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The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.

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Conference Proceedings
Light Weight Multifunctional Composites with Enhanced Mechanical Properties
Diego Pedrazzoli, Alessandro Pegoretti, Kyriaki Kalaitzidou, May 2014
In this study, polypropylene (PP) composites reinforced with short glass fibers (GF) and expanded graphite nanoplatelets (xGnP) were produced by melt compounding and injection molding. Quasi-static tensile tests and morphological observations were carried out in order to investigate how the morphology and the mechanical properties of the composites were affected by the combined effect of two fillers of rather different size scales (i.e. micro- and nano- scale). The results indicate that it is possible to introduce the nano-materials at the GF-PP interphase and significantly improve the tensile modulus of the composites, leading to lighter and stronger composites, as part of the higher density GF can be replaced with a small amount of the nano-materials. In addition to decreasing the weight of the composite, the processability is significantly improved as the increase in polymer viscosity reduces with decreasing the GF content. In conclusion, the results lead to hybrid composites that combine the advantages of nano-materials and micro-size reinforcements.
Gas Plasma for Molecular Re-Engineering of Microfluidic Devices
Mikki Larner, Khoren Sahagian, May 2014
Technology advances in the microfluidics industry are rapidly expanding global usage of low cost Point-of-Care and companion diagnostics. Although commodity polymers meet the cost profile, they often do not meet all key performance criteria; most notably stable surface wetting of biological fluids or reagents. Gas plasma technologies are increasingly employed to meet the demands of material selection through the molecular re-engineering of surfaces. Plasma modification using low temperature gas enables stable wetting with long shelf-life, chemical functionalization without wet chemistries, and thin film coating for promoting adhesion, barrier, or anti-fouling properties. The work herein provides an overview of plasma surface technologies and their role in the emerging diagnostic arena.
Thermotropic Liquid Crystalline Polymers and Their Fiber Reinforced Composites for Hydrogen Storage Applications
Chen Qian, Craig Mansfield, Donald G. Baird, May 2014
Thermotropic liquid crystalline polymers (TLCPs) are attractive candidates for manufacturing hydrogen fuel storage vessels because of the combination of their outstanding mechanical, barrier, and thermal properties. In this paper, basic mechanical properties of both unfilled and fiber reinforced TLCPs are reported. Significant enhancement in stiffness is observed by incorporating glass fiber and carbon fiber into TLCP matrices. Solidification behavior of TLCPs was studied by rheological experiments in an effort to establish processing conditions. Results reported in this paper build a solid foundation for understanding TLCPs' behavior and help establish parameters for processing these materials via extrusion blow molding.
The Influence of Atmospheric Pressure Plasma Surface-Modified Polymers PVDF, ECTFE, and Peek on Primary Mesenchymal Stem Cell Response
Trevor Spence, Jessica Pellegrino, John Ricci, Paulo Coelho, May 2014
The body’s response to an implanted material depends upon many factors, including biological interactions at the interface of the implant and its surroundings. Selectively modifying the surface of biomaterials is a practical approach to induce a site-specific desirable biological response. The fluoropolymers, polyvinylidenedifluoride (PVDF), ethylene-chlorotrifluoroethylene (ECTFE), and engineering resin, polyetheretherketone (PEEK), are known for their chemical resistance, thermal stability, and low surface energy, a great combination for low biological activity and, thus long-term stability, but very little integration with surrounding tissue. Atmospheric pressure plasma (APP) a clinically-safe plasma method, was applied to the substrates to functionalize the plastic surfaces for a more polar and hydrophilic environment. Freshly isolated mesenchymal stem cells (MSCs) were cultured on the surfaces in order to expand on the limited knowledge of topographical effects on differentiation of stem cells. To assess the cellular activity on each surface, modified and unmodified, biological assays were performed to understand cellular morphology, cytoskeletal structure, viability, and differentiation. Surface energy calculations via contact angle measurements showed a significant increase after plasmatreatment on each material. Crystal violet assay indicated an increase in cell viability from APP compared to unmodified surfaces. Visualization of nuclei and - tubulin via immunofluorescence indicated greater cellular activity from APP treatment. Scanning electron microscopy (SEM) imaging showed spherically-shaped MSCs had greater activity and attachment on the APP treated surfaces.
Fabrication and Improved Performance Evaluation of Poly-(3-Hydroxybutyrate-co-3-Hydroxyvalerate) with High Molecular Weight Natural Rubber for Novel Composites
Sunny J. Modi, Katrina Cornish, Kurt Koelling, Yael Vodovotz, May 2014
PHBV (Poly (3-hydroxybutyrate-co-3-hydroxyvalerate)) is a bio-derived semi-crystalline polymer of interest to the packaging industry looking for alternatives to the petroleum based materials currently used. The brittle nature of PHBV material requires blending with other polymers such as Poly (?-caprolactone) (PCL), Poly (L-lactic acid) (PLA), and natural rubber. Natural rubbers (NR), cis-1,4-polyisoprene, are classified as elastomers due to their high elasticity and yield strength. Therefore, the objective of this study was to characterize the thermal and mechanical properties of PHBV blended with natural rubber in two different concentrations.
The Open Hole Compression Test for Evaluation of the Effects of Fiber Waviness in Fiber Reinforced Composites
Rani F. Elhajjar, Seyedmohammad S. Shams, May 2014
In this study, we investigate the open-hole compression (OHC) test for evaluating the effects of fiber waviness in continuous fiber reinforced composites. The OHC specimens are fabricated from carbon fiber / epoxy into unidirectional laminate containing intentional waviness defects. The effect of the waviness morphology is also investigated by evaluating the effects of the resin pocket at the root of the waviness profile. Temporal evaluations of the load-deformation response, microscopy and acoustic emissions are used to understand the failure modes from the waviness specimens. The waviness specimens show different failure modes and can be structurally correlated to either kink zone formation and fiber fracture or interlaminar damage. The results also show the influence of the notch and the resin pocket on the interlaminar strain responsible for initiation of damage in the composite specimens.
Improvement of Melt Strength and Crystallization Rate of Polylactic Acid and its Blends with Medium-Chain-Length Polyhydroxyalkanoate through Reactive Modification
Manoj Nerkar, Juliana Ramsay, Bruce Ramsay, Marianna Kontopoulou, May 2014
Poly(lactic acid) (PLA) was reactively modified by using a multifunctional co-agent (triallyl trimesate) in the presence of dicumyl peroxide. The viscosity, elasticity and melt strength of PLA increased substantially following reactive compounding. Furthermore, the rate of crystallization of co-agent in modified PLA was significantly higher than that of the pristine PLA and a distinct crystallization peak appeared. Reactively modified blends of PLA with an elastomeric polyhydroxyoctanoate exhibited similar features, and significant improvements in blend morphology.
Catastrophic Failure of Fiber-Reinforced Thermoplastic Lawnmower Wheels
Ronald J. Parrington, May 2014
Three instances of riding lawnmower, fiber-reinforced thermoplastic wheel failures resulting in serious injuries have been examined. The wheels fractured violently due to the presence of fatigue cracks. The failure mechanism is fatigue initiation and growth during normal service followed by brittle overload fracture upon handling (e.g., tire inflation). One of the wheel failures is described in detail herein. Several design and manufacturing issues may have contributed to the failure: (1) cracks initiate and grow by fatigue at weak points in the design; (2) glass fiber orientation is nonrandom and predominantly in a direction that is ineffective in preventing fatigue crack propagation; (3) voids in the plastic weaken the part by reducing the effective cross sectional area; and (4) the polypropylene resin was apparently contaminated with polyamide. Crack path analysis was a very valuable tool used to understand the fractures.
Thermal, Mechanical, Rheological and Dielectric Properties of Clay-Containing SEBS Nanocomposites: Effect of Morphology
Emna Helal, Nicole Demarquette, Eric David, Danilo J. Carastan, Leice G. Amurin, Michel F. Fréchette, May 2014
In this paper, intercalated vs. exfoliated structures of clay-containing nanocomposites of polystyrene-b-poly (ethylene-co-butylene)-b-polystyrene are studied. The morphology of the nanocomposites, characterized earlier by microscopy and Small Angle X-Ray Scattering, is confirmed through the study of the thermal, mechanical, rheological and dielectric behavior. In particular, the improvement of the thermal stability of the polymer matrix was induced by the intercalated structure while the viscoelastic behavior and the mechanical and dielectric relaxation phenomena were more sensitive to the exfoliated structure.
Effect of Solvent Volatility on Diameter Selection of Nanofibers Produced by Gas Jet Fiber Process
Stuti S. Rajgarhia, Sadhan C. Jana, May 2014
Gas Jet Fiber (GJF) process involves aerodynamic forces to draw a jet of polymer solution from a nozzle and to convert it into polymer nanofibers. The jet of polymer solution undergoes rapid stretching and turns into solid nanofibers as the solvent evaporates. The nanofibers are collected as non-woven mat. An important parameter defining the nanofiber properties is fiber diameter. This work investigates selection of diameter of nanofibers from homogenous solutions of two immiscible polymers in two mutually miscible solvents. Several morphological forms such as interpenetrating network, bilobal, and core-shell are obtained by selecting two solvents with different vapor pressure and solubility parameters. This paper addresses the roles of polymer solution viscosity and solvent volatility in defining polymer fiber diameter varying between 1 µm and 100 nm.
Increased Strength and Thermal Conductivity in MWCNT/Epoxy Composites by Ultrasonication Aided Internal Mixing
Jin Sha, Guo Li, Riping Luo, Linsheng Xie, Yulu Ma, May 2014
To explode epoxy processing methods and overcome limitations of shear mixing and ultrasonication, internal mixer containing laminated kneading block structured rotors are designed and then the unites assemble configuration is optimized by evaluating mixing parameters of epoxy mixing field with the help of POLYFLOW software. Moreover, tip ultrasonication horn is integrated into the sealed barrel positioning at confluence areas between couple rotors to apply ultrasonication field simultaneously during mixing. Kinds of multi-wall carbon nanotubes are mixed with epoxy to prepare reinforced composite. Series characterizations are performed, including SEM, TGA/DSC, tensile test and thermal conductivity measurements to verify the equipment’s mixing capability. At 1.5wt% loading rate, significant mechanical improvements (above 27%) and thermal conductivity increase (above 22%) are observed, indicating excellent nanotubes dispersion and distribution in epoxy matrix.
Bio-Based Elastomers from Cationic/Free Radical Polymerization of Soybean Oil
Kendra Allen, David Grewell, Vijay Thakur, Michael R. Kessler, May 2014
Recently bio-based polymers procured from different natural resources have attracted greater attention as the viable eco-friendly alternatives to traditional petroleum-based products. Among various bio-based materials, vegetable oils represent one of the most abundant, low cost renewable material having the potential to be an ideal alternative to chemical feedstock/ traditional synthetic polymeric materials. Different derivatives of vegetable oils can be used as preliminary resources for the synthesis of a variety of materials (e.g. polyols, glycol, lubricants and plasticizers for polymers) owing to the high reactivity of their oxirane rings. So in this project, we have synthesized different soybean oil based elastomer using cationic/ free radical polymerization. Some preliminary study on the dynamic mechanical behavior of the synthesized elastomer has also been carried out.
Study of Mechanical Properties of Soy Flour Additives in Elastomer Composites
Kendra Allen, David Grewell, Vijay Thakur, Michael R. Kessler, May 2014
Bio-based polymers and biofiller polymers are becoming viable alternatives to petroleum-based plastics and offer increase bio-content at the end of service life compared to conventional plastics and rubbers. Advantages of soy flour include being lightweight, low cost, high strength and stiffness but interfacial adhesion poses to be an issue. In this project, soy flour as an additive to synthetic rubber matrix based composites were studied. Surface modification such as acetylation and grafting with PMMA were compared to untreated soy flour composites. In general, untreated as soy concentration increased, the mechanical properties of the composites decreased. In contrast, pretreated soy flour (acetylated soy flour and grafted soy flour) at 10wt% performed comparable to that of the neat rubber and resulted in an increase in tensile stress.
Effect of Feature Spacing when Injection Molding Parts with Microstructured Surfaces
Smita D. Birkar, Jin-Goo Park, Joey Mead, Carol Barry, May 2014
The effects of microfeature spacing on the replication of thermoplastic elastomer features was investigated using micropillars with two diameters (10 and 20 ?m) and three spacing ratios (0.5:1, 1:1, and 2:1). The tooling and part features were characterized for feature depth and height as well as feature definition using scanning electron microscopy and optical profilometry. Feature spacing significantly affected the replication of micropillars using a thermoplastic elastomer. This replication was competition between cooling and pressurization of the melt. Wider spacing between smaller features allowed cooling in the tooling lands to dominate the feature filling. Higher pressures did not always produce better feature replication, suggesting that cooling effects in the tooling “holes” restricted filling. High pressures also produced surface porosity in the molded pillars.
Comparison of Microstructured Surfaces Using Injection Molding and Nanoimprint Lithography
Marisely De Jesus Vega, Smita D. Birkar, Carol Barry, Joey Mead, May 2014
For the first time, thicker (2.4-mm) polycarbonate and polymethylmethacrylate sheets were employed in thermal nanoimprint lithography. The replication of microfeatures using this process was influenced primarily by imprinting temperature and not by imprinting pressure and time. Imprinting of thicker sheets generally showed the same replication trends as injection molding – i.e., channel depth increased with lower viscosity materials, definition of the channel bottom improved with increased solidification time, and land formation required complete replication of the channels. The higher temperatures in injection molding increase thermal and shear-induced stresses, thus increasing shrinkage and decreasing feature definition.
Quantitative Modeling of Scratch-induced Deformation in Ductile Amorphous Polymers
Mohammad M. Hossain, Hung-Jue Sue, May 2014
Scratch-induced surface deformation in polymeric materials is a complex mechanical process due to the rate, time, temperature and pressure dependent behavior of polymers. In this study, attempts were made to quantitatively predict the development of different scratch-induced deformation features of a model ductile amorphous polymer. By including the rate and pressure dependent mechanical and frictional behavior in the FEM model, good agreement has been obtained between FEM simulation and experimental findings. Usefulness of the present numerical modeling for designing scratch resistant polymers is discussed.
Degassing of Residual Monomer during Reactive Extrusion of PA6: Experimental Analysis
Eike Klünker, Christian Hopmann, May 2014
Polyamide 6 (PA6) with different molecular weight is polymerized in a twin-screw extruder based on the anionic polymerization. Due to a thermal equilibrium a temperature depending content of 10% (wt/wt) residual monomer remains in the PA6. Product quality requires a monomer content < 1% (wt/wt) A two-step vacuum degassing was adapted to realize an in-line monomer removal. The influence of the main degassing parameters on the amount of residual monomer and the relative viscosity of the PA6 is investigated. It was found, that a two-step degassing and injection of water as entrainer provides a content of residual monomer of 2.1% (wt/wt) based on high molecular weight PA6 and a polymer throughput of 10 kg/h. With decreasing content of residual monomer the melt viscosity increases causing a higher shear energy dissipation and melt temperature. At elevated melt temperatures side reactions and thermal degradation of the PA6 can occur, which were detected by changes in relative viscosity.
The Effect of Openair® Atmospheric Plasma on the Adhesion of UV Curable Coatings to Plastics
Andy F. Stecher, Paul Mills, May 2014
Ultraviolet (UV) cured liquid and powder coatings provide plastic part manufacturers with a number of desirable benefits including enhanced appearance, improved performance and various process advantages. At the same time, the rapid film formation and densely cross-linked chemistry that characterize UV curable materials also increases the likelihood of adhesion failures. That these coatings are formulated with little or no solvents makes attaining adhesion even more challenging. This paper examines adhesion problems inherent in UV curable liquid and powder coatings, and explores the tradeoffs associated with popular methods to mitigate adhesion problems. We find that atmospheric plasma treatment provides an especially effective means of improving adhesion of UV cure coatings to a wide range of plastic substrates.
Polylactic Acid-Based Polymer Blends for Durable Applications
Adam Finniss, Sushant Agarwal, Rakesh K. Gupta, May 2014
Elevated temperature and humidity lead to rapid degradation of polylactic acid (PLA). Consequently, PLA is not used for durable applications since properties cannot be maintained. The effects of blending PLA with polycarbonate (PC), heat treatment, and graphene inclusion were investigated in the presence of high humidity at 50°C. Samples were studied for up to 1 year of equivalent outdoor aging. While crystallization and adding graphene enhance short-term stability, it was determined that PC-rich blends in which the PC encapsulated the dispersed PLA had significantly improved hydrolytic resistance and mechanical properties as compared to both PLA and PLA-rich blends.
Thermoplastic Starch: The Prepation Method
Camila Fernanda D. Oliveira, Ticiane S. Valera, Nicole Demarquette, Natalia N. Fidalgo, May 2014
This work presents a systematic study about thermoplastic starches. Corn starch was mixed with 2 and 4 wt.% of carboxylic acid and 20 to 30 wt.% of water. The samples were prepared in an internal mixer coupled to a torque rheometer, and the torque values were monitored during mixing. The specimens for mechanical tests were calendered and cut with a knife. The mixtures were characterized by mechanical testing (tensile strength), scanning electron microscopy, and thermal analysis. The torque curves indicated that the samples with and without adipic acid addition suffer retrogradation. When the water content is increased, the glass transition temperature values decrease because water acts as a plasticizer for starch. The mechanical test results showed that samples with 2 wt.% acid content present the highest values of elastic modulus and tensile strength, and the lowest values of elongation at rupture.

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