Analytical Study of the Influence of Recycled Content on the Thermal and Mechanical Properties of Polyethylene Terephthalate Bottles for the Nigerian Beverage Industry

The Nigerian beverage industry is a major consumer of polyethylene terephthalate bottles, with growing regulatory and market pressure to incorporate recycled content. However, the effect of recycled polyethylene terephthalate content on the thermal and mechanical performance of production bottles has not been established for conditions prevailing in Nigerian bottle-blowing facilities. This study analytically characterises the effect of recycled polyethylene terephthalate blended at 15, 30, and 45 percent by weight with virgin resin on the mechanical and thermal properties of stretch blow-moulded bottles produced at a facility in Lagos State, South West Nigeria. Intrinsic viscosity, acetaldehyde content, melting behaviour by differential scanning calorimetry, tensile properties, top load strength, and stress crack resistance were evaluated on bottle preforms and finished bottles. Acetaldehyde evolution, critical for flavour protection in water and carbonated soft drink bottles, was measured by headspace gas chromatography. Results indicate intrinsic viscosity declined from 0.82 dL/g at 0 percent recycled content to 0.76 dL/g at 45 percent recycled content. Top load strength of carbonated beverage bottles decreased by 12 percent at 45 percent recycled content, remaining within specification limits for standard bottle designs. Acetaldehyde content increased with recycled content, reaching 4.8 micrograms per litre at 45 percent recycled content, approaching regulatory limits for still water packaging. Stress crack resistance declined significantly at 45 percent recycled content in alkaline environment testing. The study recommends recycled content limits of 30 percent for still water bottles and 20 percent for carbonated beverage bottles to maintain product quality standards in Nigerian beverage production. Keywords: recycled PET, bottle production, beverage industry, acetaldehyde, intrinsic viscosity