Synthesis and characterization of bio-adhesive using natural rubber latex and bio-based fillers for medium density fibreboard manufacturing

The over-exploitation of synthetic adhesives in wood composite manufacturing industries has become a major threat to environment and consumers’ health due to its carcinogenic formaldehyde emissions. In order to overcome this issue, this study has been focused towards the development of bio-based adhesive from natural rubber latex (NRL) incorporated with rice starch (RS) and lignin as the fillers, by blending technique.These fillers are vital in order to enhance the mechanical properties of NRL and thus, their respective compatibility with the base material upon blending is compared.. Prior to the blending, RS were subjected to chemical modification using hydrochloric acid (HCl) and sodium hydroxide (NaOH). Acid hydrolysis of 1M HCl for 60 minutes at 55°C and alkaline hydrolysis using 2M NaOH for 60 minutes at 45°C yielded modified RS with the best working shear strength of 0.38MPa and 0.43MPa respectively. Both acid and alkali modified RS were blended with NRL in weight content of 0%,25%,50%,75% and 100% accordingly.The bio-adhesives were characterized physically into gel time, viscosity and solid content. Consequently, all formulations were applied for medium density fibreboard(MDF) manufacturing via hot pressing at 180°C for 4 minutes and board specimens were characterized mechanically in terms of modulus of rupture(MOR), modulus of elasticity (MOE), internal bonding(IB) and thickness swelling(TS). Thermal stability is analyzed through thermogravimetric analysis (TGA) while the chemical interaction that resulted through incorporation of fillers with NRL is studied through Fourier transform infrared spectroscopy(FTIR) and the morphological analysis is observed through scanning electron microscopy(SEM). The results indicated that bio-adhesive formulation that contains the highest by weight content of acid and alkali modified RS exhibited outstanding MOR of 26.4MPa and 36.7MPa while IB of 0.39MPa and 0.66MPa respectively. As an overall, alkali modified RS exhibited greater mechanical adhesive performances compared to HCl modified RS. Moreover, thermal analysis proved that RS content by weight of 75% in bio-adhesive formulation exhibited significant weight loss at 361.73 °C, indicating that incorporation of RS actually enhances the thermal oxidative stability of bio-adhesive. The second part of this study revolves around the development and application of bio-adhesive from NRL, incorporated withE. Blending with NRL was performed by varying filler weight content (0%,25%,50%,75%,100%).Similar physical, mechanical, morphological and thermal analysis were investigated. Samples bonded with NRL-EHL bio-adhesives showed deteriorating effect on the MOR and IB values of MDF, where MOR declined from 15MPa to 4MPa when EHL loading was increased from 25wt% to 100wt% due to incompatibility between EHL and NRL matrices. Alkaline activation of EHL using 3M NaOH was applied to improve the performance of EHL based bio-adhesive. Consequently, bio-adhesive formulation with equivalent weight content of NRL and NaOH activated EHL exceeded ASTM standard requirement by yielding MDF with MOR of 36 MPa. The IB recorded was 0.75MPa which proved that alkaline modification of EHL enhanced the dispersion of filler into NRL matrix and caused better cross-linking between bio-polymers. Thoroughly, alkaline activated EHL incorporation into NRL formulation gave better physical, mechanical and thermal performance of the bio-adhesives compared to modified RS and EHL. As a conclusion, this study serves as a platform to prove that bio-polymers such as RS and EHL can be viable filler for NRL, with activated EHL to be the best option of fillers

STUDY OF DIFFERENT TREATMENT METHODS ON CHICKEN FEATHER BIOMASS

The chicken feathers (CFs)  consist of up to 10 % of total chicken dry mass and they have many potential industrial applications. CFs contains protein fibers named as keratin, which is an insoluble protein. Primary sanitization phases are complex because of the presence of lots of blood born microbes, pathogens and parasites in raw biomass. The extraction process of keratins from the unprocessed feathers is also a challenging task. Prior to the extraction cleaning/sanitization of feathers is a very necessary step. Thus, the present work was conducted to optimize  an efficient surfactant  for the cleaning process of the  CFs by using ionic and non-ionic surfactants. The experiment was conducted by the washing of feathers with double distilled water (ddH2O), detergents, ether and lastly with boiling water. The washed feathers treated with surfactants and the effect of each surfactant was analyzed by a microbiological test which tells about the extent of  the presence of different bacteria on the treated feathers. SEM, EDX, FTIR were used to study the morphology and composition of  untreated and treated CFs. SEM showed there was no detectable fiber damage after treatment. Cetrimonium bromide (CTAB) (t3) was one of the best surfactant for the treatment of CFs among all the surfactant used. The present study described the best treatment method  for the CFs.

Novel natural rubber latex/lignin-based bio-adhesive: synthesis and its application on medium density fiber-board

The phenolic content in lignin makes it a potential substitute for formaldehyde-based synthetic wood adhesives. In the present work, lignin isolated from Hevea brasiliensis was treated with laccase enzyme to obtain active lignin. The activated lignin (NaOH treated) was further formulated with natural rubber latex (NR-latex) to prepare bio-adhesive. Complementary analysis such as modulus of rupture (MoR), modules of elasticity (MoE), internal bonding (IB), Fourier transform infrared (FTIR) spectroscopy, thickness swelling (TS), and scanning electron microscopy (SEM) were applied to characterize a medium density fibre-board (MDF) prepared based on bio-adhesive formulation. It was found that bio-adhesive formulation of 10 g NR-latex with 10 g of lignin has the highest MoR of 16 MPa, while the formulation of 15 g NR-latex with 5 g lignin showed the highest MoE of 15 MPa. The TS result showed that there is a weight gain on MDFs with a lower proportion of NR-latex content which consequently increases the density of the composites. The FTIR analysis of formulated bio-adhesive revealed the significant difference in chemical composition with different proportions of lignin and NR-latex in bio-adhesive. Finally, SEM examination of the interfaces of formulated bio-adhesive and wood fibre material showed the better dispersion with no adhesive lumps