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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Thermomechanical Probing of Molecular Mobilities in Nanoconfined and Structurally Constrained Polymeric Systems
The molecular mobility in nanoconfined and structurally constrained polymeric systems is a vital parameter in the advancement of future technological applications. We employed two scanning force microscopy methods, with which thermally activated structural transitions and molecular relaxation processes of ultrathin polymer films were examined. The potentials of these methods are illustrated involving polyelectrolyte membranes, dendronized nonlinear optical polymers and thin glassy homopolymer films.
The Use of Inverse Gas Chromatography to Study Surface Thermal Oxidation of Polypropylene
Thermo-oxidative effects on the surface energy of polypropylene were measured by Inverse Gas Chromatography as a function of exposure time and temperature. Unaltered polypropylene had a surface energy of 26mJ/m2. Oxidized polypropylene, after exposure to air at temperatures from 100°C- 110°C, had a range of surface energies from 32-34mJ/m2. Comparisons between DSC melting point onset, FTIR carbonyl peak growth and the surface energy showed strong correlations between these three means of detecting oxidation.
Development of a Gelation Model for Methyl Cellulose Hydrogels
The development of a gelation model for methylcellulose (MC) hydrogels is presented. The heat of gelation for aqueous solutions of different concentrations of MC SM4000 was measured using micro-DSC. Different mathematical formulations for modeling the experimental data were considered. The necessary constants were obtained empirically. Further analysis was performed to predict the total heat, the degree, and the rate of gelation. The effect of MC concentration on these parameters was investigated and discussed.
Fiber Reinforced Extruded Starch Foams
Cereal or tuber starches have been utilized in making low-density foam using a baking process. Foams made only of starch tend to embrittle and have poor mechanical properties. Fiber reinforced foams were made that had flexural properties similar to foam materials used in commercial food containers. Pulped fiber from wheat and rice straw was as effective as pulped hard and softwood fiber in improving foam properties.
Characterization of Structure and Viscoelastic Properties of Polypropylene Nanopolymer
High quality polypropylene nanopolymer has been synthesized over a range temperature and shear rate for the first time. Scanning electron microscopy, particle size analyzer and BET analysis reveals that it is spherical in nature and could be produced within a range of 0.17 to 45 ?m in diameter and minimum surface area of 16.2 m2/gm. Infrared spectroscopy, X-ray diffraction, dynamic mechanical analyzer and thermogravimetric analyzer are also used to characterize its structure, viscoelastic properties and thermal stability.
Optimum Content of Clay for Microcellular LDPE/Clay Nanocomposite Foams Blown with CO2
This research investigates the optimum content of clay required to achieve microcellular LDPE/clay nanocomposite foams blown with CO2. The effects of clay content and clay dispersion on cell morphology are thoroughly investigated. Less than 0.1 wt% of clay addition produces a microcellular structure with a cell density of over 109 cells/cm3 and a cell size of about 5 ?m.
Nucleation in Foams as Assessed by In-Line Ultrasonic Measurements
The conditions that induce the bubble nucleation for the thermoplastic foam extrusion process in which physical foaming agents (PFA) are involved are obviously linked to the solubility parameters, i.e. temperature and pressure at a given PFA content, conditions that can be modified adding a nucleating agent. An in-line detection method based on ultrasonic sensors, sensitive to the onset of the phase separation, was used to investigate the influence of both talc and HFC-134a blowing agent concentrations on the nucleation cell density and degassing conditions for polystyrene foaming.
Methods of Expanding Polystyrene to Ultra Low-Density Foam
Ultra low-density expanded polystyrene is obtained by an optimum formulation or by extended exposure to atmospheric steam. A polystyrene resin is rheologically modified to have both ease of flow and resistance against collapse. The collapse resistance is imparted either by light crosslinking of the resin with a silane compound or by adding a small amount of polyphenylene ether. Extended exposure to steam permits continuous extension of cell walls by reducing orientation. An expanded polystyrene loose fill material having an expansion ratio exceeding 200 has been achieved.
Torsion Properties of Cylindrical Polymer Foams
Solid state viscoelastic shear moduli (G' and G) of cylindrical polymer foams were measured as a function of frequency. Extruded samples were produced via a cylindrical die to obtain foams of various morphologies. To perform the shear measurements a modification of the torsion rectangular setup on an ARES rheometer was made. The setup calibration and test conditions are presented. The data are discussed and compared to simple models taken from the literature."
Prediction of Density Variation in Thick Microcellular Sheets
Earlier a process to produce thick flat microcellular sheets, in the 3 - 15 mm range for a number of thermoplastics such as PMMA, PS, ABS and PC was reported. In this paper a model to predict the density variation across the thickness of microcellular sheet is presented. This model builds on both the steady-state mass balance model and the skin thickness model for the solid-state microcellular process. The model is applied to predict density variation and mean density in a 1.5 mm thick microcellular PC and preliminary results are presented.
Effects of Nano-Particles on Density Reduction and Cell Morphology of Extruded mPE/Wood-Fiber/Nano Composites
This paper investigates the effects of nano-particles on cell morphology and foam expansion in the extrusion foaming of mPE/wood-fiber/nano-composites with a chemical blowing agent. The results indicate that the addition of clay generally decreases cell size, increases cell density and facilitates foam expansion. Furthermore, the foam material with added clay shows good char formation when it is burned.
Increase of Open-Cell Content by Plasticizing the Soft Regions with a Secondary Blowing Agent
This paper describes the effects of n-butane mixed with primary CO2 as a secondary blowing agent on cellpopulation densities, volume expansion ratios, and open-cell contents of low-density polyethylene (LDPE) and LDPE/polystyrene (PS) blends in extrusion. With the plasticizing effect of n-butane, a high open-cell content (up to 100%) over a wide range of processing temperatures was successfully achieved.
Solid-State Polyimide Foaming from Powder Precursors: Effect of Particle Morphology on the Diffusive Phenomena
Solid-state foaming of polyimide powder precursors is studied by examining concurrent and competitive phenomena that determine the morphology and physical properties of the foam unit cell. Effects of particle size and shape on bubble nucleation and growth will be addressed.
Porous Polystyrene Foam Produced at Supercritical Conditions
This work examines four polystyrene (PS) resins and PS resins with fillers. The materials .are processed into sheets and then the sheets are foamed at various supercritical conditions. The morphology of foam is studied and a large porous PS foam is also developed for a vacuum insulation panel.
Effects of CO2 Content on the Expansion Behaviors of PS Foams
This paper discusses the effects of the blowing-agent content on the expansion behaviours of PS foams blown with CO2. Three groups of interchangeable filamentary dies were used to investigate the effect of the die geometry on the expansion ratio. A high CO2 content would be favourable to increase the expansion ratio. But the high CO2 content increased the solubility pressure and the amount of premature cell growth. When the amount of premature cell-growth exceeded a critical value, the expansion ratios were dramatically decreased, even at the optimum temperature.
Entrained Gas Process for Injection Molding
Entrained gas for injection molding, such as structural foam, microcellular foam, gas assist processing, has some common technical issues and safety concerns which are important to be fully understood for a safety system, and acceptable processing conditions. Several major issues are addressed and analyzed for machine and mold design, part design and handling.
Effects of Incorporating Recycled HDPE to Virgin HDPE and LDPE to Produce Tubular Film
This work presents the effects of incorporating post-consumer and post-industrial recycled HDPE to their virgin counterparts and to LDPE in different contents to produce tubular film for packaging. Tensile, surface and optical properties for each blend were measured.A reduction in the HDPEs blends physical properties and an increment in those of the LDPE/recycled HDPE blends were obtained as the recycled HDPE component was increased.
Nylon 66 - Maleated EPDM Polyblends
Nylon 66 was blended with maleated EPDM containing 0.5% of maleic anhydride. At 25% of maleated EPDM, impact strength increased 8-fold. On the other hand, modulus, strength, and DTUL decreased. The data suggested that the blend was too miscible, and might be improved by decreasing the maleic anhydride content to enhance phase separation.
Short Fiber Glass Reinforcement of Ductile Resins
In three ductile resins, polyphenylene ether sulfone (PPSU), a polycarbonate-acrylonitrile butadiene styrene (PC-ABS) blend and polycarbonate-polybutylene terephthalate blends (PC-PBT) use of a fiberglass coating that has little adhesion (non-bonding) to the resin matrix give superior impact strength compared to a traditional fiber coating with good matrix adhesion. The non-bonding glass gives reduced flexural and tensile strength but has comparable modulus to the traditional glass fibers with good matrix adhesion.
A Study on Processing and Characterization of Short Glass Fiber Reinforced ABS/Nylon 6 Blends
The properties of short glass fiber reinforced poly(acrylonitrile-butadiene-styrene)/Nylon 6 (ABS/PA6) blends were studied using the interfacial adhesion approach. Work of adhesion and interlaminar shear strength values were calculated from experimentally determined interfacial tensions and short beam flexural tests. APS was selected as the coupling agent for the glass fibers because of its compatibility with PA6. Increasing wt% of the PA6 in the short glass fiber reinforced blend increased the tensile strength and tensile modulus.
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