Gypsum board quality common reasons for analysis

Gypsum board paper core bonding bad reason: gypsum board as a kind of new environmental protection building materials have been accepted by the masses, its production capacity and market are growing, gypsum board production technology has become more mature, plate inner quality stable, the appearance quality improving, some large enterprise products has reached international advanced level. However, in the process of the production and use of gypsum board there are still some common problems, such as paper core bonding performance has been the major problems affecting enterprise production rate. This issue has been a major enterprise solution and a lot of problems, mainly because of its affected factors and complex.

1 the effect of protective paper

1.1 the permeability of paper is too low. Porosity actually refers to the ability of air resistance. The air permeability of paper mainly affect the forming speed of gypsum board. Under the same production rate, the greater the porosity of paper (s / 100 ml) notation, dryer out of plank is wet, the bigger the plate deflection. In order to ensure the quality of production to reduce the production rate, reduce production. But if the permeability is low, plasterboard in the process of drying moisture evaporates quickly, within the gypsum core with the evaporation of moisture in starch through the paper core is at the junction, the migration to the paper, which affect the paper, the core of dry binder properties, sheet and brittle.

1.2 paper too high or too low water imbibition. Absorbent paper is associated with the sizing degree of protective paper. Gypsum hydration process, the growth of acicular crystals grow into the protective paper, thus forming a good combination with the protective paper. If the sizing is overweight, paper is relatively hard, is not conducive to crystal into; If too little glue, water imbibition is too big, the moisture is absorbed by a large number of gypsum slurry and evaporate quickly, is not conducive to gypsum crystal growth, will also affect good adhesion of paper core. The air permeability of paper how appropriate, depends on the actual situation of production line, cannot treat as the same. Generally, water and solid than big production line should choose quantitative slants big, slightly larger water imbibition protective paper. In general, water solid ratio of 60 ~ 70 production line using quantitative 220 g/m2 in front of the paper, the general water imbibition is 15 ~ 20 g/m2. Cardboard and quantitative determination of water must be combined with production process, industrial and mining conditions of gypsum board. Such as production speed, drying process, etc.
2 the influence factors of raw materials such as gypsum

Gypsum plasterboard of face is the production of the main raw material, the performance of gypsum are the important factors influencing the gypsum board every performance. The grade of gypsum and its impurity content, building gypsum setting time and the use of various additives on protective paper and bonding properties of the gypsum core have influence.

2.1 the grade of the plaster is too low

In general, the grade of the requirements of natural gypsum is not lower than 75%, if the gypsum dihydrate calcium sulphate content is too low, the plasterboard gypsum crystals formed in the forming process of too little, can affect the protective paper and adhesive plaster core.

Gypsum content of impurities such as K, Na in 2.2

In general, the content of impurities such as K, Na, not too high, but its effect on the properties of the adhesive of the paper gypsum is very big, therefore, general requirement of K, Na in gypsum board is not higher than 0.02%. If, gypsum in the high content of impurities such as K, Na, in the process of gypsum board molding and drying, the paper core mold junction to form a layer of salt. When plate at low temperature, humidity larger environment, plank is extremely easy bibulous, makes the paper core release.

2.3 the influence of additives such as foaming agent

In order to improve the physical properties of building gypsum and gypsum board, gypsum board paper in the production of add water reducing agent, foaming agent, coagulant and other additives. And the use of these additives will certain negative influence on the plate. First of all, some additives contained a certain amount of Na inorganic salt, which increases the accumulation of Na in the gypsum slurry, to a certain extent affect the paper core bonding; Second, if the negligence in the process of selection and purchase of additive PH worth control, affected by the gypsum slurry PH value will fluctuate, and influence of slurry setting time and paper core bonding performance; In addition, the foam stability of foaming agent has been affecting the performance and use effect of the important indicators, and the index of foaming agent of domestic majority in the required critical state, such as the bubble diameter is larger or stability of foaming agent on the low side, in the mixed with slurry after the formation of the big bubble is more, more even more concentrated, plasterboard of face will cause poor local bond.
3 gypsum board process control factors

3.1 the gypsum slurry is too thin, contains a lot of big bubbles or moisture, cause after drying, plate core focus a lot of the big gap in sheet or too light, make gypsum crystals and protective paper reduce the contact point, affect the protective paper good bonding with gypsum core.

3.2 gypsum slurry condensation too fast or too slow, also has a harmful effect on the bond properties of gypsum board paper core. The gypsum slurry should be setting after the trip to flat, on the forming belt to complete the final set. If condensation quickly, before the trip plate knife set, after a trip to tablet, can damage into crystals of protective paper. Such as setting too slow, not on the forming belt to complete the final set, in subsequent roller conveyor, not forming plate affected by vibration and its bonding and cut off, even into the drying machine board core with strong paper is not binding, after entering drying area, the temperature is above 80 ℃ when gypsum slurry will no longer continue to condensation, and the moisture inside the plate quickly evaporate, outward will cause serious non-stick paper core.

3.3 not harmonious, the drying speed and temperature sheet caused by water or burnt. With gypsum or building performance change, should timely adjust the molding production process, to make it compatible with material sex. Otherwise, will cause the plank of burnt or owe to burn, and plank burnt or owe to burn, have different levels of performance for paper core is bad.

4 or starch modified starch dosage too less mobility is not enough.

Starch is not protective paper and gypsum core is the main influencing factors of bonding, modified starch in gypsum as the moisture evaporation, and constantly to gypsum and paper junction migration, protect interface gypsum crystals to overheating, and strengthen the paper and the adhesive of the core.

5 add uneven or foam stability of foaming agent of foaming agent is poorer, this kind of situation in local bond, the bubble or vesicles after the formation of the larger space of paper, core is easy to appear bad. The uniformity of the foaming agent is added to add and mix own related to the speed; Foam stability is mainly related to the performance of foaming agent itself.

6 the conclusion

Factors influencing the caking property of gypsum board paper core involves multiple aspects, such as raw materials and process control in most cases is a result of the combined action of several factors, difficult to precise control, only in combination with the practical situation of production in the actual production, choose suitable production process of the original, auxiliary materials, monitor its fluctuations, and timely adjust process control indicators, reach the harmony of fluctuation process to try to reduce paper, core bonding bad problem, and finally improve the quality of gypsum board and production efficiency.