Polymer-clay Nanocomposites

PhDPolymer-clay nanocomposites are attracting global interest principally because property enhancements are obtained at low clay particle loadings (1-5 wt%). However there is lack of fundamental understanding of such composites. The aim of this work is to provide an insight into the interaction between polymer and clay. This includes the driving force for intercalation, the reinforcement mechanisms and property-volume fraction relationships. Functionalised poly(ethylene glycol)-clay, poly(c-caprolactone)-clay and thermoplastic starch-clay nanocomposites with a range of polymer molecular weights, clay volume fractions and with different clays were prepared using solution methods, melt-processing methods, and in situ polymerisation. A reliable X-ray diffraction technique for low angle basal plane spacing of clay, the essential parameter for structure determination, was established obtaining ±0.005 Mn between three diffractometers. The basal plane spacing was found to be unaffected by polymer molecular weight and preparation method but was affected by the nature of the polymer and clay. Increasing clay loading could lead to a lower spacing. As a cautionary observation, poly(ethylene glycol) with high molecular weight (2: 10,000) was found to undergo degradation readily during preparation of nanocomposites with and without clay. Competitive sorption experiments for molecular weight showed that high molecular weight fractions of polymer intercalate preferentially into clay during solution preparation. Thermodynamic studies on the intercalation process found that significant enthalpic change occurred during intercalation, which is coincident with the observation that heat-treated clays without interlayer water can intercalate polymer. The calculation of true volume fraction against nominal volume fraction provided reasonable explanation of property enhancement and helps understand the relation between nanocomposites and conventional composites. At a given clay loading, nanocomposites with better dispersion gave more property enhancement than those with lower dispersion or conventional composites. The crystallinity of semicrystalline polymer was also affected by varying extents of dispersion of clay. The use of X-ray diffraction with an internal standard was explored for quantitative analysis of intercalation and exfoliation

Facile Fabrication of Porous Conductive Thermoplastic Polyurethane Nanocomposite Films via Solution Casting

Content of Dataset 1. FTIR spectra 2. Tensile Properties 3. Conductivity 4. Piezoresistive Properties 5. Resistance vs. Strain 6. Porosity Notes : This dataset is linked to Paper: Scientific Reports,2017,DOI: 10.1038/s41598-017-17647-

Tensile and impact properties of melt-blended nylon 6/ethylene-octene copolymer/graphene oxide nanocomposites.

The addition of stiff nanoparticles to a polymer matrix usually proves beneficial for the enhancement in stiffness and strength, however, the impact strength is usually lowered. Conversely, the use of elastomeric additives can enhance the toughness and impact strength but causes a reduction in overall stiffness and strength. To take advantage of the desirable effects of both additives, they may be simultaneously added to the host matrix. Graphene oxide (GO), along with a thermoplastic elastomer ethylene-octene copolymer (EOC), was chosen to be added to nylon 6 for the current investigation. Maleated EOC (EOC-g-MA) was used as a compatibilizer for this study. 3 wt% GO nanoparticles, 20 wt% ethylene-octene copolymer (EOC) and 3 wt% EOC-g-MA were added to nylon 6 to prepare the nylon 6/EOC/GO blend-based nanocomposites. A high shear rate screw running at 300 rpm was used for melt-blending with a twin-screw extruder. Increased stiffness and tensile strength were observed by the addition of GO nanoparticles while elongation at break, toughness and impact strength were lowered by the addition of GO. The addition of EOC and EOC-g-MA enhanced the elongation at break, toughness and impact strength. However, the stiffness and strength of nylon 6/EOC blend was lower than that of the neat nylon 6. The addition of GO nanoparticles and EOC to neat nylon 6 caused a reduction in its impact strength. However, simultaneous addition of EOC and EOC-g-MA to nylon 6 caused a significant increase in the impact strength compared to neat nylon 6 and yielded a nylon 6/EOC/EOC-g-MA bend with the highest impact strength. The addition of GO nanoparticles to this blend, however, again caused a significant reduction in the impact strength. Nylon 6/EOC/EOC-g-MA blend showed the highest toughness and impact strength. Simultaneous addition of EOC and GO helped achieve a balanced stiffness and toughness

Effect of processing conditions on the structure, electrical and mechanical properties of melt mixed high density polyethylene/multi-walled CNT composites in compression molding

Abstract Processing conditions can significantly influence the structure and properties of polymer nanocomposites. In the present study, melt mixed high density polyethylene (HDPE)/multi-walled carbon nanotube (MWCNT) nanocomposites were prepared via twin-screw extrusion and then compression molded (CM). The effect of heating temperature, pressing time and cooling rate on the structure, electrical and mechanical properties of the CM nanocomposites was systematically investigated. Volume resistivity tests indicate that the nanocomposite with 2 wt.-% MWCNTs, which is in the region of the electrical percolation threshold, is very sensitive to the CM parameters such that heating temperature &gt; pressing time &gt; cooling rate. Generally, the resistivity of nanocomposites decreases with increasing heating temperature and pressing time. Interestingly, the electrical resistivity of the rapidly cooled nanocomposite with 2 wt.-% MWCNTs is about 2 orders lower than that of the slowly cooled nanocomposite which is attributed to the lower crystallinity and smaller crystallites presenting less of an obstacle to the formation of conductive pathways. The tensile properties of the nanocomposite with 2 wt.-% MWCNTs are also influenced by the compression molding parameters to some extent, while those of the nanocomposites with higher MWCNT loading are insensitive to the changes in processing conditions. The modulus of the nanocomposites increases by about 25 to 50 % and 110 to 130 %, respectively, with the incorporation of 2 and 4 wt.-% MWCNTs, which agrees well with the theoretical values predicted from Halpin-Tsai and Mori-Tanaka models. This work has important implications for both process control and the tailoring of electrical and mechanical properties in the commercial manufacture of conductive HDPE/MWCNT nanocomposites.</jats:p

On the mechanical properties of melt-blended nylon 6/ethylene-octene copolymer/graphene nanoplatelet nanocomposites.

Ethylene-octene copolymer (EOC) with a loading level of 20 wt%, maleated EOC (EOC-g-MA) with a loading level of 3 wt% and graphene nanoplatelets (GnPs) at four different loading levels, i.e., 3 wt%, 5 wt%, 10 wt% and 15 wt% were added to nylon 6 to prepare nanocomposites using a twin-screw extruder with a high shear rate screw running at 300 rpm. Increased stiffness was observed with the addition of GnPs while tensile strength of nanocomposites was only slightly influenced. Addition of GnPs into nylon 6 and nylon 6/EOC blend caused either a reduction in the Charpy impact strength or it remained unaffected. Similarly, the Izod impact strength of compatibilized nylon 6/EOC blend increased while that of nylon 6/EOC blend-based nanocomposites decreased. An increase was observed in the compressive Izod impact strength of compatibilized nylon 6/EOC blend. Addition of GnPs to nylon 6/EOC blend caused an increase in the fracture toughness due to their influence on the morphology and fracture mechanisms. This study shows that simultaneous addition of high surface area GnPs and an impact modifier to neat nylon 6 can help achieve enhancement and tailoring of stiffness and toughness

The synthesis and characterization of 1111-type diluted magnetic semiconductors (La1-xSrx)(Zn1-xTMx)AsO (TM = Mn, Fe, Co)

The doping effect of Sr and transition metals Mn, Fe, Co into the direct-gap semiconductor LaZnAsO has been investigated. Our results indicate that the single phase ZrCuSiAs-type tetragonal crystal structure is preserved in (La1-xSrx)(Zn1-xTMx)AsO (TM = Mn, Fe, Co) with the doping level up to x = 0.1. While the system remains semiconducting, doping with Sr and Mn results in ferromagnetic order with TC ~ 30K, and doping with Sr and Fe results in a spin glass like state below ~6K with a saturation moment of ~0.02 muB/Fe, an order of magnitude smaller than the ~0.4 muB/Mn of Sr and Mn doped samples. The same type of magnetic state is observed neither for (Zn,Fe) substitution without carrier doping, nor for Sr and Co doped specimens.Comment: Accepted for publication in EP

Efficacy Dependence of Photodynamic Therapy Mediated by Upconversion Nanoparticles: Subcellular Positioning and Irradiation Productivity

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136433/1/smll201602053_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136433/2/smll201602053-sup-0001-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136433/3/smll201602053.pd

Surface interactions and viability of coronaviruses

The recently emerged coronavirus pandemic (COVID-19) has become a worldwide threat affecting millions of people, causing respiratory system related problems that can end up with extremely serious consequences. As the infection rate rises significantly and this is followed by a dramatic increase in mortality, the whole world is struggling to accommodate change and is trying to adapt to new conditions. While a significant amount of effort is focused on developing a vaccine in order to make a game-changing anti-COVID-19 breakthrough, novel coronavirus (SARS-CoV-2) is also developing mutations rapidly as it transmits just like any other virus and there is always a substantial chance of the invented antibodies becoming ineffective as a function of time, thus failing to inhibit virus-to-cell binding efficiency as the spiked protein keeps evolving. Hence, controlling the transmission of the virus is crucial. Therefore, this review summarizes the viability of coronaviruses on inanimate surfaces under different conditions while addressing the current state of known chemical disinfectants for deactivation of the coronaviruses. The review attempts to bring together a wide spectrum of surface-virus-cleaning agent interactions to help identify material selection for inanimate surfaces that have frequent human contact and cleaning procedures for effective prevention of COVID-19 transmission.Peer reviewe

Effects of Blending Sequence on Morphology and Mechanical Properties of Polypropylene/Ethylene-octene Copolymer/Clay Nanocomposites

Abstract The objective of this study was to investigate the effects of three blending sequences on morphology and properties of the ternary nanocomposite of polypropylene (PP)/ethylene-octene copolymer (EOC)/clay with double compatibilizers of maleated PP (PP-g-MA) and maleated EOC (EOC-g-MA) prepared by twin-screw extrusion. The X-ray diffraction results in conjuction with transmission electron microscopy images indicated the mixture of exfoliated and intercalated structures possessed by the nanocomposite prepared by simultaneous addition of the ingredients. The nanocomposite in which clay was first mixed with PP and EOC-g-MA and then with EOC and PP-g-MA showed the same morphology. However, in the nanocomposite when clay was first mixed with PP and PP-g-MA and then mixed with EOC and EOC-g-MA, an intercalated structure was observed. The results of mechanical testing showed that there was no significant difference in the yield strength, tensile modulus and flexural modulus among the three nanocomposites. However, the Charpy impact strength of the nanocomposite prepared by simultaneous addition of ingredients was higher than that of the nanocomposites prepared in two mixing steps because of the presence of more organoclay inside the EOC phase in the former

Biomimetic poly(glycerol sebacate)/poly(L-lactic acid) blend scaffolds for adipose tissue engineering

Large three-dimensional poly(glycerol sebacate) (PGS)/poly(l-lactic acid) (PLLA) scaffolds with similar bulk mechanical properties to native low and high stress adapted adipose tissue were fabricated via a freeze-drying and a subsequent curing process. PGS/PLLA scaffolds containing 73 vol.% PGS were prepared using two different organic solvents, resulting in highly interconnected open-pore structures with porosities and pore sizes in the range of 91–92% and 109–141 μm, respectively. Scanning electron microscopic analysis indicated that the scaffolds featured different microstructure characteristics, depending on the organic solvent in use. The PGS/PLLA scaffolds had a tensile Young’s modulus of 0.030 MPa, tensile strength of 0.007 MPa, elongation at the maximum stress of 25% and full shape recovery capability upon release of the compressive load. In vitro degradation tests presented mass losses of 11–16% and 54–55% without and with the presence of lipase enzyme in 31 days, respectively. In vitro cell tests exhibited clear evidence that the PGS/PLLA scaffolds prepared with 1,4-dioxane as the solvent are suitable for culture of adipose derived stem cells. Compared to pristine PLLA scaffolds prepared with the same procedure, these scaffolds provided favourable porous microstructures, good hydrophilic characteristics, and appropriate mechanical properties for soft tissue applications, as well as enhanced scaffold cell penetration and tissue in-growth characteristics. This work demonstrates that the PGS/PLLA scaffolds have potential for applications in adipose tissue engineering