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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Foamability of Thermoplastic Vulcanizates (TPV) with Carbon Dioxide (CO2) and Nitrogen (N2)
The foamability of thermoplastic vulcanizate (TPV) has been investigated in a customized foaming system using carbon dioxide (CO2) and nitrogen (N2) as a physical blowing agent. TPV or dynamic vulcanizate is a special class of thermoplastic elastomer that is produced by mixing a crosslinked rubber and a thermoplastic simultaneously. The influence of blowing agent content and the processing conditions on the expansion behaviour, the cell-number density and the foam structure are discussed.
The Effect of Wood Powder on Polymer Foam Nucleation
It is usually reported that wood particles in wood/polymer composite foams can act as nucleating sites. Since high wood contents are used, it is difficult to determine exactly the effect of wood particles. In this study, LDPE was chemically foamed in a twin-screw extruder and small amounts of wood (0-5 phr) were added to determine their effect. Particle size was investigated using three mesh sizes: 45-61, 104-125 and 180-210 ?m. As expected, wood particles are acting as nucleating agents reducing substantially cell size and increasing cell density.
Interpretation of Flow Curves from Semi-Hyperboloidal Dies
The contributions of shear and elongation to the measured pressure drop in flow of polypropylene melts through semi-hyperboloidal dies have been investigated with and without external lubrication. This was done with a set of dies having a fixed ratio of inlet area to outlet area and three different lengths. The flow curves obtained without lubrication have been analyzed for the dependence on length. Two distinct terms have been identified that represent the shear contributions to the measured pressure drop in unlubricated flow.
Rheological Investigation of Entangled Hybrid Copolymers of Polystyrene (PS) with Polyhedral Oligosilsesquioxane (POSS)
The thermal properties and rheological behaviors of polystyrene (PS)-based thermoplastics bearing polyhedral oligosilsesquioxane (POSS) were investigated with variation of isobutyl (iBu)-POSS weight percentage. The incorporation of POSS-group significantly decreases the glass transition temperature and the rubbery plateau modulus. These findings are attributed to an influence of the nanometer-scale POSS pendant group on the microscopic topology of the host polymeric chains and negligible interactions between POSS and PS matrix.
HDPE/Clay Nanocomposite Foams Blown with Supercritical CO2
In order to investigate the effect of clay particles on the cell morphology of HDPE/clay nanocomposite foams, research on the batch foaming process of HDPE/clay nanocomposites using supercritical CO2 was conducted. Our study demonstrates that, in comparison with pure HDPE, nanocomposites produce much finer and more uniform cell structures. Additionally, an attempt to produce a nanocellular structure was successfully performed using HDPE/clay nanocomposites.
Graphite Nanocomposites: Nylon 6 and Nylon 66 Systems
Natural crystalline graphite based graphite intercalated compounds [GICs] were exfoliated and milled into submicron graphite flakes. Graphite nanocomposites were fabricated with nylon 6 or nylon 66 resins. To examine the effectiveness of the exfoliated graphite as a reinforcement, composites with commercially available reinforcing materials were also fabricated and compared. The mechanical and electrical properties were investigated and exfoliated graphite showed comparable or better properties compared to the other reinforcing materials.
Effects of Clay Dispersion on the Mechanical Properties and Flammability of Polyethylene/Clay Nanocomposites
Intercalated and exfoliated high density polyethylene (HDPE)/clay nanocomposites were prepared by melt blending with and without the aid of maleated polyethylene (PE-g-MAn) as a compatiblizer. Their morphology was determined by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effects of clay dispersion on the tensile properties and flammability of nanocomposites, especially those containing only a small amount of clay in the range of 0.05 ~ 1.0%, were investigated in this study.
Quantitative Mixing Uniformity Assessment in Two Laboratory Scale Devices
A technique is described to quantitatively assess mixing effectiveness. The technique utilizes infrared (IR) analysis of dissimilar polymer blends. The rheology of the blend system can be tuned through temperature to easily derive a spectrum of viscosity ratios. The technique has been applied to two common laboratory mixing apparatus, a batch mixer and a mini-twin screw extruder. Mixing effectiveness of these two devices will be described within both spatial and temporal considerations. The relative merits of the different mixing techniques will be additionally discussed.
CET Resins, A New Alternative for Medical Applications
The present paper introduces CET resins as an alternative for clear, sterilizable medical applications. CET resins are clear SMMA (styrene-methyl methacrylate) copolymers that compete with materials which include PMMA, polycarbonate, and PETG in medical applications and provides good scratch resistance and better sterilization properties when compared with impact acrylics, and slightly better resistance to alcohol, blood and lipids for medical applications when compared to PC as well.
Effect of Sequence of Stretch and Blowing on Preform Growth in PET Injection Stretch Blow Molding
The instantaneous images of preform during stretch blow molding were obtained by using a transparent mold and a digital camcorder. Delay time of preblow is a determining factor to the preform growth. Effect of sequence of stretch and blowing on the preform growth was investigated experimentally. Four types of perform growth were found. The axial thickness distributions of the bottle were also analyzed.
Dupont Sorona® Polymer: A New Sustainable Platform for Growth
Responding to environmental, sustainability, business and market needs, DuPont has recently commercialized a new polymer platform Sorona®. Sorona® polymer is produced from fiber-grade 1,3- propanediol (PDO). It is a linear semi-crystalline polymer with a melting temperature of ~228°C and a glass transition temperature of about 50°C. (See Figure 1)
Thermal Stabilization of High Molecular Weight L-Polylactide
Polylactide (PLA) polymers are among the most promising plastic made from renewable resources. Thermal stablization of these polymers remains a challenging issue of their industrial processing. We have studied the effect of TNPP in the scope of preventing the molecular weight reduction of PLA at its processing temperature. The stabilizing effect of TNPP was found to strongly depend on the concentration used.
Thickness Optimization of Blow Molded Parts Using FEM/AANN/GA Methods
An artificial neural network (ANN) model based on the numerical simulation data was developed to build the relationship between parison thickness distributions and part thickness distributions. A real-coded genetic algorithm (GA) was used to search for the optimal parison thickness distributions to produce a blow molded part with a uniform thickness distribution. The results showed that the hybrid method was an effective algorithm to optimize the parison thickness.
Temperature Profiles within Reheated Preform in Stretch Blow Molding
A thermal model was developed for the perform reheating in the two-stage injection stretch blow molding. The temperature distributions through the thickness of the preform and along its length were obtained by solving the model with ANSYS finite element software. With the use of real-time temperature measuring system, experiments were carried out to obtain the temperature evolution within reheated preform as it rotated. The numerical results were compared with experimental data.
Preparation of Interconnected Polycaprolactone Porous Scaffolds by a Combination Polymer and Salt Particulate Leaching
Porous poly(?-caprolactone) (PCL) scaffolds were prepared by melt blending PCL with poly(ethylene oxide) (PEO) and NaCl salt particulates using twin-screw extrusion, followed by leaching out of water soluble PEO and NaCl. Scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) were carried out to caracterized their morphology. The scaffolds were highly porous (75-85%) and exhibited an open cellular pore structures.
Viscosity Measurement of PS/CO2 Solution at Low Temperatures
The shear viscosity of solution of polystyrene(PS) in supercritical carbon dioxide(CO2) was measured at low temperatures between 100°C and 130°C at CO2 pressures up to 21MPa using Couette viscometer. The flow curves allow reasonable estimates of the zero shear viscosity as a function of temperature and pressure, otherwise difficult to obtain. Measured viscosity at Newtonian region was correlated to the WLF (Williams, Landel and Ferry) equation.
Protective Coatings for Implantable Medical Devices
While many families of polymers have been used to provide protection of device components in an implanted environment, poly-p-xylylene based (Parylene) coatings have been shown to have favorable compatibility, durability and barrier properties. An overview of the use of Parylene coatings in medical implant devices is presented. This paper describes critical factors related to performance and provides an example of coating barrier properties as measured on printed circuit boards (PCBs) with standardized circuits immersed in phosphate-buffered saline solution under expected use and accelerated conditions.
Oriented Porous Poly(L/DL-Lactide) Scaffolds for Bone Regeneration
A new structure of poly(L-lactide-co-30%-DLlactide) PLDL created by a unique process that formed oriented longitudinal pores in combination with smaller random pores fully interconnected throughout was evaluated in vivo to determine its ability to facilitate bone regeneration in a critical size defect in the rat femur. Using quantitative micro-CT analysis, the PLDL-treated defects exhibited significantly greater bone volume and vascular volume fractions than untreated defects at 16 weeks post-operation.
Bismuth Oxychloride for Radiopaque Medical Devices
Bismuth oxychloride has been used as filler for many applications for several decades. The unique properties of bismuth oxychloride, such as high radiopacity, excellent physical and chemical stability, high density and good dispersibiltiy, make it one of the ideal fillers for radiopaque products, such as radiopaque medical devices. Detailed comparisons of bismuth oxychloride with commonly used fillers for radiopaque medical devices were performed.
An Analysis of Polyamide 6,6 and Semi-Aromatic Polyamide 6,6 Copolymer Containers for the Storage of Radioactive Materials
Testing and analysis of Polyamide 6,6 and Semi-Aromatic Polyamide 6,6 Copolymers have provided a series of results, which have been used to evaluate the lifetime performance of a polymeric container used for the storage of radioactive materials. Techniques such as Neutron Activation Analysis have been used to monitor the ingression of aqueous solutions into the polymer materials. Irradiation using the SLOWPOKE-2 Research Reactor has mimicked the radiation exposure to the container resulting from the stored radioactive materials.
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