SPE Library
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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Recycling
Designing Injection Molded Bioplastics Products
Rolf Koster, Bregtje van Dijken, Lobke van Erve, May 2007
The ongoing need to keep reducing trial-and error in product design definitely applies to plastics products, and perhaps even more to bioplastics. It remains essential to optimize unavoidable weak spots in injection molded products, such as flow weld lines. Critical product properties were investigated for a poly-hydroxybutyrate, an experimental wood fiber-filled poly-hydroxybutyrate, and a general purpose polystyrene for comparison. Specimens from products molded with poly-hydroxybutyrate were found to have quite good impact strengths in weld line regions. Certain non-trivial injection molding settings, which reduce the impact strength in neat product regions, were found beneficial for weld line properties.
Designing Sustainable Products Using Bio-Based Nanocomposites
Emre Tufekcioglu, Rolf Koster, Daniël Vlasveld, Remy Jongboom, May 2007
Environmental materials-related factors can be best addressed in the design stage. Conversion of materials to products is critically important in dealing with new and partly unknown challenges and opportunities. Experiments to explore bio-based nanocomposites included investigating injection molding processability and product properties. Several nanocompounds with modified poly(lactic acid) were prepared and geometries were molded with typical product characteristics, including flow weld lines. Further molding optimization is needed, preferably in conjunction with new mold design principles and dedicated molding machines.
Reinforcing Virgin, Reprocessed or Recycled Polypropylene with Agave Fiber and a Polymeric Coupling Agent
Carlos F. Jasso-Gastinel, Reyes J. Sanjuan-Raygoza, May 2007
The capability of using residual agave fibers from the tequila production process, to reinforce virgin, reprocessed or recycled polypropylene, is studied. Polypropylene composites were prepared with milled (65 mesh) agave fibers and Epolene E-43 in a twin screw extruder, varying the amount of fiber. Tensile, impact and dynamic tests, along with scanning electron microscopy observations were carried out. The importance of polymer-fiber interaction through the presence of the coupling agent is clearly shown.
Rheological and Degradation Properties of Renewable Resource Polymer Blends
Jason D. Conrad, James P. Eickhoff, Graham M. Harrison, May 2007
Over the past decade, considerable interest has emerged in replacing conventional fossil fuel-based polymers with bio-derived polymers. Two bio-derived polymers that have garnered significant interest are PHA and PLA. In this study, shear and extensional rheology, coupled with degradation studies using GPC, are used to investigate the flow properties of blends of these two polymers. The development of blends with tailored flow and thermal/mechanical properties is pursued.
Sharkskin and Melt Fracture of Some Biodegradable Polymers
D. Kanev, E. Takacs, J. Vlachopoulos, May 2007
Sharkskin and melt fracture phenomena have been investigated in two commercial biodegradable polyesters– aliphatic-aromatic co-polyester (AAC), poly(lactic acid) (PLA) and their blends. The study was conducted in a two bore capillary rheometer. It was observed that at high shear rates and stresses PLA exhibits sharkskin and gross melt fracture, while AAC exhibits only gross melt fracture. Experiments indicate that the blends exhibit both phenomena and that blending is beneficial for postponing the onset of flow instabilities to higher shear stresses.
Structural, Thermal, and Mechanical Properties of Miscanthusderived Biocomposites
Gediminas Markevicius, Sean C. Jones, Vivak M. Malhotra, May 2007
Miscanthus, a high yield, fast growing perennial grass with low mineral content, was put under a microscope to explore its potential as a source of natural and environmentally friendly fibers and polymers for composite manufacturing. The manipulation of miscanthus’ structural and thermal properties at 25°C < T < 550°C, as probed by SEM, DSC, TGA, and in situ diffuse reflectance-FTIR, suggested that composites with flexural strength as high as ~ 65 MPa could be formulated without the addition of external polymers.
Development of Renewable Polymers from 1,3-Propane Diol and Malonic Acid
Mathew D. Rowe, Erin M. Smith, Keisha B. Walters, May 2007
The goal of this research is to develop biodegradable copolymers from biomass-derived starting materials. The monomers, 1,3-propane diol and malonic acid, were selected based on the presence of reactive functional groups and availability of these materials in biomass. The effects of varying catalyst and temperature on polymer yield were determined. FTIR spectroscopy and nuclear magnetic resonance (NMR) were used to confirm polyester synthesis. The polymerization yields, using aluminum chloride, tin(II) chloride, and iron(III) chloride as the catalyst, ranged from 18-58%, 20- 43%, and 32-47%, respectively, over the 125-175 ºC reaction temperature range.
Effect of Molding Conditions on Morphology and Structure of Recycled-PET
T. Ohta, Y.W. Leong, K. Yamada, H. Hamada, May 2007
Mechanical and morphological properties of injection moldings are known to be highly dependant on molding conditions, e.g. barrel and mold temperatures, injection speed, and injection pressure. However, the not all conditions impart the same degree of influence on the final properties of the moldings. Here, the properties of recycled poly(ethylene terephthalate) (RPET) were gauged based on accurately measured injection molding conditions, i.e. transducers embedded in the mold cavity were used to measure the resin pressure and speed. Initial investigations have shown that injection speed exerts more influence on the properties of RPET than injection pressure.
Effect of Multiple Shear Histories on Rheological Behavior and Devolatilization of Poly(Ether Ether Ketone)
Jeffrey Galloway, Richard Hoffman, Sanjiv Bhatt, May 2007
The effect of shear history on the properties of poly(ether ether ketone) (PEEK) was investigated by processing it through a twin screw extruder 20 times. Samples were taken at various stages in the recycling sequence for testing. The melt rheological behavior, solid mechanical properties, and total outgassing performance were monitored to evaluate the degradation of the PEEK as a function of processing history.The results of rheological testing suggest that degradation is initially dominated by chain scission with cross-linking becoming more significant with more reprocessing cycles. The rheological and mechanical behavior shows similarities to liquid crystalline polymers and filled polymer systems. The results of outgassing testing showed that the total amount of volatiles decreased with increasing processing cycles.
Environmental Stress Cracking in Polycarbonate – Prediction of the Long Term Behavior by the Use of Short Time Tests
Walter Michaeli, Jan Henseler, May 2007
The environmental stress cracking is the most common failure reason of polymer parts during their use. There are already many tests to verify the stress crack resistance. Most methods use combinations of an external strain and aggressive liquids to achieve a quick test result. The extrapolation to longer time periods is only successful with the help of the expert knowledge of the raw material producers. The development of a new testing method enables a simulation of the material long-term behavior on the basis of a short time test of plastics under the influence of a medium.
Environmental Stress Crazing in Polystyrene: The Roles of Chain Length and Architecture in Craze Initiation
Davide S.A. De Focatiis, C. Paul Buckley, Lian R. Hutchings, May 2007
This work aims to assist in optimising the solid state performance of polymer products, by developing an understanding of the molecular factors involved in initiation of environmental stress crazing. Experiments measuring craze initiation stress in miniature rectangular beam samples saturated in diethylene glycol were performed on 26 isotropic atactic polystyrenes with molar mass from 66 kD to 1148 kD, including a wide range of monodisperse linear and branched materials. Results indicate that both solid-state molecular disentanglement and chain scission play roles, depending on the chain architecture and length of the polymer. A simple rule is suggested for predicting ESC raze initiation in polydisperse polymers.
Failure Analysis and Prevention – A New European SIG
Jan Spoormaker, Erik Andreassen, Anton Heidweiller, May 2007
The new European Failure Analysis and Prevention Special Interest Group (FAPSIG) is creating a database with failure cases. The members share this database and contribute with their own failure investigations. The two main groups are Failure Causes and Failure Mechanisms. Failure Causes are subdivided in: Stress concentrations, low mass and/or mould temperature, highly stressed weld lines, faulty ribbing; too high stiffness of construction elements, incorrect joining, and incorrect material selection.Failure Mechanisms are subdivided in: Creep and stress relaxation, wear, fatigue, UV degradation, chemical attack, environmental stress cracking.The paper will present some examples for designers of plastic products.
Improving the Toughness of Poly(Lactic Acid)(PLA) through Co-Continuous, Immiscible, Biodegradable Blends with PHA
Jinkoo Lee, Stephen McCarthy, May 2007
Poly(lactic acid) (PLA) and Polyhydroxy octanoate (PHO) were melt blended using a torque rheometer in the ratios of 80/20, 60/40, 50/50, 40/60, and 20/80. In this study, the rheological, thermal, and mechanical properties of the blends were investigated. Differential scanning calorimetry showed that the two components in these blends were found with two crystalline phases and two amorphous phases confirming the coexistence of two immiscible components. The addition of modified PHO in PLA increased the toughness of the PLA and increased the elongation to break more than 158%. Results obtained from rheological test indicated that the melt viscosities of PLA/modified PHO decreased as a function of modified PHO content.
Investigation of Fracture Mechanism of HDPE Subjected to Environmental Stress Cracking
Byoung-Ho Choi, Jeffrey Weinhold, David Reuschle, Mridula Kapur, May 2007
Environmental stress crack resistance (ESCR) is a commonly used test to characterize cracking failure of high density polyethylene (HDPE) used in rigid packaging applications. From a resin design standpoint it is important to understand the mechanism of environmental stress cracking (ESC) especially in the case of materials with significantly different ESCR values. In this report, the morphology of ESC is studied by scanning electron microscopy (SEM). A model to predict polymer ESCR using tie chain concentration considering the permeability of IGEPAL® solution is proposed.
Ionic Liquids as Additives for Thermoplastics
K.I. Park, M. Xanthos, May 2007
In attempts to develop new process modifiers for thermoplastics, two ionic liquids with long chain hydrophobic cations and different anions were introduced in a biodegradable polymer. Methods of incorporation included melt blending, solvent casting and microencapsulation from w/o/w systems at concentrations up to 10 wt%. The modified polymers were characterized rheologically and by TGA to determine process and thermal stability, respectively, and by DSC to determine miscibility and types of the polymer-ionic liquid interactions. Potential applications in plasticization, lubrication and emulsification are discussed for selected polymer-ionic liquid combinations.
Manufacture and Mechanical Characterization of a Composite Material Made of Wasted Tires and Recycled Polyethylenetherephtalate (PET)
R. Mis-Fernandez, J.A. Azamar-Barrios, J. Rodriguez-Laviada, C.R. Rios-oberanis, May 2007
Solid residue was obtained by two processes to reduce discarded tires: pyrolysis and thermal shock. Techniques such as X-ray, FTIR, TGA and SEM were used to characterize the samples. Two types of polyethylenetherephtalate, PET (virgin and recycled) were analysed physicochemical and mechanically to be used as matrix. A composite material was manufactured by employing a Brabender mixing chamber in order to use the granules as filler on PET at different concentrations. The mixed material was laminated and tension test were undertaken in samples to acquire the mechanical properties. Studies of fractography were performed to understand the failure mechanics.
Micropatterning Poly(Acrylamide) on PLA Films Using Photolithography
Rahul M. Rasal, Douglas E. Hirt, May 2007
Micropatterning is a robust tool to surface-modify bioplastics like poly(lactic acid) (PLA) for biomedical applications. We used a sequential two-step photografting and photomask approach to micropattern poly(acrylamide) (PAAm) on PLA film. In step one, a PLA specimen, dip coated in benzophenone solution in ethanol covered with the photomask, was sandwiched between two glass plates and exposed to UV in an inert atmosphere. In step two, benzophenone-micropatterned film was immersed in 10% v/v monomer solution in water and exposed to UV for 3 h to grow poly(acrylamide) (PAAm) from the film surface. The resultant film surfaces were examined by AFM and optical microscopy, which revealed the resolution and acuity of the micropatterns.
New Materials from Polylactide Bioplastics
Rahul Bhardwaj, Amar K. Mohanty, May 2007
Renewable resource based bioplastic are the next generation of materials, which will play a major role in building of a sustainable bioeconomy. Polylactide (PLA) is a renewable resource based bioplastic. The realm of PLA bioplastic is expanding through innovative research methodology, products and processes. There is pressing want to enhance the versatility of this bioplastic, so that it can compete with conventional polymers. Inclusion of nanostructures in polymeric matrices is looked upon as unique approach to create revolutionary material combinations. Harnessing the benefits of nanotechnology in generating new biobased material is considered as a benign approach. Biodegradable polymer-clay nanocomposites have already been explored extensively. The niche application of nanotechnology to bring breakthrough research in the field of biobased polymer is still elusive. Recently, polylactide (PLA) has been modified with a new technology based on nanoscopic hyperbranched polymers (HBP) at Michigan State University. The modified PLA has shown a unique balance of stiffness and toughness. Such modified PLA bioplastic will act as ideal matrix for nano-clay, talc as well as natural fiber reinforcements leading to the development of new materials from PLA bioplastics.
Opening the Pandora's Box to Find Elastic Breakup as the Origin of Various Nonlinear Flow Behavior of Entangled Polymers
Shi-Qing Wang, P. Boukany, S. Ravindranath, Y. Wang, May 2007
Chain entanglement is an essential concept in polymer science. It has been explored for six decades since the 1946 transient network theory of Green and Tobolsky. Another three decades after the 1971 de Gennes' reptation idea have passed before a method has been devised in computer simulation to depict chain entanglement [1]. More recently, the time-resolved determination of velocity profiles during and after shear of entangled polymers [2] have led to a specific molecular mechanism for chain disentanglement [3]. This work describes the latest understanding on the subject of polymer flow.
Phosphate Esters as Stress Crack Agents – Case Studies in Failure Analysis
Dale B. Edwards, Alan I. Kasner, May 2007
With a recent push toward non-brominated flame retardants, phosphorus-based alternatives, such as phosphate esters, are used more frequently for various applications. Their use as plasticizers is also well known. However, their function as environmental stress crack agents of various thermoplastics is less well recognized. Two case studies, one - in which a triaryl phosphate was a component of the formulation, the other – in which it was migrating from an adjacent component illustrate some of the problems with their use. Fractographic analysis and various analytical techniques were used to determine a root cause of each of the two failures.
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