Research on unit load stability aids manufacturing facilities in selecting the most efficient load stabilizer when shipping their products to market. This study's objective was to compare the performance a variety of different commonly used load stabilizers to stretch hooding. Stretch hooding is a method of load stabilization in which a tubular film is heat sealed at the top, stretched by four mechanical arms to a desired width, pulled down over the unit load. The film is slowly released as the arms descend, and is released under the pallet. 400ga stretch hooding, 80ga and 63ga stretch wrap and strapping were tested. Twenty unit loads for both vibration and impact testing were used, with 5 replications per load stabilizer. Container displacement and pallet-container displacement were measured, and the number of tares in the load stabilizer film, on the corners of the test units, after testing, was noted. Container displacement was significantly greater during impact testing than in vibration testing. Strapping was the most effective stabilizer during vibration testing because of its ability to restrict vertical displacement. The stretch hooding was the most effective stabilizer during impact testing because of its ability to restrict horizontal displacement. / Master of Science

There are three main factors affecting the stability of a palletized load that is unitized by a stretch wrapping mechanism. These factors include the type of unitized load, wrapping configuration and shipping method. The wrapping configuration is determined on the basis of the type of unitized load and shipping method. For this study, the aforementioned components were referred to as the package, the product, and the distribution environment. These components come together to make up a stretch wrapping system. The package corresponds to the stretch wrap film that is packaging the unitized load and pallet. The product corresponds to the goods placed on the pallet to be packaged by the stretch wrapper. The distribution environment corresponds to the hazards that the packaged product will encounter in transit. This study was designed to observe and understand the interactions between each of the components of the stretch wrap system. Prior to stretch wrapping a pallet of product, the film is elongated or pre-stretched. The elastic nature of the stretch wrap forces the film to conform around the palletized load. It is hypothesized that the film force that the stretch wrap applies to the palletized load contributes to improved load containment. Hence, the objective of this study was to determine the existence of a correlation between percentage pre-stretch to change in film force and load containment. For the study, a range of pre-stretched unitized loads were subjected to ISTA 3E distribution testing. Simultaneously the film force was monitored during the period of distribution testing. Subsequent to distribution testing, the load dispersion was quantified. The data obtained from this test suggested that there is no correlation between percentage pre-stretch and change in film force or load containment. The study also compared three methods of calculating pre-stretch: the marking wheel procedure, tapeless measure, and film cut and weigh. It was found that the most consistent method was the marking wheel procedure, followed by the cut and weigh procedure, and the tapeless measure procedure.

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.