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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

Linear and NonLinear Rheology of Poly(Butylene succinate)/Fumed Silica Nanocomposites
Xun Chen, Bin Tan, Margaret J. Sobkowicz, May 2015

In this work, the role of shear deformation on the microstructure of nanocomposites formed by compounding poly(butylene succinate) (PBS) with neat and surface functionalized fumed silica is explored by melt state rheology. The rheology results uncover a unique structural evolution from shear start-up in nanocomposites, including formation of a physical network under steady shear. The linear viscoelastic responses show that the shear-induced network can result in increased elasticity and a second shear thinning regime at low frequency. The materials compounded with hydrophobic organically modified silica display shear-induced reinforcement at lower particle loadings than those with hydrophilic fumed silica. These results indicate that reinforcement in nanocomposites can be controlled by filler surface functionality and shearing effects. This method enables improved mechanical properties with low filler loadings.

Effects of Shear and Extensional Flows on the Electrical Properties of Polycarbonate/Carbon Nanotube Composites during Injection Molding
Sidney Carson, Joao Maia, Joseph C. Golba, May 2015

Electrically conductive composites made from polycarbonate (PC) and two different types of carbon nanotube (CNT) were compounded and subsequently molded in order to glean effects of the injection molding process on the electrical properties of the materials. A typical multiwalled CNT and a highly branched, crosslinked CNT were investigated to determine the effect of initial nanotube morphology. All composites were molded through three geometries: shear dominated, mixture of shear and extension, and extension dominated. It was determined that the initial nanotube morphology was the largest contributing factor to the final electrical properties of the composites.

Toughness Study of Center Cracked Polypropylene Films with Temperature Effect
Arzu Hayirlioglu Topuzlu, Hoang Pham, Lon Grant, Alex Xue, Yatin Patil, Andy Poslinski, May 2015

The manufacturing of a cast film with high orientation has little forgiveness for imperfections embedded within the polymer web. Imperfections such as gels, dirt and other contaminants can lead to web breakage and hence downtime which affects productivity. In this study, the effect of defect size on the failure of a web is studied using a model system that simulates the defect by a slit crack. The toughness of the film can be assessed as a function of defect size. In this study, polypropylene (PP) cast films were used for this investigation and the toughness is determined using an MTS Sintech Tensile tester.

Our test results showed that un-notched PP homopolymer films exhibit fully ductile behavior at both temperatures, 23øC and 40øC. However, increasing the center crack length resulted in decreased in toughness and at above 3 mm in crack length, the PP cast film failure mechanism changed from fully ductile to brittle like failure.

Development of Crosslinked Polyethylene by Using a Tin-Free Silane Cocktail
Samim Alam, Roy Rojas-Wahl, May 2015

A linear low density polyethylene was crosslinked using a vinyl cyclic alkoxy silane, initiator, and non-tin catalyst. At first, silane cocktails were developed by mixing vinyl cyclic alkoxy silane, initiator, anti-oxidant, and various non-tin catalysts. Next, using such silane cocktails, a series of crosslinked polyethylenes (XLPEs) were produced. The mechanical properties and extent of crosslinking of resulting XLPEs were compared to those of a XLPE produced by using dibutyl tin dilaurate as a catalyst. The result indicated that cyclic silane cocktails containing non-tin catalyst can effectively crosslink the polyethylene.

Rheological Characterization on Thermal Stability and Flow Instability of Ethylene-Tetrafluoroethylene Copolymer
Seigo Kotera, Masayuki Yamaguchi, May 2015

Viscoelastic properties of ethylene-tetrafluoroethylene copolymer (ETFE) in the molten state are evaluated in detail considering the thermal stability during the measurement at high temperature with/without oxygen. It is found that random chain scission reaction occurs without crosslinking even under a nitrogen atmosphere at 300 §C. The steady-state shear compliance Je0, which is affected by the molecular weight distribution strongly, is unchanged during the chain scission, suggesting that the chain scission occurs with keeping the molecular weight distribution. According to the classical theory on the random scission reaction, this result demonstrates that the polydispersity (Mw/Mn) of the virgin ETFE sample, prior to the exposure to thermal history, is closed to 2. On the other hand, ETFE shows crosslinking reaction under air condition even in the cone-and-plate rheometer. The degree of crosslinking is estimated by the plateau modulus G?plateau in the low frequency region.
In addition, flow instability at the capillary extrusion is evaluated. ETFE shows several types of melt fracture over a critical shear stress, e.g., shark-skin, slip-stick and wavy melt fracture. It is interesting to note that quasi-stable flow region is observed between slip-stick and wavy melt fracture regions. It suggests that ETFE can be processed at a high out-put rate condition by the steady slip.

Bioplastics for Solar Thermal Applications: Potential of Bio-Poly(Ethylene) and Poly(Trimethylene Terephthalate) for Swimming Pool Solar Collectors
Andrea Klein, Katharina Resch, Gernot Oreski, May 2015

Within this study bioplastics ? bio-poly(ethylene) and poly(trimethylene terephthalate) ? i.e. polymers based on renewable resources, are comprehensively evaluated and tested as to their principle applicability as absorber mate?rial in swimming pool solar collectors. Investigations showed that the considered bioplastics possess a high potential for application in solar thermal devices in general. However, further optimization, especially of long-term performance and maximum operating temper?ature by tailoring molecular and super-molecular structure as well as by addition of additives and fillers is required.

A New Method for the Calculation of the Spherulite Growth in Solidifying Semi-Crystalline Polymer Melts
Marcel Spekowius, Claudio Schirrmann, Roberto Spina, Christian Hopmann, May 2015

This paper presents a new algorithm named Continuous Cellular Growth" (CCG) method for the calculation of the crystal growth process of spherulites in solidifying semi-crystalline polymer melts. The concept is developed in one dimension then transferred to three dimensions and finally implemented as an executable algorithm in the in-house code Sph„roSim. The CCG method is compared to an inaccurate but fast Monte-Carlo based and an accurate but slow integration based growth algorithm which uses a Raytracing method. It turns out that the results of the CCG method are very close to those of the integration method with differences of only a few percent. Howeverthe computation time was reduced by two orders of magnitude compared to the Raytracing method and thus is only slightly above the computation time of the Monte Carlo algorithm."

A Novel Method to Make Highly Crystalline PET Articles by Powder Compaction
Zahir Bashir, Toseef Ahmad, May 2015

Highly crystalline parts of PET are difficult to produce by conventional injection moulding methods, as PET crystallises slowly from the melt. Here, a method adapted from powder metallurgy is employed to fabricate highly crystalline PET articles. It involves using highly crystalline PET powder and compacting it at 5-30øC below the bulk melting temperature of the PET (that is, at 230 to 255øC). This allows consolidation of the powder to form a part with the high crystallinity levels similar to the original powder. The highly crystalline articles of PET made by powder compaction had a Vicat softening point > 200øC, high modulus, high hardness, and high creep resistance.

Development of a Relaxation Model for Annealing of Plastic Films and Sheets
Wenyi Huang, Michael D. Read, Todd A. Hogan, May 2015

Controlling shrinkage levels during converting is one of the most important critical customer requirements for many applications of plastic films and sheets. Shrinkage levels of 40-60% are common for cast films and calendared sheets. Shrinkage reduction can be accomplished by a subsequent annealing process after the extrusion casting/calendaring process. In this paper, we established a relaxation model for predicting the shrinkage level of plastic films/sheets upon the completion of the annealing process. Specifically, this model correlated shrinkage level of plastic films/sheets after annealing with the relaxation time of a polymer obtained by dynamic rheological measurement as well as the annealing conditions such as temperature profile and residence time. This relaxation model is very useful for determining the design parameters of an annealing process as well as for optimizing the annealing conditions such as annealing temperature and line speed.

Effects of Compounding Set-Up on Electrical Conductivity Properties of Carbon Black Filled Compounds
Daniele Bonacchi, Christine Van Bellingen, May 2015

Conductive carbon black is commonly used to permanently modify the electrical properties of plastic compounds from insulating to conductive. Some applications require a high degree of dispersion; for example, thin sheets for electronic packaging, cable semicons or electrically conductive pipes do not tolerate undispersed carbon black. In this article we investigate three compounding routes via twin screw extruder showing how incorrect setups can dramatically decrease the quality of the final compounds. We also show that poor carbon black feeding or very high melt viscosity of concentrated compounds (like masterbatch) can have detrimental effects on the electrical properties. Finally, we show that the degree of dispersion is strongly dependent not only on the melt viscosity but also on the carbon black selected.

Direct Adhesion of Plastic and Stainless Steel Using Conductive Heating in the Injection Molding Process
Christian Hopmann, Julian Schild, May 2015

The injection molding process enables the production of plastic/metal hybrid components in large scales. State of the art is the use of adhesion promoters to achieve a joining of the incompatible materials. This material bonding technology allows a wide, homogeneous force transmission into the hybrid component. Therefore the metal components are coated upstream.
It is possible to waive adhesion promoters and achieve a direct bond between plastic and metal. In this case the metal insert has to be heated up to a temperature in the range of the melt temperature of the polymer. This paper describes an innovative heating concept for metallic inserts wherein the metal insert acts as a direct heating resistor.

New Materials for Fluid Injection Technique ? Improved Properties with Reactive Polyurethanes
Christian Hopmann, Christian Holz, Kai Fischer, May 2015

Even though the solidification behavior of reactive polyurethane (PU) differs from that of thermoplastics, this material can be used for the projectile injection technique. The technology combines the excellent properties of PU with the economic benefits of injection molding and enables the production of complex elastomeric fluid-conducting hoses with adjustable flexibility and high impact strength. Additionally, the integration of a continuous fiber reinforcement leads to improved bursting strength in comparison to short fiber-reinforced thermoplastics.

The Effect of Crosslinks on the Mechanical Properties of Elastomers: Experimental Characterization and Modeling
Philipp Bruns, Christian Hopmann, May 2015

The conditions of the forming process influence the crosslinking distribution in rubber parts and therefore the resulting mechanical properties significantly. In order to ensure a precise dimensioning of rubber parts, a method has been developed that considers the process-related crosslinking distribution in structural simulations. The dependency of the mechanical properties on the local crosslinking degree is taken into account by coupling a process simulation with a program for structural finite element analysis (FEA). For this purpose, an interface is implemented, which correlates the crosslinking parameters of the process simulation with mechanical characteristics and passes these data to a subsequent structural analysis simulator. The developed method is based on physical and mechanical tests of partially and fully crosslinked elastomers.

LLDPE-EVOH High Barrier Blend Films Fabricated by Multiplication Extrusion
Guojun Zhang, Hong Xu, Kari Maclnnis, Eric Baer, May 2015

Blends of linear low-density polyethylene (LLDPE) and ethylene vinyl alcohol (EVOH) with different weight fractions are prepared by a twin-screw extruder at A. Schulman Inc., Akron. These compounded blends are then melt-extruded to fabricate thin films at CWRU, Cleveland. We discover that with 50-50 weight fraction, co-continuous morphology exists. Different numbers of multipliers are therefore utilized to tailor the morphology of the extruded blend films with 50-50 weight fraction. As the number of multipliers increases, the blend film morphology transforms from an elongated and layer-like structure to homogeneous mixture feature. This is because during the multiplication process, the multipliers behave similar to static mixers that physically break the elongated and layer-like structure into tiny domains. As the morphology evolves, the physical properties of the extruded blend films change dramatically accordingly. Both the gas permeability and the light transmission rate of these films increase as the number of multipliers increases. More interestingly, the tensile mechanical behaviors become isotropic at different deformation directions. Atomic force microscopy (AFM) is utilized to investigate the morphology of the blend films. Oxygen transport rate (OTR) and water vapor transport rate (WVTR) of these blend films are measured by MOCON units. The transmission rate and mechanical properties are studied by UV-vis and a mechanical tensile stretcher (MTS), respectively.

Degradation of Microcellular PLGA-PEG Copolymer for Use in a Drug Delivery System for the Urinary Bladder
Daniel Kaltbeitzel, Christian Hopmann, Theresa Kauth, Joachim Grosse, Nadine Huppertz, Ulrich Schwantes, Claudia Neumeister, Barbara Dittrich, Matthias von Walter, May 2015

For the treatment of diseases of the bladder a drug delivery system (DDS) has been developed which can be applied intravesically. The DDS is composed of multiple carriers that consist of non-absorbable, drug-carrying microspheres which are embedded in a foamed absorbable matrix. After degradation of the absorbable matrix, the non-absorbable microspheres are eliminated through the urethra.
The foamed absorbable matrix is fabricated out of a poly(D,L-lactide-co-glycolide)-co-polyethylen glycol diblock copolymers due to its short degradation time. These polymers are temperature sensitive and therefore manufactured by the CESP process (Controlled Expansion of Saturated Polymers). The foam structure, which influences the degradation, is controlled by the process parameters.
Within this paper the influence of the process parameters on the degradation of the implants is investigated.

Failure Analysis of a Fractured Polyamide 6 Shock Absorber Housing
Brian Ralston, May 2015

A polyamide 6 shock absorber housing on a jogging stroller fractured completely during service. A range of techniques were utilized in the failure analysis, including DSC, TGA, FTIR, ICP-OES, SEM-EDS, and mechanical testing. Lithium grease, calcium, and chlorine were detected on and near the fracture surface. Fracture morphology observed by SEM suggests chemical interaction played a role in initiating the fracture. The combination of mechanical stress and the presence of known environmental stress cracking (ESC) agents in CaCl2 and LiCl is suspected to have led to time-dependent crazing, cracking, and eventual fracture of the housing.

Comparison of Compounding Approaches for Wood-Derived Cellulose Nanocrystals and Polyamide 6
Craig Clemons, May 2015

A simple, water-assisted approach to compounding cellulose-nanocrystal-reinforced polyamide 6 was investigated and compared to solvent blending using formic acid and melt compounding using freeze-dried CNCs. The watter-assisted approach did not result in any apparent degradation of the CNCs during compounding and dispersion improved in the following order: freeze-dried compounding < water-assisted compounding < solvent blending. Improved dispersion resulted in less thermal degradation during injection molding and improved tensile properties. Future work to improve both the processing and performance of these composites is suggested.

Improving the Dispersion of Ionic Liquid-Modified Montmorillonite in Poly(Ethylene Terephthalate)
Kazem Majdzadeh-Ardakani, Saleh A. Jabarin, May 2015

A two-step centrifugation method was applied to remove large particles from commercial montmorillonite (MMT) and provide nanoclays with smaller particle size distributions. Both centrifuged clay (CMMT) and MMT were modified with thermally stable imidazolium- and phosphonium-based ionic liquids. Thermal gravimetric analysis results indicated that clays modified with thermally stable ionic liquids degraded above 300 §C and could survive PET processing temperatures. X-ray diffraction, and Transmission electron microscopy revealed an improvement in the dispersion of centrifuged nanoclays (modified with both imidazolium and phosphonium ionic liquids) into the polymer matrix compared to non-centrifuged modified MMT with larger particle sizes. PET/clay bottles prepared with ionic liquid-modified clay showed a significant improvement in mechanical and barrier properties compared to those prepared with unmodified clay, and to PET bottles.

Low Gloss PC/ASA Blends for Automotive Interior Applications
Bin Sun, Douglas Howie, Stephen Taylor, May 2015

A new low gloss acrylonitrile-styrene-acrylate (ASA) impact modified polycarbonate (PC) blend is developed to address product performance needs for the low gloss finish in automotive interior applications. To provide inherent matte and/or low gloss surface finish properties, low gloss additives were added in the PC/ASA blends. A direct comparison of the product performance between the optimized formulation and the existing commercialized low gloss PC/ASA material revealed improved low gloss characteristics of the resulting new product with enhanced heat and impact properties. The custom solution technology for the new low gloss PC/ASA product presented here enabled the new business development in automotive interior applications and is highly translatable across the automotive industry.

In-Situ Saxs Study of Phase Segregation and Morphology of Styrenic Block Copolymers
Thomas Oomman, Tamara Mace, Hristo Hristov, Benjamin Hsiao, May 2015

The equilibrium morphologies of the styrenic block copolymers have been studied extensively [1,2,3], however the structural developments in dynamic regime are virtually unknown. In-situ Small Angle X-ray Scattering (SAXS) measurements were performed on a series of thermoplastic elastomers at the synchrotron light source at Brookhaven National Laboratory. The results from the scattering experiments were compared to different structural models. It was found that the styrenic blocks segregate very rapidly at high temperatures (200oC ? 250oC). It was established that the molten polymers start from the disordered state at high temperatures and on cooling, rapid phase segregation with significant phase fluctuations occurs. The hard block segments segregated into hexagonally packed cylinders before leaving the spinneret of the extruder. The rapid segregation is followed by a slower process of 3-D spatial ordering, which could take up to two weeks for completion depending on the annealing conditions.










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