Index and Cause Analysis of Influencing Medium Density Plate Quality
Medium density board in the production process, will go through layers of links, and there will be different factors in this layer of links, resulting in different quality of the board. The indexes that affect the quality of MDF mainly include static bending strength, plane tensile strength, dimensional stability, nail holding force, moisture absorption expansion rate and so on. What is the reason that affects these indexes?
Low Static Strength
The reasons are as follows: 1. low density of products; 2. slow closure and compression speed; low density gradient of products, i.e. unreasonable density distribution of cross section; 3. insufficient dosage of adhesives, uneven distribution, poor quality of adhesives, too high or too low moisture content of slabs, resulting in incomplete curing of adhesives; 4. poor quality of fiber raw materials or low separation of fibers; 5. long or insufficient hot pressing time.
Low plane tensile strength
The reasons are as follows: 1. insufficient sizing amount and poor quality of adhesives; 2. too fast or too slow pressure; 3. insufficient or too long hot pressing time; 4. too high or too low moisture content in slab, low temperature, and not completely cured adhesives; 5. low density or unreasonable density distribution of cross-section; 6. too large proportion of recycled fibers; 7. poor quality of fibers; 8. insufficient cooling of board, too high stacking temperature; 9. no sizing. All.
Medium Density Plate Production Line
Dimensional stability and deformation
The reasons are as follows: 1. The density and thickness of each layer are not proportionate, the difference is large, the distribution of upper and lower layers is asymmetrical and the moisture content is not uniform; 2. The density gradient of surface and core is too large or too small; 3. The temperature difference between upper and lower hot pressing plates or the same hot pressing plate is large when hot pressing; 4. Insufficient cooling of plates means improper stacking and supporting of stacking mattress plates; 5. Thin plates are stacked without mattress plates; 6. High air humidity in storage area; 7. Upper and lower surfaces. Sanding quantity is different, or the thickness of upper and lower hard layer is different.
Nail holding power is low.
The reasons are as follows: 1. The density is too low; 2. The density gradient of the surface core layer is too large; 3. The sizing quantity is insufficient and the sizing uniformity is poor.
High moisture absorption expansion rate
The reasons are as follows: 1. insufficient sizing or insufficient curing of adhesives; quality problems of adhesives; 2. low wax application or uneven distribution; 3. low board density, poor fiber morphology and quality; 4. improper control of PH value of adhesives affects curing of adhesives or self-condensation of fibers.
Above is the index that affects the quality of MDF production and the reason that affects these indexes. MDF manufacturers need to check every step in the production process, pay attention to the detail control of each link, to ensure that the products produced from the warehouse are of good quality.