Polyethylene terephthalate (PET)/nano‐hydroxyapatite (nHAp) composite granules were obtained using twin‐screw extruder. Preforms were prepared by injection molding and then PET/nHAp bottles were produced by blow molding. For PET bottles with nHAp, the migration amounts of carboxylic acid (COOH), acetaldehyde (AA), diethylene glycol (DEG), and isophthalic acid (IPA); glass transition temperature (Tg); melting temperature (Tm); and the maximum crystallization temperature (Tcry) were measured. The load‐carrying capacity, burst strength, stress cracking, and regional material distribution tests were carried out on the bottles. X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and ultraviolet transmittance analyses were conducted to explain the changes in mechanical, chemical, physical properties, and light transmission of bottles. It was found out that the COOH amount increased and the AA content decreased with increasing nHAp amount. On the other hand, no change was observed in the amounts of DEG and IPA. Although the mechanical properties such as load‐carrying capacity and burst strength of the bottles have improved, it has been determined that the standard environmental stress crack resistance test procedure cannot be applied to such a composite. Experimental findings indicate that nHAp disrupts the chemical structure of PET and it isolates harmful chemicals such as AA by forming intermolecular bonds. Moreover, with the addition of up to 0.8% nHAp, PET bottles block the light transmission approximately 80% within 400–700 nm wave length zone. The study demonstrates that the PET/nHAp composite bottles can be used in the food industry, particularly in the packaging of milk and milk products which are vulnerable to light exposure.

This study deals with the improvement of light barrier properties and stress cracking strength of polyethylene terephthalate (PET) packaging materials by incorporating calcium metaborate (CaB 2 O 4 ). CaB 2 O 4 powders were synthesized by the sol-gel method. After the extrusion process produced PET/ CaB 2 O 4 granules, the preform and bottle production was carried out by injection molding and blow molding. Compared to pure PET, UV transmittance is reduced (~88%), and it is more effective at lower wavelengths (<800 nm). Similarly, the presence of CaB 2 O 4 improved the environmental stress cracking performance of PET packaging materials. While the burst strength increased in the range of 0.05%-0.2% CaB 2 O 4 concentration, it decreased at higher concentrations. The load-carrying capacity is approximately 109% higher than pure PET. Acetic acid (COOH) degradation increased with the incorporation of CaB 2 O 4 particles, while isophthalic acid and diethylene glycol degradations did not change. The experimental data indicate that the photocatalytic degradation of the PET bottle is prevented significantly, and its mechanical performance is also improved with the incorporation of CaB 2 O 4 . Thanks to this novel product, the quality of food and beverages in PET packaging materials can be protected from the harmful effects of light, and the deformation of PET packaging materials can be prevented for various reasons.