Professional training would be good for most of the Plywood QC/QA Parts 4 :HPL plywood

HPL plywood ,from the name ,you can know that the top face and bottom back is HPL sheets laminated .So,how to grade and inspect the HPL Plywood ?The platform are overlaid with HPL (High Pressure Laminate) on one or both sides. On the reverse side balance paper can be applied.

Let’s start from the HPL sheets ,HPL (High Pressure Laminate) is a decorative high-pressure laminate. HPL is made of layers of Kraft paper impregnated with phenol resins (the core) and decorative melamine impregnated paper (the surface layer), manufactured under high pressure and temperature.HPL is the direct descendant of the original plastic laminate. It is considered to be one of the most durable decorative surface materials and is available with special performance properties including chemical, fire and wear resistance. Special grades of HPL can be postformed around curved edges by application of heat and restraint. HPL is produced by saturating multiple layers of kraft paper with phenolic resin. A layer of printed décor paper is placed on top of the kraft paper before pressing. The resulting sandwich is fused together under heat and pressure .

HPL overlay is glued with D2, D3 or D4 class glues,most of the chinese plywood factories using different kinds of glue to make HPL plywood,cold pressing always ,need about 4 to 6 hours per shift .

HPL  Plywood,means ,the inside core is veneer core ,the top fc and bottom bk is HPL sheets .It is like the melamine Paper and Film of the film faced plywod,the quality decided by the Printed paper and the glue used for making the HPL sheets and hot pressing temperature and pressure .

Furniture industry: kitchen and laboratory furniture components and worktops; furniture for shops.
Transport industry and construction: finishing works of walls and ceiling, surfaces where high wear resistance and appearance are required.

Chinese HPL Plywood is a plywood platform or substrate  plywood overlaid on both sides with an attractive, hard wearing HPL (high pressure laminate). The HPL provides the plywood with a durable, decorative surface and is now available in a selection of modern colours. The strength and stability of the Chinese Poplar and Eucalyptus , combined with the hard wearing HPL surface, allows for a wide range of furniture and joinery applications. Clashing of sheet edges is not required as the fine veneer lay-up provides the  HPL with an attractive edge detail which can be clear finished to emphasise the superior multi-ply edge detail.

THE HPL SHEETS thickness used for plywood are normally 0.5mm,0.6mm,0.8mm present .IF special items,the thickness can be changed .

Somebody called the HPL also fireproof plywood ,but we tested ,most of the HPL plywood is not fireproof if no special production process and no chemical addictives added .So ,don’t missunderstand this .

The famous HPL is formica ,famous and good quality .

The HPL has many different colors and finishes ,HPL: Smooth and rough/textured ,also called gloss and matt finish .
HPL color:white, maple grain or other fancy wood grain etcmm,

Thickness are normally 4.8mm, 5mm, 5.2mm, 5.5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 15mm, 16mm, 17mm, 18mm, 20mm, 21mm, 22mm, 25mm, 28mm, 30mm

When inspect the HPL plywood or the HPL sheets,make sure you can fully understand the HPL quality basic defects ,take the HPL samples with you ,check the color difference ,thickness ,wood grain or solid color ,any bubbles of the sheets ,delamianted kraft paper ?Brisk or damaged edges ,easy break or not ?As it is cold pressed ,check the edges of the HPL plywood to see if is good glue bond the HPL to the substrate ?

Especially the texture of the HPL sheets ,must be the same like the samples the customers required .Just test it .

HPL should be bonded to a suitable substrate such as standard or moisture resistant particleboard, standard or moisture resistant medium density fibreboard (MDF) or marine grade plywood. A smooth surface is important. Rougher substrates such as large chip reconstituted wood panels may result in a visually unacceptable finish.

Visual inspection (testing), Dimensional tolerances,  enables to produce high pressure laminates withoutdefects like warping and air pockets.Laminates, Decorative materials, Classification systems, Surface defects, Visual inspection (testing), Dimensional tolerances, Physical properties of materials, Dimensional changes, Fire resistance, Thermal resistance, Thermosetting polymers, Plastics, Sheet materials, Impregnated materials, Composite materials, Strength of materials, Grades (quality), Designations, Performance, Defects, Ratings, Water absorption, Stains (discoloration), Impact strength, Colour fastness

Thickness tolerance  Length tolerance Width tolerance  Straightness of edges  Flatness (length) ≤ 60 mm/m EN 438-2 Edge defects ≤ 20 mm EN  Surface defects Density

The boards are laminated under high temperature and pressure, the boards are free from defects like waviness, telescopy, air pockets and other bonding defects

The last is the Cold press Glue used for HPL ,

Let’s discuss the Cold Press Veneer Glue for HPL

Coverage: 250 sq. ft. per gallon

Total assembly time: 15 min.

Full strength time: 24 hrs.

Minimum clamp time: 30 min.

Cold Press for HPL is specifically formulated for cold press laminating of High Pressure Laminates (HPL) and HPL backed veneers to porous materials.It offers a moderate speed of set, a translucent glue line and contains none of the harmful or corrosive fumes typical of most contact cements.

Hot presses work on pressure and heat. The heat makes the glue work faster, so the press time is shorter. One panel at a time, press 3 to 5 minutes, and let set for 4 to 6 hours; then it’s ready to use.

Cold presses works on pressure. The cold press is meant to get maximum pressure for a short period of time on a maximum amount of material. You can press 10 to 20 pieces of material at a time, for approximately 20 minuntes, then let set for 6 to 8 hours and the material is ready to use.

When gluing veneer, the best possible bond is achieved with a hot press. Millions of board feet of plywood are produced this way every day. HPL, on the other hand, can be successfully glued with contact cement or PVA (white glue) using a pinch roller. Far from being a new method, it’s actually been done for years by many skilled lay-up persons. – See more at:

 

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