Six Common Problems of Paper Plasterboard

1. Air bubbles and blisters on the surface of the plate.
The main reasons for blistering and bulging on the surface of paper faced gypsum boards are that the slurry is too thin or the foaming agent is improperly used during production, and the aerating property of face protection paper is poor. Sometimes the diameter of bubbles is less than 1cm, but it is almost all over the board surface. This is mainly because the gypsum slurry is too thin or the foam of the foaming agent has poor stability, and there are many large bubbles, so that a large number of bubbles concentrate on the surface to form large bubbles. Especially after the board is placed for a period of time and moisture absorption, the bubbles are more obvious. Some bubbles are larger and sometimes more regular, such as forming a straight line along the edge; There are also cases where the number of bubbles is small and it is difficult to determine their regularity, which is related to the low and uneven aeration of face protection paper and the low interlayer adhesion. The low air permeability of the paper makes it difficult for the moisture in the paper to evaporate, and the interlayer adhesion of the face protection paper is low. During production or storage, local poor adhesion or delamination of the paper surface occur, resulting in bulges on the surface of the board, which can be seriously manifested as a large area of non adhesion.
2. The plate is prone to deformation.
With the development and competition of the paper faced gypsum board industry and related industries, the unit quality of face protection paper and gypsum board has decreased to a certain extent. First of all, the reduction in the quantity of face protection paper and the excessive shrinkage of the paper lead to insufficient tightness of the face protection paper, resulting in insufficient stiffness of the gypsum board on the paper surface. After moisture absorption, the machine is prone to deformation; Secondly, if the permeability of face protection paper is low, the permeability is slow, and the drying is slow, the deflection of the dried board after moisture absorption is large; In addition, during the molding process, if the consistency of the slurry is adjusted depending on the water consumption, resulting in a large water consumption, large voids will be generated in the plate after drying and evaporation, resulting in the plate being too light or soft, and increased deformation and deflection.
3. Paper rubbing on the surface of the board.
"Paper rubbing on the surface of a board can not only affect the appearance quality of the board, but also have a negative impact on internal quality indicators such as the strength of the board to a certain extent, which cannot be ignored.". The main influencing factor of the paper rubbing on the surface of the board is the face protection paper.
The interlayer adhesion of face protection paper is poor and the water content of the paper is too high. During the molding and water absorption process, the interlayer adhesion of the paper will further decrease. During the relative movement between the plates and the equipment, there will be paper rubbing due to mutual friction. In severe cases, the paper balls produced by the paper rubbing can cause scratches on the surface of the plate, leading to serious quality problems such as breakage. Therefore, in the production process of paper faced gypsum board, it is necessary to choose face protection paper with stable indicators such as moisture content and water absorption.
4. Uneven phenomena such as corrugated plate surface and pulling groove. The occurrence of such problems is related to issues such as paper specifications and process control.
① The factor of paper. The banner weight, moisture content, and air permeability of the face protection paper are uneven, resulting in different tightness, thickness, and water absorption of the paper. In places with high moisture content, the moisture expansion is small, and in places with low moisture content, the moisture expansion is large, causing severe shrinkage in the dry area, while in places with low moisture content around, the dry shrinkage is small, resulting in inconsistent expansion and contraction of the paper, causing ripples or pulling grooves.
② Problems with process equipment. Inadequate flatness or improper adjustment of the molding platform can also cause uneven surface. The problems caused by this reason are relatively concentrated and easy to find. However, improvement of the surface flatness must be achieved through improvement of process equipment.
③ The fluctuation of material properties and slurry is also one of the important reasons for uneven plate surface. Due to fluctuations in raw materials and additional materials, as well as fluctuations caused by the milling process, it is inevitable that certain changes occur in the setting time, weight rise, and other indicators of the powder and slurry. However, if the fluctuations are too frequent or large, it will be difficult to timely adjust and control the process of subsequent processes, and can also lead to adverse phenomena such as plate grooves.
5. Poor adhesion between the face protection paper and the gypsum core leads to the problem of exposed board core or partial non adhesion of paper. This type of problem is related to production processes such as face protection paper, raw material quality, and drying.
① "If the Geller value of the paper's aeration rate is too high, or its water absorption is too high or too low, it can easily cause rapid loss of moisture and lead to poor binding.";
② The grade of gypsum in the raw material is too low, there are many impurities, or the content of harmful impurities such as K and Na is too high, which affects the adhesion of paper and gypsum core.
③ The setting time of building gypsum is too slow, and it fails to completely solidify or has a false setting phenomenon before entering the drying zone, resulting in incomplete hydration of building gypsum, which leads to the peeling of the dried board.
④ The molding and drying speed cannot be adjusted in a timely manner with the fluctuations of the face protection paper or slurry, resulting in a mismatch between the permeability, water absorption, and drying speed of the face protection paper, and a mismatch between the setting time of the gypsum slurry and the molding speed, resulting in a lack of adhesion between the paper and the gypsum core or excessive burning of the board.
⑤ Too thin slurry, uneven foam, and too many or too concentrated macropores in the dried board will also cause poor adhesion of paper and core.
6. Low strength, easy to break and crack plates.
The main manifestation of plate breakage is lateral fracture, which eliminates the undesirable operation during plate lifting. The main influencing factor for plate breakage should consider the longitudinal strength of the face protection paper. The strength of face protection paper has an important relationship with its quantitative and other indicators. At present, with the development and competition of the gypsum board and face protection paper industries, the quantity of face protection paper has decreased from 230g/㎡ to 250g/㎡ to 180g/㎡ to 210g/㎡, which inevitably leads to a decrease in strength and changes in other indicators.
As the main raw material of gypsum board, its grade and physical properties are another important factor affecting the strength of gypsum board. For natural gypsum, the grade is generally required to be not less than 75%, and the 2h flexural strength of building gypsum is not less than 1. 8Mpa, which is the most basic requirement for ensuring the strength of paper faced gypsum board. In addition, impurities and acid-base properties of gypsum can also have a negative impact on the strength of gypsum. In the production of paper faced gypsum board, glass fiber and other reinforcing materials are often used to improve the strength of the board. Therefore, if insufficient reinforcement fibers are added during production, the strength of the plate will be reduced, resulting in easy fracture of the plate. At the same time, if the material of the reinforcing fiber fails to meet the requirements, its reinforcing effect will be greatly reduced. If glass fiber is used as reinforcement material, it is generally used as alkali free fiber, which has a certain degree of flexibility and high strength. If alkali containing fibers are used, even high alkali fibers cannot play their due reinforcement role due to the brittle material and low strength of alkali containing fibers, resulting in brittle fracture of the plate.
The easy fracture of the plate due to the scratch on the plate surface is also a cause that cannot be ignored. During the production process, if there are hard particles such as rust and sand left on the surface of the board, during the relative movement of the board, it is extremely easy to create scratches on the surface of the face protection paper of the board and cause the board to break along the scratches. This type of problem generally does not occur in large quantities, and is easy to detect and remove by careful observation. Cracking mainly occurs along the longitudinal direction of the plate. In addition to the low lateral strength of the cover paper and the low strength of the gypsum, another important reason is the warping of the plate, which causes cracks in the stress concentration area of the plate when it is pressed during storage and transportation. There are many reasons for plate edge warping. For example, the expansion ratio of face protection paper is large or the shrinkage ratio of upper and lower paper is inconsistent; Too thin slurry or unstable material properties can lead to unstable process control and poor operability, which can lead to plate edge warping. Therefore, in order to improve the strength of the board and reduce problems such as breakage and cracking, it is necessary to try to choose protective paper and high-grade gypsum with strength, aeration, and water content suitable for production requirements; Strictly control the various indicators of the powder processing and molding process.