The automotive manufacturing industry is facing an interesting period of trial when a lot of improvement is expected of them in a short period of time to contribute to a cleaner planet by applying technologies that will reduce fossil fuel consumption. Electrification was good, but this must be accompanied by substantial curb weight reduction, which was provided by alloys such as A365, Aural 5 (AlSi8MnMg), Aural 2 (AlSi10MnMg), and Mercalloy 367 (AlSi9MgMnSr) for making structural parts. The use of these Al alloys is accompanied with extensive heat treatment which on its own involves fossil fuel consumption. In this research, test plates were made utilizing high vacuum high pressure die casting (HVHPDC) and a unique Al-Fe based eutectic alloy with Zn and Mg as precipitation strengtheners. Experimental results demonstrated that they age naturally, with their mechanical properties rising to the industry requirement within three days. DSC experiments carried out at various ages gave further experimental evidence to this natural ageing phenomenon. A portion of the samples was then given an experimental "paint bake" treatment at different ages. This is typical on an assembly line where the coated parts are baked at a temperature range of 120 - 200oC for thirty minutes. It was evidently defensible that samples of various ages respond to the treatment in different ways. The mechanical characteristics of the samples decreased after treatment to same value and progressively increased to match the values of the control samples. During the duration of the experiment, some samples rose quickly while others remained "nearly dead" in the state of low mechanical characteristics or climbed sluggishly to catch up with the natural ageing curve. The poorest results were seen in samples handled at the early stage when the initial clusters are forming indicating that it might not be a good idea to interfere with the NA process at those times. / Thesis / Master of Applied Science (MASc) / Fueled by the desire to produce an Al alloy with good mechanical properties arising from natural ageing, high vacuum high pressure die casting (HVHPDC) was used in making castings of this alloy which contains Fe for improvement on its castability and recyclability, contains Zn and Mg which act as the precipitating strengtheners driving the natural ageing phenomenon. Tests and experiments like uniaxial tensile tests, differential scanning calorimetry and electrical conductivity tests were carried out to ascertain its suitability to be used for structural automotive parts without heat treatment. The results showed that the new Nemalloy HE700 met with the minimum industry requirements for mechanical properties of materials for structural automotive applications within 3 days of natural ageing. The alloy was then subjected to experimental paint bake treatment to observe its reaction to paint bake process and the results were able to show when to do paint bake for best outcome.

This research was conducted to characterize the flexural and tensile characteristics of thin, very high-strength, discontinuously reinforced concrete panels developed by the U.S. Army Engineer Research and Development Center. Panels were produced from a unique blend of cementitous material and fiberglass reinforcing fibers, achieving compressive strength and fracture toughness levels that far exceeded that of typical concrete.The research program included third-point flexural experiments, novel direct tension experiments, implementation of micromechanically based analytical models, and development of finite element numerical models. The experimental, analytical, and numerical efforts were used conjunctively to determine parameters such as elastic modulus, first-crack strength, post-crack modulus and fiber/matrix interfacial bond strength. Furthermore, analytical and numerical models implemented in the work showed potential for use as design tools in future engineered material improvements.

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<p>Cellulose is the most abundant biopolymer on earth, derived from a variety of living species. An attractive source to obtain cellulose is from agriculture wastes, for instance, potato peel. Potato is one of the most important crops for human consumption, but in recent years its consumption in raw form has decreased, especially in developed countries. Many potatoes are processed into value-added products to meet the demand of fast food industries. So far the main use of the potato peel is sold for animal feed at very low prices. In addition, there are significant quantities of rotten potatoes generated during the years of heavy rain fall, which represent a substantial financial loss to the farmers unless an alternative industrial use can be found for the biomass. Therefore, extracting cellulose from potato peel and processing them into a higher valuable product is not only an environment-friendly solution to the disposal issues but also creates a non-food based economy for potatoes.</p> <p>Cellulose nanocrystals (CN) are a promising material and have been widely studied over the past two decades. This material is interesting as nanofiller due to its nanoscale dimensions, high specific area, and highly rigid crystalline structure. In comparison to mineral or metal nanofillers that are industrially available, cellulose nanocrystals are prepared from renewable feedstocks, feature low density, are relatively low cost, and remain biodegradable.</p> <p>This study investigated the effectiveness of cellulose nanocrystal derived from potato peel waste to improve the mechanical and barrier properties of a polymer. The nanocrystals were chemically derived from the cellulosic material in potato peel waste by alkali treatment and subsequently acid hydrolysis with sulfuric acid. Infrared spectroscopy indicated sufficient removal of lignin and hemicellulose from the raw potato peel biomass whereas X-ray diffraction confirmed that the prepared nanocrystals maintained their original crystalline lattice structure as the extracted cellulose, with a crystallinity of 85%. TEM images showed that the average fiber length of the nanocrystals was 410 nm with a diameter of 10 nm (aspect ratio of 41). Cellulose nanocrystal-filled polyvinyl alcohol (PVA) and thermoplastic starch (TPS) were prepared by solution casting method to maintain uniform dispersion of the 1-2% (w/w) fibers. An increase of 19% and 38% (starch composite) and 32% and 54% (PVA composite) in Young’s modulus was observed for the 1% and 2% CN-reinforced composites, respectively. Water vapor transmission rate measurements showed a reduction of water permeability for the PVA nanocomposite, whereas no effect was observed for starch nanocomposite.</p> / Master of Applied Science (MASc)

A series of modified poly(arylene ether sulfone)s (PAES) incorporating hexafluoroisopropylidene units and co-monomers, bisphenol A (BA), 4,4′-dihydroxyterphenyl (DHTP) and triptycene-1,4-hydroquinone (TPDH), were synthesized using a polyetherification synthetic method. These thermoplastic PAES were copolymerized with the elastomer, polydimethylsiloxane (PDMS) to form segmented block copolymers. The segmented block copolymers with diverse PAES structures were studied and investigated for their thermal, tensile, and morphological properties. These multiphase segmented block copolymer materials have the potential to impart useful combinations of optical transparency, thermal stability, and enhanced tensile properties, and enhanced environmentally resistant properties for various high impact, high performance applications. In Chapter 2, hexafluoroisopropylidene bisphenol PAES (BAF PAES) segmented block copolymers containing various volume fraction of PDMS were synthesized. Analysis of the segmented block copolymer films by atomic force microscopy (AFM) and small angle x-ray scattering (SAXS) show the materials are microphase separated. Further analysis of the BAF PAES segmented block copolymers by transmission electron microscopy (TEM) show an increased morphological order with decreasing PDMS content, with lamellar morphologies formed at higher or near equal PAES and PDMS volume fractions. Comparatively, the morphological properties of the BAF PAES segmented block copolymers are considerably different from the isopropylidene bisphenol PAES (BA PAES) segmented block copolymer of similar PDMS volume percents. In this document, segmented block copolymers prepared from BA PAES incorporating 4,4′-dihydroxyterphenyl (DHTP) and triptycene-1,4-hydroquinone (TPDH) co-monomers were characterized by proton nuclear magnetic resonance spectroscopy (¹H NMR). Films of these materials, prepared from THF solution, were tested for thermal and tensile properties. These materials provide higher thermal stabilities over the BA PAES segmented block copolymers with thermal degradation ranging 380–435 °C under nitrogen at 5%-wt. loss. Similarly, the PAES incorporating co-monomers gave higher Tg (200 °C) than the BA PAES (183 °C) synthesized in our labs. Previously synthesized BA PAES segmented block copolymers showed plastic to elastomeric tensile properties upon increasing addition of PDMS content. These new segmented block copolymers, incorporating co-monomers, provided comparable results with the reported BA PAES segmented block copolymers analogues. The last research topic discussed in this dissertation covers the preparation of blends from 5% of segmented block copolymer and 95% of Udel®, donated by Solvay Advanced Polymers. The preparation of blends from the segmented block copolymers containing random copolymers led to materials with higher moduli than Udel® as observed by dynamic mechanical analysis (DMA). Tensile measurements performed by Instron also show the blends have high moduli, though no changes in the tensile elongation comparable to Udel®. / Ph. D.

Preparation of thermoplastics composites using engineering thermoplastics and plant fibers or fillers is a technical challenge because the processing temperature of the thermoplastics is generally above the temperature of degradation of plant fibers of fillers. There have been numerous attempts for processing high melting point engineering thermoplastics like Nylon-6 with plant natural fibers and fillers. Low temperature processing methods, fiber modification or addition of additives which drops polymer melting point are some of proposed solutions for this problem. The objective of this thesis was to develop a formulation using wheat straw (WS) as a reinforcing fiber for Nylon-6. The concentration of WS was 15 wt-%. The thermoplastic composites were prepared by mixing grinded wheat straw and Nylon-6 using a laboratory scale twin-screw extruder; follow by preparation of samples using injection moulding. The strategy investigated in this thesis was utilization of additives to lower the melting point or to decrease the viscosity of Nylon-6. Lithium chloride salt (LiCl) and N-Butyl benzene Sulfon amide plasticizer (N-BBSA) were used as process additives to decrease melting point and to reduce the processing temperature and time. The addition of the wheat straw (15 wt-%) to the Nylon-6 increased modulus by 26.9 % but decreased the strength by 9.9 %. Effect of different level of these two additives on mechanical, thermal, physical properties and processability of the composite runs were studied. Addition of 4 wt-% LiCl was found to decrease the melting point from 222 °C to 191 °C, to increase modulus by 14 % in comparison to Nylon-6/wheat straw (15 wt-%). However, it decreased the processability and strength by 12.7 %. Plasticizer was investigated to easing processability and decreasing the degradation by reducing the residence time in the extruder, it does not affect the melting point of Nylon-6. The addition of 4 wt-% of plasticizer (N-BBSA) increased modulus and strength only by 2.6 % and 3 %, respectively, in comparison to Nylon-6/wheat straw (15 wt-%) composites. The results of mechanical properties were used as a benchmark for comparisons among samples with different formulations (levels of additives) to find out levels of LiCl and N-BBSA for the best mechanical properties. It was found that samples with 2 wt-% LiCl and 2 wt-% of N-BBSA had 29.3 % higher tensile modulus than neat Nylon-6, while its strength was almost same as neat Nylon-6 and 6.3 % higher than Nylon-6/WS (15 wt-%). These results were used to correlate the mechanical properties as a function of percentage of salt and plasticizer in the formulation. Differential scanning calorimetry (DSC) was used to evaluate the percentage of crystallinity and the melting point of the thermoplastic phase and thermal gravimetric analysis (TGA) was used to measure the thermal stability of different formulation. The kinetics of crystallization and degradation were evaluated using results from DSC and TGA, respectively. The activation energy for thermal degradation and the percentage of crystallinity of the thermoplastic composites were correlated to mechanical properties using linear regression. It was found that fiber degradation had a significant effect on strength but the effects of percentage of crystallinity on composites strength were insignificant. On the other hand, the percentage of crystallinity affects stiffness and impact strength. The ductility was a function of both crystallinity and thermal stability.

Preparation of thermoplastics composites using engineering thermoplastics and plant fibers or fillers is a technical challenge because the processing temperature of the thermoplastics is generally above the temperature of degradation of plant fibers of fillers. There have been numerous attempts for processing high melting point engineering thermoplastics like Nylon-6 with plant natural fibers and fillers. Low temperature processing methods, fiber modification or addition of additives which drops polymer melting point are some of proposed solutions for this problem. The objective of this thesis was to develop a formulation using wheat straw (WS) as a reinforcing fiber for Nylon-6. The concentration of WS was 15 wt-%. The thermoplastic composites were prepared by mixing grinded wheat straw and Nylon-6 using a laboratory scale twin-screw extruder; follow by preparation of samples using injection moulding. The strategy investigated in this thesis was utilization of additives to lower the melting point or to decrease the viscosity of Nylon-6. Lithium chloride salt (LiCl) and N-Butyl benzene Sulfon amide plasticizer (N-BBSA) were used as process additives to decrease melting point and to reduce the processing temperature and time. The addition of the wheat straw (15 wt-%) to the Nylon-6 increased modulus by 26.9 % but decreased the strength by 9.9 %. Effect of different level of these two additives on mechanical, thermal, physical properties and processability of the composite runs were studied. Addition of 4 wt-% LiCl was found to decrease the melting point from 222 °C to 191 °C, to increase modulus by 14 % in comparison to Nylon-6/wheat straw (15 wt-%). However, it decreased the processability and strength by 12.7 %. Plasticizer was investigated to easing processability and decreasing the degradation by reducing the residence time in the extruder, it does not affect the melting point of Nylon-6. The addition of 4 wt-% of plasticizer (N-BBSA) increased modulus and strength only by 2.6 % and 3 %, respectively, in comparison to Nylon-6/wheat straw (15 wt-%) composites. The results of mechanical properties were used as a benchmark for comparisons among samples with different formulations (levels of additives) to find out levels of LiCl and N-BBSA for the best mechanical properties. It was found that samples with 2 wt-% LiCl and 2 wt-% of N-BBSA had 29.3 % higher tensile modulus than neat Nylon-6, while its strength was almost same as neat Nylon-6 and 6.3 % higher than Nylon-6/WS (15 wt-%). These results were used to correlate the mechanical properties as a function of percentage of salt and plasticizer in the formulation. Differential scanning calorimetry (DSC) was used to evaluate the percentage of crystallinity and the melting point of the thermoplastic phase and thermal gravimetric analysis (TGA) was used to measure the thermal stability of different formulation. The kinetics of crystallization and degradation were evaluated using results from DSC and TGA, respectively. The activation energy for thermal degradation and the percentage of crystallinity of the thermoplastic composites were correlated to mechanical properties using linear regression. It was found that fiber degradation had a significant effect on strength but the effects of percentage of crystallinity on composites strength were insignificant. On the other hand, the percentage of crystallinity affects stiffness and impact strength. The ductility was a function of both crystallinity and thermal stability.

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