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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Harnessing Natural Polymers and Fibers for the Development of Biocomposites
Economic and environmental forces are providing an impetus for the development of biocomposites from renewable agricultural byproducts. In pursuit of this goal, we are developing biocomposites from wheat-, kenaf-, and corn-byproducts without external additives. Our differential scanning calorimetry (DSC) measurements suggest that micronized wheat straw and inner kenaf fibers have similar thermal characteristics at 50°C < T < 400°C, thus they can be co-processed. The flexural strength of the composites formulated from micronized wheat straw and kenaf fibers increases as the concentration of straw in the composite increases. Postcuring the composites at 190°C also decreases the strength.
Characteristics and Performance of Starch-Poly- (Vinyl Alcohol) (PVA) Blends with Agricultural Waste Fiber
The renewable polymers are environmentally friendly and naturally biodegradable, and could serve as an inexpensive source of raw material for single-use engineered products. Efforts are underway to develop ecocompatible consumer plastics by incorporating renewable polymers as an alternative to petroleum-derived chemicals. Therefore, gaining fundamental understanding of biobased polymers is critical for the design and development of consumer products. The research efforts at the USDA laboratory pertaining to the development of biopolymer blends, polymer processing, characterization and lifetime evaluation are presented.
Novel Solvent-Free Method for Functionalization of Polyhydroxyalkanoates: Synthesis and Characterizations
Functionalization of PHB was successfully achieved by free radical grafting of maleic anhydride using a peroxy initiator by reactive extrusion processing. The crystallization behavior and morphological changes in the PHB upon maleation were followed from the DSC, TGA, FTIR and Optical Microscopy measurements. The presence of succinic anhydride groups was substantiated by stretching vibration at 1782 cm-1 in FTIR. For maleated sample the Tm and Tc decreased up to 20 degree celsius and 10 degree celsius, respectively, indicating a decrease in its crystallinity and rate of crystallization. Decrease in the crystallinity was quantified from the enthalpy of melting (Tm endotherms). These trends were further substantiated by reduction in the crystallinity sensitive peak at 1185 cm-1 in the FTIR spectrum. Moreover, larger the graft degree smaller is the spherulite size and slower is their growth rate as observed in the optical micrographs. Disordered spherulite structure upon maleation also implies the structural changes in the polymer backbone, imperfect crystal formation. These functionally modified PHB can be used as modifiers for variety of applications.
Effect of Heat-Sealing Temperature on Mechanical Properties at Heat-Sealed Parts in Biodegradable Plastic Film
The heat-sealing machine is a vital tool in plastic bag manufacture. Processing conditions such as heat-sealing temperature and pressure greatly affect mechanical properties of the heat sealed part. In this study, the mechanical properties of the heat sealed part of a biodegradable plastic film were examined. Based on the results obtained from peeling test, circular notch tensile test and DSC measurement, the optimum heat sealing was established at 130-135 °C. The mechanical properties of the heat seals decreased with increasing heat sealing temperature.
Morphological and Functional Properties of Acetylated Starch Foams Extruded with Cellulose
Starch acetates with degrees of substitution (DS) of 1.68 and 2.3 were extruded with 10, 20 and 30% (w/w) cellulose and 20% (w/w) ethanol in a twin screw extruder at 150, 160 and 170 °C barrel temperatures with 170, 200 and 230 rpm screw speeds. X-ray diffractogram (XRD), differential scanning calormetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the morphological properties of extruded foams. A central composite response surface design was applied to analyze the effects of starch type, cellulose content, barrel temperature and screw speed on specific mechanical energy requirement of extruding foams and the radial expansion ratio and compressibility of the extruded foams. XRD showed losses of DS starch and cellulose crystallinity and the formation of new complexes. FTIR spectra revealed that functional groups and chemical bonds were maintained after extrusion. Melting temperatures changed significantly when higher DS starch acetate was used. Cellulose content, barrel temperature and screw speed showed significant effects on thermal, physical and mechanical properties of extruded foams and the specific mechanical energy requirement.
Synthesis and Characterization of Nanopolymer: High Density Polyethylene
Here, we have reported the successful preparation of the smallest nanopolymer, high density polyethylene, which has a diameter of about 0.17 ?m (but the number average molecular weight is greater than 1,00,000). The success of obtaining very small nanopolymer opens the door to unprecedented applications of this fascinating material as a true 1D material. This nanopolymer is characterized using particle size analyzer, scanning electron microscopy, infrared spectroscopy, X-ray diffraction, viscoelastic properties, etc. Similar synthesis strategies, involving careful selection of desired conditions and smart manipulation of favorable thermodynamic properties could be extended for the preparation of various nanopolymers: low density polyethylene, polypropylene, polystyrene, etc. To the best of our knowledge, this is the first demonstration for a preparation of nanopolymer in the literature.
Synthesis and Characterization of Nano Polystyrene: Effect of Temperature, Shear Rate and Solvents
Polystyrene nanopolymer (Number average molecular weight greater than 1,00,000), which has a diameter of about 0.17 ?m is prepared for the first time. This observation is confirmed using scanning electron microscopy. Infrared spectroscopy, X-ray diffraction, viscoelastic properties, etc are used to characterize it. The novel technique produces nanopolymer within a range of 0.17 to 51 ?m measured by particle size analyzer. BET surface area shows its minimum surface area of 17.7 m2/gm. We have elucidated the thermodynamic parameters for formation of nanopolymer.
Scanning Electron Microscopy, Spectroscopy and Viscoelastic Studies of Nano Low Density Polyethylene
Low density polyethylene nanopolymer is characterized by scanning electron microscopy, particle size analyzer and BET surface to prove the formation of nanopolymer over a range of diameter from 0.17 to 70 ?m. BET surface area reveals that its mimimum surface area is 17.0 m2/gm. The findings prove that the small diameter low density polyethylene nanopolymer is proved to be able to show good properties without any confinement that limits its material dimensions. Infrared spectroscopy and X-ray diffraction studies are also used to characterize it.
Kinetics of Gas Sorption and Diffusion in Polymer-Clay Nanocomposites
Gas solubility and transport properties control cell structure during polymer foam processing. This study reports the sorption and diffusion kinetics of sub and supercritical CO2 gas in nanocomposites of poly(methyl-methacrylate) containing organically modified smectite clay. Various methods for preparing the PMMA-clay nanocomposites were investigated and a solution co-precipitation method was selected. PMMA-clay nanocomposites containing 2, 4 and 6 wt. % nanoclay loadings were prepared. Using wide-angle X-ray diffraction (XRD) and scanning electron microscopy (SEM) the resulting materials were found to have well dispersed intercalated clay structures. CO2 solubility studies at 45°C and pressures up to 60 atm using an in situ gravimetric technique were performed on compression molded films. From the results diffusion coefficients were determined using the appropriate transport models for these test conditions.
Moisture Resistant Nylon - Dimensional Stability
The effects of moisture absorption on dimensional stability and mechanical properties of various polyamide/polyolefin blends are being studied. The morphology of the blends has also been investigated by using transmission electron microscopy (TEM). Furthermore, the correlation between the morphology of the blends and their moisture absorption rate and dimensional changes upon absorbing moisture has been examined as well.Results of this investigation indicate the moisture absorption rate, dimensional stability and mechanical property retention of polyamide and polyolefin blends are strongly affected by the degree of compatibility of the blend. The finer the dispersion polyolefin particles, the slower the water absorption rate, and the lower the dimension changes after being equilibrated at 50%RH or 100%RH.
Effect of Additives on the Solubility and Diffusivity of CO2 in Polystyrene
Carbon dioxide is widely recognized as an environmental-friendly blowing agent for foam extrusion. However, it is also more difficult to process than other gases because of its low solubility and high diffusivity. In order to improve processing, it might be suitable to use additives. The aim of this work was to study the effect of such additives on the solubility and diffusivity of carbon dioxide in the solid state and to validate their effectiveness in a foam extrusion process.Three “CO2-philic” additives were added to polystyrene and sorption experiments were conducted to measure the solubility and diffusivity at room temperature. Results show that all three additives had a small but measurable effect on gas solubility, which was a consequence of the free volume increase in the polymer blend and in some cases, due to the specific interaction of carbon dioxide with the compounds. Diffusion was also affected depending on the concentration of additive.
Fundamental Understanding of the ABS-CO2 Interactions, its Retrograde Behavior and Development of Nanocellular Structures
The fundamental transport parameters for Acrylonitrile-butadienestyrene, ABS – CO2 system was determined using a high pressure gravimetric technique. Solubility in the range 0 to 65°C and pressures up to 55 atm were determined and values as high as 25wt% were obtained at 0°C and 34 atm. Diffusion coefficients derived from the sorption kinetic data resulted in determination of the plasticized glass transition temperatures. The existence of the retrograde vitrification for this system was confirmed and thus used to develop nanofoams. The favorable interaction of CO2 with ABS has resulted in foams with average cell size of 0.47 ?m and cell density of 2 × 1012 cells/g at a processing temperature of 60°C. Heat of sorption and activation energy for diffusion of CO2 in ABS was determined from the experimental data and found to be -15.5 and 28.3 kJ mol-1 respectively.
An Investigation of Microcellular Injection Moulding on the Structure-Property Relationships of Engineering Thermoplastics Used in Exterior Automotive Applications
The purpose of this study was to investigate the effect of MuCell processing on the structure-property relationships of critical engineering thermoplastics. Such techniques as differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM) as well as a variety of standard testing equipment were used to show that through an effective design of experiment, the expected decrease in performance of key physical, mechanical and thermal properties can be minimised, and even improved in some cases.
Fundamental Study of CBA-Blown Bubble Growth and Collapse under Atmospheric Pressure
This paper focuses on gaining a fundamental understanding of the bubble growth and collapse phenomena occurring in a CBA-based foaming of plastics under atmospheric pressure. The behavior of CBA-blown bubbles exposed to various processing conditions was observed using a hot-stage optical microscope-based digital image processing system. A mathematical model that accounts for the effects of diffusion, surface tension, viscosity, and elasticity has been employed. It has been found that the processing temperature, diffusivity, and gas bulk concentration have dominant effects on the lifespan of CBA-blown bubbles.
Comparison of SS-Based and SL-Based Estimation of Gas Solubility
Most solubility data that is available has been determined by taking into account the swollen volume, which is estimated by the Sanchez-Lacombe (SL) equation of state (EOS). The swollen volume is typically determined with an interaction parameter that is chosen to minimize the differences between the experimentally measured and theoretically calculated solubility data.This paper presents a similar approach to ascertain the solubility based on the Simha-Somcynsky (SS) EOS. As a case example, we measured the apparent solubility of CO2 in a polystyrene melt at elevated pressure using a magnetic suspension balance. The solubilities determined by the two EOS were observed as being the same value below 1500 psi. When the pressure was above 1500 psi, the buoyancy effect was enhanced significantly because of the increased swollen volume and increased CO2 density. Consequently, the corrected solubilities that were determined by the two EOS at elevated pressures were observed to be different and the difference was 10% at 3000 psi.
Physical and Mechanical Properties of Composites Based on Syndiotactic Polistyrene
The process of polymerization of syndiotactic polystyrene formed in presence of catalysts CpTiCl2(OC6H4Cl)/MAO was investigated. At the moment syndiotactic polystyrene is produced in pilot plant. The yield of syndiotactic polystyrene obtained in the reactor 240 dcm3 was about 7- 15 kg/charge. The molecular weight of syndiotactic polystyrene was about 200 000 g/mole and syndiatacticity about 96%. After process of synthesis composites based on syndiotactic polystyrene have been obtained. The powder of syndiotactic polystyrene has been granulated with stabilizers, and modifiers in twin-screw extruder with double degassing. Irganox 1076 have been used as the stabilizer. Syndiotactic polystyrene was reinforced by glass fiber or talc. Syndiotactic polystyrene was modified by polyoxyphenylene, linear polyethylene and hydrocarbon resin. The structure and physical and mechanical properties of composites were investigated.
Isothermal Crystallization Kinetics and Morphology of Polypropylenes and Propylene/Ethylene (P/E) Copolymers
The bulk isothermal crystallization kinetics and spherulite growth rate of a (1) metallocene polypropylene (m-PP) and metallocene propylene/ethylene copolymers (m-P/Es), (2) Ziegler-Natta polypropylene (ZN-PP) and Ziegler-Natta propylene/ethylene copolymers (ZN-P/Es), and (3) a new (n-PP) polypropylene and Development Performance Plastomers (DPPs) were studied. Crystallization half time (t1/2) and spherulite growth rate (G) as a function of melt crystallization temperature were analyzed for the three homopolymers and their corresponding copolymers containing 4, 8, and 13 mole % ethylene, respectively. With increasing ethylene content, all three polymer systems exhibited increased t1/2 and decreased G. At low comonomer contents, n-PP and DPPs exhibited slower t1/2s and Gs, however at high comonomer contents, m-PPs exhibited slower kinetic behavior.
Comparison of the Elastomeric Properties of Developmental Performance Elastomers (DPE's) and Ethylene-Octene (E/O) Elastomers
The time-dependent elastic properties of a new Developmental Performance Elastomer (DPE) product family made with propylene-ethylene copolymers are investigated. These materials were previously referred to as new propylene-ethylene copolymers".Although these materials show some degree of permanent set upon initial tensile deformation the materials created as a result of a tensile "conditioning" process exhibit almost complete instantaneous strain recovery after a long period of stress relaxation. The stress relaxation behavior of the new DPE's are compared to that of elastomeric metallocene propylene-ethylene and ethylene-octene copolymers."
Structure-Property Relationships and Applications of Novel Flexible TPO Based on Blends of Developmental Performance Elastomer and Polypropylene
Blends of developmental performance elastomers (DPE), produced by INSITE™ technology, and polypropylene exhibit a superior balance of flexibility and heat resistance. These blends provide a new family of flexible TPO that can be engineered to meet performance requirements of many applications. Generalized blend design strategies for flexible TPO based on thermodynamic considerations are reviewed. Thermal, dynamic mechanical and tensile properties of the blends will be presented. The utility and potential applications of these blends will be highlighted.
Novel Propylene Based Fibers
Fibers made with novel propylene based polymers produced with INSITE™ technology from The Dow Chemical Company have been shown to offer distinctive processing, mechanical, and thermal characteristics. These unusual properties were attributed to differences in structure as measured by a variety of methods. The performance capabilities of these new fibers have been shown to offer properties previously unavailable with homopolymer polypropylene fiber and Ziegler-Natta polyethylene fiber. As a result, these novel propylenebased polymers were shown to expand the product offering capabilities of current fiber conversion technology.
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