Integrated kano model and quality function deployment method for circular product design: Application in the PVC sector

The strategic imperative for firms to align with circular economy principles has become crucial for sustainability and resource efficiency. Product design plays a critical role in this process by ensuring efficient resource utilization, reducing waste, and extending product lifespan. A review of the related literature reveals a lack of studies focusing on customer-oriented product design within the context of circularity strategies. Building on this gap, the objective of this study is to analyze how customer requirements can be identified and addressed by firms in the circular product design process using an integrated approach that combines the Kano Model and Quality Function Deployment (QFD) methodology. The application was carried out in a PVC door and window manufacturing company, Uzay Plastik A.Ş., located in Trabzon, Turkey. A three-phase implementation process was followed for this purpose. In the first phase, circular product design features for PVC door and window products were identified. In the second phase, customer demands in circular product design were classified using the Kano Model. For this, a survey was conducted with a total of 409 customers selected through a convenience sampling method. The third phase involved applying QFD at Uzay Plastik A.Ş. to determine how customer requirements could be technically addressed by the firm. In this phase, the importance weights of customer requirements were calculated, and technical requirements were identified. Subsequently, a relationship matrix was developed using fuzzy linguistic expressions to link customer requirements with technical requirements through the Quality Function Deployment method. Correlations among technical requirements were identified, and the technical requirements were prioritized using the Fuzzy TOPSIS method. Finally, a sensitivity analysis was conducted. Findings obtained using the Kano Model classified customer requirements into three different categories, including two attractive features. The weights of these features were calculated, with reliability emerging as the most important product feature. According to the analysis results, where technical requirements were prioritized using the Fuzzy TOPSIS method, modular product design was identified as the top priority technical requirement. Sensitivity analysis indicated that different scenarios did not alter the importance rankings of the technical requirements.