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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Study on Morphology Development for In-Situ Fiber Reinforced Composites by Blending Polypropylene and Polycaprolactone
In-situ fiber reinforced composites were prepared by blending of polyolefin and polycaprolactone. The dispersions in this blend materials were deformation into fibers using a polymer extrusion. Polymer processing conditions, such as drawing ratio, were measured to study its effect on elongation of dispersed phases. The dispersions have dramatically changed from spherical to spheroidal and filament shapes depending on drawing ratio. Reduced capillary number was used to characterize droplet deformation, thus giving us many informations on fiber formation of the dispersions.
Mechanical and Morphological Properties of Kevlar-Fiber Reinforced Polyamide 6,6 (PA66) Composites
The effects of fiber loading and surface treatment on the mechanical and morphological properties of nylon 6 (PA66)/Kevlar composites were studied. The effect of fiber surface treatment on modulus is not pronounced for 10% Kevlar fiber-reinforced composite (KFRC) but it succeeded in enhancing modulus in 24% KFRC. The reinforcement of PA66 by Kevlar fibers was indicated by the increase in tensile strength with increasing fiber content. However, there was no evidence to suggest that the surface treatments have any significant effect on the tensile strength of the composites. The failure surfaces of both surface treatments are similar to the untreated fiber as indicated by the massive fiber pulled out. However, less fiber splitting can be seen on the failure surfaces of the treated samples. Fiber breakage is also indicative of good interfacial bonding but the massive fiber pullout in high fiber content samples would complement the toughness and strength of the fibers itself.
Preparation of High Barrier Containers Based on Nanocomposies
The current study deals with application of nanocomposies to high barrier products such as blow bottle, sheet, and film. Olefin based barrier containers have been prepared for storage of hydrocarbon solvents. Solvent permeation tests have shown that incorporation of small amount of nano clay particles (3-5%) with appropriate carrier, led to significant reduction of permeation of hydrocarbon solvent by a factor of 40 to 200, compared to neat HDPE.The patent pending technology of the above application based on nano-clay dispersion with a appropriate carrier, which is named as single wall barrier nanocomposite.
Online Determination of Wear Using X-Ray Fluorescence Spectroscopy
According to new developments in the field of X-ray fluorescence spectroscopy (XFS) the wear of processing devices (e. g. plastics processing machines) can be determined. This method allows the determination of the time-dependent development of wear processes. The main advantages of XFS are the broad detection range and the simultaneous detection of different elements. Up to now the analysis of wear is mainly done by means of gravimetric methods. These methods have the disadvantage of slow evaluation and low precision when low abrasive media are used. The disadvantages can be overcome by XFS methods. Some detailed results from studies of wear processes are shown and discussed.
Application and Limitations on Thermal and Spectroscopic Methods for Polymer Shelf-Life Prediction
In medical products, shelf-life after thermoplastic processing and radiation sterilization is important. Previously, we have successfully applied thermal analytical methods to predict shelf-life for many polyolefins. However, as the material of construction becoming more sophisticated: multiphase alloys and blends, multilayer constructions etc., issues existed that require clarification as to what extent these methodologies are applicable.In sharp contrast with previous studies, it was found that complexities through alloying has rendered ineffective the predictive method based solely on thermal techniques. In an expanded study, we employed thermal methods in conjunction with other spectroscopic and morphological methods to study the applicability and limitation of the combined techniques. Results comparing with real life simulated aging experiments are presented in this article.
Gas Chromatography/Mass Spectroscopy for Plastics Failure Analysis
Gas Chromatography/mass spectroscopy is particularly useful as an analytical method for plastics failure analysis in cases where detection of an unknown contaminant or other compositional factor may be the cause or a contributor to failure. It takes advantage of the fact that GC is a method of separating compounds in a mixture, permitting their identification and possibly quantification. MS is not only a very sensitive detector but also gives mass spectra of GC peaks, permitting their identification in many cases.In thermal desorption GC/MS compounds are transferred from the sample to the GC with heat. Completely nonvolatile materials are not detected. Using desorption temperatures up to 300-350°C, many components of plastics can be analyzed. In pyrolysis GC/MS the sample is decomposed at temperatures up to 900°C; GC/MS analyzes the pyrolyzate. Examples are given of causes of plastics failures that have been determined by GC/MS.
FTIR and TOF-SIMS Analysis and Imaging of Cracked Polybutylene Piping
Polybutylene resin was used in the manufacture of water supply piping for a number of years from the late 70's through to the mid 90's. A number of lawsuits were filed in the 1980's to recoup homeowner losses when their polybutylene water pipes failed in service.The cracks in a number of these pipes which had failed in service were examined by Fourier transform infrared spectroscopy (FTIR) suing a microscope attachment. The microscopic FTIR examination of the cracks enabled us to show the location and extent of the oxidative degradation of the polymer. Deconvolution of the carbonyl peak arising from the oxidation provides information regarding the likely functional groups present in the oxidized layer.These cracks were also examined in cross section and plan view using time-of-flight secondary ion mass spectrometry (TOF-SIMS). This very surface sensitive technique enables one to isolate and image the location of specific mass units. The relative compositions of the cracked areas and reference areas will be discussed in terms of the presence and distribution of various mass fragments.
Photo-Induced Scission and Crosslinking in LDPE, LLDPE and HDPE
Chain scission and crosslinking concentrations have been derived from molecular weight distributions obtained by gel permeation chromatography after three weeks and six weeks laboratory ultraviolet (UV) exposure on samples taken at different depths from the exposed surfaces of 3mm thick injection molded bars made from LDPE, LLDPE and HDPE. Degradation was rapid near the exposed surfaces but very little change occurred in the bar centers, due to oxygen starvation. The most rapid rises in scission and crosslink concentrations were observed with LDPE, for which the concentrations after 6 weeks exposure were approximately double those measured after 3 weeks. With LLDPE and HDPE the scission and crosslink concentrations after 6 weeks exposure were much greater than twice those after 3 weeks. Scission dominated over crosslinking at all depths and for all materials and was always ?3, with a value of ~9 recorded for HDPE near the exposed surface after 6 weeks exposure.
Lifetime Prediction of Glass Fiber/DERAKANE 411-350 Composites
The goal of the present effort is to develop and verify a lifetime prediction approach for glass fiber reinforced DERAKANE 411-350 composites subjected to fatigue loading, as well as moisture aging. The approach taken is to use fatigue lifetime data taken from samples that were not aged and use it in conjunction with long-term immersed aging data (for a different laminate), as inputs to a residual strength based lifetime prediction scheme entitled MRLife. We will compare our predicted results to those measured experimentally, and comment on discrepancies observed.
Oxidation Induction Time Analysis of Degradation of Poly(1-Butene) Pipe
The Oxidation Induction Time Test is a powerful technique for evaluating the oxidative stability and or degradation of polymers. It is especially effective in examining the relative utility of antioxidants on the stability of oxidizable polymers. It is also useful in determining whether or not antioxidants have been leached from the polymer, thus negating their effectiveness. In this study OIT has been used to show the loss in antioxidant from the interior surface of poly(1-butene) pipe used to convey potable water. The loss in antioxidant was confirmed by significantly reduced OIT times. Confirmation of oxidation of the polymer was subsequently made by IR analysis.
Newer Compatible Conducting Polymeric Composites for Elimination of Electromagnetic Radiations
Conducting polyaniline composites prepared by using hybrid dopant systems with different loading levels provided highly compatible structures, with a significant increase in intermolecular adhesion. Composites with even lower loading of 1.5% was much efficient to remove the static charge from the surface, while the composites with higher loadings from 20% to 50% were found to be highly efficient for the elimination of electromagnetic interference. A constant increase in shielding value was observed with the increased loading level, followed by a decrease in the tensile strength. Composites shows higher thermal stability while morphological studies represents complete dominance of one phase over the other at higher loading levels. The intermolecular interaction between two different polymeric matrix results in the formation of a thermodynamically homogenous stable structures, resulting the formation of highly compatible conducting composite systems.
Weibull Distribution Function
The Weibull Distribution Function is a useful statistical tool. To show this utility, several problems are solved that involve plastic processing. Some of the analyses provide direct solutions to difficult problems. Other analyses permitted a greater understanding of the technical issues within the problems.In one case involving the tensile elongation data of nylon Ty-Wraps, several variables not under process control are shown to have influence in causing:Skew in the distribution of the data, andThe occurrence of more than one distribution curve.Benefits of Weibull are that it identifies data inconsistency, wide sigma variations, distribution skew, and even multiple distributions. When an understanding of the variables leading to these factors is defined, it may lead the user to: improved precision, higher quality in events, higher product quality, better procedures, enhanced processes, estimation of product life, etc.
Effect of Moisture Content and Drying Conditions on the Molecular Weight and Melt Flow Index of Polycarbonate and Polyetylene Terephtalate
It is well known that moisture traces can play an advert effect, by hydrolysis in the melt, on the mechanical properties of certain polymers such as polycarbonate and PET. Single water molecules can easily split the polymer’s long chains, causing severe damage to molecular weight distribution, MWD and mechanical properties, while increasing melt flow index (MFI).The purpose of this paper is to show the influence of moisture content on the molecular weight and melt flow index of polycarbonate (PC) and polyethylene terephtalate (PET). A method that allows minimizing moisture pick up after drying and during the MFI measurement will be described.
PhotoDSC Analysis of UV-Curable Hydrogels
Photopolymerization is a widely used technique to synthesize polymers and hydrogels. The commonly used ultra-violet (UV)-curable mono-, di- or multifunctional vinylated monomers or macromonomers are often volatile, causing difficulty in the accurate measurement of reaction kinetics using Photo Differential Scanning Calorimetry (PhotoDSC). In this work, the DSC sample pan is chemically and physically modified such that the resin sample can be laid uniformly in the sample pan with minimum sample weight loss during measurement. Such treatment substantially improved experimental accuracy for volatile materials, which in turn provides a better understanding of the reaction kinetics of UV-curable polymers. Kinetic experiments are carried out for poly(2- hydroxyethyl methacryate) (HEMA) and poly(methacrylic acid) (MAA) based hydrogels by using PhotoDSC and modified sample pans.
Micro/Nanoscale Bonding and Surface Glass Transition Temperature of Polymers under Carbon Dioxide
Studies of polymer thin films revealed that properties of polymers at the surface are different from those in the bulk. The most striking among these properties is the glass transition temperature, Tg. In this study, the surface Tg of poly(DL-lactide-co-glycolide) (PLGA) under carbon dioxide (CO2) was evaluated by embedding gold nanoparticles onto PLGA surfaces. The Tg profiles at the surface were determined by measuring the apparent height of embedded nanoparticles using atomic force microscopy (AFM). It was shown that CO2 could greatly depress the Tg near the surface. Using this idea, we demonstrated near room temperature bonding of polymers at a length scale as small as 3.9 ?m. This CO2 bonding technique was successfully applied to seal polystyrenebased microfluidic chips and construct three-dimensional (3D) PLGA tissue scaffolds with well-defined structure.
Impact Modification of Polypropylene
Without the advent of impact modified polypropylene car batteries they would still be a heavy , black, hard rubber Product. The new commercial battery is a blend of polyethylene, EPR(ethylene propylene rubber) and isotactic polypropylene as the continuous phase. It is lighter and semi-transparent. The problem is to produce a consistant product. In a continuous process, material analysis is complicated by not knowing the precise amount of rubbery 2nd phase which was produced and what is its rheological characteristics relative to the rigid phase. It is well known that there is an optimal particle size for the best product performance. The problem is to determine the controlling polymerization and product performance factors. Microscopy can be used to observe and quantify particle size and EPR content. From this work the optimum particle size occurs at an MFR ratio slightly less than one and an average diameter of ca.0.4 microns.
Polycarbonate Microfoams with a Smooth Surface and Higher Notched Impact Strength
Polycarbonate microfoams produced by physical blowing agent usually have an unacceptable surface quality. The surface is rough and the visual difference in the surface quality is striking. However, the surface quality can be improved by the gas counterpressure technology. Polycarbonate has a high elongation at break but low notched impact strength. Previously, the microfoams show higher notched impact strength, but a considerably reduced elongation at break. Foams produced by gas counterpressure technology have both positive mechanical properties.
Cold Forging Method for Polymer Microfabrication
Polymer microfabrication using cold forging method was investigated. The advantage of cold forging is that the cooling stage in thermoplastic molding is eliminated, thus facilitating rapid production of plastic microstructures. High aspect ratio microchannels (100 ?m x 500 ?m) were fabricated on Teflon substrates. The dimension of replicated channels was found to be consistent from shot to shot. Due to instantaneous elastic recovery, the channel has a width about 30% smaller than that on the die. The final channel size is contingent upon the forging pressure, the forging speed, and the dwell time, as well as on the post relaxation process. Upsetting experiments of Teflon cylindrical samples were carried out to study the fundamental issues on dimensional recovery so as to predict and consequently control the dimensional changes in polymer micro forging.
Challenge to Manufacture of Low-Density Microcellular Polycarbonate Foams Using CO2
This research investigated the expansion behavior of polycarbonate (PC) foams blown with CO2 to achieve a low-density microcellular foam. The expansion behavior of PC foam was interpreted by the amount of retained gas in the cell structure in consideration of cell opening, cell-tocell diffusion, and melt stiffening. The expansion ratio curve plotted against the die temperature showed a typical mountain shape, confirming our previous results. Three filamentary dies were designed to investigate the effect of the die geometry. A high pressure drop rate was favorable for a high expansion ratio. By controlling all these parameters, an expansion ratio over 14 times with a cell density over 1010 cells/cm3 could be achieved.
Foaming Polyethylene with CO2-Based Mixtures of Blowing Agents
Carbon dioxide (CO2) is presenting many highly desirable properties as physical foaming agent. It is a low cost and non-flammable gas with good blowing power and fast dissolution in polymers. Unfortunately, extrusion of low density foams blown from CO2 is still very difficult. This is especially true for foams made from semi-crystalline polymers such as polyethylene (PE). This paper describes the properties and performance of polyethylene foams made from mixtures of CO2 and 1,1,1,2-tetrafluoroethane (HFC-134a). The use of HFC- 134a as co-blowing agent was shown to enable the extrusion of lower density foams as compared to samples processed with CO2 alone.
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