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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
This work is a continuation of an earlier study on poly(Llactic acid)/hydrotalcite composites prepared by solution mixing. Two types of these synthetic magnesium/aluminum carbonate/hydroxide minerals, at 30wt% filler level, were used; surface coated and uncoated. Differential scanning calorimetric and thermogravimetric analysis of the unfilled polymer and its composites showed significant differences in structure and morphology through the addition of the filler. The composites were exposed to a phosphate buffer saline solution, at 37°C, to study the “in vitro” degradation of the polymer, and also to simulated physiological solution to detect bioactivity by the formation of an apatite type structure layer. The composites were analyzed before and after immersion for predetermined time periods in both solutions, by weight changes, SEM, EDX and RAMAN microscopy. Preliminary results suggest that these novel composites could have a potential use in tissue engineering applications.
In composite materials is important an adequate dispersion of the filler on the polymer due to the effect exerted on the material's behavior and as a consequence in its biomedical application. For this reason the objective of the present work is to analyze the thermal and tensil properties of HDPE composites with different hydroxyapatite compositions (10-30 wt.%) prepared by two different methods, extrusion and solution in decaline. The results showed that a better dispersion was reached and as a consequence, resistance at break and Young modulus increased for the composites prepared through solution.
Both thermal analysis and rheological approaches were employed to study the cure behavior of a medical grade silicone elastomer. Isothermal cure experiments were conducted calorimetrically at temperatures from 80 to 100 °C and rheometrically at higher temperatures from 100 to 180 °C. Non-isothermal cure experiments were also performed at different heating rates from 5 to 50 °C/min. It has been observed that the glass transition temperatures for uncured and cured materials remain almost unchanged and that the rheometric measurements are more suitable for characterizing the process of curing, especially for the prolonged, later stages of cure. Based on the changes in dynamic viscoelastic properties measured under isothermal conditions, the characteristic times of cure, including the gelation and peak cure time were determined, and presented as functions of cure temperature. These results were used in an attempt to develop a robust and viable molding process. It has been found that the post-molding cure is essential for stabilizing and optimizing mechanical properties of molded silicone elastomers.
The phenolic resin system widely used, such as fiber reinforced composites, honeycomb panelling, electrical laminates, acid resistant coatings and wood panels and so on. phenolic resins like other thermoset resins demand analysis about cure behavior to enhance property of final products. Therefore, investigation of cure kinetics is very important to achieve the full cure state for the proper properties, not to pass vitrification states. The optimum contents of hardener, HMTA(Hexamethylenetetramine), were determined by measuring the heat of cure and mechanical property. And then we conducted the isothermal cure kinetics of novolac type phenolic resin by performing differential scanning calorimeter.
The cure conditions as well as resin structure is the most important factors for coming up to possibilities of the hidden strength of the thermoset polymers like phenolic resin which are widely used for the industrial binder due to their excellent thermal and chemical properties. And it is very difficult to eliminate or minimize the unreacted phenol contents below ppm levels in the phenolic resins whereas the containing of phenol is definitely undesirable things especially for the electric/electronic applications and highly thermal resisted applications. In this work we studied the cure temperature effects on their cured properties, also quantitatively investigated the unreacted free phenol effects upon the cure behavior and cured properties of phenolic resins by performing the differential scanning calorimeter, dynamic mechanical analyzer, and izod impact tester. Thus we could figure out the higher temperature above 140? can not be recommended to reach the full cure state, and cure acceleration effects rather than the plasticizer effects of free phenol components on their thermal and mechanical properties when the resins were cured at high temperature which it could be easily reach the vitrified state.
In thin - wall injection molding processes, parts thinner than 1 mm are produced using high injection pressures and velocities. Modeling has not been successful in predicting process physics during molding. A dimensional analysis is performed, considering the most relevant variables of the process, the geometry and the non – linear material properties. Using similarity analysis with the material and process related dimensionless groups, the process is scaled by reducing the thickness. The scaled dimensionless groups are used to find relations between process conditions, material properties and other physical parameters, which lead to reasonable conclusions.
The time scales of coalescence in several processing flows were determined from a mechanistic model based on ballistic aproximation and drainage of partially mobile interfaces and compared with the characteristic times of flow through runners and filling of strip molds. It was found that coalescence takes place in a zone between the centerline and the walls of runner of circular cross-section and far away from the injection point in the filling of the strip mold. Qualitative agreement was found between model predictions and experiments carried out in a capillary die and in an injection mold.
The orientation of polymer chains after Injection Molding is usually studied using techniques that measure the average orientation of a polymer segment. Small-angle neutron scattering (SANS) is a technique for measuring orientation at molecular scales and is very sensitive to molecular anisotropy. The residual orientation and conformation of polyethylene and polystyrene chains after injection micro-molding has been measured using SANS. We have found that, for micro-moldings, the residual orientation decreases with increasing injection speed and that the residual chain orientation at the molecular scale is not necessarily related to the average orientation of short chain segments.
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