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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Impact-Compression-Morphology Relationship in Polyolefin Foams
The relationship between the morphology and the mechanical properties, both at low testing speed and in impact conditions, of polyethylene (PE) low density foams with a predominantly closed-cell structure was studied. A careful characterization of the cell size distribution and anisotropy was performed and related to the foams mechanical response. The results indicate that the mechanical response of the foams is anisotropic and can be expressed as a function of the foam morphology, using a unique morphological parameter taking into account the cell size in the appropriate direction and foam density. The use of this parameter is thus extended from PS to PE foams.
An Analytical Model for Life Prediction of Closed Cell Structural PVC Cores
Closed cell PVC foams are used as cores in the manufacture of sandwich panels. These panels are used in many structural applications where they are subjected to cyclic tensile loads. In such cases the tensile fatigue of closed cell foams becomes important. In order to select the most appropriate cores for these applications, the fatigue properties must be known, however generating fatigue data can be time consuming and expensive. Therefore, an analytical model to predict the number of cycles to failure, Nf and fatigue crack propagation rate, da/dN for closed cell PVC foams has been developed. The model is based on the bending of cell walls and is extended to closed cell foams. It considers the cell faces and also includes volume fraction of solid contained in cell walls and faces in the formulation. The prediction from this new model is in good agreement with the experimental data.
Continuous Foam Extrusion of Rigid-Rod Polyphenylenes
A novel family of processable rigid-rod polymers with outstanding mechanical properties have been recently introduced (Parmax® Self Reinforced Polymers (SRPs)). These materials, among other applications, are of interest in the field of high-performance, rigid structural foam. In this study, the foam processability of Parmax® SRP resin is investigated using a single screw foam extrusion setup and butane as a blowing agent. The effects of die temperature (i.e., the foaming temperature) on the cell size, cell density, cell morphology and volume expansion ratios were investigated. Blowing agent concentrations and their effects on foam creation were also examined. Microcellular Parmax® SRP foams with cell-population densities on the order of 109 to 1010 cells/cm3 and expansion ratios ranging from 1.5 to 2 were fabricated.
A Study of Thermal Conductivity for Porous Polystyrene Foams
This current study uses thermal conductivity of open cell polystyrene foams as the main axis of study, and carries out analysis comparison between the prediction value of theoretical thermal conductivity formula with the actually measured value of thermal conductivity meter (please refer to ASTM C518 for measurement standard) and to find the thermal formula of open cell polystyrene foams that are most suitable to be developed by this study, and make discussion according to the physical properties of open cell polystyrene foams. Under mean temperature of 25?, there is 4.482% of mean deviation between the thermal conductivity derived from theoretical thermal conductivity formula and actually measured value.
Ethylene and Styrene or Alfa-Methyl Styrene Copolymer with Homogeneous Metallocene Catalyst
Styrene and alfa-methyl-Styrene were employed in ethylene copolymerization with the homogeneous metallocene catalyst Et-(Flu)2ZrCl2/ MAO. It was observed that the catalyst activity has increased with the addition of very low amounts of comonomer in comparison with the homopolymerization of ethylene. The obtained polymers were characterized according to their melting temperature (Tm) and crystalline degree (Xc), through DSC analysis. The lowest melting temperature of the E-Sty copolymers obtained was 119°C, which correspond to 1.5 %molar of styrene in the polymer chain. On the other hand, the addition of increasing amount of alfa-methylstyrene to ethylene polymerization has significantly increased the crystalline degree of the polymers, although have not changed their Tm, probably meaning that the substituted styrene has acted as chain transfer agent.
Polyethylene-Clay Nanocomposites with Metallocene Catalyst Supported on Brazilian Bentonite
Polyethylene-clay nanocomposites have been prepared using in situ polymerization. In this study we have evaluated two minerals, silica and bentonite (smectite), as catalyst carriers for the polymerization of ethylene with commercially available zirconocene. The activities of the homogeneous and supported metallocene systems were also compared. We have observed that at high temperatures, ethylene consumption sharply decreases with time by employing homogeneous catalyst. Also, the polymerization profiles for both supported systems have rapidly achieved a steady state. Moreover, the performance of the smectite-supported system was very similar to that of the silica-supported catalyst. The obtained polymers were characterized according to their melting temperature (Tm) and crystallinity degree (Xc), through DSC analysis. The polyethylene melting temperature has significantly increased with the use of both supported systems in comparison with the homogeneous counterpart. The highest Tm of the obtained polyethylenes was 136.8°C, which corresponds to that synthesized by the smectite-supported catalyst.
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.
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