The following is a list of the abstracts for papers which will be presented in the THIRD INTERNATIONAL SYMPOSIUM ON INTERFACES IN POLYMER COMPOSITES The listing is alphabetical by presenting author. This list is updated continually to add abstracts as they become available and make appropriate corrections. This list may be conveniently searched by using the editor provided with most popular browsers (e.g. Microsoft Explorer, Netscape, ... etc.)
Development of Water Permeable & Bio-compatible Membrane and Albumin Adsorption Effect
Hydrophilic groups were substituted on the inner wall of the porous Poly-tetrafuluoroethylene (PTFE) membrane by applying a water pressure and irradiating with an ArF excimer laser; which resulted in development of an artificial biomembrane that spontaneously controls the water outflow and has high tissue affinity.
Porous PTFE has several excellent properties such as heat resistance, chemical resistance, resistance to hostile environments, water repellency and air permeability because of its porosity structure. When being implanted in a living body, however, the porous PTFE is weak in adhesive to tissue due to its water and oil repellency. The biomembrane of porous PTFE should be properly fluid.
In order to substitute the hydrophilic groups on the 25Ám pores of the sample, the water pressure of 50mmHg was applied on the porous PTFE; which was then irradiated with the ArF excimer laser.
The penetration test was conducted with balanced salt solution [BSS]. The porous PTFE without treatment required 50 mmHg for the BSS to penetrate; however, the sample with treatment needed 10mmHg at the laser shot number of 3000 and laser fluencies of 15 mJ/cm2 to let the BSS penetrate. Furthermore, it became clear that changing the laser shot number freely controls the osmotic pressure difference. Of the non-treated or treated sample, its protein adhesive was evaluated with aqueous bovine serum albumin [ALB] and fibrin [FIB] solution as a protein index. From the results, it was confirmed that the ALB and FIB sticking increased as the substitution density of hydrophilic improved.
Using Theory and Simulation to Design Self-Healing Nanocomposite Thin Films
Thin films that are composed of polymers and inorganic nanoparticles offer the flexibility and processability of the polymers and the mechanical, optical and electromagnetic properties of the inorganics. Thus, these composite films are vital to the fabrication of various high-performance, lightweight materials. These thin layers are, however, susceptible to crack formation, which can form within the interior or at the surface of the system. Using a hybrid computational model, we focus on thin films of polymers and nanoparticles to design materials where the nanoparticles migrate to cracks within the system and effectively form patches to repair the damaged regions. We also use a micromechanical simulation to probe the structural integrity of the repaired layers. By contrasting the properties of the system in the damaged and healed states, we can determine the effect of the nanoparticle patches. Through these studies, we can isolate optimal conditions for harnessing nanoparticles to act as responsive band-aids for composite materials and to maximize the performance of the patched interfaces.
111 Center for Composite Materials, University of Delaware, Newark, DE-19716, DE
Thermal, Mechanical and Morphological Performance of TiO2-SC79 Epoxy Nanocomposite
Epoxy SC79 resin has been modified by incorporating TiO2 nanoparticles. Ultrasonic cavitation process was employed to disperse the particles into the resin system. The modified resin was then kept in a degassing chamber to remove cavities and bubbles. The liquid resin containing nanoparticles was cast to make epoxy-nanocomposite. Test coupons were cut to carry out morphological and mechanical characterization. From TEM investigation, it is found that the particles are nano size and disperse the entire volume of the polymeric resin. Dynamic and quasi -static mechanical analysis was also conducted with neat and nanophased resin. In dynamic mechanical analysis, nanophased resin shows significant increase in storage modulus, glass transition temperature and thermal stability. One the other hand quasi-static mechanical analysis, nanophased resin shows enhance stiffness and strength in flexural loading. Effect on crosslink density and viscosity were also investigated. Investigation was performed under various size and percentage of loading of nanoparticles. Details of fabrication and characterization will be discussed in the conference.
Tailoring the Interface in Thermoplastics / Organic Filler Composites via Crosslinking
Composites made of hydrophilic organic fillers in hydrophobic polymeric matrix suffer usually from low interaction on the phase boundaries. Various compatibilizers are commonly used to improve generally insufficient ultimate properties of the materials. We have investigated free - radical initiated crosslinking as a tool for improving the adhesion on the interface. It was demonstrated that organic - peroxide initiated crosslinking results in a substantial increase of the adhesion in systems such as polyethylene - switchgrass or polycaprolactone - pine wood flour, leading to an increase in tensile strength as well as Young's modulus and elongation at break. A formation of covalent bonds between matrix macromolecules and filler surface is the reason for observed changes in the properties compared to uncrosslinked composites.
Different effects have been observed for polyolefines filled with inorganic particles, e.g. silica or nanocomposites. In these cases, an increase in the resistance to crack formation and a decrease in crack growth rate results in increased toughness of the crosslinked composites, while a decrease in tensile strength and Young's modulus values have been attributed mainly to a drop in crystallinity degree of the crosslinked matrix.
(Acknowledgement: VEGA grant No 2/4024/04), and APVT grant No51-018502. This project has been funded in part by the National Academy of Sciences under the Collaboration in Basic Science and Engineering Programme / Twinning Programme supported by Contract No INT 0002341 from the National Science Foundation. The contents of this publication do not necessarily reflect the view or policies of NAS or the NSF, nor does mention of trade names, commercial products or organizations imply endorsement by the National Academy of Sciences or National Science Foundation.)
Implications of a Granular Interface in Carbon Nanotube Reinforced Polymers
The mechanics of the interface between a carbon nanotube and a polymer matrix may provide a strategy for making the most effective use of nanotubes as reinforcing elements. This work modifies the Cox composite stiffness model to account for the granularity of an interface at the boundary of micro and nanoscale effects. Finite element analysis of the reinforcement/matrix interface shows the effect of several interface distribution strategies on the stiffness of the nanocomposite. The best interface is a fully bonded continuous interface; however, this cannot be achieved because it destroys the nanotube. Granular interfaces provide the best performance when the bonds are concentrated at the ends of the nanotube.
Development of PET Ligament with High Adhesive Strength with Biological Tissues by Using ArF Excimer Laser
The hydrophilic functional group was photo-chemically substituted on a polyethylene terephthalate [PET] surface with an ArF excimer laser irradiation; which resulted in development of a PET artificial ligament that has high initial bonding strength to biological tissues.
Biological tissue affinity is indispensable for an artificial ligament, in addition to its function and mechanical property. The PET, which has been used as an artificial ligament, possesses its function and mechanical property but does not satisfy the requirement of the tissue affinity because of its water repellency; that is, the initial bonding strength to biological tissues is weak. For that reason, it is imperative for the PET surface to be modified into hydrophilic. We have, thus, photo-chemically substituted the hydrophilic functional groups on the PET surface with the ArF excimer laser irradiation.
The adhesion strength of the PET samples bonded with collagen was measured to evaluate the tissue affinity. Of the non-treatment sample, the contact angle with water was 75 degrees and the adhesion strength was 0.8 kgf/cm2. In comparison, the contact angle of the modified sample that had been irradiated with the laser fluence of 10mJ/cm2 and 400 shots improved to 30 degrees, and the adhesion strength increased by 21 times to 16.8 kgf/cm2.
A New Method to Improve the Interfacial Adhesion Between Wood and Polyethylene in Wood-polyethylene Composites
Wood-filled thermoplastics, commonly called wood-plastic composites (WPCs), are the fastest growing composite materials in the past decade. However, the weak interfacial adhesion between hydrophilic wood and hydrophobic plastics becomes one of the major obstacles for the continued growth and success of WPCs. In this study, we investigated a compatibilizer system to improve the interfacial adhesion between wood and polyethylene (PE). This new compatibilizer system comprises two components: polymeric diphenylmethane diisocyanate (PMDI) and stearic anhydride. Wood flour was first treated with PMDI, stearic anhydride, or a combination of PMDI and stearic anhydride, thoroughly mixed with PE, and then compression-molded into wood-PE composite boards. PMDI or stearic anhydride increased the modulus of rupture (MOR) and the modulus of elasticity (MOE) of the resulting wood-PE composites. A combination of PMDI and stearic anhydride resulted in much higher MOR and MOE than PMDI or stearic anhydride alone. This PMDI-stearic anhydride compatibilizer system was even more effective than maleic anhydride-grafted polyethylene, the most effective, commercially available compatibilizer for wood-PE composites, in terms of increasing the strength and stiffness of the resulting wood-PE composites. Mechanisms by which this new compatibilizer system enhances the interfacial adhesion will be discussed in detail.
Photochemical Adhesion of Fused Silica Glasses with Silicon Oil
The adhesive method that is pervious to ultraviolet light of 200nm and under in the wavelength has been developed by putting one silica glass to another with the silicone oil photo-oxidized in oxygen atmosphere.
The silicone oil (dimethyl siloxane) is composed of siloxane bonds of the main chain like as quartz and the methyl group has the side chain. Therefore, the organic silicone oil has been photo-oxidized by irradiating ultraviolet rays in oxygen atmosphere to change into inorganic glass. Then, the silicone oil was poured into the thin gap between the two pieces of silica glass in oxygen atmosphere and was irradiated with the Xe2 excimer lamp. Consequently, the siloxane of the silicone oil was bonded with the O atoms that had been absorbed on the glass surface to form SiO2.
The UV transmittance of the silicone oil was 29.2% before the lamp irradiation; which improved to 90.6% after the irradiation for 60 minutes. Furthermore, the adhesive strength of the silicone oil was enhanced from 0 kgf/cm2 of before-irradiation to 180 kgf/cm2 of after-irradiation.
S. Satija, NIST, Gaithersburg, MD
M. Bronner, Yale University, New Haven, CT
M. Snow, Cornell University, Ithaca NY
B. Cohen, HAFTR HS, Cedarhurst, NY
J. Nissel, DRS HS, Woodmere, NY
The Effects on Nanoparticles on Interfacial Fracture Toughness and
We have shown that the addition of small amounts of nanoparticles can drastically reduce the interfacial fracture toughness between polymers. The fracture toughness was found to increase with time as , t1/2, regardless of filler concentration, indicating that interfacial formation was diffusion limited. This was interpreted as being due to strong interactions between the filler particles and the polymer chains which hinder interfacial dynamics.Separate measurements of the interfacial diffusion were performed using either secondary ion mass spectrometry or neturon reflectivity, which were consistent with these observations. Finally, since there have been recent concerns regarding the biological impact of nanoparticles , we also tested the effects of the nanoparticles used on cell adhesion and proliferation. Resulsts indicate, minimal effects only for the large aspect ratio particles, such as clay.
Comparison of Hydrophilic and Oleophilic Groups Substitution on PTFE Surface with V-UV Photon Irradiation for Protein Adsorption
(Abstract not yet available)
Rensselaer Polytechnic Institute, Troy, NY
Polymer Nanocomposites - Designed Interfaces
Nanofilled polymers offer great promise as multifunctional composites that are strong, stiff, conducting, and transparent. The small size of the particles provides an opportunity for transparent polymer composites, and the large interfacial area provides an opportunity for a second mechanism or reinforcement. The second mechanism of reinforcement is the result of the interaction zone, the region surrounding the polymer in which the polymer morphology and dynamics is different from the bulk. Our work has been focusing on understanding the effect of the nanoparticle interface on polymer structure and properties in the interaction zone, and on designing interfaces to control nanocomposite properties. RAFT polymerization has been used to place monodisperse polymer layers on nanoparticles. Taking advantage of both RAFT controlled interfaces and other chemistries, we have been studying the role of the particle surface on the properties of the interaction zone and the resulting composite properties. In amorphous polymer nanocomposites, we have observed significant changes in the glass transition temperature and have correlated this to thin film results. We have also observed significant changes in mechanical properties. This presentation will present our latest results in this area.
Plasma Fluoropolymer Surfaces and Interfaces
Ultra-thin polymer films are of interest for advanced microelectronic, biomedical, automotive, aerospace and protective coating applications. The numerous advantages of thin fluoropolymer films include a low surface energy, a low coefficient of friction, a low dielectric constant, a high chemical resistance and good biocompatibility. Plasma polymerization is a solvent- free, room temperature process that can be used to rapidly deposit thin polymer films on a wide variety of substrates. Plasma polymers were deposited from several fluorinated monomers, their molecular structures and surface energies evaluated, and the metal / plasma fluoropolymer interface was explored. The plasma fluoropolymers were transparent, yellow films that adhered strongly to the substrate and were deposited at constant deposition rates that ranged from 0.03 Ám/min to 0.34 Ám/min. The surface energy was strongly affected by the gas feed composition. There is metal - fluorine interaction during the initial seconds of deposition following which the deposition of fluorocarbon begins to dominate the surface. The relationships between processing conditions, molecular structure and properties will be discussed.
Interphase Characterization in Filled Thermoplastics
The properties of filled thermoplastics are often critically dependent upon the properties of the interphase between the filler and matrix. Understanding interphase behavior and gaining the ability to design and construct interphases with specific properties remains a challenging task in many area of materials science. Wood-plastic composites are a rapidly growing segment of the building materials and injection molding industries. Development of various techniques to characterize this interphase in these systems will be presented. These techniques include pull-out tests, instrumented impact testing, calorimetry, dynamic mechanical analysis and microscopy studies. Correlation of the interphase properties with the mechanical properties of the final composite product offer insights into the design and development of novel systems with improved properties.
1) Core R&D - Materials Research, The Dow Chemical Company, 2301 N. Brazosport Blvd., B-1603, Freeport, TX 77541-3257
2) Exxon Mobil, Houston, Texas
3) Departments of Engineering Science and Mechanics and Chemistry respectively, Virginia Tech, Blacksburg, Virginia
Thermoset Polymer Matrix Composite Interface Design, Mechanics and Durability
Thermoplastic fiber sizings are examined as a means to improve fiber reinforced thermosetting composites. Specifically, we target carbon fiber composites in vinyl ester matrixes, candidates for rapidly processed, low cost composites for civil infrastructure and marine applications. Evaluation of three sizings, poly(vinylpyrrolidone) (PVP), a carboxyl modified polyhydroxyether (PHE), and a standard industrial sizing (G') have revealed tremendous improvements in static mechanical and enviro-mechanical properties. We discuss these findings in the context of the micromechanics of the interface/phase and the potential to enhance damage tolerance and resist moisture degradation. In this study focusing on hygrothermal exposure, a nanoindenter is effectively used to obtain interfacial shear strength using the microindentation technique. The results show that although the LSP material outperforms the PVP and G' materials in bulk composite properties, it is equivalent in interfacial shear strength to G' and experiences hygrothermal degradation in interfacial adhesion that the PVP does not. The PHE loses 10% of its original interfacial shear strength after 576 hours, while PVP improves by 25%. The tensile strengths for PHE and PVP decrease 7% and 10% respectively at 576 hours of hygrothermal exposure. The relationship between tensile strength and interfacial adhesion proves to be small with processing defects and other failure processes having apparently stronger influences.