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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Plastics in the Twenties
Plastics are to continue their growth in the next twenty years and beyond, from 160 million tons in 2000 to 550 million tons in 2020.The general quantitative forecasts, however, show varying rates of growth, with:Population growth tapering and average income fast growing, Faster growing areas, outside the traditional Triad, USA, Europe, Japan, Faster growing applications, in structural and durables, New plastics coming, high performance, alloys, composites, silica based, And, maybe, entirely new paradigms for the next 25 years, with the decline of fossil fuels as energy The paper is divided into three parts:The world economic scene and forecastsPlastics end-uses, markets and applicationsWorld plastics consumption and forecasts
Effects of Heat Aging on the Properties of Rigid Medical Packaging Materials
Retention of physical, thermal and optical properties at an elevated temperature of 50°C was monitored in a heat aging study of two materials, following conditions of ASTM D-3045. XT® polymer acrylicbased multipolymer compounds were stable through 24 weeks of aging, with only minor optical changes. In contrast, EASTAR 6763 copolyester suffered significant property changes, notably embrittlement and higher glass transition enthalpy. Ethylene Oxide (EtO) sterilization further widened the performance gap. Retained strength of rigid medical packages is important for adequate protection through the rigors of storage and transportation.
Simplifying Failure Analysis for Adhesive Joining Operations
Troubleshooting a failure in an adhesively bonded joint can be a daunting task due to the wide variety of processing and performance variables that can affect joint performance. Fortunately most failures can be attributed to one of four causes: No/Poor Cure of the Adhesive; Poor Bond Strength to a Substrate; Insufficient Adhesive for the Joint; or Wrong Adhesive for the Application. In this paper, techniques for identifying these causes of joint failure and solutions will be described.The adhesive families most commonly used for bonding plastics on medical devices are cyanoacrylates and light cure acrylics. This paper will provide background on both chemistries, give a detailed review of the potential causes of each of the main failure modes associated with these adhesives and potential solutions. It is hoped that this will aid the reader in applying the same failure mode analysis to other adhesives that are not covered in this paper. To help illustrate these concepts, some real life examples of adhesive failures and the steps in the process used to resolve them will be discussed.
Electron Beam Compatible Polymers
An overview of electron beam systems provides a summary of system configurations and significance of important energy measurements related to systems capabilities. The overview includes the benefits of direct vs. indirect systems, horizontal vs. vertical beam sources, and the importance of power and energy values to throughput and penetration of systems.The radiation effects on polymers are described and the mechanisms of these changes are defined. The responses of a number of polymers important to the medical industry are summarized. A few key guidelines for polymer selection are:Selection of the highest molecular weight polymer to help reduce any effects of degradation.Aromatic polymers exhibit better radiation resistance than aliphatic polymers.Antioxidants can often be added to improve radiation stability.Less oxygen dissolved in the polymer and surrounding the polymers will help reduce oxidative degradation.The material properties required for radiation resistance and suitability for electron beam sterilization are delineated and discussed.
Superior Stabilization of Polypropylene for Radiation Sterilized Medical Devices and Packages
Hindered amine light stabilizers (HALS) have been used for decades as some of the principal stabilizers for the protection of polypropylene from the effects of sterilizing doses of high-energy radiation. ExxonMobil Chemical Company has now found proprietary (HALS) additive packages that provide superior stabilization to radiation-sterilized polypropylene. When further improved by blending with small amounts of metallocene-catalyzed, ethylene-based plastomers, these formulations are highly resistant to degradation after irradiation and useful for a broad range of medical device and packaging applications.
Micro Molding Challenges
As miniature molded parts approach micro or nano in size, several challenges exist to molding them in a production environment.This paper explores some of these challenges such as polymer property changes induced by shear stress through near micron-sized gates, humidity control for extremely small shot sizes, and integrating macro to micro technologies to produce near micron level geometry in precision, micro mold components.New mold manufacturing technologies exist to remove variation from micromolded features and further work is being done with scientific micromolding process control, both of which are critical to long-term micromolding process capability. ANTEC
Plastic Bio-MEMS Sensors
A novel method for the production of polymer microcantilevers is described, along with the characterization (i.e., determination of stiffness and resonant frequency) of parts produced with said method. The manufacturing method consists of casting a polymersolvent solution upon a glass base, gold-coating and precision cutting of the produced film, and mounting of the cut film pieces onto injection-molded bases for characterization in a commercial atomic force microscope (AFM). The technique is repeatable and has produced polymeric beams of micron thickness, with lengths up to 25 mm and widths down to 25 microns. With this wide size range, production of polymeric beams with stiffnesses commensurate with those of probes used in atomic force microscopy is possible, and indeed the stiffnesses of the beams produced for this work range from roughly 0.001 N/meter to 0.1 N/meter.
TekFlow Processing for Miniature and Micro-Size Applications for Medical Plastics
The number of micro-sized medical applications is increasing each year due to advances in equipment used for medical / pharmaceutical testing and also as components in new minimally invasive surgical devices. These applications involve miniature and micro-size devices which rely the processor's ability to fabricate smaller plastic parts, parts with thinner walls, parts with micro features (like holes, channels, or posts) or even micro-surface textures. Unfortunately, most engineering grade plastic materials also exhibit low flow characteristics and are processed at higher temperatures. The result is that it is difficult to fill thin wall sections and small features with molten plastic. Even when the plastic does fill these thin, small sections, often it shrinks so much afterward that the dimensional stability is compromised and the tolerances are unacceptable. The purpose of this presentation is to discuss the benefits to micro-processing which are proposed by TekFlow Processing, a disentanglement technology which reduces the processing temperatures and pressures normally required, thereby assisting the fabricator/ processor to create challenging miniature and micro shapes and tolerances. The lower processing temperatures and pressures also allow the processor the option of using thermally or pressure sensitive inserts or additives.
Radiation Grafting for Surface Modification of Nano-Fibers
The performance of polymeric materials in a particular application depends to a great extent on the properties of the interface or interphase between the polymer and the applied environment. Grafting is a useful technique for modifying polymer surface properties and for constructing materials whose bulk and surface properties are different. Radiation grafting provides significant advantages over chemical grafting methods. Radiation sources include electron beam (EB) ultraviolet light (UV) and plasma. The concept of using radiation grafting as a method for tailoring polymer surface properties has been applied to a wide variety of applications including bio-medical, textile, electrical, and membrane applications. In this work, we focus on applying radiation grafting technology to nanoscale polymer systems, specifically nanofibers produced by electrospinning polysulfone (PSF). Using EB, hydrophilic monomers such as acrylamide have been grafted on PSF fibers and the modified materials have been evaluated using surface analysis techniques including XPS, ATR-FTIR, ESEM, and contact angle measurements. Our results indicate that we have successfully grafted acrylamide onto polysulfone electrospun fibers while maintaining the fine fibrous structure in these systems.
The E-Beam Curing of Epoxy Resins
The electron beam curing of epoxies is actively explored for application in composites and adhesives. The dynamics of epoxy homopolymerization was studied at different doses of irradiation – from 0.05 to 17 Mrad. The results enabled estimation of the maximal uncured dose and minimal cured dose. These values are useful for repeatable electron beam processing, for example to ensure proper ply consolidation during Automated Tape Placement (ATP) with in-situ EB cure. DSC tests were used to study the dynamics of heat postcuring for preliminary irradiated resins and to estimate the values of residual exotherms of irradiated epoxies.
A Rapid, Nondestructive, In-Situ Analysis of Plastics for Heavy Metals with Portable X-Ray Flourescence Analyzer
Recently introduced regulations, such as European Community “Packaging Directive” - ECDirective 94/62/EEC (1), impose the maximum limit on total amount of metals such as Cd, Cr, Hg and Pb in plastic packaging materials to less than 100 mg/kg. Another EU Directive, 91/338/EC (2), sets the maximum allowable concentration of cadmium in plastics used for consumer goods at 100 mg/kg. In the US, the “Proposition 65” introduced in California banned cadmium from use.Effective enforcement of these regulations creates the need for analytical methods capable of rapid, accurate, nondestructive in-situ analysis of plastics. An X-ray Fluorescence Analysis (XRF for short) is very well suited for this task.In this paper we report on successful application of a small, portable X-ray fluorescence analyzer in analysis of plastic for metals. The analyzer can quantify heavy elements such as lead and cadmium in plastics down to 10 and 25 mg/kg, respectively, at a 120 sec. measurement time per sample.
Sustainable Polymers: From a Glorious Past to a Bright Future
In the coming decades it will become increasingly difficult to cheaply satisfy society's thirst for petroleum-based polymers. Additionally, the problems associated with disposal of non-renewable, non-degradable petroleum based polymers will drive the search for agriculture based plastics that do not sacrifice cost or performance. Although agriculture based plastics have been around for over a century, they were largely forgotten after the advent of synthetic, petroleum based polymers. This paper revisits the literature left to us by early twentieth century engineers who made protein based plastics from casein and soy protein on an industrial scale. In recent years, there has been a resurgence of interest in this type of material. This paper reviews current research on biopolymers such as casein and soy protein based plastics as well as polylactide acid, or PLA.
Use of Natural Fibre as Reinforcing Agent in Biodegradable Foamed Packaging Materials Made from Wheat Flour
The use of packaging materials is expected to increase annually on average by about 5 percent in the foreseeable future, but the technology for reusing and recycling of packaging waste is lagging behind. This paper considers the evaluation of an alternative packaging material, derived from renewable resources, which is economical to use, biodegradable and recyclable by composting. In this paper consideration will be given to the preparation, characterisation and properties of starch-based materials derived from wheat flour. A range of techniques, used to characterise these materials will be discussed, including image analysis, SEM, thermogravimetric analysis, compressive strength, impact and recovery measurements.
Melt Processing of Traditionally Solution-Processed Polymers with CO2
The effects of using near critical and supercritical carbon dioxide (CO2) to plasticize polymers that are difficult to melt process are studied, in particular acrylonitrile (AN) and methyl acrylate (MA) copolymers. Previous work with PAN/MA copolymers included differential scanning calorimetry (DSC), used to evaluate the resulting shift in the glass transition temperature (Tg) following plasticization, and pressurized capillary rheometry to evaluate the melt rheology and entry pressure effects prior to and after plasticization. A slit-die rheometer has been designed to allow the attachment of various nozzles to the exit to maintain high pressure and single-phase flow, suitable for measuring viscosity reduction with CO2 in a continuous process. Comparisons are made between capillary and slit die rheometry for quantifying the effect of CO2 plasticization on a model 65% AN, 25% MA, and 10% rubber copolymer.
The Effect of Composition on Properties of Blends from Recylced Rubber and Polypropylene
Incorporation of waste (ethylene propylene diene rubber) EPDM into polyolefins has emerged as a new recycling technique that is eco-friendly and cost effective. The purpose of this study was to recycle EPDM, as well as to develop new impact modified blends. This study, which involved reactive blending of waste EPDM and polypropylene (PP) in a co-rotating twin screw extruder in the ratio range of 10/90 to 60/40, determined the effect of t-butyl hydroperoxide compatibilizer, low and high MFI grade of PP and ethylene-propylene impact copolymer on the mechanical properties of the blends. Formulations were injection molded and subsequently tested for tensile, flexural and impact properties. It was noted that the peroxide and the impact copolymer significantly improved the tensile elongation at break and impact resistance, but resulted in a decrease in the modulus. The approach of this investigation was to determine the optimum blending ratio of the components to achieve a balance in the flexural modulus and impact strength.
Polymer/Clay Nanocomposites with Halogenated Polymers
To investigate the possible formation of polymer/clay nanocomposites halogenated polymers were melt compounded with montmorillonite clays. Natural and organic-treated montmorillonite clays were melt compounded with chlorinated and fluorinated polymers. The formation of polymer nanocomposites was confirmed by X-ray diffraction (WAXS) and transmission electron microscopy (TEM) characterizations. All chlorinated polymers studied including polyvinyl chloride (PVC), chlorinated polyethylene (CPE), polychloroprene (CR), polyvinylidene chloride (PVDC), chlorinated PVC (CPVC), and VDF containing fluoropolymers, polyvinylidene fluoride (PVDF), poly(vinylidene fluoride – hexafluoropropylene) P(VDF-HFP), poly(vinylidene fluoride – hexafluoropropylene – tetrafluoroethylene) P(VDF-HFP-TFE), poly(vinylidene fluoride – tetrafluoroethylene – perfluoromethyl vinyl ether – curesitemonomer) P(VDF-TFE-MVE-CSM) produced polymer/clay nanocomposites with organic-treated montmorillonite clay. Either polyolefin or natural montmorillonite clay did not form nanocomposites. The organophilicity of organoclays and polarity of halogenated polymers seems to contribute to the creation of polymer nanocomposites. The polarity of polymers could be estimated by Debye equation which shows the relationship between dipole moment and dielectric constant. The dielectric constant of polymers could be conveniently used to predict the successful formation of polymer/clay nanocomposites by melt intercalation.
Polyampholytes as Aqueous Viscosifiers: An Investigation of Stimuli-Responsive Rheology
Solution rheological analyses of polyampholyte terpolymers composed of acrylamide (AM), sodium 3- acrylamido-3-methylbutanoate (NaAMB), 3- acrylamidopropyltrimethylammonium chloride (APTAC) were performed at varying polymer concentrations, solution pHs, NaCl concentrations, and molecular weights (MW). Steady-state shear sweeps and dynamic frequency sweeps of semi-dilute solutions were used to measure solution viscosity and viscoelasticity. Results are interpreted in terms of how experimental variables affect the solutions’ electrostatic charges and polymer/solvent interactions, which ultimately affect rheological properties.
Flame Retarding Nylon 12 Elastomers Using Nanoclays as Char-Forming Flame Retardant
Our recent studies have shown that high levels of montmorillonite clay can be added to nylon 12 elastomers to achieve UL-94 rating in 1/8” thickness with minor detrimental effects on physical properties.In the past, in order to achieve this rating we had to use levels of flame retardant systems containing halogen and antimony oxide in excess of fifty percent by weight. This high level of flame retardant had detrimental effects on both the physical properties and the environment.Our goal was to reduce the use of this type of flame retardant system by twenty five percent and still maintain good physical properties. In fact our previous studies show that both impact and flexural modulus increase with increasing levels of nano clay with minimal reduction of elongation.
Surface Modification of Poly (Lactic Acid) Films via Grafting Hydrophilic Polymers
The major objective of this research was to modify poly(lactic acid) (PLA) film surfaces with an ultimate aim of making a bioactive surface that will show selective protein adsorption and faster degradation. The PLA film was solvent cast and the film surfaces were activated by a plasma treatment procedure or UV irradiation. Poly(acrylic acid) (PAA) was then grafted to the PLA film surface using a UV induced photopolymerization process. The film surface resulting from each reaction step was analyzed using ATR-FTIR spectroscopy and contact angle measurements. The molecular weight of the grafted PAA film was estimated by measuring the molecular weight of the homopolymer formed in the solution during the reaction using GPC. Results showed that PAA (Mw ~ 2000) was grafted from PLA film surfaces in 2 or 3 h depending on the method of activation.
Solid Phase Graft Copolymerization of PE-g-MA
The solid phase graft copolymerization method was used to graft maleic anhydride onto commercial polyethylenes. This process is environmentally friendly since it requires minimal recovery or no use of solvent and the process conditions are mild. NMR analysis confirms the successful grafting of maleic anhydride onto the backbones of both linear low-density polyethylene (LLDPE) and ultra high molecular weight polyethylene (UHMWPE). Graft levels for all the polymers were quantified by FTIR absorbance as well as wet-chemical titration. Significant processing parameters were identified based on statistical design of experiments.
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