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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Observation and Modeling of Stress Corrosion Cracking in Plastic Pipes
There are four stages of stress corrosion crack (SCC) such as initiation, individual SC crack propagation, many crack interaction and clusters of crack formation, and finally crack or cluster instability and dynamic growth leading to the ultimate failure. The second stage is critical in determining the lifetime of pipe. Crack Layer model is adopted in this study to predict the individual SC crack propagation kinetics and the time interval from crack initiation to instability and break through. In addition, numerical simulation of Stress Corrosion Crack Layer (SCCL) and comparison with experimental observations of SCCL propagation in various thermoplastics is presented.
Polymorphism and Crystallisation in Metallocene PP-Copolymer Nanocomposites
The structures, polymorphism and crystallisation behaviour of a range of maleated and acrylated polypropylene (PP) layered-silicate nanocomposites were studied using wide-angle X-ray diffraction (WAXD), small-angle X-ray diffraction (SAXD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) techniques. The dispersed silicate layers were shown to restrict the ?-crystalline phase and selectively suppress the (220), (040) and (060) crystallographic planes of the PP. The PP crystallinity and crystallisation temperature decreased with an increasing degree of layered-silicate intercalation and exfoliation, by up to 26 % and 10 degC respectively. This is attributed partly to interaction of the polymer and layered-silicate with the compatibiliser. The unique damping mechanism of the silicate layers reduced the PP ?-phase glass transition temperature (Tg). The endothermic crystalline peak pattern of the compatibiliser, determined by DSC was found to be a novel technique for characterising the degree of layeredsilicate exfoliation in the PP matrix.
Dimensional Stability in LDPE Foams
Unbalance between the effusion rate of the blowing agent and the infusion rate of air in post-extrusion LDPE foam sheets causes dimensional instability of the sheets. A one-dimensional diffusion model coupled with a constitutive Voigt equation was proposed to study the time-dependent dimension in LDPE foams. The features of shrinkage-restoration or swell-relaxation were captured by varying the permeability ratio of gases. Comparisons with experimental results were made to retrieve the parameters used in the model. These parameters are related to the physical properties of the materials used and are expected to correlate to the structures of the foams such as the global porosity and cell size distribution.
Evaluation of Time to Ductile Failure in Creep of PEs from Short-Term Testing
Ductile failure of PE pipe in sustained pressure test results from instability of steady creep process. The instability is manifested in formation of localized necking, which appears in form of ballooning under internal pressure. The condition of instability of the steady creep is an unbounded increase of the strain rate: ? ? ?. A strain rate ~ stress relation combined with basic stability analysis leads to simple relation between the applied stress and the creep time prior to PE pipe ductile failure.A simple method of evaluation of PE steady creep behavior from short-term ramp tests data is proposed in this work. It opens a new and straightforward approach to screening a large number of material formulations and therefore to connecting molecular architecture with material durability.
Chrome Plated Automotive Plastic Components
Original equipment manufacturers (OEMs) are demanding a chrome look on many vehicles. As a result, chrome plated plastic components are required in many automotive exterior and interior components. The chrome part must not only look good but also be durable and not delaminate. To meet the OEMs aesthetic and durability requirements, there are many variables that one must consider for chrome plating an automotive plastic component. Some important variables to consider are the material, the part design, the mold design, the molding considerations, rack design, and the electroplating process. This paper examines the importance of material and molding variables in the manufacture of chrome plated automotive plastic components.
Thermoset Materials in Microelectronics Packaging
Thermoset materials have been instrumental in the growth of the microelectronics industry, and Professor Gillham’s research has been a key enabler of the value of these materials. Thermosets have long been a staple of electronics and packaging from the first use of phenolic resins in early electrical switches, connectors, and appliances. In the automotive industry, thermosets were the material of choice for the early distributor caps and connector blocks because of their high temperature properties, which made them suitable for under the hood applications. But as important as these applications were, and still are in many cases, they do not compare to the tremendous contributions that thermoset materials have made to the explosive growth of the microelectronics and integrated circuit industries, and the impact these industries have had in transforming our lives and our economic infrastructure. In this presentation, I will highlight molded plastic packaging, one of the more innovative applications of thermosets in microelectronics, and demonstrate how many of these innovations can trace their origins to the pioneering work of John Gillham.
Clay Aerogel/Polymer Composites
Aerogels can be produced from low cost, smectic clays, using a simple freeze drying process. The resulting material possesses an open structure which resembles a house of cards and a low bulk density (ca. 0.05 g/cc). These aerogels can be used as is, or after thermal consolidation to produce composites. Composite processes including solution infiltration with pre-formed polymers, and in situ polymerizations within the aerogels will be discussed, along with novel composite properties which result. These clay aerogel composites are structurally different from typical clay/polymer composites in that the clays are not exfoliated, but are used as mesoporous structural elements.
A Study of Laboratory and Pilot Scale Extruded LDPE Nanocomposite Films
A nanocomposite formulation consisting of low density polyethylene (LDPE), montmorillonite layered silicates (MLS), and a compatibilizer were compounded and extruded into blown films on laboratory and pilot scale extruders. This study evaluates the compounded pellets and extruded films for their morphological, thermal, mechanical and barrier properties. Wide angle x-ray diffraction and transmission electron microscopy experiments confirmed an intercalated morphology in all the samples. Thermogravimetric analysis revealed slightly higher degradation temperatures in the laboratory scale film samples than the pilot scale films. Mechanical and barrier properties were comparable for films produced by laboratory and pilot scale. Overall, this was a successful transition from laboratory scale to pilot scale processing, allowing the Army to consider this nanocomposite for the outer pouch of the Meals Ready- To Eat (MRE) package.
Blends of Polycarbonate with Co-Polycarbonate of Bisphenol a and 4, 4’-Dihydroxydiphenyl
In comparison to a bisphenol A (BPA) based polycarbonate and a co-polycarbonate of BPA and 4, 4’-dihydroxydiphenyl, transparent blends of polycarbonate with 20 to 40 weight % of copolycarbonate have a higher notched Izod impact strength at low temperatures and thick section.Surprisingly, a blend containing 70% of copolycarbonate has shown more resistance to embrittlement after heat aging at 130°C for 20 days than all other blends. Its resistance to embrittlement is, indeed, comparable to the outstanding resistance of co-polycarbonate by itself.
Biocomposites: Sustainable, Value-Added Biobased Materials
Polymeric and composite materials from plant derived fiber (Natural/Bio-fiber) and crop-derived plastics (Bio-plastic) are novel materials of the 21st century and have the potential to be of great importance to the materials world, not only as a solution to growing environmental threat but also as a solution to alleviating the uncertainty of petroleum supply. As this new generation of biobased polymers enters the commercial market, success in competing with established petroleum based polymers will depend on their performance, properties and cost as determined primarily in the commercial marketplace. While environmental consciousness continues to grow, and some governmental programs have been established to assist with the entrée of biobased materials into the marketplace. E.g., the US Research and Development Act of 2000 along with Presidential Executive Orders 13134 & 13104 and the “Farm Bill” signed by President Bush on May 13, 2002, have a goal of achieving a performance/cost ratio competitive with petroleum-based polymers for value-added applications. The technology road map for plant/crop-based renewable resources 2020, sponsored by the U.S. Department of Agriculture (USDA) and the U.S. Department of Energy (DOE), has set a goal of increasing the utilization of basic chemicals from biobased renewable resources of 10% by 2020, and further increase to 50% by 2050.While the chemistry, reaction pathways and processing steps to producing biobased chemicals and polymers are relatively straight forward, it is the use of these materials in high performance, value-added applications that will be critically important to achieve sustainability and economic viability. The most promising path to achieve sustainability and economic viability is through the addition of biofibers to biobased polymers to produce biocomposites. Research underway in the Composite Materials and Structures Center at Michigan State University and other Universities has been directed at defining, de
Biobased Nanocomposites from Organo-Clay and Blends of Unsaturated Polyester and Functionalized Vegetable Oil
Biobased neat unsaturated polyester materials containing epoxidized methyl soyate (EMS) and their clay nanocomposites were processed with cobalt naphthenate as a promoter and 2-butanone peroxide as an initiator. A certain amount of unsaturated polyester resin (UPE) was replaced by EMS. The combination of the UPE and EMS resulted in an excellent combination, to a new biobased thermoset material showing relatively high elastic modulus and the constant glass transition temperature with up to 25 wt.% replacements with EMS. Izod impact strength was almost constant while changing the amount of EMS and adding clay nanoplatelets.
Microwave Processing of Chopped Natural Fiber Composites and Their Thermal and Morphological Characterizations
Experiments have been performed to investigate the effectiveness of microwave curing of natural fiber reinforced composites. Industrial hemp, flax, kenaf, henequen and glass (15 weight percent) reinforced epoxy (diglycidyl ether of bisphenol-A (DGEBA) cured with diaminodiphenyl sulfone (DDS)) composites were studied. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and environmental scanning electron microscopy (ESEM) were used to investigate material properties. Samples were processed using both microwave and thermal curing for comparison. Several composites reached a greater final extent of cure with microwave curing. ESEM micrographs indicate a lack of bonding at the interfaces between the fibers and the matrix.
Elastic Films from Polyolefin Elastomers
Vistamaxx Specialty Elastomers, hereby referred to as Specialty Polyolefin Elastomers, or SPE polymers, are polyolefin elastomers with isotactic propylene crystallinity1, 2. These polymers contain a predominant (>80%) amount of propylene with isotactic propylene crystallinity, with the balance of the composition being ethylene and other ?-olefins. This new family of thermoplastic elastomers are highly elastic and exhibit excellent recovery from deformation. These polymers share the processability of conventional polyolefins such as polyethylene and isotactic polypropylene and can, thus, be easily formed into cast and blown films using conventional plastic processing processes. The paper will discuss the processing and elastic properties of elastic films made using these polymers.
Elastic Nonwoven Fabrics from Polyolefin Elastomers
Vistamaxx™ Specialty Elastomers, herein referred to as Specialty Polyolfin Elastomers, or SPE polymers, are polyolefin elastomers with isotactic propylene crystallinity. These polymers contain a predominant (>80%) amount of propylene with isotactic propylene crystallinity, with the balance of the composition being ethylene and other ?-olefins. This new family of thermoplastic elastomers are highly elastic and exhibit excellent recovery from deformation. These polymers share the processability of conventional polyolefins such as polyethylene and isotactic polypropylene and can, thus, be easily formed into spunbond and meltblown nonwoven fabrics using conventional plastic processing processes. The paper will discuss the processing and elastic properties of nonwoven fabrics made using these polymers, with an emphasis on the influence of polymer characteristics and processing conditions on the elastic behavior of the fabrics.
Soft TPO Formulations Containing Specialty Propylene Elastomers
Vistamaxx™ polymers are Specialty Propylene Elastomers (SPE) 1 containing isotactic propylene crystallinity. The presence of the iPP crystallinity renders these polymers very compatible with polypropylene (PP). When these polymers are blended with PP, the flexural modulus of the composition is substantially reduced at low weight fraction of SPE. This paper describes the physical, rheological and morphological characteristics of SPE/PP blends, comprising SPE resins of varying MFR and crystallinity. The SPE composition in blends with a 3 MFR PP homopolymer is varied from 20 wt. % to 90 wt. The performance data is analyzed using regression models, correlating the blend properties with SPE and PP type and content in the formulation. Our results indicate that the SPE type, particularly crystallinity, has a strong influence on the physical properties of the blend formulations.
Elastomeric Modification of an IR Cured Unsaturated Polyester Resin to Improve Mechanical Properties
An elastomeric modification of the “core layer” in an Unsaturated Polyester Resin reinforced with two fiber glass chopped strand mats, was used to improve impact resistance. Stress-strain and rheological properties were also measured to evaluate overall performance. Prior to resin-modifier mixing, either cis-polybutadiene or 1,7 octadiene were prereacted (10 min. or 20 min.) with styrene. The reinforced three layer samples were cured in a medium wave IR oven. Results show that both modifiers impart a considerable increase in impact resistance, with a small decrease in Young´s and storage moduli.
Elongational Viscosity as a Tool to Predict the Foamability of Polyolefins
The foaming of Polyolefin’s (PO) by direct gas injection is a delicate balance between the melt strength of the expanding polymer and the pressure of the blowing gas in the growing cells.Important parameters in this process are: melting and crystallization temperature of the polyolefin grade, viscosity in the crystallization temperature range and elongational viscosity in the crystallization temperature range. In particular the increase in elongational viscosity or so-called strain hardening is vital for a successful foam structure.This paper shows how the elongational viscosity is measured according to the Rheological Melt Extension (RME) method. The experimental conditions for LDPE, LLDPE, mPE Plastomers and PP are defined and used for a series of 25 PO grades.These experiments show that the strain hardening ratio (SHR) is influenced by the average molecular length, Molecular Weight Distribution (MWD) and the Long Chain Branching (LCB).
Injection Molded Novel Green Materials from the Byproduct of Corn Based Ethanol Industry
The corn gluten meal (CGM) is one of the major byproducts of ethanol industries. The current use of CGM is more towards livestock feed. This research looks forward in using CGM in making novel biodegradable plastics by blending with one petroleum-derived biodegradable polymer like poly (?-caprolactone), PCL. The CGM was plasticized with glycerol and destructurized with guanidine hydrochloride (GHCl) followed by blending with PCL. Extrusion followed by injection molding processing was adopted in fabricating the new blended green materials. The processing conditions affected the performance of the blends. The resulting green materials were studied for their mechanical properties using dynamic mechanical analyzer (DMA), united testing system (UTS) and izod impact tester.
Characteristics of the Vitrification in the TTT Diagram
Vitrification corresponds a solidification of a polymeric thermosetting material when the glass transition temperature Tg of the material precedes the experimental temperature T. Relating the vitrification progress at various isothermal temperatures to the cure time builds the Time- Temperature Transformation (TTT) diagram for thermosets. There are a number of possible routes in this diagram that could lead the material to a representative glass state, including the isothermal cure route, continuous heating route, cyclic heating route, and temperature cooling route after allotted cure. However, the glass transitions involved in the different routes are different in nature, even though the material may have the identical chemical conversion (?) and the same Tg. Such a behavior may lead to interesting density profiles of the thermosetting material upon curing that might introduce potential richness of other chemical/physical responses in the glassy state.
pCBT: A New Material for High Performance Composites in Automotive Applications
Cyclic oligomers of butylene terephthalate (CBT®) represent a new chemical route to semicrystalline thermoplastic polybutylene terephthalate (PBT). The oligomers of interest melt completely at about 150°C to produce a low viscosity fluid that is ideal for wetting and dispersing fibrous fillers and reinforcements thereby enabling the development of composites that were previously not possible when working with high viscosity commercial PBT. Introduction of catalyst to undiluted molten cyclic oligomer leads to rapid ring opening polymerization and the formation of high molecular weight thermoplastic PBT without the generation of volatile organic compounds. The polymer resulting from this polymerization will be hereby referred to as pCBT. Treatment of cyclic oligomers in this fashion results in pCBT thermoplastic resin with a high melting point (230°C) and physical performance similar to that of other commercially available PBT resins. The low viscosity oligomers enables the selection of processing technologies that are typically reserved for thermosetting systems that work in conjunction with easy flowing monomers or pre-polymers. The combination of excellent mechanical performance and the ability utilize processing techniques typically reserved for thermosets enables broad uses for these oligomers in a range of applications including; interior, exterior and structural automotive components. Additionally, the thermoplastic nature of pCBT holds promise to provide a low capital route to a new family of pCBT based recyclable materials made using a range of plastic processing technologies.
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