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    3D printing materials for large-scale insulation and support matrices : thesis by publications presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering, Massey University, Albany, New Zealand
    (Massey University, 2019) Harris, Muhammad
    Additive manufacturing (AM) techniques have promising applications in daily life due to their superiority over conventional manufacturing techniques in terms of complexity and ease of use. However, current applications of polymer-based 3D printing (3DP) are limited to small scale only due to the high cost of materials, print times, and physical sizes of the available machines. In addition, the applications of 3DP are yet to be explored for insulation of different large-scale mechanical structures. For example, milk vats are large structures with complex assemblies (like pipes, joints, couplings, valves, ladders, vessel doors) that requires insulation to store the milk at a low temperature of 6 °C as per the NZCP1 regulations in New Zealand. Generally, milk vats lack any kind of proper insulation around them and require additional cooling systems to keep the milk at a prescribed temperature. Any variations in the temperature can lead to deterioration in the quality of milk. Therefore, there exists a research gap that can not only help to solve an industrial issue but also can be a first step towards real large-scale 3DP applications that can potentially lead to many others in future. For example, pipe insulation, food storage tanks, chemical storage tanks, water treatment. This research explores new and inexpensive materials for large-scale 3DP. For this purpose, the current state of the 3DP materials is analyzed and based upon this analysis two distinct approaches are devised: 1) in-process approach to improve the mechanical properties of the existing materials like polylactic acid (PLA), and 2) modification of inexpensive materials (like materials used in injection, rotational, and blow moulding) to make them printable. In the first approach, by controlling the process parameters, mechanical properties are studied. While in the second approach, blends of high density polyethylene (HDPE) and polypropylene (PP) with different thermoplastics (acrylonitrile butadiene styrene, ABS and polylactic acid, PLA) are investigated to achieve printability. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) are used to analyze the proposed materials. The overall objective of this research is to devise low-cost materials comparable to the conventional processes that are capable of providing good mechanical properties (tensile, compressive and flexural) along with high resistance to thermal, moisture, and soil degradation. The results present significant enhancement, up to 30%, in tensile strength of PLA through in-process heat treatment. However, the softness induced during printing above 70 °C directs to the second approach of developing the novel blends of HDPE and PP. In this regard, the research develops three novel blend materials: 1) PLA/HDPE, 2) ABS/HDPE, and 3) ABS/PP. These materials are compatibilized by a common compatibilizer, polyethylene graft maleic anhydride (PE-g-MAH). PLA/HDPE/PE-g-MAH provides highest tensile strength among all existing FDM blends (73.0 MPa) with superior resistance to thermal, moisture and soil degradation. ABS/HDPE and ABS/PP provide one of the highest mechanical properties (tensile, compressive, and flexural) in ABS based FDM blends with superior thermal resistance to six days aging. ii The chemical characterization of aforementioned novel FDM blends shows partial miscibility with sufficient signs of chemical grafting. The significant intermolecular interactions are noted in FTIR that shows the grafting through compatibilizer (PE-g-MAH). The DSC analysis shows visible enhancement in different thermal parameters like glass transition, melt crystallization and degradation along with signs of partial miscibility. Furthermore, TGA analysis confirms the partial miscibility along with the enhanced onset of degradation temperature. The increase in onset temperatures of each of the three blends proves the thermal stability to high temperatures. Hence, each of the developed blends is capable of resisting any material deterioration during routine cleaning operation at 70 °C of milk vats. This research has resulted in 5 journal publication (four published and one submitted), two conference proceedings and a number of posters presented at local conferences. This research is the part of food industry and enabling technologies (FIET) research program funded by the ministry of business, innovation and employment (MBIE), New Zealand in collaboration with Massey University, Auckland.
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    The "laminate film" method for measuring the permeation of volatile organic compounds through polymer films : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Packaging Technology at Massey University
    (Massey University, 1992) Matheson, Fiona Jean
    The use of barrier polymers for packaging foods has created a need to test the transmission of organic penetrants, such as flavour and aroma compounds, that can be lost from the food to the polymer. Many studies have been carried out on organic penetrants but due to the large number of possible penetrant-polymer combinations and the interactions between these plus the factors that can affect these interactions, there are many conflicting results. In addition, the tests were generally carried out at high penetrant concentrations and the results were not applicable to the low concentrations found in food packages. Traditional methods for measuring permeation of organic compounds are slow and capital intensive, with no standard test method or test conditions existing. A simple, inexpensive method, known as the "laminate film" method was developed by Holland and Santangelo in 1988 in which the transmission of a penetrant is measured by the change in absorbance in a polymer film. This "laminate film" method was used to measure the sorption of d-limonene and vanillin by low density polyethylene, nylon 6 and polyvinylidene chloride coated nylon 6 at 10, 25, and 40°C and in ethylene-vinyl alcohol films at 25°C and 90% relative humidity. Different thicknesses of the polymers were also tested. The sorption of d-limonene and vanillin was studied over long periods of time up to 8000 hours. The amounts of vanillin sorbed and the rate of uptake of vanillin were lowest in low density polyethylene and polyvinylidene chloride coated nylon 6. Nylon 6 and moist ethylene-vinyl alcohol films rapidly picked up large amounts of vanillin. Increasing the temperature increased the rate and amount of vanillin sorbed. Both orientation of the film and increasing the proportion of ethylene in the ethylene-vinyl alcohol films decreased the amount of vanillin sorbed, but increasing the relative humidity increased it. Increasing the thickness of the films increased the amount of vanillin sorbed but did not affect the rate or method of uptake. Therefore, more layers can be used to accurately estimate small diffusion coefficients without affecting the permeation of the penetrant. The results became less reproducible with time due to effects such as oxidation of the penetrant, degradation of the polymer film and concentration effects. Diffusion, partition (or solubility) and permeation coefficients were calculated for all films with vanillin. For low density polyethylene, these were of the order of 10-9cm2 3 12 2 12 2 2 10-13cm2/s; polyvinylidene chloride coated nylon 6 10-14cm2/ s, 10-2 10-15cm2/s and ethylene-vinyl alcohol films 10-13cm2/ s, 10-2 10-13cm2/s. The units used for the coefficients allow for the direct comparison of results for other penetrants as no conversion is necessary when comparing solid, liquid or gaseous penetrants. D-Limonene was not an appropriate compound to be used with this method as it had a low extinction coefficient and the absorbance was not easily measured. From this study, there are certain requirements that need to be met ,if this method is to be used as a standard test method. The compound to be tested needs a large extinction coefficient so that sorption of the penetrant can be accurately measured, and the polymer must be transparent. Temperature and relative humidity, (if the film is moisture sensitive), must be controlled as these factors can have dramatic effects on the permeation. The "laminate film" method would be useful in industry, where a simple and inexpensive method is needed to measure transmission of flavours and aromas in polymer films in order to enable the best barrier film for a packaging application to be chosen.
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    Optical properties of organic NLO chromophores for terahertz applications : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physics at Massey University, Palmerston North, New Zealand
    (Massey University, 2012) Kutuvantavida, Yasar
    This thesis was motivated by the potential of organic nonlinear optical (NLO) zwitterionic chromophores to be used as active components in THz emitters and detectors. This study presents the results from measurements of the electro-optic (EO) coefficient, photostability and the THz properties of organic NLO chromophores. An EO coefficient of over 700 pm/V was measured for some EO polymers using the Teng-Man modulation ellipsometry technique at low frequencies. A roll off in the value of the EO coefficient was observed for frequencies over 10 kHz and converging to the theoretically estimated value of ∼ 2 pm/V. The large over estimate of the EO coefficient at low frequencies using the Teng-Man method is attributed to contributions from the cavity resonance and interference effects. The EO coefficient was also measured using a new method based on the electric field induced modulation of diffraction gratings. The measured EO coefficient using this technique is an order of magnitude lower than that measured using the Teng- Man method but it is an order of magnitude higher that the theoretically expected value. By investigating DC and AC measurements it was possible to deduce that the large apparent EO coefficient is due to the inverse piezoelectric effect and thin film interference. The large EO coefficient at low frequencies may also have a contribution from dipole clusters. The small EO coefficient at high frequency shows that the chromophores may not be particularly useful for THz applications. However, they have potential in low frequency applications such as modulators, and dense wavelength division multiplexing. The current photodegradation models are shown to be inadequate and the photodegradation can be modeled by considering a distribution in the photodegradation quantum efficiencies. The addition of a singlet oxygen quencher has been found to enhance the photostability of some chromophores by up to 6 times. Structural modifications also affect the photostability. A correlation between the photostability and bond length alternation (BLA) was found where there is a trade-off between the chromophores molecular NLO effect and photostability. Calculations based on the THz dielectric properties showed that the EO polymers have a reasonable coherence length for THz generation using optical rectification. Low wavenumber Raman spectroscopy measurements made on recrystallised compounds exposed some theoretically predicted modes that were not been reported found experimentally. Low temperature and low energy Raman spectroscopy measurements made on some selected organic compounds showed a strong temperature dependence of the low energy vibrational modes. The temperature dependent redshift and line broadening have been primarily attributed to thermal expansion and a distribution in the distance between monomers.
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    Experimental tests of polymer reptation : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Physics at Massey University
    (Massey University, 1999) Komlosh, Michal; Komlosh, Michal
    Pulsed Gradient Spin Echo Nuclear Magnetic Resonance (PGSE-NMR) and rheology measurements were used to test whether the dynamics of entangled polymer chains in semidilute solution follow the reptation theory. Nine molar masses from 1 to 20 million daltons at a fixed concentration of 4.96% w/v along with a range of concentrations from 4.96% to 23.58% w/v at fixed molar mass of 3 million daltons were studied using PGSE-NMR techniques. The response to mechanical deformation of five different concentrations from 4.96% to 23.58% w/v at fixed molar mass of 3.9 million daltons was also studied. The distance and time scales accessed by PGSE-NMR were 20 to 1000 nm and 10 to 3000 ms respectively. As a result the mean square segmental motion over three reptation regimes was obtained and the reptation finger print, 〈(r(t) - r(0))〉 ~ t1/4, was observed. The resulting concentration and molecular weight scaling laws for the tube disengagement time, center of mass diffusion and the tube diameter, which were obtained in PGSE-NMR and rheology experiments, were found to be in good agreement with the reptation theory and its standard modifications, and a good quantitative fit to the mean square displacement was given by this theory. Local anisotropic motion of polymer chains at the level of the Rouse time was observed using double-PGSE NMR methods. These suggested a possible cooperative motion of polymer chains in entangled environment which challenges the basic assumptions of the reptation theory. Evidence of intra-chain spin diffusion was found. As a consequence relevant corrections incorporating the phenomenon into the PGSE-NMR data had to be made.
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    The synthesis and properties of polyether substituted oligothiophenes : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University, Palmerston North, New Zealand
    (Massey University, 2003) Grant, Daina Kim
    A number of novel dialkoxystyryl-substituted terthiophenes were synthesised as precursors to form conducting polymers. These compounds contained either crown ethers or polyether chains designed to complex metal cations, and polymerisable terthiophene moieties. Two isomeric cross-linked bis(terthiophene) crown ethers were also synthesised as monomers for conducting polymer synthesis, but could not be investigated further due to their insolubility. The solubility issue was circumvented by the formation of hemicrown compounds, containing two styryl-terthiophene units linked by a polyether chain. Thiophene analogues of the crown ether, open-chain ether, bis(terthiophene) crown ether and hemicrown compounds were also successfully synthesised and characterised. The response of the terthiophene crown compounds, open-chain compounds and hemicrowns to a large range of metal cations was investigated by UV and fluorescence spectroscopy. The results obtained from this work were consistent with complexation based on size-fit and charge density of ions, and with hard-soft-acid-base theory. Chemical polymerisation of the terthiophene crown monomers and open-chain ether terthiophene compounds was carried out using FeCl3. This led to the isolation of dimeric sexithiophene compounds in high yield. Characterisation of the pure sexithiophene derivatives showed that they were the product of regioselective dimerisation, caused by the asymmetric reactivity of the terthiophene-based monomers. This is believed to be due to uneven electron spin-density distribution, and theoretical calculations on the radical cation support this view. Producing dialkoxystyryl-substituted sexithiophenes by this synthetic route gave excellent yields of isomerically-pure product. Chemical oxidation of terthiophene compounds using Cu(ClO4)2 was observed with UV/VIS/NIR spectroscopy. This allowed the observation and identification of absorption bands due to oxidised species. Reduction of these species led to sexithiophene dimers, as seen for chemical polymerisation using FeCl3. Electrochemical polymerisations of the terthiophene, thiophene and sexithiophene compounds were carried out by cyclic voltammetry. Those that formed adherent films were analysed by UV/VIS/NIR spectroscopy in both the neutral and oxidised form. The electrochemical and spectroscopic evidence again pointed to the formation of dimers as the primary product of oxidation from terthiophene-based monomers. The surface morphology of the films was investigated by scanning electron microscopy, and showed a variety of morphologies.
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    Computational approaches to the calculation of spectroscopic, structural and mechanical properties of polysaccharide chains : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 2010) Anjukandi, Padmesh
    In this thesis atomistic, statistical mechanical and coarse grained simulation techniques are used to study the properties of biopolymers and in particular the plant polysaccharide pectin. Spectroscopic aspects, structural and conformational behavior, and mechanical properties of the molecule in di erent physical states are addressed. After an introduction to the area and the theoretical techniques utilised herein (chapter 1), chapter 2 deals with the spectroscopic characterisation of pectin. Spectra were obtained theoretically by undertaking complete energy minimisation and Hessien calculations using DFT techniques implemented in Gamess (PC & US) packages. The calculated IR absorptions of di erent pectinic species and oligomers coupled on di erent surfaces were compared with experimental results. Herein, it is con rmed that experimental FTIR studies coupled with DFT calculations can be used as an e ective tool for the characterisation of pectin, and studying chemical coupling of the biopolymer to surfaces. In chapter 3, the properties of single chain polymer systems in controlled solvent conditions were studied using Brownian dynamics simulations, motivated by the formation of secondary structure architectures in biopolymer systems. We focus on the conformational properties of the chain in the presence of an additional torsional potential. New, interesting, and biologically relevant structures were found at the single molecule scale when a torsional potential was considered in the calculations. In chapter 4, results from DFT calculations carried out on single pectin sugar molecules (lengths and the free energies) are incorporated into a statistical mechanical model of polymer stretching, in order to obtain the force-extension behaviour of a single molecule pectin. This captures a good deal of the phenomenology of the single molecule stretching behavior of pectin. Chapter 5 summarises the conclusions of the work and nally chapter 6 suggests direction for further work.