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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Impact of UV Cured Inks and UV Exposure on Physical Properties of BOPP Films
Biaxially oriented Poly (propylene) [BOPP] films are extensively used in food packaging industry primarily because of their good barrier properties, machinability and printability1. We investigated the effect of flexographic UV-cured acrylic inks on to BOPP films with a focus on permeability towards oxygen and moisture. Temperature dependence on mechanical properties of the printed films was studied. Instron tensile strength, Mocon permeability tests, and thermodynamic results were obtained that suggest that there is no appreciable change in the physical properties when the films are printed with UV curing inks.
Thermal and Rheological Characterization of Feedstocks for Powder Injection Molding
The rheological and thermal behavior of a powder injection molding feedstock (highly filled polymer blend) was studied using rheometry, and thermal techniques. The feedstocks were prepared using two mixing schemes. In the first scheme, an internal mixer and a twin-screw extruder were used. In the second scheme the blends were prepared in a laboratory internal mixer. The filler material was stainless steel and its content in the samples is above 90 % by weight. The rheological behavior of the feedstock was studied in dynamic mode. The techniques used and the results obtained are presented.
Sacrificial Material Assisted Laser Welding of Polymeric Microfluidic Devices
A critical phase in fabricating microfluidic polymer chips is welding of a cover to a channel in order to produce tube type geometry. A possible method to weld such a cover is by through transmission laser welding of polymer components. The major issue in welding of microstructured parts is blockage of the flow path by molten polymer (flash) resulting from a typical welding process. In this study, a sacrificial material technique is developed, in which a water-soluble material is used as a mold material to prevent weld flash from being allowed to flow into the channels. In detail, a sacrificial mold remains in the embossed parts instead of being separated from the part (De-embossing) after molding. A cover or other embossed part is then welded to this part. In this study, through transmission laser welding was used to fabricate such parts. The sacrificial material was then removed by dissolution in an appropriate solvent. Different mold preparation methods are discussed and examples of welded structures are given here.
Finite Element Analysis of Cell Coarsening in Polymer Foaming
In this work, cell coarsening in polymer foaming was investigated through numerical simulation. Cell coarsening occurring on two adjacent bubbles of different sizes in a finite volume of polymer melt was considered to be representative of the whole foaming system. A quadratic triangle-based finite element analysis with an implicit scheme for time evolution was utilized to solve the governing diffusion equation in the axisymmetric coordinate system. The effects of the bulk gas concentration, the intercellular distance, and the initial bubble sizes on cell coarsening were estimated. Efforts were made to improve a fundamental understanding of cell coarsening in polymer foaming.
A Unique Surface Modification Technique for Extending Surface Activation of Flexible Packaging Substrates
Flexible packaging polyolefin materials such as polypropylene and polyethylene have low levels of polar functional groups on the surface and have poor wettability and adhesion properties, making it difficult to apply other functional layers such as inks, adhesives and coatings. To enhance surface polarity, surface treatments such as flame, corona or plasma can be applied to improve wettability and adhesion. To improve the stability of achieved surface polarities which can be impaired by the effects of aging, humidity and heat, the combination of a unique molecular grafting technology with atmospheric plasma treatment significantly enhanced treatment longevity and surface adhesion.
Optimizing Performance of Benzoate and Phthalate Blends for Vinyl Applications
To achieve required performance, blends of plasticizers are commonly used in flexible vinyl applications. Typically, when fast fusion is required high solvating phthalates have been utilized in plasticizer blends. Benzoate esters are high solvators and can also be used in these blends. However, eventhough benzoate plasticizers offer additional performance benefits that can complement general purpose phthalate performance most published literature does not include the use of benzoate plasticizers in blends with phthalates. The purpose of this paper is to demonstrate the performance benefits of blending benzoate and phthalate plasticizers. The approach selected to accomplish this was to develop performance data utilizing a mixture design approach with DOE software. A resilient flooring plastisol formulation was selected as the model. The following properties were obtained: degassing, low and high shear viscosity, viscosity stability of the plastisol, gel and fustion characteristics, tensile strength vs temperature, vinyl heat staiblity, stain resistance, volatility and UV stability. The data indicates how to utilize the advantage of benzoates as “process aides” to speed production rates and improve product quality.
Polylactides. A New Era of Biodegradable Polymers for Packaging Application
Polylactide polymers have garnered enormous attention as a replacement for conventional synthetic packaging materials since they are biodegradable, compostable, and recyclable. In this study, commercially available PLA films, bottles, and trays were evaluated. PLA films show better ultraviolet light barrier properties than polyethylene, but were slightly worse than polystyrene (PS) and polyethylene terephthalate (PET). PLA films show better mechanical properties than PS, and comparable to those of PET. PLA has lower melting and glass transition temperature than PET and PS. Solubility parameter predictions indicate that PLA will interact with nitrogen compounds, anhydrides, and some alcohols, and it will not interact with aromatic hydrocarbons, ketones, esters, and water. In terms of barrier, PLA showed O2 and CO2 permeability coefficients lower than PS and higher than PET. The amount of lactic acid and its derivatives that migrate to food simulant solutions from PLA was much lower than any of the current average dietary lactic acid intake values reported by governmental organizations.
Synthesis and Characterization of Polypropylene Nanocomposite Fibers
Nanocomposite fibers were produced by the melt spinning of a polypropylene/organoclay compound, maleated with maleic anhydride functionalised propylene oligomers. XRD and TEM analyses showed that the organoclay exfoliation associated with property improvement was enhanced significantly by the elongational melt deformation during the melt spinning process. SEM and FTIR results revealed the preservation of a homogeneous monodispersed phase in the nanocomposite fibers. In addition, there was an overall improvement in the mechanical properties, including tenacity, when the organoclay were optimally delaminated. Rheological analysis and polarizing optical microscopy study showed a significant enhancement in the melt spinability and optical birefringence of the nanocomposites. The DMA results suggested the fiber matrix was simultaneously reinforced and plasticized by the exfoliated organoclay layers. A simple model was also proposed to illustrate the organoclay exfoliation mechanism during the melt spinning process.
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.
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