The purpose of this research was to correlate the applied material properties of stretch film with its elastic properties measured in a laboratory setting. There are currently no tools available for a packaging engineer to make a scientific decision on how one stretch film performs against another without applying the film. The system for stretch wrap comparison is mostly based on trial and error which can lead to a significant loss of product when testing a new film or shipping a new product for the first time. If the properties of applied stretch film could be predicted using a tensile test method, many different films could be compared at once without actually applying the film, saving time and money and reducing risk. The current method for evaluating the tensile properties of stretch film advises the user apply a hysteresis test to a standard sample size and calculate several standard engineering values. This test does not represent how the material is actually used. Therefore, a new tensile testing method was developed that considers the film gauge (thickness) and its prestretch. The results of this testing method allowed for the calculation of the material stiffness (Bisha Stiffness) and were used to predict its performance in unit load containment. Applied stretch film is currently compared measuring containment force, which current standards define as the amount of force required to pull out a 15.2cm diameter plate, 10.1cm out, located 25.4cm down from the top and 45.7cm over from the side of a standard 121.9cm width unit load. Given this definition, increasing the amount of force required to pull the plate out can be achieved by manipulating two different stretch film properties, either increasing the stiffness of the film or increasing the tension of the film across the face of the unit load during the application process. Therefore, for this research, the traditional definition of containment force has been broken down into two components. Applied film stiffness was defined as the amount of force required to pull the film a given distance off the unit load. Containment force was defined as the amount of force that an applied film exerts on the corner of the unit load. The applied stretch film was evaluated using two different methods. The first method used the standard 10.1cm pull plate (same plate as ASTM D 4649) to measure the force required to pull the film out at different increments from the center on the face of the unit load. This measurement force was transformed into a material stiffness and film tension (which were subsequently resolved into containment force). The second, newly developed, method involved wrapping a bar under the film, on the corner of the unit load, and pulling out on the bar with a tensile testing machine. This method allowed for the direct measurement of the containment force and material stiffness. The results indicated that while some statistically significant differences were found for certain films, the material stiffness and containment were relatively consistent and comparable using either method.The use of the Bisha Stiffness to predict the applied stiffness and containment force yielded a statistically significant correlation but with a very low coefficient of determination. These results suggest that while film thickness and prestretch are key variables that can predict applied stiffness and containment force, more research should be conducted to study other variables that may allow for a better. High variability of the predictions observed were caused by the differences in film morphology between the different method of elongation (tensile vs application). This study was the first that attempted to define and correlate the tensile properties of stretch film and the applied properties of stretch film. From this research many, terms have been clarified, myths have been dispelled, formulas have been properly derived and applied to the data collected and a clear path forward had been laid out for future researchers to be able to predict applied stiffness and containment force from the elastic properties of stretch film. / Ph. D.

Thesis summarizes the problems of production and use of stretch film. The change of strength, ductility and relative relaxation effect in different times of drawing from role in three weeks was observed. Further, change of strength and ductility due to changes in the rate of deformation, exposure to accelerated aging in a UV chamber and changes in the loading direction were observed. Mechanical tests were realized on a tensile tester, relaxation tests on DMA and crystallinity changes were observed on the DSC. Relationship between chemical composition of stretch film and mechanical and thermomechanical properties were studied. It was found that chemical composition essential for stretch film properties. However, due to the impossibility to distinguish effects of chemical composition and process parameters was impossible to find clear relation describing this relationship.

El actual estudio tiene como propósito principal describir la reducción de las importaciones de resinas sintéticas y su impacto en los costos de producción de stretch film para el packaging del sector alimenticio en Lima Metropolitana año 2020, para ello; se estudiaron las variables de disminución de importaciones, costos de producción de stretch film y su impacto en la industria del packaging del sector alimenticio a través de dimensiones como: tiempo de importación, escasez de resinas sintéticas, costos de producción, costo unitario, ventas y precio de venta fijado. El contenido del estudio consta de cinco capítulos; El marco teórico del primer capítulo, expone las teorías científicas y las bases legales que sustentan la investigación. El segundo capítulo incluye el plan de investigación, conformado por el planteamiento del problema en el contexto de la pandemia por el COVID 19, los objetivos generales, los objetivos específicos, los supuestos específicos y los supuestos generales de la tesis. El capítulo III presenta en detalle la metodología de la investigación cualitativa y cuantitativa. El capítulo IV, presenta el análisis de los resultados cualitativos y cuantitativos y, se comprueba la hipótesis general acerca de la reducción en importación de resinas sintéticas para la fabricación del stretch film durante el 2020 y su impacto negativo en los costos de producción según la información suministrada en los instrumentos de recolección de datos, para el packaging del sector alimenticio en Lima Metropolitana. Finalmente, en el capítulo V, se analizan las conclusiones y recomendaciones de acuerdo a los resultados obtenidos de forma coherente con los objetivos propuestos, destacando la pertinencia del estudio y su impactó en el sector industrial. / The main purpose of this study is to describe the reduction in imports of synthetic resins and their impact on the production costs of stretch film for packaging in the food sector in Metropolitan Lima in 2020, for this; The variables of decrease in imports, production costs of stretch film and its impact on the packaging industry of the food sector were studied through dimensions such as: import time, shortage of synthetic resins, production costs, unit cost, sales and fixed selling price. The content of the study consists of five chapters; The theoretical framework of the first chapter exposes the scientific theories and the legal bases that support the investigation. The second chapter includes the research plan, made up of the problem statement in the context of the COVID 19 pandemic, the general objectives, the specific objectives, the specific assumptions and the general assumptions of the thesis. Chapter III presents in detail the methodology of qualitative and quantitative research. Chapter IV presents the analysis of the qualitative and quantitative results and the general hypothesis about the reduction in the import of synthetic resins for the manufacture of stretch film during 2020 and its negative impact on production costs according to the information provided in the data collection instruments, for the packaging of the food sector in Metropolitan Lima. Finally, in chapter V, the conclusions and recommendations are analyzed according to the results obtained in a manner consistent with the proposed objectives, highlighting the relevance of the study and its impact on the industrial sector. / Tesis