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.
Polymer nanocomposites are of interest due to improvement in certain material properties relative to virgin polymer or conventional composite materials. For example, compared to conventional materials, Nylon 6/Montmorillonite nanocomposites demonstrate improvements including high strength, high modulus and high heat distortion temperature. Generally speaking, optimal composite properties have been achieved with polar polymer matrixes, which readily disperse polar fillers. A plausible hypothesis proposes that similar improvements could be achieved with non-polar polypropylene (PP)/clay nanocomposites, thus expanding their use in automotive and packaging applications. As a result, both academic and industrials labs have extensively investigated these PP nanocomposites. Consistent with most filler-polymer composite systems, this one demonstrates increased stiffness; however, this improvement is often accompanied by a decrease in toughness. This work examines key factors, which influence the stiffness-toughness balance of PP nanocomposites.
As reported earlier, a preliminary, computer assisted 3D-chromographic representation of all 16.7 million possible RGB colors in the standard CIE L*a*b* (or L*C*h) color space reveals important deviations from well established theoretical concepts. Taking into consideration that the newly defined standard color space appears to have the shape of an anisometric, strongly distorted, RGB cube, we have developed, by binary programming, a complete tridimentional color atlas which, within that space, encompasses all possible colors around a white-to-black lightness axis. The longitudinal distribution of the atlas’ 360 “hue pages” and the latitudinal stacking of its 101 individual “lightness strata” allows the user to pinpoint any one specific color of the thousants that compose the particular CIE h page or CIE L* stratum selected by the user and have it isolated and displayed on screen. A simple mouse click on the chosen color makes a larger sample of that same color appear on screen, accompanied by its correct colorimetric values in all imaginable color spaces and systems. Comparisons between complex 3D-chromographic spectra - which can be fingerprints of anything that shines, glows and spakles in plastics, paints and coatings - become much easier when individual colors composing such spectra can be matched with colors readily identifiable with the novel atlas.
Greater blow molded products can be produced in a shorter time if the promises of finite element analysis programs are true. Reliable and accurate simulation software will allow product designers to make better-informed decisions. Currently in the blow molding industry simulation software is rarely used, because its reliability is unknown.Extrusion blow molded bottles were produced for testing. The bottles were then measured and thicknesses applied to the simulation model. The bottles were tested and compared to results from simulation software. Finite Element Analysis (FEA) was run to simulate loading of the top surface and side loading.
An attempt was made to develop blends having self-lubricating properties. The approach was to melt blend various base polymers used in the medical industry with hydrophilic polymers known to impart lubricity when applied on the surface as coatings.Different base polymers used were nylon based elastomers and nylons. Hydrophilic polymers used were polyethyl oxazoline and polyvinyl pyrrolidone.These polymers were melt-blended at concentrations of 25% and 50% using a twin-screw extruder. Rheology, coefficient of friction and mechanical properties were studied.
The distributive mixing profiles were studied during melt-melt blending of two polypropylene melts in a corotating twin screw extruder using the interfacial reaction between two functionalized macromolecular tracers, which were separately blended into each of the polymer melts. The mixing performance is directly related to the conversion of this interfacial reaction. We studied the effect of operating conditions and kneading disk configurations with various combinations of staggering angles (forward 30°, neutral 90°, and reverse 30°) and thicknesses (thick and thin) on distributive mixing.
The ability to quantitatively identify specific restricted or “hazardous” elements (lead, cadmium, etc.) in polymer matrices is an analytical challenge. Many companies, particularly those in the electrical and electronic manufacturing industry supply chains, are attempting to obtain the necessary data to comply with a variety of customer-driven and/or legislative restricted substance requirements. Two analysis testing approaches being employed are traditional elemental analysis procedures, and x-ray fluorescence spectrometry (XRF).The purpose of this work was to empirically evaluate the effectiveness of XRF quantitative elemental analysis in polymeric matrices and compare this approach to traditional acid digestion – inductively coupled plasma (ICP) measurement techniques. While others are included in this evaluation, the primary elements of interest are lead, cadmium, mercury, and chromium.XRF and Acid Digestion - ICP measurements were conducted on twenty-two polymeric materials, including PVC and polyolefin materials. The polymeric specimens included certified reference materials, custom compounded materials, and others. The data includes measurements performed by four different XRF instrument manufacturers as well as Underwriters Laboratories (UL). Both fundamental parameter and simple “standards” calibration XRF data was collected. The majority of the Acid Digestion - ICP measurements were performed by UL.Although correlation between XRF and Acid Digestion – ICP methods varied widely in some instances, this study’s results suggest promise for the use of XRF as a qualitative screening tool for the material types investigated. Additional work needs to be done, however, to realize the full capability of the XRF analysis approach, particularly using a fundamental parameter or simple calibration approach.
Getting the proper combination of different process parameters such as injection speed, melt temperature and mold temperature is important in getting a part that minimizes warpage and has the desired mechanical properties. Very often a successful design in injection molding comes at the end of a long trial and error process. Design Sensitivity Analysis (DSA) can help the processors improve the design and can produce substantial investment savings in both time and money. This paper investigates the ability of the sensitivity analysis to drive an optimization tool in order to improve the quality of the injected part. The paper presents the solution of the filling stage of the injection molding process by a 3D finite element solution algorithm. The sensitivity of the solution with respect to different process parameters is computed by using the continuous sensitivity equation method. Solutions are shown for the non-isothermal filling of a rectangular plate with a polymer melt behaving as a non-Newtonian fluid. Sensitivity of the solution is used to build the surface response of the injection pressure with respect to a given design parameter (the injection speed in the present case). This is then used to determine the conditions corresponding to the minimum injection pressure.
An investigation of the foaming behavior of polybutylene terephthalate (PBT) resins in extrusion was performed. Commercial grades of PBT with different molecular weights and rheological characteristics were chosen. PBT’s with a high temperature chemical blowing agent were extruded under different material and operational conditions (e.g. amount of blowing agent, set temperature at the die, screw rpm, etc.) to allow the understanding of the effects of those conditions on product characteristics. The foamed extrudates were analyzed for density, morphology, and crystallinity. It is shown that the foaming behavior and the foam quality of PBT are functions of the characteristic properties of the resins including rheological and crystallization behavior.
The healthcare industry is poised to experience both unparalleled challenges and growth as the Baby Boom generation ages. The steadily increasing volume of persons needing advanced care, new developments in diagnosis and treatment, and the increased lifespan resulting from these developments all combine to produce new opportunities in the area of medical plastics: new materials, processing and product design will make possible the next generation of medical products. During the 1980s 60 patents were issued in the area of medical plastics. That number jumped to 209 in the 1990s. During the first 4 years of the 2000s 218 patents were issued in this field. The growth of the medical plastics industry will only continue. The areas seeing the strongest growth will be discussed in this paper, as will likely future trends.
The preparation of nanoclay-reinforced polyolefin nanocomposites by means of melt processing was investigated. Different types of compatibilizers based on glycidyl-methacrylate-grafted polypropylene (PP) have been developed for the formation of PP nanocomposites. Different formulations and processing conditions were used to optimize the chemical interaction between the organic and inorganic phases (i.e. the polymer matrix and the clay) in order to maximize the clay dispersion and the clay-matrix interface. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to study the chemical interactions between the polymer and the organoclay as well as the dispersion of the organoclays and the nanocomposite morphology. Various properties of the resulting nanocomposites, such as the physicochemical properties, the mechanical properties (including fracture toughness from essential work of fracture), and the thermal stability, were also evaluated. The relationship between formulation, structure, and performance is discussed.
Thermoplastic olefin (TPO) is currently the material of choice for automotive bumpers and fascias. The part is generally painted with thermoset paint after molding. Unless removed, this paint layer creates problems during recycling of rejected parts. It causes a change in the processing characteristics and properties. The techniques used for removing the paint layer from the TPO create additional steps in the process and adds extra costs. The concept studied is the possible reuse of painted regrind by reducing the paint particle size in an injection molding process; possibly eliminating the need for paint removal in some recycling applications.A modified progressive double row grater screw was used to reduce the particle size of the paint flakes. The physical properties of these material blends are compared to similar blends obtained using a general-purpose screw. It is shown that reducing the paint flake size has a marginal effect on mechanical properties. However, the surface finish is greatly enhanced when the paint flake size is reduced.
The average free volume hole size
Acrylate based hydro gels synthesized at very high controlled conditions exhibit structures at three different length scales (10-6, 10-4 and 10-2 m) as well as an unusual combination of surface properties, morphology, mechanical properties and swelling capacity. These properties depend strongly on the thermal history during the synthesis and on the cross-linking agent concentration. Mechanical properties, swelling capacity and structures at different length scales of these hydro gels show transitions at a critical concentration of cross-linking agent and a critical temperature of synthesis.
Microcellular closed-cell PMMA foams are prepared using a two stage batch process method. The foam structure is controlled by altering the foaming temperature, foaming time and saturation pressure. The effects of processing parameters on the mechanical properties of the foamed material are characterized under different foaming conditions. Elastic modulus, tensile strength and elongation at break were studied as functions of the different foaming parameters. The mechanical properties are found to be greatly affected by the foaming parameters and vary with cell morphologies. The experimental results are compared with existing analytical and numerical models to evaluate them and predict the mechanical properties of microcellular polymeric foams. The results of this work help to optimize the foam processing parameters and achieve desired mechanical properties and material density.
This study is designed to observe the effects of temperature on the pinch-off strength of extrusion blow molded bottles. Pinch-off design is a crucial component because it welds the sides of the parison as the mold closes. The strength of this weld is important because a weak weld will result in part failure.This experiment examines the effects of processing. To assure a uniform parison wall thickness, the die and mandrel were adjusted for each combination. Special attention was placed on accurate wall thickness. The thicknesses were confirmed by measuring the parison. This study was performed by changing melt temperatures for the HDPE bottles.
Heat-induced gelation was observed above 80°C on a chitosan solution neutralized with a weak base, ? - glycerophosphate. Urea, a hydrogen bonding decomposing agent, was also used in some of these solutions to investigate the presence of hydrogen bonds in the resulting gels. The solution behaviour and gelation process were investigated using linear viscoelasticity.In solution state, the addition of urea decreased the rheological properties due to the reduction of hydrogen bonding interactions. During the gelation tests, the evolution of the storage and loss moduli was monitored as a function of temperature. Heating resulted in sol-gel transition at a critical temperature, the so-called gelation temperature Tgel. It was found that adding urea decreased the resulting gel strength and increased Tgel, corresponding to the retardation of the gelation process. These results indicate that hydrogen bonding is an important parameter in the chitosan physical gels formed, even at high temperature, which is not the usual belief. In parallel, pH and conductivity measurements revealed that gelation was also caused by polymer-polymer hydrophobic associations enhanced at high temperature, due to increased ionic strength.
This work is part of a study aimed at creating surface grafted polymer layers. After deposition of amineterminated monolayers, poly(tert-butyl acrylate) (PtBA) was grafted ‘from the melt’ to silicon wafer substrates as a function of reaction temperature. The polymer layer of interest in this study was PtBA because it is relatively easy to subsequently substitute the tert-butyl ester groups with other functional groups to create a chemically tailored layer. The thickness of the monolayer and grafted polymer layer were monitored using ellipsometry and static contact angle was used to characterize the surface energy.
The fracture behavior of two natural fiber composites was investigated. Tensile and fracture tests were performed on sisal reinforced HIPS and sisal/starch based composites. An increasing trend of stiffness with fiber content was found in both cases, whereas tensile strength decreased for sisal/HIPS composites. A maximum in sisal/HIPS composites quasi-static fracture toughness with fiber loading was observed, while they exhibited lower impact toughness values than HIPS. For the biodegradable composites, fracture toughness increased with fiber content and it depends on fiber orientation. In puncture tests, these composites exhibited higher values of fracture energy than neat matrix and fiber orientation affected the damage zone.
While the advantages of homocomposites over heterogeneous composites are obvious, the fabrication of homocomposites for fast crystallizing polymers is challenging because the melting temperatures of the fiber and the matrix are very close. In the present study, an approach of using poly(ethylene terephthalate) (PET), a slowly crystallizing polymer, to form homocomposites was investigated. Because PET experiences slow crystallization during typical polymer processing, distinct physical forms with a large difference in crystallinity and thus in melting temperature can be readily obtained. In the experiment, highly crystalline PET fibers laid between two amorphous PET films were compressed between heated platens at 180°C, a much lower temperature than the melting temperature of the fiber, and rapidly cooled after a holding stage of 90 seconds. The resulting homocomposites have a tensile strength about twice higher than the non-reinforced PET processed under the same condition.
In this paper, we studied the effect of organically modified montmorillonite clay (OMMT) on morphology development in the mixing of polyamide 6 (PA6) and polypropylene (PP). The clay particles were initially present in the PP-phase. All morphological forms, e.g. lamella, fibrils, and droplets were seen as in blends without clay. Much finer PP-phase droplets were observed during breakup of the fibrils into droplets. The thread breakup studies revealed that the changed interfacial tension due to presence of clay was responsible for finer morphology. In addition, the clay particles in the PP-phase disrupted the break pattern of fibers and expedited fibril-droplet transition.
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