THE EFFECTS OF SOLVENT MIXTURE ON THE THERMAL AND MECHANICAL PROPERTIES OF SOLVENT CAST POLY-LACTIC ACID (PLA) FILM

CH 1 ABSTRACT The objective of this study was to investigate the effects of various solvents on the crystallinity and thermal expansion stability of PLA film. Three different PLA films were produced by the solvent casting technique; PLA in chloroform (PLA-C), PLA in methylene chloride (PLA-M), and PLA in methylene chloride: acetonitrile = 50: 50 (PLA-MA). The PLA-MA had higher % crystallinity, 46.15, than the PLA-C, 24.03, and the PLA-M, 14.25. With this increase in crystallinity, the PLA-MA had improved thermal expansion stability as shown by very low accumulated dimensional changes at 20-100 ¡C. Wide angle x-ray diffraction identified multiple crystalline structures for the PLA-MA. Film barrier properties were also measured. PLA-MA had the lowest oxygen permeability. However, there was no significant difference in water vapor permeability among the three PLA films. The mechanical property tests revealed that the PLA-C and PLA-M were ductile while the PLA-MA was brittle in behavior. The PLA-MA was very hazy as compared to the PLA-C and PLA-M. This work has shown that the PLA-MA had increased % crystallinity and, more importantly it had improved thermal expansion stability which can be very beneficial for the flexible packaging industry. CH 2 ABSTRACT The objective of this research was to determine the optimum solvent mixture to improve flexibility while maintaining the thermal stability of PLA solvent-cast films. PLA films were produced from mixed solvent solutions of (M: methylene chloride) and (A: acetonitrile) using the solvent-casting technique. The ratio of solvents used were 70% methylene chloride with 30% acetonitrile (73MA), 60% methylene chloride with 40% acetonitrile (64MA) and 50% methylene chloride with 50% acetonitrile (55MA). The single solvent solution was 100% methylene chloride (100M). Differential Scanning Calorimetry (DSC) showed films with increased amounts of acetonitrile had higher amounts of % crystallinity due to the full formation of crystals during the casting process and no enthalpy of crystallization. Thermomechanical Analysis (TMA) revealed the addition of acetonitrile increases the thermal stability of the PLA films. Stress strain curves showed that high crystalline films were brittle while less crystalline films were ductile. Both Wide Angle X-ray Diffraction (WAXD) and Transmission Electron Microscopy (TEM) showed 55MA and 64MA had the highest % crystallinity, more developed crystal structure and more pronounced lattice images. Film 73MA was the only film that exhibited both flexibility and good thermal stability. The 30% concentration of acetonitrile developed crystals that stopped growing due to solvent evaporation, but upon heating in TMA, the crystals began to grow fully thus improving thermal stability. This work shows that PLA film produced by solvent casting from solvent mixture compared to a traditional single solvent will have better thermal and mechanical performance. CH 3 ABSTRACT The objective of this study was to investigate the effects of various solvents on the crystallinity and thermal expansion stability of PLA film. Four different PLA films were produced by the solvent casting technique; PLA in chloroform (100C), 70% chloroform: 30% acetonitrile (73CA), 60% chloroform: 40% acetonitrile (64CA) and 50:50 chloroform acetonitrile (55CA). 55CA had the highest % crystallinity at 26.1%. 73CA showed the least amount of % crystallinity. With this increase in crystallinity, 64CA had improved thermal expansion stability with no accumulated dimensional changes. 73CA with low % crystallinity showed improvements as well. Wide angle x-ray diffraction identified multiple crystalline structures for all films with acetonitrile. The mechanical property tests revealed that 100C and 73CA were ductile while 55CA and 64CA were brittle. More haze was seen in the more crystalline 55CA and 64CA compared to 73CA and single solvent 100C. 73CA had increased thermal expansion stability with the addition of acetonitrile to increase crystallinity, yet behaved like an amorphous film with improved flexibility

Modeling loan losses a macroeconomic approach

A sound banking system is essential to a well-functioning economy. With the financial crisis beginning in 2007, a renewed interest in the safety of financial institutions has dominated both the political and financial landscape. Mounting loan losses in real estate lending led to the failing of over 460 banks from 2008 to 2012. This crisis is not unique; in fact, the Savings & Loan Crisis of the 1980\u27s to early 1990\u27s led to the closure of 700 savings institutions. Both instances created a panic in financial markets and heavy losses to deposit insurance funds. These losses are ultimately borne by taxpayers and prudently managed banks, especially if the insurance fund requires re-capitalization. The focus of this paper is on explaining the contributing factors to different categories of loan losses. Namely, total loan losses, residential real estate loan losses, commercial real estate loan losses, and commercial and industrial loan losses are examined. A multivariate regression approach is taken in this paper to explain the four rates of loan losses for the period of 2001 to 2012. Aggregate macroeconomic data from 2001 to 2012 is used to explain loan losses across categories. It was found that the delinquency rate of loans, the consumer financial obligations ratio, and the financial crisis were all significant factors in explaining loan losses

Introduction to integrated environmental modelling to solve real world problems: methods, vision and challenges

Across the world, stakeholders are asking questions of their governments and decision makers to quantify the risks of environmental threats to their well-being. These questions manifest themselves as ‘deceptively simple questions’, which are easy to articulate but difficult to solve. An example of which is: ‘how much will the eruption of an Icelandic volcano cost the UK economy’. Answering these questions requires predictions of the interaction of multiple environmental processes, this requires the development and maintenance of systems that allow these processes to be simulated, and that is the nascent science of integrated environmental modelling (IEM). Such processes may be long-term (e.g. those that are impacted by climate change) or short-term threats, such as the impact of drought on UK agriculture or the impact of space weather on energy supply systems

Looking forward to making predictions

As described in the preceding pages, since the BGS was established in 1835, the British population has coped with many challenges. These have ranged from finding resources to fuel the Industrial Revolution, understanding and combating water-borne diseases such as typhoid, the threat of invasion and aerial bombardment, through to modern-day environmental problems and climate change. To help deal with these problems, decisionmakers from governments and other organisations have required our help and advice

An examination of the sonnets of E.E. Cummings

This dissertation examines E. E. Cummings's writings in the sonnet genre and in those genres to which the sonnet is related in various ways. Its fundamental point is that, despite the surface impression of poetic iconoclasm for which Cummings has a popular reputation, in choosing to write sonnets he engages in a traditional literary practice. He does this because his purpose is always to be an artist, as defined by the Aesthetic movement which influenced him. In order to argue his embracing of a traditional artistic role, the theory of genres espoused by Alastair Fowler in his book, Kinds of Literature, is used. Chapter 1 of the thesis comprises general introductory material, both to the range of Aesthetic ideas to which Cummings subscribed, and to Fowler's theory of genres. Several key generic kinds are also described. The second chapter makes use of two of these generic models, the sonnet sequence and the silva, as a way of examining Cummings's deployment of the sonnet within the larger context of his poetry collections. It is a survey of the structure of the anthologies he compiled from Tulips & Chimneys (1922) to 95 Poems (1958). The third chapter explores the three sonnet modes which Cummings first identifies and names when compiling the manuscript of Tulips & Chimneys, and continues to use in his collections up to and including is 5 (1926). Chapter 4 shows how certain themes and concerns from these early sonnets are altered and synthesised as Cummings matures from an aesthete to a Romantic poet. Sonnets from his later books are taken to be representative of three central kinds in all of his work after is 5. Chapters 3 and 4 proceed by means of relatively close readings of individual sonnets. This practice fulfils a double role: it penetrates the apparent obscurity of the more difficult poems, and it attempts to preserve the integrity of individual poems which exemplify different generic tendencies in Cummings's work. One of Cummings's reasons for writing sonnets is that the form favours the achievement of what Wordsworth calls "a feeling of intense unity". In undertaking close readings of a few sonnets I have attempted to preserve that feeling

Automated Sensitivity Analysis of Interplanetary Trajectories for Optimal Mission Design

This work describes a suite of Python tools known as the Python EMTG Automated Trade Study Application (PEATSA). PEATSA was written to automate the operation of trajectory optimization software, simplify the process of performing sensitivity analysis, and was ultimately found to out-perform a human trajectory designer in unexpected ways. These benefits will be discussed and demonstrated on sample mission designs

Improving professional practice in the disclosure of a diagnosis of dementia : a modeling experiment to evaluate a theory-based intervention

The original publication is available at www.springerlink.com.Peer reviewedPostprin