properties of plywood wood species
Plywood has a wide variety of classifications. According to the tree species, it can divided into softwood and hardwood. According to the use. it can divided into ordinary, structural , cement formwork , fireproof and special plywood.
What Are The Regulations For Plywood Production?
The physical and mechanical properties of plywood can described by its:
water content, density, thermal conductivity, bonding strength.
In the production process of ordinary plywood. the International Organization for Standardization provides for its structure. moisture content and quality of finished products.
（1）Structure. The textures of the adjacent layer veneers should be at right angles to each other. they are symmetrical about the center layer. The tree species and thickness of each layer should be the same. The face and back plate are facing outward.
（2） Moisture content. Between 12 and 14% (according to Chinese national standards. the absolute moisture content of Class I and II plywood does not exceed 13% on average. The moisture content of Class III and IV plywood does not exceed 15%).
（3）Quality. The product should have a rectangular straight edge and a sharp corner. the smallest number of layers per thickness is to follow the relevant regulations.
What Is The Density Of Plywood?
The density of plywood is greater than that of wood of the same species. The greater the unit pressure at the time of gluing, the greater the density of the plywood. Because wood is prone to plastic deformation at high temperatures. hot pressing is more compressive than cold pressing. Because the plywood made up of criss-crossing veneers. its thermal conductivity is lower than that of the same wood.
What Are The Regulations For The Bonding Strength Of Plywood?
The bonding strength of plywood is under Chinese national standards:
1.2 to 1.6 MPa for Class I plywood, 1 to 1.4 MPa for Class II, 1 to 1.2 MPa for Class III, and 1 MPa for Class IV.
What Are The Quality Requirements For Plywood?
The quality requirements of plywood include:
appearance grade, size and physical and mechanical properties. The three tests of :
appearance grade, specification size and physical. and mechanical properties all judge that the product is a qualified product. otherwise it unqualified. Plywood must certified by the quality inspection department of the manufacturer. and must state:
the type, specification, grade, bonding strength and moisture content of the plywood.
Specifications of ordinary plywood: The thickness of plywood is 2.7mm, 3.3mm, 4.5mm, 5.5mm, 6mm... From 6mm, increase by lmm. The thickness is from 4 mm or less to thin plywood. 3mm, 3.5mm, 4mm thick plywood is a common specification. Other thickness plywood must produced after agreement between the supplier and the buyer.
After the ordinary plywood processed, the defects. and processing defects of the visible materials divided into four grades:
special grade, first grade, second grade, third grade, etc.,
The above four grades of panels should sanded (scratched). and those with special needs may not sand (scrape) light or double-faced sand (scraping) light. Sanding plywood refers to plywood that sanded (or scraped) by a sander (or scraper). The grade is generally determined by visual inspection of the allowable defects on the plywood. The grade depends on the allowed material defects, processing defects. and the requirements for splicing.
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