Film Faced Plywood is a kind of water-resistant plywood, it is used more and more widely as formwork in formwork scaffolding system because of the advantages: flat surface, no adhesion to concrete, fast construction, flexibility, friendly to the environment and users,… and has a reasonable price.
The working environment of Film Face Plywood is harsh environment due to direct contact to water and high temperature generated by concrete solidify process.
The quality of the formwork determines the quality of the concrete surface, the cost of construction, the cost of finishing the ceiling, walls, …
To make the formwork durable and reusable many times, the key issue lies in the quality of the glue.
Adhesive between layers of wood, it is largely determined by the type of glue, the quality of the glue used.
In the current water-resistant Plywood production industry, the most commonly used glue is Melamine Formaldehyde (MF) because of its good water-resistant properties, reasonable price, and suitable for industrial production capacity. Here we learn the basic features of MF glue.
1. What is Melamin Formaldehyde glue– MF ?
Melamine Formaldehyde glue is often abbreviated as Melamine glue. Melamine glue is a high-molecular-weight compound formed by the multi-condensation reaction of melamine and formaldehyde under the action of a catalyst.
The molecular formula of colloidal melamine is C3H6N6 in appearance, it is a colorless crystal, slightly soluble in cold water, the saturation increases with temperature, the solubility in alcohol and organic solutions is very low, but it is very soluble in water. high temperature formaldehyde solution.
The addition reaction and the multi-capacitor reaction to form MF colloid with the chemical formula C3H6N6-m – (HOCH)m take place as follows:
2. Factors affecting the quality of MF glue
In the process of configuring MF glue, the factors affecting the colloid include: Molar ratio of raw materials, conditions of pH value of reaction medium, reaction temperature, content of substances of raw materials, how to recover the endpoint of the maximum reaction….
Currently in Vietnam Melamine glue is produced according to different regulations leading to different prices and quality.
On an industrial scale, glue is produced in large factories such as AICA; BETTER RESIN…which is invested with modern equipment, self-produces and synthesizes Formalin (Formaldehyde solution) and uses imported Melamine.
The quality of glue produced at these factories is usually stable due to the standardization of raw materials, very few impurities, accurate quantification of reactants, and control reaction process by catalysts through advanced measuring equipment.
At small-scale spontaneous glue annealing, Melamine glue usually does not have stable quality due to the raw materials having many impurities, unstable heat sources, inaccurate reaction quantification, reaction reactions are often based on experience. The products of the person in charge and the output equipment are not synchronized and modern.
In addition to reducing product costs, glue ingredients often use some cheaper compounds to replace Melamine such as Urea, this when performed incorrectly can reduce the glue, increase the ability formaldehyde emission, which affects the health of producers and users.
3. Advantages and Disadvantages of MF glue and modification methods.
Advantages:
Very high adhesion, very good resistance to hot and cold water, high chemical reactivity, good curing ability when heated without curing additives. The adhesive film after curing has high hardness, good wear resistance, and is stable even at high temperatures.
Therefore, Melamine glue is suitable for the production of water-resistant plywood, exterior board;
Disadvantages:
The production cost of MF glue is relatively high, the storage time is short, the glue film after solidify is brittle, making the joints prone to cracks.
To improve and overcome these limitations, reputable glue manufacturers often use a number of methods to modify glue in the production process:
- Improve brittleness by adding alcohol C2H5OH, polyester, polyamide,…;
- Improve storage time by adding pure alcohol C60H90O5, diluent;
- Reduce costs by using appropriate small amounts of melamine substitutes such as Urea.
4. Film Faced Plywood Glue
Due to the requirement of good water resistance and heat resistance, Melamine glue is often used to produce film-coated formwork with different % Melamine content depending on the quality needs of the product.
Currently, glue cooking facilities often use the names: Min 5% glue; Min glue 10%; Min glue 12%; Min glue 15%; glue Min 18%, etc., call the glues they cook themselves to serve the production of Film Coated Plywood with the implication referring to the % mass of Melamine they use when cooking the glue.
However, this naming has only relative meaning, self-regulation and does not accurately reflect the percentage of Melamine chemicals used to produce glue.
In contrast to people’s glue factories, glue factories often have their own production formulas and their own modification methods to produce glue.
The technical parameters of each type of glue are measured specifically to check the quality of the finished glue, including: Viscosity, solid content, flocculation time, free formaline content, pH,….
The adhesion quality of different glues will be shown through the boiling time without delamination, the tensile strength of wood samples under standard test conditions.
There is a conversion from the concept of % melamine content and corresponding plywood quality, which is generally accepted when naming and comparing types of melamine glue produced by factories and glue factories as follows:
| Named follow % Melamine | Time to boiling follow commitment | The grade of veneer should be used | Time to reused |
| Melamin glue 5% | >2 h | ABC | 1-2 |
| Melamin glue 8% | 2-4 h. | ABC | 2-4 |
| Melamin glue 10% | 4-6 h. | ABC | 4-6 |
| Melamin glue 12% | 6-8 h. | ABB | 6-8 |
| Melamin glue 15% | 10-12 h. | AAB | 8-10 |
| Melamin glue 18% | 12-15 h. | AAA | 10-12 |
| Melamine glue 25% | 20 h. | AAA | 15-20 |
This post introduces an overview of Melamine Glue (MF) a commonly used glue for the production of Film Faced Plywood.
In general, the quality of glue makes an important contribution to the quality of the board, in addition to the uniform quality of other materials (veneer, film paper, production process and quality monitoring).
The cost of glue normally accounts for 10-15% of the production cost of Film Faced Plywood.
But with its important role, Glue should be the last object to think about when you want to reduce production costs by adjusting it’s quantity and quality.
Written by: NhatminhCI
