the base material is on the high side;
(3) The surface of the template is not clean, and there is no release agent or release agent failure or uneven coating in the resin.
(4) The impregnation amount of the film paper is too large and the volatile content is too high.
(5) inaccurate slab positioning during hot pressing.
In summary, in order to produce qualified plastic film paper veneered wood-based panels, melamine impregnated paper and base materials with excellent technical indicators must be selected, and reasonable processing technology must be adopted for pressing.