Thesis (M.S.)--Michigan State University. Packaging, 2008. / Title from PDF t.p. (Proquest, viewed on Aug. 11, 2009) Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 255-263). Available also in a digital version from Dissertation Abstracts.

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Yes / The shrinkage force exerted by restrained shape memory polymers can potentially be used to close cracks in structural concrete. This paper describes the physical processing and experimental work undertaken to develop high shrinkage die-drawn Polyethylene Terephthalate (PET) shape memory polymer tendons for use within a crack closure system. The extrusion and die-drawing procedure used to manufacture a series of PET tendon samples is described. The results from a set of restrained shrinkage tests, undertaken at differing activation temperatures, are also presented along with the mechanical properties of the most promising samples. The stress developed within the tendons is found to be related to the activation temperature, the cross-sectional area and to the draw rate used during manufacture. Comparisons with commercially-available PET strip samples used in previous research are made, demonstrating an increase in restrained shrinkage stress by a factor of two for manufactured PET filament samples. / Thanks must go to the EPSRC for their funding of the Materials for Life (M4L) project (EP/K026631/1) and to Costain Group PLC. for their industrial sponsorship of the project and author.

Results of an experimental test program are presented to determine the bursting strength of polyethylene terephthalate film and fabric cylinders containing axial silts of various lengths. The results demonstrate that the fabric material is superior to the film material as regards residual strength in the presence of a slit. It is shown that the strength-weight ratio of the fabric cylinders is approximately twice that of the film cylinders, largely due to the strength advantage of fiber over film. The results are compared with the predicted bursting strength obtained from two different semiempirical analyses, one based on notch strength analysis and the other employing fracture mechanics concepts. The comparison demonstrates that large errors can result from the application of the notch-strength analysis yields a scatter band which is consistent with the data scatter and follows the trend of the data. / Master of Science

Polyethylene Terephthalate (PET) is one of the most important polymers in use today for packaging due to its outstanding properties. The usage of PET has grown at the highest rate compared with other plastic packaging over the last 20 years, and it is anticipated that the increase in global demand will be around 6% in the 2010-2015 period. The rheological behaviour, thermal properties, tensile modulus, permeability properties and degradation phenomena of PET/clay nanocomposites have been investigated in this project. An overall, important finding is that incorporation of nanoclays in PET gives rise to improvements in several key process and product parameters together - processability/ reduced process energy, thermal properties, barrier properties and stiffness. The PET pellets have been compounded with carefully selected nanoclays (Somasif MAE, Somasif MTE and Cloisite 25A) via twin screw extrusion to produce PET/clay nanocomposites at various weight fractions of nanoclay (1, 3, 5, 20 wt.%). The nanoclays vary in the aspect ratio of the platelets, surfactant and/or gallery spacing so different effect are to be expected. The materials were carefully prepared prior to processing in terms of sufficient drying and re-crystallisation of the amorphous pellets as well as the use of dual motor feeders for feeding the materials to the extruder. The rheological properties of PET melts have been found to be enhanced by decreasing the viscosity of the PET i.e. increasing the 'flowability' of the PET melt during the injection or/and extrusion processes. The apparent shear viscosity of PETNCs is show to be significantly lower than un-filled PET at high shear rates. The viscosity exhibits shear thinning behaviour which can be explained by two mechanisms which can occur simultaneously. The first mechanism proposed is that some polymer has entangled and few oriented molecular chain at rest and when applying high shear rates, the level of entanglements is reduced and the molecular chains tend to orient with the flow direction. The other mechanism is that the nanoparticles align with the flow direction at high shear rates. At low shear rate, the magnitudes of the shear viscosity are dependent on the nanoclay concentrations and processing shear rate. Increasing nanoclay concentration leads to increases in shear viscosity. The viscosity was observed to deviate from Newtonian behaviour and exhibited shear thinning at a 3 wt.% concentration. It is possible that the formation of aggregates of clay is responsible for an increase in shear viscosity. Reducing the shear viscosity has positive benefits for downstream manufacturers by reducing power consumption. It was observed that all ii three nanoclays used in this project act as nucleation agents for crystallisation by increasing the crystallisation temperature from the melt and decreasing the crystallisation temperature from the solid and increasing the crystallisation rate, while retaining the melt temperature and glass transition temperatures without significant change. This enhancement in the thermal properties leads to a decrease in the required cycle time for manufacturing processes thus potentially reducing operational costs and increasing production output. It was observed that the nanoclay significantly enhanced the barrier properties of the PET film by up to 50% this potentially allows new PET packaging applications for longer shelf lives or high gas pressures. PET final products require high stiffness whether for carbonated soft drinks or rough handling during distribution. The PET/Somasif nanocomposites exhibit an increase in the tensile modulus of PET nanocomposite films by up to 125% which can be attributed to many reasons including the good dispersion of these clays within the PET matrix as shown by TEM images as well as the good compatibility between the PET chains and the Somasif clays. The tensile test results for the PET/clay nanocomposites micro-moulded samples shows that the injection speed is crucial factor affecting the mechanical properties of polymer injection moulded products.

D. Tech. (Department of Mechanical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / Cracked concrete slabs are a problem due to several factors such as poor maintenance, insufficient reinforcement or steel corrosion leading to crack propagation. There is a need to increase the load-bearing capacity of concrete slabs and increase their life span. The use of waste Polyethylene Terephthalate (PET) fibres and fly ash in a hybrid composite slab dramatically alleviates the problem of crack propagation and failure sustainably. This study aimed to optimize a waste PET fibre/fly ash hybrid cement composite for use in slabs. This study characterized the raw materials used, including fly ash and aggregates. After that, concrete test specimens were fabricated using the PET fibres and fly ash following the full factorial experimental design. The developed specimens were then tested to ascertain their material strength properties. Model development was carried out using Minitab Software Version 14, and subsequent experimental validation was carried out. After that, the PET and fly ash optimisation for maximum favourable response outcome was carried out. The fly ash was found to belong to the Class F category with particle size ranging from 0.31 μm to 800 μm. The fly ash was mainly spherical and consisted of Ca, Al, P, Si, and trace amounts of Ti and Mg. The spherical shape of the fly ash helped improve the concrete's workability. The river sand had a fineness modulus of 3.69, considered coarse sand. The fine aggregate showed uniform particle size distribution with a uniformity coefficient of 4.007. The coarse aggregate characterisation was carried out and revealed that the aggregate particle size was 13 mm in size. The coarse aggregate had a uniformity coefficient of 4.007, which implied the aggregate was well graded. The coarse aggregate had a high flakiness index of 74.82 % and an acceptable elongation index of 46.72 %. Full factorial methodology experimental design was employed to fabricate the test specimens by simultaneously varying the independent factors to develop a model for overall response variation. The slump value was observed to increase with the addition of fly ash. However, the addition of PET fibre decreased the slump value with incremental amounts of fibre. The combined effect of fibre addition and fly ash showed a general decreasing slump value for all quantities of fly ash content. The compressive strength of PET fibre only composite had maximum strength at 0.5% fibre addition, and the composite with fly ash alone had the maximum compressive strength at 15%. The combined optimum compressive strength for fibre and fly ash was at 0.5 % and 15 %, respectively, with a 15.54 N/mm2. The split tensile strength decreased with an increase in fibre content. However, the fibre provided crack retardation. Fly ash increased the split tensile strength significantly to a peak of 2.35 N/mm2 for 20 % fly ash addition. The combined addition of fibre and fly ash had an optimum split tensile strength of 2.79 N/mm2 at 0.5 % fibre and 20 % fly ash. The addition of fibre had an optimum split tensile strength at 0.5% of 1.82 N/mm2. The fly ash increased the flexural strength, with optimum strength at 15 %. The combined addition of fibre and fly ash created optimum flexural strength at 0.5% and 30 %, respectively. The trend observed by the rebound number followed that of the compressive strength. However, the non-destructive rebound hammer method gave significantly lower strength values than the destructive test method. The addition of fly ash had the effect of lowering the cost of producing the slab. However, the addition of fibres marginally increased the cost. The combined effect of fibre and fly ash resulted in a significant cost saving. Numerical optimisation was carried out concerning the fibre reinforced concrete's fresh and hardened mechanical properties. Predictive modified quadratic equations were developed for slump value, compressive, flexural, split tensile strength and total cost. Analysis of variance test carried out for all the responses indicated that the model could predict the slump value and mechanical properties of the fibre reinforced concrete correctly and effectively with a coefficient of determination in the range of 0.4151 to 0.9467. The developed model can predict the required fibre reinforced fresh and hardened properties in order to assist in decision making in construction in slabs. The optimum constituent combination for maximum mechanical strength at the lowest possible cost was found to be 15.7576 % Fly ash and 0.3232 % PET fibre with optimum responses as shown in Table 4-26. These predictions were validated experimentally, and a good correlation was observed between the actual and predicted values based on the observed standard deviations of 0.1335, 0.031, 0.005, 0.676, 0.02 for compressive strength, flexural strength, tensile strength, slump value and cost, respectively. Concrete slabs were optimised for various possible end uses, and the optimum PET fibre % and fly ash % were ascertained as shown in Table 4-27.