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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Rheological Characterization on Thermal Stability and Flow Instability of Ethylene-Tetrafluoroethylene Copolymer
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
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
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
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
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
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
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
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
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
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
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
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
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)
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
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
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.
Lignin Powder as a Filler for Thermoplastic Automotive Lightweight Components
Lightweight design is an essential part of the overall Volkswagen strategy reducing the CO2 emissions. The use of lignin as a filler for thermoplastic materials offers an enormous lightweight potential. Here, a Lignin-PP compound filled with up to 30% Lignin powder offers a 20% weight reduction compared to traditional filled PP compounds assuring the same mechanical performance. Furthermore, in comparison to unfilled thermoplastics a potential cost reduction potential of up to 30% by using lignin as filler seems possible. Today, the use of lignin as filler for thermoplastic materials in automotive components in mass series applications is unknown.
Key aspects for the investigation of novel lignin based fillers are: the examination and quantification of lignin, the optimization of the manufacturing processes, the characterization and quantification of the mechanical properties of the novel lignin filled thermoplastics within an established material pre-validation process and a final economic efficiency and sustainability analysis.
Furthermore, the process ability of the products and demonstrators as well as the suitability for high volume production of the developed processes are investigated as main issues for successful implementation in future lightweight vehicle concepts.
Conversion of Lignin: Sustainable and Cost-Effective Carbon Fibers Usable within the Automotive Industry
Lightweight design is an essential part of the automotive strategy for reducing the CO2 emission. The use of carbon fiber reinforced polymers (CFRP) offers an enormous lightweight potential in comparison to aluminum, enabling a weight reduction, if a load-adapted (unidirectional) CFRP-design is used, of up to 60% in automobile parts without a degradation of the functionalities. Today, the use of CFRP is limited in mass series applications of the automotive industry by the cost of the conventional carbon fiber precursor Poly-Acrylic-Nitrile (PAN). Fifty percent of the cost of a conventional carbon fiber already belongs to the cost of the PAN precursor.
The analysis of lignin as an alternative precursor shows clearly a significant reduction in the cost of CFRP and reduction of CO2 emission during carbon fiber production. This fact is essential to make carbon fibers ready for a mainstream use within the automotive industry.
For qualifying Lignin as a precursor for automotive carbon fiber a detailed chemical understanding of the material is necessary. Lignin, which was used for carbon fiber production, is analyzed with the help of nuclear magnetic resonance spectroscopy and infrared spectroscopy in this paper, and the major chemical reactions during conversion process are highlighted.
On the Potential of Stereo Digital Image Correlation in Thermoforming
Process insight in thermoforming is a critical factor to secure the production of high quality parts. In thin gauge thermoforming, different tools exist to monitor this complex process and to gain insight. In heavy gauge thermoforming, this is not yet the case. The current paper demonstrates by means of three applications how in situ digital image correlation (DIC) can be used as a tool to acquire in depth knowledge of the ongoing process. In the first application, it is used as a 3D reconstruction tool. The second describes how full fields wall thickness distribution can be retrieved. The third application combines the previous two and demonstrates how the effects of asymmetric heating can be quantified. The technique makes it possible to visualize in a simple and straightforward way the amount of thinning of the sheet in every step of the process. In all three cases, the main goal is to provide more process insight, making it easier for the thermoformer to master his process, reduce the setup time for new products and control the process parameters.
Advanced Polymer Materials Synthesized by New Living Radical Polymerization Method (TERP)
The polymers synthesized by living radical polymerization (LRP) have a wide potential application in various areas. The recent progress of research has enabled the polymerization method to be scaled up for commercial production. Organotellurium-mediated living radical polymerization (TERP) using an organotellurium compound as a promoter is one of the new living radical polymerization methods. Compared with the conventional living radical polymerization, TERP has a wide monomer compatibility (applicability) from acrylates and styrene to?non-conjugated vinyl monomers, along with a molecular-weight controllability even in a high molecular-weight range over 100,000.
Utilizing these characteristics, we have introduced the materials for the pigment dispersants and pressure sensitive adhesives. TERP enables us to choose the best structure of block A and B for each dispersion system from a broad range of monomers and molecular weights. TERP block copolymer has the ability to maintain small particle size even with the reduced dosage compared to existing commercial products.TERP enables us to control molecular weight and its distribution to reduce oligomer that leads to excellent contamination resistance. Due to the well-defined structure of random copolymer and homogeneity of the polar functional group in one polymer chain, cohesion strength of PSA prepared by TERP become stronger. Therefore the PSA prepared by TERP demonstrates good heat resistance, good durability, and adhesive residue free. Here we report on the reduced adhesive residue of the PSA prepared by TERP compared to FRP products.
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