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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Processing and Cell Structure of Nano-Clay Modified Microcellular Foams
Applications of nanometer-sized particles can facilitate the formation of microcellular foams in the continuous extrusion foaming process. Both intercalated and exfoliated polystyrene/nanoclay composites were foamed using CO2 as the foaming agent. The resulting foam structure is compared with that of pure polystyrene and polystyrene/talc composite. It is found that unique foam structure can be created by changing the content and the dispersion of nanoclay particles. The effects of nanoclay dispersion on the polymer melt rheology and the foaming process are discussed. Combining nanoclay compounding with microcellular foaming provides a new technique for the design and control of foam structure.
Processing and Characterization of Recycled PC/ABS Blends with High Recycle Content
In order to develop a polycarbonate (PC)/ acrylonitrile-butadiene-styrene (ABS) product with a high content of recycled PC, a low molecular weight virgin PC was added to recycled PC to minimize batch-to-batch property variations in the compounded product. Six PC/ABS blends were prepared on a twin screw extruder by mixing 50 wt% virgin ABS and 0-25 wt% low molecular weight virgin PC with 25-50 wt% high purity recycled PC recovered from end-of-life electronics. These blends were characterized rheologically and mechanically. Results showed that this strategy could yield consistent quality resin blends with a high recycle content.
Processing Properties of Some Ethylene and ?-Olefin Copolymers
Ethylene-1-butene, ethylene-1-pentene, ethylene-1-hexene, ethylene-1-heptene, ethylene-octene and ethylene-1-nonene random copolymers were prepared by Ziegler-Natta catalyst system and their rheological and thermal properties were determined. The rheological properties (zero shear viscosity, zero shear first normal stress coefficient, steady state viscosities and components of complex modulus are decreasing with the increase of co-unit size because the entanglement density decreases with the increase of co unit side group length. The melting point, heat of fusion also decrease with the increase of co-unit side group length because of the decrease of crystallinity.
Processing-Structure Relationship Using Rheological Constitutive Equations for Immiscible Polymer Blends
This works tries to correlate the influence of the thermal and deformation histories that the polymer blend undergoes during its manufacturing on its microstructure. This is done by using a rheological model for polymer blends in the numerical simulation of this deformational field. The applied model is a modification of Bousmina et al in the Grmela's  model for two immiscible viscoelastic fluids and allows to obtain the size and shape of the dispersed particle of these heterogeneous systems through the deformational parameters, as shear rate and physical properties, as interfacial tension and viscosity of the polymers.
Production, Research and University Courses in the Field of Plastics in Croatia
Plastics are undivided parts of today's human life and their possibilities in new applications are growing almost every day. Production and processing of plastics are very promising industries and research fields. In this work it will be presented history and present situation, and future possibilities in Croatian plastics industry. It will be also presented educational and research institutions that are concentrated at four Croatian Universities in: Zagreb (the biggest one), Osijek, Rijeka and Split, their field of interests, research results and knowledge that they are offering to students and industry experts.
Properties of Expanded PTFE Sheet Gasket for Fluid Sealing Applications
Advances in plastic expansion technology have created a new class of gasket material, called expanded polytetrafluoroethylene (ePTFE). The material comprises a highly fibrillated and porous microstructure that contributes to its excellent sealing capability. Its mechanical and sealing properties have been studied by the room temperature tightness test. The results suggest that ePTFE has better compressibility, creep resistance and sealability than other PTFE-based gaskets. These properties combined with excellent chemical resistance and thermal stability make ePTFE one of the most versatile gasket materials available today. The key factor that leads ePTFE to its excellent properties is the specialized process technology.
Properties of Hydrosilylated Polypropylene Blends
Low molecular weight polypropylene (Eastman, Epolene N-15) has been chemically modified during reactive processing using a catalytic hydrosilylation reaction in a batch mixer under various processing conditions (1,2). The hydrosilylated PP (Si-PP) has been blended with a commodity polypropylene resin (Montell, KF 6100) in a batch mixer at concentrations ranging from 5-20 wt%. This PP blends have been characterized in terms of their rheological properties as well as their thermal and impact properties. Addition of the hydrosilylated PP reduces the processing torque and the shear viscosity, while the impact properties depend on the crystallinity, Si-PP content and dispersed phase morphology.
Properties of mLLDPE Blown Films Extruded Utilizing Boron Nitride Based Polymer Process Aids
The Saint-Gobain Advanced Ceramics Corp. of Amherst, N.Y. introduces, CarboGlide™, a new family of polymer process aids for thermoplastic resins. These boron nitride based polymer process aids eliminate shark skin melt fracture and postpone, to much higher shear rates, the onset of gross melt fracture. Extrusions of CarboGlide™ and mLLDPE into blown film have resulted in a three-fold increase in rate. In addition, improvements in film quality, such as, better caliper control, mitigation of film streaking, control of coefficient of friction, enhanced gloss, reduced haze and enhanced heat seal-ability are realized with CarboGlide™. Mechanical properties of the film, such as yield strength and Graves tear, are not debased. This unique combination of both process and product improvements, at equivalent to fluoroelastomer process aid costs, demonstrates that CarboGlide™ is the next generation of polymer process aids.
Property Comparison for Talc, Glass Fiber, Mineral Fiber and Mica Filled Polypropylene
The performance of muscovite mica as a reinforcing agent is compared with chopped glass fiber (CGF), milled glass fiber (MGF), the processed mineral fiber (PMF®FIBER), and talc in polypropylene. The effect of type, particle size, mixing energy, surface treatment, and coupling agent on physical properties and weld line strength is evaluated.Due to its high hardness, large area to thickness ratio, polar surface, and lubricating nature, mica reinforced polypropylene has higher rigidity, lower shrinkage, the highest surface hardness, lighter color and better processability than the reinforcing agents.
Pultrusion Compounding of Commingled Glass and Polypropylene Fibers
Much of the recent interest in commingled glass and polymer rovings has centered on woven materials. These commingled rovings can also be used in pultrusion forming, or filament winding. However, these processes require that the commingled material be in a tape form and that the glass fibers be well wetted with polymer. An instrumented pultrusion compounding process was developed to perform this wetting and forming operation. It consisted of an unwinding station, preheater guide, impregnation chamber, shaping die, cooling chamber, puller guide, and pulling station.The quality of the pultruded tape as a function of process parameters was assessed using short span flexural testing, glass fiber weight content, and scanning electron microscopy.
Qualitative and Quantitative Methods Used to Satisfy ISO 10993-18: Biological Evaluation of Medical Devices-Material and Chemical Characterization
The international standard 10993 has been and continues to be the driving force behind the biological safety evaluation of biomaterials and medical devices. An important step in the process is that of characterizing the materials and the chemicals that can migrate or extract from the polymer components to the patient. Such basic information is critical to understanding biological response and risk management of the device. Whether to evaluate the polymer, simulated extracts, or degradation products will be discussed. Appropriate testing to do at the raw material, component part and final device stages will be presented.
Rapid Tooling – What Works and What Doesn't
This paper is third in a series of updates on rapid and alternative tooling technology for plastic molding and manufacturing. Examination of LENS, sintered metal, allow embedding technology, as well as newer processes using LSA and layer deposition is detailed. Tolerance, cosmetics, cost and lead times are update for users of commercial processes so expert decision can be made on best use for various molding and processing applications.Overall, during the last year, the leaps and bounds of the past progress in rapid tooling slowed almost as much as the economy. The lack of progress can be attributed to various factors including lack of funds, lack of interest, lack of defined goals, and lack of diversity of R&D efforts.
Reactive Blending of Poly(Ethylene Terephthalate) and Ionomerfor Recycling
The reactive blending in melt state of poly(ethylene terephthalate) and sodium and zinc ionomers based on ethylene-methacrylic acid copolymers was investigated using a torque rheometer. The components were blended in mixer during 90 min for recycling simulation. The torque increases with processing time according to typical profiles depending on the metal type. Torque changes were attributed to chemical reactions between components generating high molecular weight species. In addition to PET degradation, the ionomers react with PET carboxyl or hydroxyl end groups forming graft copolymers and crosslinked species identified by multiple internal reflection (MIR) FTIR technique.
Reactive Melt Modification of Polypropylene/ Unsaturated Polyester Blends
Melt blending of polypropylene (PP) with a low molecular weight unsaturated polyester (UP) was studied in a batch mixer in the presence of peroxide free radical initiator. Competing degradation and crosslinking reactions of the peroxide with the blend components resulted in a finer and more uniform morphology for this immiscible blend system. The blends were characterized by FTIR, DSC, microscopy and rheology in order to examine the possibility of the formation of block" or "graft" PP-UP structures which would enhance phase interaction and promote compatibility. The batch data were used to define the process requirements for the continuous modification by reactive extrusion."
Real Time Development of Orientation in PP during Stretching as Detected by Spectral Birefringence Technique
The true stress- true strain and birefringence development in a series of PP films with varying levels of tacticity has been measured using a newly developed uniaxial stretching system. This system allows the real time study of the structural reorganization processes at industrially meaningful temperature and deformation rates. The system is fast enough to follow the deformation at high rates of strains and allows us see their deformation at temperatures well below the melting temperature of the samples provided that severe necking does not occur. It has been found that birefringence increases steadily with true strain. Certain stress is required to start to increase birefringence at lower temperature, meanwhile, the birefringence changes almost linearly with stress essentially following stress optical law behavior, as long as the temperatures are near melt temperature.
Recent Trends in Regulatory Activity by the Center for Biologics Evaluation and Research
The apparent trend in medical therapeutics is to move toward a biologically derived therapy stemming from human or xenobiology. The applications of this trend to the medical plastics industry are severe in the level of scrutiny and care necessary to meet the intent and letter of the legal regulations associated with biologic processing, control, and packaging. The Center for Biologics Evaluation and Research (CBER) is the responsible arm of the Food and Drug Administration charged with regulating the biologics industry. This paper will address some of the recent trends in regulatory activity by CBER.
Recommended Factors of Safety and Related Considerations
The only available mechanical design rules for plastics parts pertain to proportioning the sizes of ribs fillets, draft angles etc. Such rules help only to design the individual elements, but leaves a long way to go in settling questions in stress analysis. More specifically, such rules stop at ensuring success with the chosen process.Further, there is little formal guideline in the industry about dealing with creep strains, fatigue life, combined (thermal + molded-in + service) stresses etc., although enough technology is available to calculate them. Also, there is also little recognition of the fact that the long term presence of stress (or strain) depends on the cause of the stress.This paper addresses one of the resolutions to this situation by proposing minimum factors of safety for various service loading types, along with qualitative reasoning to back up. The proposal is motivated by (i) the arbitrariness in plastics of what stress levels are acceptable and what are not (ii) successful history of the use of factor of safety in bringing all structural performance to one common denominator (iii) coupled material behavior of plastic.Lastly, it is pointed out that all the factors are for products that are to survive loads, over certain period of time, and not for those which are designed to come apart at a specified force application.
Recyclability of Crosslinked Polyethylene Based on Creep
Crosslinking of polyethylene greatly improves the material's properties. The crosslinking process causes problems with the material's ability to be recycled. It prevents the material from remelting, making it nearly impossible to process in an injection molding machine.The crosslink density has an effect on both the material's ability to creep and on its ability to be recycled. Creep data was studied to determine the effects of increasing crosslink density on an injection molded polyethylene part. This data will be used as a baseline for how parts made from 25% recycled crosslinked regrind compares with the original crosslinked part. This paper will focus on recycling crosslinked polyethylene (PEX) determined by its creep data.
Reducing Curl in Multilayer Blown Film. Part I: Experimental Results, Model Development and Strategies
Multilayer films often curl or roll-up on themselves, making them difficult to be used in packaging equipment. Curl is particularly acute in asymmetric barrier blown films. Experimental results from simple two- and three-layer structures are described in an effort to understand the underlying mechanisms behind curl. A model from the literature based on beam theory" is adapted to film applications. In this model force and momentum balances are used to solve for curl as a function of each layer's thickness stiffness and shrinkage during fabrication. Of these inputs differential shrinkage is the most difficult to determine. Pressure-Volume-Temperature (PVT) curves are introduced to relate differences in volume change among polymers during quenching. PVT data alone are not sufficient for a predictive model. Qualitative agreement however between the experimental results and model predictions are obtained leading to several strategies for curl reduction. These include reducing crystallinity matching thermal expansion coefficients matching freezing points and increasing the rate of quenching. Another strategy is to change the thickness and distribution of layers in the film allowing the stiffness of one or more layers to counterbalance the curl. Such an approach can be greatly enhanced by a truly predictive model and is the subject of Part II."
Reducing Curl in Multilayer Blown Film. Part II: Application of Predictive Modeling to t Barrier Cereal Liner Film
Multilayer blown films often curl, particularly if the layers are not distributed symmetrically. A quantitative model is developed for predicting curl based on continuum mechanics: curl is the result of differential shrinkage between layers during quenching and is moderated by the stiffness and thickness of the layers. The difficulty in using such an approach is estimating differential shrinkage. Pressure-Volume-Temperature (PVT) data give good qualitative information on differential shrinkage, but they are generated under experimental conditions that differ greatly from commercial blown film processes. To correct the PVT data, a semiempirical approach is utilized. The model is run backwards" to compute the differential shrinkage in two-layer structures where the curl has been measured. From this PVT correction factors are obtained to predict the curl of multilayer structures.The model is applied to a (HDPE-tie-EVOH-tie-sealant) cereal liner structure. A sensitivity analysis shows that increasing the thickness of the HDPE layer reducing the shrinkage of the HDPE and reducing the thickness and stiffness of the EVOH layer can reduce curl. Experiments on a five-layer blown film line confirm the model predictions: a standard cereal liner structure had severe curl yet by using the model as a guide we were able to make essentially flat film."
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