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| The Effect of Boric Acid on the Adhesive Properties of Polyethylene glycol-Polyvinyl Alcohol Composite |
Orlando Ketebu, Kotingo Kelvin and Egai Tariboladei Nimiye
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Abstract:
The use of organic solvents such as formaldehydes and its mixtures as conventionally adhesives has been identified as toxic and dangerous to human health because of its ability to cause cancer and affect the environment negatively. The need for an eco-friendly adhesive has been of greater concern. Synthetic polymers such as polyvinyl alcohol (PVA) which are water-soluble polymers with hydroxyl groups can be cross-linked and combined with other natural polymers or synthetic polymers to improve its mechanical properties for use as adhesives. This work looks at combining PVA with another water soluble polymer Polyethylene glycol (PEG) and the composite PVA-PEG cross linked with different concentration of boric acid (BOR) to improve the adhesive and mechanical properties of PVA-PEG adhesives as an alternative for organic adhesive. The experimental result showed that with the addition of 0.5 % and 1% boric acid to form PVA-PEG-BOR adhesive showed an increase in the adhesive properties of PVA-PEG composite from 0%, to 0.5 % and 1%. The XRD diffraction peaks (100) and (200) at 2? angles 17.89o and 23.48o respectively indicates the formation PVA-PEG composite adhesives. The broadening of the diffraction peaks (100) and (200) in PVA-PEG-BOR (0.5%) and PVA-PEG-BOR (1%) compared to PVA-PEG control shows reduced PVA chains crystallization due to increased plasticization between water and PEG. This in turn favours reduced melting point of PVA and improves its mechanical properties. The Fourier infrared results showed the presence of hydroxyl group stretching at 3200 cm-1, carbon hydrogen stretching (2900 cm-1)and bending frequencies(1300 cm-1)with reduced intensities for PVA-PEG-BOR (1%) followed by PEG-BOR (0.5%)indicating structural changes due to the presence of boric acid. The viscosity of PVA-PEG-BOR composite adhesives increased by the addition of boric acid from 0.5 to 1% and since increase in viscosity is directly proportional to tensile strength; it also means increase in tensile strength and mechanical properties of the adhesive.
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