SYNTHESIS, FORMULATION AND CHARACTERIZATION OF PHENOL FORMALDEHYDE/CHITOSAN COMPOSITES
The methodology of the experiment involves three main stages. The first part describes the synthesis of the PF (novolac) resins. Novolac (resins) were prepared with an excess of phenol over formaldehyde under acidic conditions. PF molar ratio were varied from 1P:2F to 1P:8F. The structure of the PF was determined using FT-IR techniques. The preparation and characterization was reported. The physicochemical properties tests carried out on the (novolac) resins include pH, viscosity, water-tolerance, density, resin solid content, gel time, cure time and yield%. Emission tests such as free formaldehyde content and free phenol content were determined . The second part involves synthesis of chitosan from commercial chitin with different degree of substitutions determined by potentiometric titration. Characterization using FT-IR of the fresh chitin and the deacetylated chitosan was carried out and functional groups were observed and compared with the standard values. The following analysis were carried out on the chitin: loss on drying, moisture content, % solubility, solubility in chemicals, density, pH value, and ash content. The solubility of the chitosan were tested in various solutions like distilled water, acetone, ethanol, acetic acid and lactic acid. The third part was the production of the composites with different P: F molar ratio 1P:2F to 1P:8F and filler loading were varied 10% to 50%. A total of thirty five composites were produced, fabricated and subjected to mechanical properties.from the physiochemical properties of density, water absorption and tensile strength/modulus of composites at different filler loading of 10% to 50% using 5%w/v Heaxemethylenetetramine (HMTA) as the hardener, loading of 40% with 1P:4F and 1P:2F gave excellent results in terms of mechanical properties. The results of the mechanical properties revealed that the tensile strength and the tensile modulus increases with the increase of the filler loading. Further analysis was carried out to determine the optimum from the composites at different filler loading. To prove the results, optimization of 1P:2F to 1P:4F were carried out with the filler at different degree of deacetylation (DD) % values. In this case, the DD% values were increased by increasing the concentration of the alkali (NaOH) at 30%, 40% and 50%w/v at a temperature of 120oC. The approximate calculated values of 70%, 81.47% and 90.92% DD of the chitosan were obtained and composites using P: F molar ratio of 1P:2F and 1P:4F were prepared. The composites were then subjected to various analysis to obtain the optimization of the composites. In order to characterize the chitosan phenol formaldehyde composites, several analysis were carried out on the following sample, neat polymer (100%), untreated, 70%, 81.47% and 90.92% DD were carried out. Swelling behaviors tested using the following solvents water, carbon
tetrachloride, ethanol and acetone, and the results obtained were reasonable. Chemical resistance on the 40% of 1P:4F and 1P:2F were carried out in 1N HCl and 1N NaOH at 72 hours. A very good results were obtained for samples 70%, 81.47% and 90.92% with an average result of around 7%. But the basicity behaviors was poor in 1N NaOH solution with the highest value in the untreated 12.5% were observed. Other tests carried out were density and water absorption, the densities were in the range of 1.8g/cm3 for 60% to 0.82g/cm3 for untreated.The water absorption measurement was found to be excellent in all the samples, lowest value was observed in 91% and highest for 70% DD. Neat matrix showed complete resistance to water absorption. Mechanical properties tests of: tensile strength/modulus (38% improvement), flexural strength/modulus (27% improvement), impact (65% improvement) and hardness (25% improvement) of filler loading of 40% at DD of 70% gave an excellent results. Formaldehyde emission test using flask method were carried out on the composites. The effect of DD on emission was found to be highest in 70% DD and lowest in 91% DD. The effect of chitosan in reduction of formaldehyde release in the production of chitosan/P:F composite mechanism of reaction between chitosan and novolac resin were drawn. The use of chitosan in the production of composite have significantly reduced the emission. The SEM studies of the samples were investigated and. morphological results clearly showed that when the polymer resin matrix was reinforced with the different loadings of chitosan 70% to 90.92% DD surface modification took place. Wide angle x-ray analysis (XRD) was carried out to investigate the effectiveness of the resin interaction Thermal analysis of the reinforced chitosan phenol formaldehyde composites as compared to the virgin polymer had improved from 330oC to 615oC. Improved stability was manifested throughout the whole range of temperature studied. The overall results of the research show that composites which were deacetylated, reinforced and cured with hardner (HMTA) gave excellent results than those without deacetylation and curing.