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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Experiments with Hot Tool Joining of Thermoplastics to Perforated Mild Steel
Lightening of structures to improve fuel efficiency of automobiles requires joining of dissimilar materials like metals to plastics. In this work, four thermoplastics, HDPE, polypropylene, acrylic and polycarbonate, were joined to mild steel sheets in a lap shear configuration using a heated tool. The steel sheets were perforated with a fine hole pattern and heated for a preset time by pressing it against a hot tool that was kept at a high temperature. Then the steel sheet and the hot tool were retracted, and the cool thermoplastic sheet was pressed against the hot metal surface for a preset time. The hot metal would then melt the thermoplastic surface resulting in flow of thermoplastic into the holes as well as wetting of the steel surface resulting in joining of the parts. For all the thermoplastics increasing the heating time increased the joint strength until an optimum was reached. Increasing the open area in the perforated steel generally resulted in the stronger joints. The strongest average lap shear strength was 4.6 MPa for HDPE, 6.7 MPa for polypropylene, 8.3 MPa for acrylic and 7.3 MPa for polycarbonate.
Understanding Spiral Mandrel Dies: Layering Effect and Gauge Uniformity
In this paper, the effect of the number of spiral overlap on the gauge uniformity of a blown film die was investigated. A typical center-fed spiral mandrel die and a special feed block were used for the tests. Every other spiral was fed with black and white master batches respectively. The layering effect was examined by monitoring the cross section of the thick sample at the outlet of the die. The film was also produced at two different thicknesses and the gauge uniformity along the circumference of the die was checked. The results showed that with increasing the number of overlap, gauge uniformity was improved. For better understanding the complex flow in spiral mandrel die, the flow on the die was also analyzed using a commercial available software package.
Force Controlled Friction Riveting of Glass Fiber Reinforced Polyamide 6 and Aluminum Alloy 6056 Hybrid Joints
The use of metal-composite hybrid structures is an efficient solution to reduce weight and fuel consumption in the transportation industry. Some conventional joining techniques for hybrid structures, such as traditional mechanical fastening and adhesive bonding are being used but have shown limitations. The present work intends to demonstrate the feasibility of the FricRiveting process to aluminum alloy 6056-T6 and glass reinforced polyamide 6 as well as to investigate the influence of the process parameter Forging Force on the joint formation (changes in the depth and width of the metallic rivet anchoring zone) and tensile strength. For that a new joining equipment and approach were used. The process was divided in three controlled steps: the first step was controlled by spindle displacement; the second step was controlled by rotational speed while the third step was time-controlled. The correlation between the rivet deformation (volumetric ratio) and the tensile strength was studied, as well as presumptive physical-chemical changes in the polymer (thermo-mechanical degradation) due to the high temperatures achieved in the process. The maximum average ultimate tensile strength for the selected conditions was 5041ñ 170 N (95% ñ 3% of the ultimate tensile force of the metallic rivet) and the polymer did not show any significant level of thermo-mechanical degradation.
Studies on the Blending of Abs/Pla for Creation of a New Green Engineering Polymer
Studies on the development of high performing ABS/PLA polymer blends have been done. The mechanisms of individual polymers have been investigated, showing the crystallization of PLA can highly influence its toughness. This can be controlled through process engineering during the molding of the polymer. In addition, ABS has been shown to undergo a crosslinking reaction during the timeframe of melt processing. Understanding these mechanisms has been crucial in the development of high performing ABS/PLA blends that have similar properties to the original ABS. These blends and their properties are discussed.
The Testing Program at NIST on Fibers Used in Soft Body Armor Applications
A first responder?s soft body armor failed to stop a threat for which it had been designed. Subsequent work at the National Institute of Standards and Technology (NIST) through the development of a suite of tests pointed to a possible synergistic combination of hydrolytic degradation and mechanical degradation due to folding on the fiber that comprised the soft body armor. The goal of this paper and presentation is to give an update of the research effort to date being conducted at NIST on polymeric fibers used in soft body armor with a special emphasis on new fibers under consideration. The overview covers mechanical fiber testing, microscopy, and spectroscopic techniques used to understand potential mechanisms of degradation in these materials. An update of our high strain rate effort will also be given.
Linear Vibration Welding under Industrial Conditions
Due to the increasing demands for weight reduction and integration of function, especially in the automotive field, components made of metallic materials are increasingly being substituted by components made of thermoplastic materials. In contrast to this, despite the high process understanding of vibration welding and the knowledge of the process-structure-property relationships, with theoretically achievable weld strengths of 90 % to 100 % of the unreinforced base material strength are far higher than can achieved in industrial series production. The complexity of an industrially manufactured component is simulated by using plate test specimens. The results of the welding experiments show that different wall thicknesses in the weld area, component warpage and different friction angle within the weld leads to nonuniform local process conditions during linear vibration welding process. This results in local weak spots, which reduce the total component strength. These local weak spots can be reduced by using alternative process strategies, such as in-process pressure variation and IR preheating. So not only the local strengths but also the total component strength can be increased. This is shown with the example of component warpage.
Effect of Added Plasticizer on Moisture Diffusion through Polylactic Acid/Clay Nanocomposites
Polylactic acid (PLA), a bio-derived, biodegradable polymer, is being used as a substitute for conventional, non-biodegradable polymers in packaging applications. However, it has poor barrier properties for gases and water vapor, and these can be improved by dispersing nanoclay platelets in the polymer. In this work, the effects of adding nanoclay and a plasticizer, namely acetyl tributyl citrate (ATBC), on the water vapor permeability of PLA films have been evaluated; a variety of mixing methods were employed. It was found that while nanoclay addition can help in lowering the permeability through both the plasticized and unplasticized PLA, the effect was less than anticipated in the presence of the plasticizer. However, if the nanoclay dispersion was assisted by ultrasonication, the results in the two cases were comparable. In addition, it was found that the method of mixing during nanocomposite preparation also had significant effect on the permeability properties of the plasticized samples.
Coextrusion Processing of Multilayered Dielectric Polymeric Films
Current state-of-the-art biaxially oriented polypropylene (BOPP) film capacitors occupy large volume fraction in many electronics applications such as pulsed power and power conditioning technologies. Other disadvantages of BOPP films include increased losses, reduced energy density and lower breakdown strength at high temperature. Development of multilayered polymeric films with higher energy density and high temperature performance is, therefore, necessary in a wide range of applications. As demonstrated in this work, coextruded films of poly(vinylidene fluoride) (PVDF) and polycarbonate (PC) have been successfully developed for the use up to 140 øC. For further dielectric properties improvement, interfacial properties of the PC and PVDF layers were manipulated using a tie layer. Poly(methyl methacrylate) (PMMA) was used as tie layer to investigate its impact on the dielectric performance of PC/PVDF films. In previous work, PMMA was successfully used to improve the breakdown strength of the multilayered films of PVDF-copolymer and PC. This paper will demonstrate development of multilayered capacitor films and effect of PMMA tie layer on dielectric properties for high temperature applications using coextrusion technology.
Study the Effect of hBN Fibre Content and Aspect Ratio on PLA Based Composite Thermal Conductivity
As electronic devices become smaller and more powerful, heat concentration and as a result heat dissipation would highly affect their efficiency. Also with rising awareness about environmental protection, using bio-based (green) materials as electronic packaging is more important than before. In this context in this research liquid crystal polymer (LCP), hexagonal boron nitride (hBN) high thermally conductive composite fibers were produced and effects of LCP-hBN fiber content and aspect ratio in composite with Poly-lactic acid (PLA) on effective thermal conductivity of the composite were studied. Based on previous studies the largest thermal barrier effect against increasing thermal conductivity of composite is filler particles percolation and phonon scattering at filler particles boundaries. In this study it is observed that the same thermal conductivity as pure fiber can be achieved in composite with lower fiber loading, as long as suitable fibers interaction exist at optimized fibers aspect ratio. This suggest that at right filler content and aspect ratio it is possible to eliminate filler percolation thermal barrier effect and transfer all of the received phonons through the composite thermal pathways rather than scattering them.
Low-Permeation Toughened Polyoxymethylene (Pom) for Injection-Molded and Blow-Molded Tanks in Small Off-Road Engine (Sore) Applications
Polyoxymethylene (POM) polymers exhibit excellent chemical resistance against various chemical substances, such as hydrocarbons. However, due to POM?s relatively low impact strength, its use in containment of chemicals, such as chemical bottles and tanks, has been limited. The development of both injection-moldable and blow moldable low-permeable, toughened POM will be discussed. Impact-modified POM, using a coupling technology, has been molded into gasoline tanks for small off-road engine (SORE) applications. The tanks passed the impact requirement, while maintaining the fuel permeation performance below the regulation limits by US Environmental Protection Agency (EPA) and California Air Resources Board (CARB).
A Study of PEEK/hBN Composites as a Commercial Material Option
This study analyzes the bulk material properties of a PEEK/BN composite and provides a comparison to the commercial PEEK resins including unfilled, carbon fiber filled, and glass fiber filled materials. It was found that the BN filled PEEK had a similar storage modulus, measuring lower than the carbon fiber filled and higher than the glass fiber filled materials, at temperatures both above and below the glass transition temperature. The thermal conductivity of the BN filled PEEK was higher than all of the commercial grades when measured in the in-plane direction. The BN composites also possessed a similar toughness of the commercial grades, but the weld point of the BN filled matrix was more fragile than the commercial systems.
Isothermal Crystallization of Isotactic Polypropylenes: Experiments and Simulation
The isothermal crystallization of isotactic poly?propylenes (iPP) was investigated by polarization micro?scopy (PLM). The crystal radius evolution and the transformed volume fraction were obtained by PLM experiments. In this paper, a general differential system for 2D quiescent conditions was adopted to describe the crystallization evolution of iPP. Matlab was used for the simula?tion of the crystallization evolution. There was good agreement between the experimental and simulation results of the transformed volume fraction and the radii of crystals for the 2D condition.
Thermal Analysis of Polylactic Acid and Corn Zein Composites
Polylactic acid (PLA) was blended with corn zein and various compatibilizers in order to study a composite with potentially improved barrier and thermal properties. Thermogravimetric analysis (TGA) was used to characterize the thermal stability of the composites in comparison to pure PLA, and it was determined that the thermal properties, specifically the onset degradation temperature and rate of degradation of PLA and its composites are extremely dependant on the test method utilized. In this study pure Natureworks 2002D PLA displayed onset degradation temperatures ranging from 306øC to 360øC, depending on whether or not an isothermal hold was incorporated into the TGA method. Rather than improving the thermal stability of the PLA, the addition of corn zein catalyzed the reaction, increasing the rate of degradation, and decreasing the onset degradation temperature.
A Study on the Effect of Twin-Screw Melt Blended Nano-Fillers on Polypropylene Nanocomposite Hybrid Electrical and Morphological Properties for Supercapacitor Applications
The electrical conductivity of polypropylene (PP) was improved via the addition of carbon-based nanoparticles such as graphene and multi-walled carbon nanotubes (MWCNT). In addition, a hybrid composite structure consisting of PP matrix, polyaniline conductive polymer, as well as carbon-based nanofillers. The samples were fabricated via melt blending technique which is capable for large scale industrial production. Electrical conductivity measurements determined that the electrical performance of nanocomposite was increased 10 orders of magnitudes to a maximum value of 2.5?10-4 S/cm, achieved by 20wt.% polyaniline (PAni), 5wt.% MWCNT, and 75wt.% PP samples. The increase in electrical conductivity was attributed to the formation of conductive networks observed under SEM and AFM. The samples were further characterized via TGA analysis technique to verify its content. These nanocomposites are developed for future supercapacitor current collector applications.
Effect of Glass Fiber on Mechanical Properties of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)
Bacterial polyester, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), with two different 3HH molar fraction were mixed with short glass using mini-extrusion and injection moulding process. The effects of short glass fiber addition on tensile properties were analyzed. The tensile strength and elastic moduli of both resins were significantly increased while failure strain decreased with increasing fiber loadings. Young's moduli of the composites at different fiber loadings were compared with five different micromechanical models. It was found that the model proposed by Pan has the best match with our data.
Characterization of Solution Cast Exfoliated Graphite Nanoplatelet / Polylactic Acid Nanocomposite Films
Exfoliated graphite nanoplatelets (GNP) / polylactic acid (PLA) composite films are fabricated using solution casting. GNP is dispersed in a chloroform suspension via ultra-sonication and the GNP/chloroform suspension is added to a PLA/chloroform solution. The solution is then casted yielding nanocomposite films with a thickness of ~200 ?m. Film morphology, examined using scanning electron microscopy (SEM), indicates minimal surface defects, but significant micro-porosity. The thermal behavior and crystal structure are examined using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The films display high crystallinity of only one à phase crystal form. The mechanical properties are greatly improved upon compression molding the films samples after solution casting due to the evaporation of remnant solvent and the decrease in micro-voids caused by the applied pressure.
On the Entanglement Density and Chain Stiffness of Copolycarbonates Containing Rigid and Flexible Linkages
Thermal and rheological properties of LexanTM XHT (rigid) and LexanTM HFD (flexible) copolymers were investigated using oscillatory rheology and thermal characterization techniques. The incorporation of 20% rigid co-monomer on a neat Lexan TM has increased the glass transition temperature (Tg) by 30øC while increasing the entanglement molecular weight by 50%. Also, for the copolymer with a flexible co-monomer, the glass transition temperature (Tg) has decreased by 20 øC while hardly affecting the entanglement molecular weight. These results suggest properties related to chain stiffness can vary in a non-linear fashion with the nature of co-polymer content.
Fatigue Performance of Fused Deposition Modeling Style 3D Printed vs. Injection Molded Ultem 9085
Advancements in fused deposition modeling (FDM) have provided an opportunity for the production of functional, lightweight parts for advanced automotive and aerospace applications. Designing reliable parts requires a thorough understanding of the tensile and fatigue properties of not only the material, but of the complex printed structures. In this paper, polyetherimide/ polycarbonate copolymer blend (PEI/PC) tensile bars were fabricated by both FDM and single- and double-gated injection molding for tensile and fatigue properties studies. FDM bars were printed vertically and horizontally to compare the anisotropic effects inherent to the fabrication method. The density of the FDM parts was also varied by controlling the degree of contact between printed toolpaths. All FDM samples exhibited lower modulus, yield/break stress, density and endurance limit compared to injection molded parts. A different fatigue behavior from classic fatigue theory was also found to occur in the FDM samples.
A New Styrenic Block Copolymer Designed for Polyolefin-like Processing for Compounding, Films and Fibers
Block copolymers are highly valued for their ability to be extruded and injection molded in combination with other materials. However, they are typically processed in the phase separated state. The high melt elasticity of the phase separated block copolymer leads to a variety of problems with mixing and small dimension articles such as films, fibers and thin walled parts. A new hydrogenated styrenic block copolymer has been designed to process as a single phase melt but retain its two phase nature at use temperatures to provide strength and creep resistance. The processing and resulting properties of the pure polymer and combinations with a variety of polyolefins will be explored.
Abrasive Wear and Speed Relationship in Technical Compounding
An accelerated wear test was performed in a 60 mm TriVolution? compounder. An aluminum element was placed before the melt zone of the extruder where wear was expected to be highest. 50 lb of an abrasive compound were mixed in the extruder and the weight of the elements was measured before and after the test. The test was repeated at different speeds. It was found that with increasing speed a rapid increase in wear per pound of material could be observed. It was determined that it is beneficial to operate the extruder at low speed and high torque as this produces less wear than operating at high speeds and low torques.
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