Summury
The main limitation of using plywood for interior and industrial applications are their flammability as wood is a natural growing material that consists mainly of combustible of organic compounds. The growing use of plywood for structural purposes has evoked considerable interest in the possibility of reducing fire hazard by use of veneer treated with fire retardant chemicals. The objective of this study were to develop a fire retardancy adhesive composition for plywood and to investigate the fire retardancy properties of the manufactured plywood using PMUF resin modified with phosphate, also the impact of adhesive on the physical and mechanical properties of the board. In order to produce Fire proof board with good properties such as; fire-resistance, environmental protection and good bonding PMUF resin was synthesized with molar ratio
of F:P:M:U at 4.6:2.0:0.42:0.29.with Tricresyl phosphate (TCP). Di-sodiumocta-borate tetra hydrate (DOT), precipitate silica and sodium silicate powder as an additive for glue formulation, Two sets of 12 mm plywood were manufactured and fire resistance and mechanical properties were studied as per IS:5509:2000. It was observed that satisfactory fire retardancy properties like flame penetration, flammability and flame penetration was achieved when tested as per IS:5509:2000. Plywood samples confirms the properties as per the requirement of IS:5509:2000.
Process of plywood manufacturing:-
PMUF Resin were synthesized according to a traditional two step procedure at F:P:M:U Molar ratio of 4.6:2:0.42:0.29. Using synthesized PMUF resin adhesive mix was formulated by mixing synthetic resin, additive at various concentrations from extension level. Under stirring with a speed regulated stirrer. The mixing was continued for 30 minutes until a homogeneous mixture was obtained. Viscosity of the glue after mixing was taken in B6 Cup (IS:3944-1982 ).
Two sets plywood were manufactured by taking Gurjan (Dipterocarpus) species as core, face and back veneer of size 2’ x2’ and 12mm thickness .Adhesive mix was applied each veneer both core and panel and conditioned for moisture content up to 14% with a roller coater at a spread rate 220 – 250gms/m2 on both sides basis .The spread veneers were then pressed in a hot press at pressure 16 Kg/cm2, 14 Kg/cm2 and temperature 1300C -1350C for 15 minutes to get 12mm thick plywood .The total assembling time ,which includes from first adhesive application to hot pressing was taken one hour.. The plywood specimen were conditioned for 07 days to achieve equilibrium mixture at 23ºC and 50% RH before cutting samples for testing as per IS:5509:2000.
Testing :-
Control and sample specimens of special dimensions were prepared and subjected to tests. To assess the fire retardancy properties, the following tests to be carried out:
- Fire resistance test as per ASTM E 162
- Flame penetration test as per IS : 1734-1983 (Part-3)
- Flammability test as per IS : 1734-1983 (Part-3)
- Rate of Burning test as per IS : 1734-1983 (Part-3)
The plywood samples control, using PMUF adhesive and plywood with adhesive and additive were tested conforming to IS5590-2000. To assess the fire retardancy properties of the plywood after coating, flammability test, flame penetration test and rate of burning test were carried out.
Results :-
It has been observed that in the presence of heat or flame the substrate reducing the penetration of heat, thus retarding the flame spread and delaying structural failure. The results of fire retardancy complies with the requirement of IS5509:2000By using the adhesive and additive composition significant improvement of fire retardancy and bonding properties was achieved by impregnation of chemicals into the veneer made the wood stiffer and brittle. Under the heating action phosphorous compounds decomposes at lower temperature to give phosphoric acid then creates an intumescent protection layer which prevents further oxidation and improves the char formation. Boron compounds decompose under heat to form a glossy protection layer which act as a barrier for polymer chain oxidation. Both phosphorous and boron compounds also act as smoke suppressant. Silicate compounds act as high thermal stability Treated plywood which shows a
marked improvement compared to untreated plywood. The improvement in tire resistance depended upon the type and concentration of treated chemical and the from the fire retardancy test thickness of the plywood. The results from mechanical test indicate that new fire retardant combination exhibit superior mechanical strength in comparison to commercial treated plywood.
Conclusion:-
In conclusion since a wide range of fire retardant treatment and coating systems for wood have been studied throughout recent years and many others are currently under development and combinations of phosphorus and nitrogen continue to prove themselves as very powerful solutions for wood-based applications. The results of this study show that the above fire retardant adhesive can be successfully used for manufacture of fire retardant plywood instead of traditional veneer and plywood treated method. By using the adhesive and additive composition significant improvement of fire retardancy and bonding properties was achieved by impregnation of chemicals into the veneer made the wood stiffer and brittle.