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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The Influence of Solid-State Morphology on the Impact Strength of Linear Low-Density Polyethylene Blown Films
In this work, we report on the influence of lamellar morphology and orientation on the dart impact strength of linear low-density polyethylene (LLDPE) blown films. Characterization of the solid-state morphology of a wide variety of LLDPE blown films reveals the importance of lamellar anisotropy on the impact strength performance of such films. Specifically, we find that lower degrees of lamellar orientation (more random lamellar orientation) favor higher impact strengths. Further, we also report on the solid-state deformations that take place as the films are stretched during the impact test and how these deformation modes discern blown films of high and low impact strength.
Influence of the Reactive Extrusion Conditions on the Free Radical Induced Carboxylation of Poly(L-Lactide)
The current research is focused on the carboxylation of poly(L-lactide) through a free radical grafting process utilizing an asymmetric functional peroxide within a co-rotating twin screw extruder. Similar experiments, as well as free radical maleation reactions, have been successfully carried out on polypropylene and PLLA. In order to maximize the grafting efficiency and minimize chain degradation, the effects of the extrusion conditions (screw design, screw speed and melt temperature) on the carboxylation reaction and molecular weight of the polymer are investigated. This report focuses on molecular weight and thermal analysis as well as titration to quantify the level of acid functionality grafted onto the PLLA chains.
Influence of Vulcanization Agents on the Rheological Behavior of Polypropylene (PP) / Styrene-Butadiene-Styrene Copolymer (SBS) Blends
The rheological behavior of Polypropylene (PP) modified with Styrene-Butadiene-Styrene copolymer (SBS), within the composition range of 10-40 wt % SBS content, was studied based on blend ratio, vulcanization agents (sulphur, peroxide) and curing times. The rubber phase was statically cured and blends with PP were mixed in a twin screw extruder. Results indicate all unvulcanized systems show an increasing melt viscosity on SBS content. Regarding vulcanizing agents, sulphur shows no variation on melt viscosity neither with shear strain nor with curing time, while peroxide shows significant changes on melt viscosity at low shear strain ranges when varying curing times from 2 to 6 min.
Influences of Solubility and Viscosity in the Polystyrene/CO2 Microcellular Foaming Extrusion
An investigation has been conducted to analyze the influences of two important parameters, solubility and viscosity, to the polystyrene/CO2 extrusion foaming process. The solubility, which decides CO2 concentration limit and the nucleation onset, is measured by an improved volumetric method. Experimental data are then fitted with the Sanchez-Lacombe equation of state that will be applied to calculate the solubility at any temperature and pressure. The viscosity reduction by injecting CO2 in the polystyrene melt is studied by connecting a slit die with backpressure control to the extruder. Therefore, the viscosity of the polystyrene/CO2 solution at any temperature, pressure, CO2 content and shear rate can be obtained. Cell structures of two polystyrenes with different viscosities are compared.
Infrared Welding of Large Semi Finished Products
Heated tool welding is a highly reliable, well established process for joining thermoplastic semi finished products in plant engineering and tank construction. The weld seam quality may be impaired by residues on the heated tool, and high welding temperatures cannot be applied via the tool without damaging its non-stick coating. Non-contact heating, by e.g. infrared radiation, does not have these drawbacks. In this paper, the examinations with different types of infrared emitters and different materials are presented. A medium wave metal foil IR emitter shows good results and also allows a high reproducibility of the process. Not only good weld seam qualities, but also a faster process can be realized.
Injection Molding of Glass Fiber Reinforced PA-6 Nanocomposites
Polymer nanocomposites (PNC) are emerging as a new class of industrially important materials that offer improvements over conventional composite systems. The high aspect ratio of the nano particles leads to higher reinforcement efficiency and therefore higher specific modulus, strength and HDT. The low organoclay content (< 5% by weight) also guarantees good processabilty as well as higher recyclability potential.In this study, short (2-3 mm) glass fiber composites with of 7, 14, 20 & 27 % by weight glass fiber content were prepared using both pure PA-6 and 2% organoclay/PA-6 PNC. These glass fiber reinforced composites were injection molded using a dog bone" mold with weld line. Mechanical properties and resulting microstructure were evaluated to ascertain the effect of fiber orientation fiber length matrix crystallinity and the fiber/matrix interface on the overall performance of the composites."
Injection Welding - A Process for Making a Bacteriological Filter in One Step
Thermal welding is a well established method for producing complex parts. However it requires a complex industrial logistics because the previously molded components has to be handled and positioned in the machine.For the production of a bacteriological filter, a one-step manufacturing process, combining injection molding of two polypropylene components, the insertion of a filter paper, and the joining of the plastic components by injection welding, was developed. In this paper, the process is described and the influence of processing variables (temperature, injection speed and pressure) is related to the morphology and properties of the welded product.
Inline / Realtime Control of Mean Particle Diameters in Flowing Polymer Melts during Blend Extrusion Processing
A new version of a unique microphotometric inline/realtime particle process sensor PMP 691 for analyzing particle dimensions and for detecting different types of inhomogenities in flowing plastic melts during extrusion processing will be presented. As examples flowing blend melts from Polystyrene and Polypropylene as matrix phases and a Polyamide 6 and two PMMA- grades of different viscosities as disperse phases have been investigated. In both blend systems the concentration range of disperse phase was varied between 0.5 to 30 Vol.-%. Depending on the optical behaviour of both blend components (relative refractive index in melt state as a function of temperature) it is possible to determine average particle diameters up to higher particle volume concentrations in comparison to light scattering, light blocking technique, focused beam reflectance analysis and light optical methods. Application of quantitative imaging analysis (QIA) on SEM- images from blend cross sections after complete dissolving the blend particles from the blend matrix results in a good agreement to the microphotometric particle measurements. Additionally the application of the PMP691 for the inline/realtime detection of seldom/stochastic particle events in flowing plastic melts like gels, bubbles, impurities will be shown. Furthermore the inline/realtime control of the homogenity of plastic melts during plastification/melting of pellets are observable.
In-Line Monitoring of Polymer Additives during Extrusion Using a UV Spectrometer
The objective of this work is to monitor the concentration of thermal stabilizers, ultraviolet (UV) stabilizers, antioxidants and various other additives in polyolefins and in poly(vinyl chloride) during extrusion. The monitoring system consists of an inexpensive charge-coupled- device (CCD) UV spectrometer connected to an extruder by a fiber optic cable. Software has been developed on a notebook computer to enable spectra, continuously obtained from the polymer melt flowing through the die, to be immediately interpreted to provide additive concentrations. At this point, initial trials have been done using a mixed metal heat stabilizer in low-density polyethylene. These results are encouraging but issues related to spectra sensitivity need to be overcome before quantitative concentration values can be obtained. This paper will summarize the current situation and work planned for the near future.
In-Mold Transient Measurement of Thermal Diffusivity for Foam and Filled Materials Using Injection Molded Cylinders
The objective of this study was to evaluate the thermal diffusivity for foams and glass-filled resins during the cooling phase of the injection molding cycle and compare the experimental values with the standard values obtained by other methods.An aluminum mold having three cylindrical shaped cavities were fabricated. A special channel cut was machined and extended to the cavity edge to insert the thermocouple co-axially at the center of the cavity. The melt temperature obtained by the data acquisition set up and analog output converted to the digital signal and thermal diffusivity data calculated from the collected signal output.
Innovations in Selected Commercially Significant Polymer Blends and Blending Processes
Since the invention of high-impact polystyrene over some 40 years ago, there have been a great deal of activity on innovative polymer blends to develop synergistic properties, and on innovative blending processes to maximize their unique characteristics. Some of these successes are of significant commercial importance. We have examined more closely the events and their implications on a few illustrious cases.In the area of polymer blend products, inventions of blends of amorphous polymers, semi-crystalline polymers, amorphous / semi-crystalline polymers will be selected for illustrations. In the area of compounding process, innovations that overcome difficulties such as coalescence, unfavorable blend viscosity ratio, and method of imparting interfacial properties will be discussed.In almost all cases, the inventions were made without knowing that a scientific breakthrough was made. Only following painstaking investigations were the scientific basis of the inventions finally uncovered.
Innovations in Thermoplastic Elastomers: The Santoprene® Story
Thermoplastic elastomers (TPEs) have been commercialized for over 40 years and numerous applications have been developed. Very few TPEs, however, provide the true characteristics of thermoset rubber -- low compression set, good oil resistance and low hardness. Santoprene® thermoplastic rubber is the first thermoplastic vulcanizate (TPV) with fully vulcanized rubber phase that provides true rubber characteristics while maintaining excellent thermoplastic processability. Santoprene® TPE has successfully penetrated many applications previously dominated by thermoset rubber. Today, TPVs have one of the highest growth rates in TPEs and the Santoprene® TPE franchise enjoys the leadership position in TPVs.The Santoprene® TPE story will be shared from how TPEs got started at Monsanto, the challenges, and achievement of commercial success.
Integrating Plastics Manufacturing and Experimental Mechanics Courses
This paper addresses the joint development of a system to demonstrate stress in truss structures. Student designed truss structures were used in an upper level experimental mechanics class experiment with rapid prototyping, to analyze stresses with the finite element method, and to visualize states of stress through the photo- elastic method.The truss member components were designed jointly and the plastics class was tasked with developing tooling and selection of materials for the manufacture of the truss members. The plastics class developed a series of truss molds to demonstrate the effect of weld lines, and location of gates on the performance of the truss members.
Interactions of Long-Fiber Reinforced Core Material with Woven Fabric Reinforced Facings during Direct-Forming of a Thermoplastic Sandwich-Structure
The material described in this paper is a combination of long-fiber and textile reinforced thermo-plastics processed by an innovative technique in one step.In order to evaluate the sandwich system an automotive component has been selected. The goal is to offer a cost effective material with increased and load oriented mechanical properties by combining the advantages of a commingled woven fabric with long fiber reinforced thermoplastics (LFT).Beside describing the development of a suitable process technique this paper describes interactions between the TWINTEX® facings and the core material during the forming process.
Interface and Encapsulation in Simultaneous Co-Injection Molding of Disk: Two-Dimensional Simulation and Experiment
A two-dimensional simulation and experimental study of the flow-rate controlled co-injection molding was carried out. A skin polymer was injected first and then both skin and core polymers were injected simultaneously into a center-gated disk cavity through a two-channel nozzle to obtain an encapsulated sandwich structure. The physical modelling and simulation were developed based on the Hele-Shaw approximation and kinematics of interface to describe the two-phase flow and the interface development. The effects of rheological properties and processing conditions on the material distribution, penetration behavior and breakthrough phenomena were investigated. The predicted and measured results were found to be in good agreement with each other.
Interfacial Tension and Coalescence Reduction in Compatibilized PP/HDPE Blends
In this paper the compatibilization of polypropylene (PP)/high-density polyethylene (HDPE) blend was studied through morphological and interfacial tension analysis. Three types of compatibilizers were tested: EPDM, EVA and SEBS. The morphology of the blends was studied by Scanning Electron Microscopy. The interfacial tension between the components of the blends was evaluated using small amplitude oscillatory shear analysis. Emulsion curves relating the average radius of the dispersed phase and the interfacial tension to the compatibilizer concentration added to the blend were obtained. It was shown that EPDM was more efficient as an emulsifier for PP/HDPE blend than EVA and SEBS. The relative role of interfacial tension reduction and coalescence reduction to particle size reduction was also addressed. It was observed that the role of coalescence reduction is small, mainly for PP/HDPE (90/10) blends compatibilized by EPDM, EVA and SEBS. The results indicated that the role of coalescence reduction to particle size reduction is lower for blends for which interfacial tension between its components is low at interface saturation.
Internal Stress and Stretchability in Blown Oriented Polystyrene Films
Blown oriented polystyrene films was stretched along one direction and subsequently cross-deformed by stretching along the perpendicular direction, the cross-deformed film showed enhanced ductility with pronounced yield softening. Stress relaxation performed in both forward and cross directions showed power law relationship between the stress rate and relaxation time. The internal stress of cross deformation was significantly lower than that of the forward deformation at the same strain. The enhancement in ductility may be attributed to the lowering of internal stress during cross deformation. The stretchability upon film blowing is discussed in the light of the role of internal stress in biaxial deformation.
Introduction of a New Rheological Long Chain Branching Index for Isotactic Polypropylene Melts
A new rheological index for long chain branching (LCB), grheo, is introduced. The method is implemented for isotactic polypropylene (iPP) melts.Using statistical analysis, the average molecular weight (MW) and molecular weight distribution (MWD) values of a large number of linear iPPs (including metallocene and iPP blends) as well as iPPs with LCB are correlated with the crossover point coordinates and the four parameters from the Carreau-Yasuda equation. This allows us to define (independently of MWD and MW) grheo, whose value is one for a linear iPP and decreases with increasing LCB content.
Investigation for Injection Molding of Long Glass Fiber Reinforced Polypropylene
Four glass fiber reinforced polypropylene (PP) with various lengths of chopped glass fiber and pellet as well as one long-fiber compound PP pellet and short-fiber compound PP were injection molded to determine the fiber distribution and orientation of injection molded parts and the glass fiber length distribution.A custom-made screw was designed to minimize the damage of glass fiber after injection molding. The results were also compared with adhesive ability between compounded and uncompounded plastics. The molded parts were tested for their tensile strength, elongation, flexural strength, and impact strength. Other tests, including fiber length distributions and SEM, were also investigated.
Investigation of Applicability of Two Biodegradable Polymers for Mechanical Applications
Three types of specimens of a polyester-amide and a poly-hydroxybutyrate have been tensile and tensile-impact tested. Important geometrical parameters for these specimens are wall thickness and gate dimensions, as well as a weld line in one specimen type. Explanation of the combined influence of geometry and injection molding settings on tensile behavior was in agreement with tensile-impact results. This influence was maintained after 20 months of storage in closed boxes but minor embrittlement was found for all specimen types and both materials. The beneficial effect of annealing on strain at break for all poly-hydroxybutyrate specimens was also shown.
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