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.
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" compounding is defined as any process in which both the compounding and the forming steps are performed at the same time. For these applications line stability is crucial and greatly affected by equipment selection and design particularly the melt pump. Presented is a performance comparison for the two most common styles of melt pumps: a gear pump and single-screw extruder. Performance will be characterized in terms of pressurization efficiency pressure stability response to system upsets power consumption melt temperature generation residence time distribution and process limitations."
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
The spatial variation of the microstructure developed along the thickness of injection-molded unfilled nylon 6 and nylon 6 nanocomposites are presented using small-angle laser light scattering (SALS) Hv-Vv patterns and micro beam wide angle X-Ray scattering (WAXS) patterns along with corresponding polarized optical microscopy pictures. The microstructure of unfilled nylon 6 changes from undeformed to deformed spherulitic case by the introduction of nanoparticles. The local spherulitic structure of the injection-molded samples from skin to core is addressed by their sizes and aspect ratios. These experiments indicate the development of significant chain orientation levels with the minor axis of the spherulites fluctuating in and out of the flow direction throughout the injection-molded part for the filled systems even at high temperatures.
Optimum conditions of thin-wall injection molding process of a cellular-phone cover are investigated via the use of computer-aided-engineering simulation and experimental measurements. CAE simulation using C-MOLD and a set of experimental tests based on design of experiments (Taguchi's method) scheduling are performed to determine optimum process conditions of an injection-molding machine by minimizing the shrinkage and warpage of the molded part. Effects of various process parameters of the injection-molding machine on the shrinkage and warpage of the molded part are also examined.
The purpose of this experiment is to find the time and temperature dependents that yield maximum crystallinity of PVDF as well as its optimum property performance point. We will experiment with a curing temperature range between the glass transition temperature (Tg) and the polymer's melting temperature (Tm) and document the density at set time intervals. We will measure the injection molded article's density to determine the maximum crystallinity because, as the part reaches final crystallization, it will also stop shrinking and will be at its densest state.
This paper examines the relationship between the impact strength of rotationally moulded polyethylene parts and the dynamic mechanical properties. A range of conventional linear low density polyethylene powders (LLDPE) and metallocene polyethylene powders (MPE) were rotationally moulded and tested. Falling weight impact tests were carried out over a temperature range from -60ºC to 20ºC. Dynamic mechanical thermal analysis (DMTA) was carried out from -100 to 90ºC, at different frequencies. Transitions evident in DMTA results are used to explain sub-zero maxima in the impact strength of the polymers tested.
Tightly intermeshing, co-rotating twin-screw extruders are commonly employed for tasks requiring good mixing. Mixing involves several mechanisms: longitudinal mixing laminar shear mixing and dispersive mixing. This work focuses on the longitudinal mixing behavior investigated for special twin screw mixing elements.We used a model extruder where two residence time probes were mounted to the barrel. For the experiments we varied throughput, screw speed and the material. By applying a deconvolution algorithm we were able to determine the local residence time distribution in the measuring section. The residence time distributions of the mixing elements were compared to those of standard elements (e.g. conveying elements).
The object of this work is to investigate the foaming characteristics of Metallocene-catalysed polyethylenes for rotational moulding. This paper reports on the results of ongoing experimental investigations in which rheological and thermal parameters are related to the polymer structure and mechanical properties of metallocene polyethylene foams. Through adjustments to moulding conditions, the significant processing and physical material parameters, which optimise metallocene polyethylene foam structure, have been identified. The results obtained from equivalent conventional grades of polyethylene (PE) are used as a basis for comparison.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
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