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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A New Evaluation Method of O-Ring Rubber Seals by Compressive Load Test
O-ring Rubber seals are widely used for hot water pipes and various parts of residential gas appliances for water heating. Although there is much know-how on design, there are few researches on the durability of O-ring rubber products. Hence, it is very important to understand the mechanical properties and durability of O-ring for long-term usage in safety. In this study, we had immersed several kinds of commercial O-rings with the same size and different components into hot water with and without aqueous chlorine solution for up to 18,000 h. And we tried to apply a compressive load test for the O-ring rubber in order to evaluate the mechanical properties after the accelerated degradation test. From the result, it was found that the compressive load for the displacement of O-ring immersed into chlorine-containing hot water indicated severely degradation as compared with that of O-ring immersed into hot water. In addition, it was also found that the measurement result of compressive load sensitively indicated the same tendency with the result of compression set test.
Effect of Screw Geometry on Long Glass Fiber Breakage during Injection Molding
The aim of this work is to compare the effects of two different 40 mm screws on fiber breakage during plastication. A polypropylene, reinforced with 30% long glass fibers, was tested. A standard three zone screw and a special profile screw were compared. The special screw has low compression ratio, a dynamic mixer and it is tapered over the whole length. The pitch is variable, increasing from the feeding zone to the screw front; the combination of these features gives higher productivity with better melt homogeneity and a very consistent dosing time end cushion. The plastication was performed at two different process conditions and the screw pull-out technique was used. The fibers length was measured at different distances from the hopper after the matrix pyrolysis. The experiments show that the different geometry of the screws, within the selected conditions, did not affect the fiber breakage. Residence time and aspect ratio of pellet length to channel width and length were also considered. A procedure was developed and validated in order to allow an accurate comparative analysis of the fiber breakage progression during plastication.
Grain Development & Grain Repair on a 7,Xxx-Series Aluminum
Engineers at GM have been developing an injection mold tooling strategy based on the use of aluminum to meet low, medium, and high volume production part requirements. This scalable tooling strategy marries the appropriate aluminum with the appropriate tool construction to satisfy production demands while minimizing tooling capital investment and piece price. Implementation has required engineers to overcome both cultural prejudices against the use of aluminum and technical roadblocks like the ability to grain a part?s surface. This paper reviews the work accomplished by GM and Alcoa in regards to grain development and repair on a 7,XXX-series aluminum, QC-10.
Direct Fiber Feeding Injection Molding of Glass Fiber Reinforced Polyoxymethylene/Poly (Lactic Acid) Blend Composites
In this study, the short glass fiber reinforced POM, PLA and POM/PLA blend composites were fabricated by a direct fiber feeding injection molding. The glass fiber contents were controlled by the matrix feeding speed. The mechanical properties were investigated by tensile testing method. It was found that the tensile modulus of all composition increased with increasing glass fiber content by the results of POM/PLA blend composites indicated the intermediate value between PLA and POM composites. Tensile strength of POM/PLA blend increased nearly the same with POM composite at low glass fiber content. The critical fiber length that was calculated by modified Kelly and Tyson`s equation was used to calculate interfacial shear strength. The critical fiber length of them did not change significantly. However, PLA composite has a high interfacial shear strength even all of them revealed a fair interfacial adhesion between glass fiber and matrix that were observed by scanning electron microscope.
Nylon in Automotive ? Four Case Studies
Nylon is a Polyamide (PA) that has been used for many years in automotive components due to its good balance of cost and performance. One drawback with nylon is its moisture absorption. After an introductory discussion, several case studies are presented where the moisture affinity of nylon was an issue in the development and testing of automotive components. One case involves a toughened nylon, a second involves a 50% glass filled nylon, a third involves a plasticized, toughened nylon and the fourth and final case reviews an issue with a decoratively coated nylon part. The focus in all cases is on one or the other of the two most common nylon materials, nylon 6 (PA6) and nylon 66 (PA66). Engineers need to be aware of potential moisture issues very early when designing parts and test programs with nylon materials.
Percolative Multilayered Dielectrics with Confined Alignment of Conductive Particles
Percolative dielectric composites are currently high-profiled due to the ultrahigh permittivity. However, the undesired giant loss and ultralow breakdown strength greatly inhibit the applications in energy field. By replacing the surfacial modification methods by a convenient route, conductive particles were alternately aligned in separate layers in this work. Polyvinylidene fluoride (PVDF)-based multilayered dielectrics containing confined carbon black (CB) were fabricated using a layer-multiplying extrusion. For a given thickness, the dielectric permittivity significantly enhanced with the layers. At the layer number of 256, the permittivity at 103 Hz became 6 times higher than neat PVDF. Furthermore, the presence of barrier PVDF layers distinctly improved the breakdown strength by hundreds times compared with PVDF/CB conventional composite at same loading. The present approach significantly broaden the choices of dielectric materials for new generation clean energy applications.
The Effect of Hydroxyapatite Surface on Osteo-differentiation of Human Mesenchymal Stem Cells using Serum Free Media
The manner by which human mesenchymal stem cells (hMSCs) are influenced to differentiate is an area that has been intensely studied. In this study we have observed that the in vitro biochemical differentiation of hMSCs was inhibited on a lamellar hydroxyapatite surface. hMSCs were differentiated on standard tissue culture treated 24 well plates and also on
hydroxyapatite coated plates using osteogenic serum free media. It was found that hMSCs did not differentiate into osteocytes under any conditions using serum free media on the hydroxyapatite coated plates, while differentiation of the cells did occur when tissue culture plates were used. Some mechanistic investigations were conducted to
determine the cause of this inhibition. As of this writing it is difficult to assign a single root cause for this result, but depletion of calcium and phosphorous levels over the hydroxy apatite surface may play a role.
Fracture Behavior of PA6 Rubber Blends Influenced by Water Absorption
It is well known that the properties of polyamide 6 (PA6) can be strongly influenced e. g. by either blending with a rubber phase, by water absorption or by a combination of both. The fracture behavior of PA6 and PA6 blends can be evaluated more thoroughly, when using the method of essential work of fracture (EWF) and the ductility level as evaluation criteria. In this investigation, differences in the blend morphology between a dispersedly dissolved rubber phase and a co-continuous morphology were detected by means of the method of EWF. An initial raise in the specific essential work of fracture in comparison to the dry-as-molded state caused by low moisture absorption, is followed by a drop with further increasing moisture. In contrast, the specific non-essential work of fracture is only influenced by a higher moisture uptake.
Effect of Varaible Fiber Orientation on Material Properties in Extruded Polymer Composties with Multi-Scale Additives
In this experiment, carbon microfibers and multi-walled carbon nanotubes were compounded into a poly-butylene terephthalate polymer matrix. PBT-based composites were compounded in a co-rotating non-intermeshing twin-screw extruder with various fractions of carbon microfiber and multi walled carbon nanotubes additives. In addition, two dies ? straight and divergent ? were used to explore differences in physical properties.
Mechanical and thermal properties were tested and the results compared for straight and divergent dies. Optical images were analyzed to study the behavior of microfibers in flows through straight and divergent channels. A correlation was shown between the die type, the structure in the optical images and the physical properties.
Degradation Analysis for Polyethylene of Raised Temperature Resistance after Long-Term Hot Water Immerssion and Hot Air Exposure Tests
Polyethylene is widely used as a lifeline pipe for water and hot water supply plumbing in domestics. Recently, plastic pipes are required the performance of not only long service life but also recyclability. Non cross-linked polyethylene with durability and recyclability are beginning to use for heating pipes, for instance the polyethylene of raised temperature resistance (PE-RT).It is meaningful that the degradation of the PE-RT mechanism at high temperature is revealed for developing higher durability pipes and diagnosing used pipe?s deteriorations
In this study, as non-cross-linked polyethylene acceleration testing of PE-RT test piece was performed for long term under hot water and air condition to clarify the degradation state chemically compared with mechanical and anti-oxidation properties. FT-IR and Raman mapping method was used to examine the distribution of oxidation state, anti-oxidant additives quantity and crystallinity.
The oxidations of polyethylene were not found, but anti-oxidant additives were remarkably reduced, which coincided with oxidation induction time (OIT) decrease. It was found particularly in about 80 ?m from the surface of only hot water test samples, the reduction was accelerated because of the elution to hot water. The tensile strengths were increased compared with initial and almost the same regardless of test times. The heat of fusion varied similarly with the tensile strength, which means thermal crystallization. On the other hand, tensile elongations at break were slightly reduced at long time. It was found the dispersion degree of crystallinity was bigger over test time from the analysis of Raman peak intensity ratio (crystal to amorphous) and the dispersion in hot air are remarkable. This inhomogeneous crystallinity is assumed to decrease the elongation by deformation or defects in micro region.
Modified Soybean Oil Plasticizer in Carbon Black Filled Sbr
Soybean oil (SO) was modified through the reaction with dicyclopentadiene (DCPD) at a pressure of 0.14-0.21 MPa and a temperature of 240øC. Carbon double bonds in the soybean oil molecules were converted into norbornyl groups of different ratios. SBR compounds with 60 phr of carbon black (CB), 30 phr of different extender oils including SO, modified SO (MSO) and naphthenic oil (NO) were prepared. The gel fraction, crosslink density, curing behavior, mechanical and dynamic properties and reactions between the SO, MSO and curatives were investigated. It was found that with an increase of the modification level, the gel fraction of the SBR/MSO vulcanizates slightly increased while the crosslink density decreased. The SBR/MSO compounds exhibited faster curing. Their vulcanizates showed lower modulus and higher elongation at break and tensile strength in comparison with the SBR/NO vulcanizates. The tire performance predictors based on the dynamic mechanical analysis indicated that the use of SBR/MSO compounds in tire tread expected to improve traction but increase rolling resistance compared to the SBR/NO compounds. After adjusting the curative recipe, the tensile properties and abrasion resistance of the SBR/MSO vulcanizates were tremendously improved. Use of this recipe is expected to achieve similar traction and lower rolling resistance compared to the SBR/NO recipe. The addition of MSO to SBR showed improved mechanical properties and had a promising possibility to replace petroleum oils in the rubber improving safety in tire production.
Correlating the Melting of Semi-Crystalline Polymers to the Shrink Wrapping Process in Shrink-Film Packaging Applications
Thermal collation shrink packaging technology involves the release of polymer orientation in the film upon heat exposure in the collation shrink heat tunnel. The selection of the resin, coextruded structure design, the extrusion film line design, and the process parameters all affect the polymer orientation and subsequent release to form the shrink package. In the typical shrink wrap process; the oven temperature and conveyor speed provide the required thermal exposure to release the polymer orientation causing the film to shrink.
It has been our experience in dealing with various customers in the Packaging industry that there exists a wide variation in the understanding of the relationship between polymer material science and the shrink process. We believe that bridging this gap would enable practitioners in the industry both design, as well as operate their shrink processes optimally.
This paper addresses the relationship between the melting processes of semi-crystalline polymers used for shrink film packaging application to the shrink process.
Development of Green Polymer Blends Made from Carbon Dioxide Based Polyol and Poly (Lactic Acid)
Poly(lactic acid) (PLA) and Poly(propylene carbonate) (PPC) polyol were melt-compounded to fabricate a novel polymer blend with balanced mechanical properties (tensile strength and ductility). Blend with 90wt.% PLA/10wt.% PPC polyol and 70wt.% PLA/30wt.% PPC polyol were prepared and evaluated in terms of mechanical performance. As for the blend with 30wt.% PPC polyol, two residence time have been applied (1min and 2min). It was found that 10wt.% loading of PPC polyol has an adverse effect on both tensile strength and elongation at break of the blend. Overall mechanical performance deteriorated with only 10wt.% PPC polyol. Major finding was that with incorporating 30wt.% PPC polyol in the polymer blend system, the ductility (elongation at break) of the blend significantly improved by 5000%. However, the tensile strength decreased drastically. The morphology of the blend was investigated through scanning electron microscopy (SEM).
Stimuli Responsive and Biomineralized Scaffold: An Implant for Bone-Tissue Engineering
Development of bioactive and stimuli responsive materials in the form of implant/scaffold is the urgent need that mimics the natural bone structure and function. To achieve such novel smart biomaterials ?PVP-CMC-CaCO3? scaffold was prepared using PVP-CMC hydrogel as a matrix, following the biomimetic mineralization process i.e. simple liquid diffusion technique. The main concern of this study is to establish its stimuli responsive nature as it is one of the important factor of biomaterials. The swelling-deswelling capacity of ?PVP-CMC-CaCO3? scaffold was carried out at 37oC using physiological solution. The morphological changes which occurred in the biomineralized scaffold during swelling-deswelling-reswelling and deswelling steps were confirmed using scanning electron microscopy. The obtained results concerning shape-size and thickness indicated that PVP-CMC-CaCO3, a hydrogel based scaffold is a true stimuli responsive biomaterial.
Rheo-Kinetic Study of a Model TPU System for Reactive Extrusion
Bulk polymerization of thermoplastic polyurethanes (TPU) in reactive extrusion is a very complicated topic. Understanding how to efficiently produce TPUs is dependent upon the relationship between the extrusion process and the polymerization. The goal of this study was to determine the response of the polymerization kinetics to both composition and shear rates. Rheological measurements were taken while concurrently collecting in situ Fourier transform infrared (FT-IR) spectra. The results indicated that polymerization kinetics were sensitive to both the hard segment (HS) composition of the system and the shear rate imposed on the system.
Environmental Qualification of Cables to IEEE Standards and End-User Specifictions
General Cable Corporation recently committed to a multi-year effort on development and qualification of 60-year life Class 1E cables. The major milestones achieved in the development include (a) Introduction of 60-year life nuclear cables in the industry (b) Approval of 60-year cables for service in the new nuclear power stations (Vogtle site and V.C. Summer site) and (c) Use in a new generation nuclear reactor power plant AP1000 designed and sold by Westinghouse Electric Company. Cable constructions tested were 600V cables, 2 kV cables and 15kV MV power cables. This paper presents the scope of overall qualification program and test results conducted per IEEE standards and end-user specifications. The cable testing will be discussed in relation to thermal aging and radiation exposure followed by DBE (Design Basis Event) accident conditions.
Fractographic Examination and Tensile Property Evaluation of 3D Printed Acrylonitrile Butadiene Styrene (ABS)
Acrylonitrile butadiene styrene (ABS) tensile specimens produced by 3D printing in two different orientations, injection molding, and subtractive machining were fractured by tensile overload in accordance with ASTM D638. In this study, the tensile properties and fracture surfaces of the different manufacturing methods are compared and contrasted using optical microscopy, computed tomography (CT) and scanning electron microscopy (SEM). CT reconstructions of the pre-failed tensile bars and images (optical and SEM) of the fracture surfaces are provided and discussed.
Soy- and Biochar-Based Fertilizer
Compounds of soy flour, biochar and a polymer matrix, such as PLA, have proven to be effective fertilizers comparable to commercial products. Prototype composites achieved NPK values of 2.85, 0.20, 0.49 and 3.08, 0.21, 0.48 %, respectively for PLA- and PHA-based composites. These composites only leached a fraction of nitrogen compared to a commercially available synthetic fertilizer. Low leachate values, as compared to commercial fertilizers, may be associated to the absorption and releasing of nutrients by biochar. The nitrogen within the soy is also not readily water soluble and is released over time by microbial action.
Study on the Relationship between the Degree of Crystallinity and the Ultrasonic Velocity for Poly(Lactic Acid) (PLA) Parts
The relationship between the degree of crystallinity and the ultrasonic velocity was analyzed in this study for injection molded poly(lactic acid) (PLA) parts undergoing an annealing process. An annealing process was first employed to produce PLA parts with different degrees of crystallinity. Next, a novel ultrasonic water immersion method was presented for calculating the ultrasonic velo?cities of these annealed PLA parts. Then, the ultrasonic velocity results were plotted with the crystallization re?sults from differential scanning calorimeter (DSC) mea?sure?ments for analysis. Experimental results show that the inverse effective ultrasonic velocity versus the degree of crystallinity over the whole crystallinity range for three different annealing temperatures show good linearity, with a correlation coefficient of around 99%. The linear rela?tionship observed in this study might provide a novel method for investigating the degree of crystallinity of semi-crystalline polymers in practical production.
Novel Porous Nano-Graphene/Polyimide Composite as Electrode Material
In this work, we have studied the electrochemical behavior of non-porous and porous nano-graphene/polyimide composite films fabricated by the thermal degradation of grafted flexible acrylic acid on polyamic acid backbone. It is observed that pore size distribution has a significant effect on specific capacitance and bulk resistance of the composite material. BET and Electrochemical impedance spectroscopy (EIS) data reveal a complex pore distribution for the materials. As the porosity of the composite material increased, its bulk resistance decreased by up to 400% and the specific capacitance increased by up to 200%. Ionic diffusion resistance associated with the pore structure for the porous composite decreased due to easy access of electrolyte ions through the pore length of the material. Specific capacitance of up to 34,240mF/g was obtained for the composite system at a scan rate of 50mV/s which remained fairly stable through the 50 cycle runs. Potassium hexaflorophosphate (KPF6) dissolved in propylene carbonate was used as electrolyte for all the electrochemical techniques.
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