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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Ethylene-Diene Copolymerization Obtained with Different Metallocene Catalysts
Copolymerizations of ethylene and 1,7- octadiene were performed with three homogeneous metallocene catalysts [Cp2ZrCl2, ?2C(Flu,Cp)ZrCl2 and Et(Ind)2ZrCl2] cocatalyzed by methylaluminoxane (MAO), and the polymerization behavior such as catalytic activity, copolymer composition and structure were examined and correlated with the catalyst type. The obtained copolymers were characterized according to their melting temperature (Tm) and crystallinity degree (Xc), through DSC analysis and unsaturation content by FTIR spectrometry. 13C NMR spectra of ethylene-diene copolymers were also recorded.
High Molecular Weight Polyehylene by Homogeneous and Supported Metallocene
Ethylene was polymerized with the homogeneous metallocene catalyst Et-(Flu)2ZrCl2/ MAO and the analogous silica/MAO-supported system. The supported catalysts were prepared at different conditions, such as metallocene impregnation time and washing method. Propylene polymerization with those catalyst systems was also performed. It was observed that the different methods employed in this work for the preparation of the supported catalysts did not influence the performance of the metallocene system in ethylene polymerization. The obtained polymers were characterized according to their melting temperature (Tm) and crystallinity degree (Xc), through DSC analysis.
Polypropylene Obtained with Very Active Metallocene Catalysts
Polypropylene was obtained using the metallocene homogeneous catalyst Methyl2Si-(2- Methyl-4-Phenyl)2ZrCl2/MAO and the corresponding silica/MAO-supported system prepared at different conditions. It was observed that long metallocene immobilization time for the preparation of silica/MAO/Zirconocene supported catalyst does not imply in higher catalytic activity.The obtained polymers were characterized according to their melting temperature (Tm) and crystallinity degree (Xc), through DSC analysis. The results showed that the supported catalyst system produce polypropylene with higher Tm and narrower range of melting in relation to the PP obtained by the homogeneous system.
Influence of Molecular Structure on Pressure and Temperature Dependent Viscosity of LDPE Melts
A capillary rheometer equipped with an especially designed additional chamber ensuring various pressure modes was used to investigate temperature and pressure effects on the rheological properties of two batches of the same LDPE grade. The variation in molecular structure of the researched batches was proved by different gel permeation chromatography and elongational viscosity behavior. The magnitudes of the pressure coefficients varied more significantly than temperature ones. I.e. the pressure effect on viscosity depends strongly on the amount of long-chain branching in polymer.
Polyaniline Blends - Preparation and Studies on Electrical Properties & Morphological Features
Polyaniline emeraldine Salt was synthesized from aniline by chemical oxidative method using hydrochloric acid as the dopant. The (PANI- HCl) was de-doped with ammonia to obtain polyaniline emeraldine base. PANI – EB was re- doped with other acids like sulphuric acid, toluene sulphonic acid and formic acid etc., to study the effect of dopant on conductivity and solution processability of PANI. Films blends of LDPE/PANI, PVC/PANI and EVA/PANI were made by solution Casting. Latex blend of PS/PANI was prepared from emulsion latex of polystyrene and dispersion of PANI in water with a suitable surfactant. The conductivity studies were done for the polyaniline salts doped with different acids and for film blends using a standard four probe method. FTIR analysis was done to find the elemental composition using Shimadzu (Japan), FTIR Model 8201PC.
Investigation of Core/Shell Latex Particle Morphology via Solid State Nuclear Magnetic Resonance
Particle morphology plays a key role in the performance of a coating, thus making characterization important. 1H spin diffusion experiments were used to characterize latex particle morphology of two different staged emulsion polymers. This data was compared to a latex blend of similar chemical composition and the spin diffusion behavior was compared. From the plots of signal intensity versus mixing time, both qualitative and quantitative data was obtained allowing for characterization of the particle interface. These experiments clearly distinguished between three different morphologies proving that spin diffusion Nuclear Magnetic Resonance (NMR) analysis can be used as an alternative to traditional microscopy techniques.This paper aims to characterize core/shell latex particle morphology using the 1H spin diffusion technique, and to determine if this technique can be used to qualitatively distinguish between a 2-stage reaction and a polymer blend of the same compositions.
Lowering Friction of a Commercial Epoxy
The range of applications of epoxies is increasing and we need epoxies with lower friction of surfaces. Previously we have obtained good results by addition of a fluoropolymer (FP) to a commercial epoxy. However, the FP in question, called FP-1, was originally developed for NASA and is prohibitively expensive. The present work is concerned with finding substitutes which would provide results similar to FP-1 but which would have affordable prices. Candidates FP-2, FP-3 and FP-4 were tested, so that 5 wt. %, 10 % and 25 % were added to the same commercial epoxy as before. Averages of static and dynamic friction were obtained. In all cases the 10 % additive concentration gave better results than the other concentrations. For FP-2 also 5 % of the additive also gave good results and for all FPs studied the 5 % concentration gives better results than the 25% concentration. The results will be connected to the surface morphology.
Novel Specialty Polyolefin Polymers as High Performance Impact Modifiers
ExxonMobil Chemical has introduced a family of Specialty Polyolefin Elastomers, a novel type of polyolefin with isotactic propylene crystallinity, under the trade name Vistamaxx™. These polymers contain a predominant amount of propylene (>80%) with isotactic crystallinity, the balance being ethylene and other ?- olefins. In this paper, we highlight the properties obtained in high flow TPO compounds made using these polymers. Data is presented for high flow TPO compounds based on homo-polypropylene and Impact copolymers. A comparison of the impact-flow-stiffness balance obtained with Vistamaxx™ polymers and conventional plastomers in use today are also discussed.
Elastic Properties of Cast Films from Propylene-Based Elastomers
Excellent elastic properties of high elongation to break and low tension set can be obtained from compression molded pads of Vistamaxx™ Specialty Polyolefin Elastomers, hereinafter referred to as SP elastomers, and its blends with PE and PP. The SP elastomers are metallocene-based propylene-dominant polymers. During a cast film operation, the orientation imposed onto the SP elastomer matrix lowers the extensibility of films made from SP and its blends. A simplified relationship between elongation to break of SP films (with or without blending) and their planar orientation has been established. Further, the deformation of polymer dispersions in the SP blends caused by planar flow during film-casting reduces their recoverability. According to finite element simulation of these blends, reduction in elastic recovery in films from SP blends with machine-direction aligned ellipsoidal dispersions was attributed to the strain amplification around the dispersions and directly related to the dispersion tip radius. By selecting polymeric dispersions that have high interfacial tensions with the SP elastomers, and high viscosities, deformation of the dispersion can be minimized. In addition, interfacial coupling between the deformed dispersions and the SP matrix can be suppressed, thereby minimizing the film-casting induced orientation. Thus, films from SP blended with HDPE of high interfacial tensions were demonstrated to have lower planar orientation in addition to reduced dispersion deformation and, hence, have better elastic properties as compared with SP films blended with low-interfacialtension PP polymers.
Business Opportunities in India
Today's India is a land of huge opportunities for global investors. India's economy is sizzling and is one of the fastest growing in the world. It has also seen a surge in foreign investment lately. There are several options available for a prospective non Indian company to invest in India. Since 1991 India has undergone a sea change in its outlook toward foreign investment and global collaboration, leading companies worldwide realize that to stay ahead, they need to reduce costs, provide the best quality, use the latest high-tech skills, and be reliable and innovative. This paper will pay a way to encourage investors in polymer business in India.
3-D Flow Field Simulation of Unusual Screw Element with Wedge-Shaped Leading Flight Flanks in Intermeshing Counter-Rotating Twin-Screw Extruders
The 3D isothermal Non-Newtonian flow simulations of a kind of unusual screw elements are performed, which has wedge shaped leading flight flanks used in intermeshing counter-rotating twin screw extruders. Physical model included screw channel region, nip region and four clearances. Boundary conditions are real velocity and pressure boundary conditions. The flow field simulation is processed by ANSYS finite element package and the velocity field and pressure field are obtained. Using those results, the extruding characteristic of unusual screw element is analyzed. The simulation results of the flow field were verified by experiments. Compared with the conventional screw elements, the unusual screw elements have more mixing capability and elongation effects.
Continuous Extrusion of Proteinaceous Polymers
Various compositions of plasticized soy protein isolate (SPI) biopolymer were continuously extruded through a ribbon die. Soy polymer tapes consisting of 45 wt% SPI, 45 wt% glycerol, and 10 wt% water were produced using die temperatures that ranged between 135°C and 145°C. For 55 wt% SPI, 35 wt% glycerol, 10 wt% water composition, a higher die temperature ranging between 140°C and 150°C could be used. Plasticized SPI tapes/films were also produced using thermal compression at temperatures ranging between 135°C and 165°C, and processing times ranging between 2 min and 1 hour. The tensile strength, strain-to-failure, and modulus of elasticity were measured to determine a suitable window for processing conditions. The optical properties, consolidation and uniformity of different extrudates, and tensile properties were then examined. Because of the highly viscoelastic nature of the high molecular weight denatured SPI, it was found that plasticizer concentration, screw speed, and extruder zone temperatures significantly affect the properties of the extruded tapes.
Experimental and Numerical Study of the Post-Extrusion Conditions in Ribbon Extrusion Process
The effect of post-extrusion conditions on ribbon deformation was numerically and experimentally studied for the system polystyrene/high density polyethylene (PS/HDPE). A thermomechanical model was used to predict uniaxial deformation under different cooling lengths (X) and draw ratios (DR). The results show that both factors influence substantially the final dimensions of the ribbon. Experimentally, the drawing force was measure online using a system based on a torquemeter principle. For blends, the minor phase deformation was measured using quantitative image analysis. A comparison between the numerical and experimental results produced excellent agreement for our system.
Study of Nonlinear Dynamics and Stability of Isothermal Film Casting using a Two-Dimensional Process Model
A two-dimensional process model has been developed extending the previous one-dimensional one to study the nonlinear dynamics and stability of isothermal film casting process. The 2-D steady as well as transient numerical simulations were thus obtained employing a finite element method (FEM) along with a suitable viscoelastic constitutive equation. They have successfully revealed various nonlinear instability phenomena occurring in film casting such as beads on the film edges and the periodic instability called draw resonance exhibiting the simultaneous fluctuations of the film width and film thickness. These simulation results yield good quantitative agreement with experimental observations.
Analyzing Air Gap Dynamics in Extrusion Coating by Means of Dimensional Analysis
A number of experimental investigations in the past have dealt with the influence of various parameters such as melt temperature, air gap distance and coating thickness on the bonding strength between a primed film and the coating. By applying dimensional analysis to the data of the experimental results published in the literature novel equations were developed to predict the relationship between adhesion and the parameters mentioned.It was found that for a given temperature the shear history and the residence time of the melt in the air gap are of utmost importance to the adhesion between the film and the coating. The application of the formulas given, is explained by a number of practical, numerical examples.
The Rheological and Mechanical Performance of Commercial uPVC Formulations
Rheological and mechanical analysis of a range of virgin, recycled, and pigmented uPVC formulations used in extruded profiles for conservatory roofing applications is reported. The shear viscosity, tensile properties and dynamic mechanical thermal properties of the various formulations were shown to be dependent on stabiliser type, thermal processing history and pigment concentration. Lead stabilised uPVCs were shown to have better impact properties than Ca/Zn stabilised compounds and slight differences in Tgs, storage modulii (E’) were recorded for all formulations.
Analysis of Disproporationate Termination Effects in Free Radical Polymerization and Damped Oscillatory Kinetics of Simple Reactions in Circle
A system of reactions in circle is modeled using the methods of Laplace transforms and the method of Jacobian matrix. The conditions of reaction rate constants when the damped oscillatory kinetics may be observed are derived for the cases of three reactants, of four reactants, eight reactants and general case. For the case of Reactions in Circle with 3 reactants the kinetics will exhibit damped oscillatory behavior when k3 < k2 + k1 + 2sqrt(k2 k1 ) or when in any one of the rate constants is less than the square of the sum of the square root of the other two rate constants respectively. For the case of Reactions in Circle with 4 reactants the kinetics will exhibit damped oscillatory behavior when B3/27 + C2/4 > 0 where B = (? - ?2/3) and C = ? + 2?3/27 - ??/3 . In terms of the rate constants ? is given by the sum of all the four reaction rate constants and ? represents the sum of all the possible binary products of rate constants and ? is the sum of all the possible triple products of rate constants in the system in circle. For the general case the characteristic equation is written whose solution will determine the exact solution of the system. The cases where complex roots result will represent the conditions of the rate constants where damped oscillatory behavior can be expected.
Ethylene-Butyl Acrylate-Carbon Monoxide Terpolymer as a Replacement Plastcisier for Polyvinyl Chloride
An ethylene-butyl acrylate-carbon monoxide terpolymer (EnBA-CO) was blended with two PVCs at various compositions. Several commercially available medical grade plasticised PVCs were also tested to assess the suitability of the PVC blends as replacements for the traditional PVCs. The results are also compared to previous work on effect of ethylene-vinyl acetatecarbon monoxide (EVA-CO) as the polymeric plasticiser for PVC. The tensile and flexural modulus of the blends decreased significantly with progressive increase in EnBA-CO, while maximum elongation at break and impact strength were recorded at 30-40% terpolymer content. A single glass transition temperature (Tg) between that of the PVC and EnBACO components was recorded (DMTA), indicating complete miscibility over the range of concentrations studied. Rheological analysis showed a decrease in shear viscosity with increasing EnBA-CO content. The properties of most of the PVC/EnBA-CO blends were similar to those of commercially available plasticised PVCs.
Poly (Lactic-Glycolic Acid) and Funtional Hydrogels for Drug Delivery Applications
Biodegradable polyesters like poly(lactide-coglycolide acid) (PLGA) and pH-sensitive hydrogels have been used increasingly for various medical and biological applications. The present work focused on the use of these functional polymers to design an assembled drug delivery system (DDS) that could integrate multiple functions in a single device and achieve different release patterns. For PLGA, The major concerns are the poor hydrophilicity, accumulated acidity during degradation, and bulk erosion characteristics. In this study, poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) (PEOPPO- PEO) tri-block copolymer and a nano-clay Cloisite® 30B were utilized as modifiers to control the degradation behavior and hydrophilicity of PLGA. For comparison, a block copolymer, poly(lactic acid)/ poly(ethylene glycol) (PLA-co-PEG) was synthesized. A pH-sensitive hydrogel together with a poly(hydroxyethyl methacrylate) (HEMA) was used as a gate to control drug release. By using this bilayered self-folding design, the drug protection and selfregulated oscillatory release were demonstrated.
Performance of Polymeric Scaffolds in Tissue Engineering
Polymeric scaffolds in tissue engineering provide temporary mechanical support for tissue regeneration while shaping the in-growing tissues. The overall stiffness of the polymer-tissue constructs in bone/cartilage tissue engineering can affect the tissue in-growth by altering the local mechanical environment around the cells. This work deals with the influence of scaffold material properties on its load-bearing characteristics. Moreover, it demonstrates the role of scaffold porosity on the load dissipation through drag forces based on a biphasic model. The final goal of this work is to improve the performance of hybrid bone/cartilage polymeric scaffolds.
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