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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Knowledge-Based, Iterative Approach for an Automatic Cavity Balancing for Injection Molding
Today, most CAD systems have integrated simulation features. These accelerate the development of injection-molded parts because of tight connection of the CAD and CAE system. Knowledge-based design and analysis features are as well implemented as tools for the determination of the gate position. The drawbacks of these solutions are the limited access to the calculation methods and the possibility for modifications or extensions. Therefore, a knowledge-based approach for an automatic flow balancing was developed. By local decreases or increases of the nominal wall thickness the filling of the cavity is improved. The positions and sizes of these geometry changes are determined iteratively during an optimization routine, which is presented in this paper. Finally, the approach is verified in a case study.
Mechanical, Thermal and Electrical Property Enhancement of Graphene-Polymer Nanocomposites
In this work, NanoXplore’s proprietary graphene nanoplatelets, heXo-G V20, are melt-extruded into thermoplastics LLDPE, HDPE and TPU. Graphene is shown to effectively increase the stiffness and the strength of a matrix TPU. The flexural and tensile moduli increase with loading levels of graphene whereas the tensile strength increases at low loading levels, but does not further increase at higher graphene concentrations. A ten fold increase in thermal conductivity was achieved by adding heXo-G V20 graphene to LLDPE matrix. The thermal conductivity percolation threshold was reached at 10% loading. At 1% loading of graphene the onset of the decomposition temperature and maximum weight loss temperatures were shifted by about 50°C, significantly improving the thermal stability of the PE matrix. Fourteen orders of magnitude increase in electrical conductivity of HDPE was obtained at 30% loading of graphene. Excellent EMI shielding of 40 dB was achieved with 20 wt% addition of graphene in a TPU matrix.
Polymer Modifications in Asphalt Roofing
Polymers have been widely used in asphalt roofing industries in order to reduce premature failure and improve final performance such as cracking and impact resistance, which is difficult to be achieved by asphalts alone. This work focuses on styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene/butylenestyrene copolymer (SEBS), and Elvaloy modifications on asphalt roof coatings. The thermal susceptibility, low temperature cracking propensity were investigated and compared with unmodified version to present the advantages and challenges of polymer modifications. From the perspective of manufactures, the possibility to double stack roof pallets were estimated based on blocking resistance evaluation via an axial rheological method.
Orienting Melt to Produce on Lab-Microscale High Performance and Ultra Thin Foils
Efficient molecular orientation of polymers in the melt- or solution state requires concentric contraction flows, which result in single or multi-filament fiber shaped products. Directed molecular orientation in pipes, sheets, foils and films, like strip bi-axially, planar or tri-axial, are difficult to achieve and require complex multi-stage processing often supported by the addition of extra external magnetic, electric, or temperature gradient fields that put constraints to the materials to be processed. Here we aim at a simple continuous process to produce uni-axially oriented foils, by designing a special die in a standard miniaturized laboratory scale film casting process. The internal of the die consist of a fiber forming, and a fiber fusing part. The specific design of the fiber forming part allows the combination of the fibers formed, without them crossing, into a line that forms a sheet. Flow in the total volume around the slit ends up in molecularly oriented flow inside the slit. To preserve orientation, an air gap extrusion process follows the exiting slit flow, to allow for a strong draw down under high melt stress. Small air-gaps and a cold cooling nose, combined with a supporting carrying film, make the total process easy, clean and cheap, and the products unique. We will demonstrate that, mounted on the miniature Xplore MC 15 lab compounder, the device is able to produce not only high performance fully oriented foils based on a thermotropic liquid crystalline polyester (Vectra), but also extremely thin foils of polyamides and polyesters. In the last application, the melt orientation is used only to temporary obtain a high melt strength that allows a high draw-ability in the air gap.
Environmentally Benign Processing of Poly(2,6-Dimethyl-1,4-Phenylene Oxide) (PPO) with Superheated Liquids
the expanding industry of polymer processing, a prominent area of current research is to process polymers efficiently without creating any environmental hazards. Processing of intractable polymers like PPO requires high processing temperature and toxic plasticizers. Very few research works have reported the use of superheated liquids to process intractable polymers. This research work presents a systematic study to explore the advantages of processing PPO with superheated liquids composed of ethanol and water. Microcellular foams of PPO having a density range from 0.13 to 0.56 g/cm3 can be produced with the aid of superheated ethanol, water and ethanol/water mixtures. Such foams also exhibit high specific strength. In addition, PPO can also be extruded with superheated ethanol or ethanol/water mixtures at a temperature which is 150 to 180 °C below the conventional extrusion temperature for PPO.
Failure Analysis and Product Improvement of Medical Device Tubing
Manufactured products are expected to serve their useful lifetime without premature failure. When premature failure does occur, it is important to determine the root cause. This is particularly important in high-consequence applications such as medical products. In this case study, the analysis of polyurethane tubing that became yellowed and cracked is presented. The mode of failure was determined using multiple analytical methods, the hypothesis was tested, and additional analyses were performed to confirm the root cause hypothesis. In addition, a modification to the composition of the medical tubing was suggested and implemented. The efficacy of the modified composition was assessed, similar to the failure analysis protocol, using microscopy, spectroscopy, and chromatographic methods. The results of this failure analysis and product improvement project will be presented.
Fabrication of High Strength and Toughened Biodegradable Electrospun Fibers: Poly(Lactic Acid)/Biomax Blends
The objective of this study is to prepare a toughened and strengthened electrospun fibrous biodegradable poly(lactic acid) (PLA) mat blended with Biomax, an ethylene copolymer designed to modify PLA to improve toughness properties, using electrospinning. Morphological, thermal, mechanical, and thermomechanical properties of PLA/Biomax blends were investigated. Morphological findings indicated that the electrospun PLA/Biomax fibers were uniform and smooth with an average diameter of 1.4-1.5 µm when Biomax contents below 2 % (w/v). The addition of 1 % of Biomax improved both thermal stability and mechanical properties of PLA/Biomax fibrous mats. PLA/Biomax mats with 1 % (w/v) of Biomax exhibited the maximum tensile strength of 4.6 MPa and tensile modulus of 103 MPa showing 64.3 % and 101 % improvement; as compared to neat PLA values of 2.83 MPa and 51 MPa, respectively. Furthermore, the presence of 1 % Biomax into electrospun PLA fiber mats improved the storage modulus by 107.5 % compared to PLA fiber mat (41.5 MPa). Strong and toughened PLA/Biomax biodegradable fibrous mat might be potentially suitable to be used in packaging, filtration, reinforcement of composite, etc.
Fabrication and Characterization of Electrospun Polyvinyl Alcohol Fibrous Nanocomposite Reinforced with Wood Flour
This paper focuses on the processing of high performance Polyvinyl alcohol (PVA) and wood flour (WF) fibrous nanocomposite mats using electrospinning. Successfully fabricated PVA filled with WF fibrous nanocomposites using electrospinning are hereby reported in the open literature for the first time. The effect of filler materials on fiber surface morphologies was investigated using environment scanning electron microscopy (ESEM). The respective mechanical and thermal properties of the resulting nanocomposite mats were determined as a function of WF contents. The mechanical properties such as tensile strength and tensile modulus improved significantly with the addition of fillers indicating good adhesion and dispersion of filler materials into the matrix. PVA/WF (20 wt%) fibrous nanocomposite showed the maximum tensile strength, and tensile modulus but minimum elongation at break. Thermal results show that introducing WF had no distinct effects in the thermal stability of nanocomposites. The developed fibrous PVA/WF nanocomposites could be of potential use for many industrial applications where high mechanical strength is needed, such as, filtration and mechanicaly reinforced applications.
Modeling the Monoaxial Stretching of Polypropylene Films by a Nonlinear Spring Dashpot Model
The stretching of semi crystalline materials such as isotactic polypropylene leads to an increase of the material characteristics (tensile strength, E-Modulus etc.). The trend towards using wider and faster film production lines causes the need to develop a better understanding of the complex correlation between molecular structure of the raw material, the processing conditions, the morphology of the cast film and the final film properties. In this investigation a viscoelastic model for the simulation of the stretching process is selected. In this study the definition of the suitable material parameters is supported by further characterization of the material.
Relationships between Low Temperature Impact Performance and Structures of Rotationally Molded Crosslinked High Density Polyethylene
The low temperature impact performance of rotationally molded specimen is of great importance for the final products. Crosslinked high density polyethylene (XL-HDPE) is a preferred material for large chemical and fuel tank due to its superior environmental stress crack resistance and high impact strength. In the present research the drop weight impact strength (defined as ARM impact strength) of rotationally molded XL-HDPE was carried out at -40°C and the relationships between impact strength and microstructures were investigated. The results confirmed that the microstructures of XLHDPE molecules in the innermost surface layer dominated the low temperature impact performance of rotationally molded XL-HDPE articles.
A Study on the Entrapped Air Bubble in the Plasticizing Process
In injection molding, gas in the melt causes various defects in molded parts. As well as many other sources of gas in the injection molded parts, the entrapped air during the plasticizing process would be an important source of gas in the parts. The entrapped air bubbles in the screw channel were examined by the screw quenching experiment. To reduce time for investigating the effect of plasticizing condition on the bubble size distribution, a bubble detecting device with a capillary and pressure sensor was designed in this work. The result from the bubble detector experiment with different plasticizing conditions showed a similar trend which is observed in the samples in the screw quenching experiment. It proves the feasibility of the bubble detecting device to examine the bubble size distribution in the screw channel.
A Study on the Halo Surface Defect of Injection Molded Products
The halo surface defect is one of the surface defects of the glossy products. A sudden change of the flow front speed causes the difference in the cooling condition of the surface, resulting in the halo. In this work, a quantified evaluation method for the halo by image processing was developed. Its feasibility was confirmed by compared with visual observation. The strongest influencing factor to the halo was the injection rate. A strategy of reducing the speed difference around the halo location was tested for eliminating the halo. The location of the halo was found by CAE analysis. As the injection rate was reduced to the minimum level at the location, the halo was successfully eliminated. The elimination of the halo was confirmed by both visual observation and the quantified evaluation method proposed in this work.
Designing Electrical and Electronics Equipment for the Circular Economy by Using Recycled Plastics
In order to conserve resources and at the same time spur economic growth, the European Union is pushing to establish a Circular Economy. For global businesses, including manufacturers of electrical and electronics equipment (E&EE), some of the principles of the Circular Economy will likely be applied globally rather than just within the European Union. This paper describes how the recycling of plastics from shredded waste electrical and electronics equipment (WEEE) fits within the Circular Economy, and provides some guidance to manufacturers looking to incorporate these recycled plastics in new E&EE. Furthermore, we provide recommendations on the design of E&EE such that plastics may be recycled more easily in the future.
Surface Texturing of Composite Materials by Induced Damage: Surface Morphology and Friction
Ice is a unique natural substance, whose solid state behavior is deceiving due to the pervasive presence of a liquid-like surface layer, especially at temperatures close to its melting point (>-10°C). As a result, ice is a very slippery, self-lubricating substance on which most materials, thought to give high traction (e.g. elastomers), cannot achieve high coefficients of friction (COF ~ 0.1). Here, we describe the high friction behavior (COF ~ 0.5) of a new class of textured elastomer fiber composites made using a facile fabrication method of cutting and rearranging molded composites. These fibrous TPU composites have uniformly distributed surface protrusions that are capable of penetrating and interlocking with an ice substrate underneath resulting in static COF that are 4- 7X higher the TPU elastomer by itself. Increasing the fiber content improves the surface structure characteristics, namely protrusion density, and hence improves the friction coefficient. Furthermore, increasing the contact pressure increases the depth of protrusion penetration and hence improves the friction force. These structure-property relationships were verifiable through a mechanics model, with the appropriate normalization, that describes the characteristic forces on a single fiber. Strong potential applications of such textured elastomer composites exist for winter safety applications such as footwear and tires.
Rotational Molding of Polylactic Acid and Agave Fiber Biocomposites
In this work, biocomposites of agave fibers (Agave tequilana Weber var. Azul) and polylactic acid (PLA) were produced by rotational molding. In particular, a simple dry-blending technique was used to disperse the agave fibers in the biodegradable polymer matrix. The effect of fiber content was studied (0, 10, 20, 30, and 40 wt.%) and the samples were characterized in terms of morphology, density and porosity to relate with mechanical properties (tensile, flexion, impact and hardness). The results showed that rotomolded biocomposites were successfully produced, but had high porosity leading to lower properties for fiber contents above 10%. It was possible to observe that low fiber contents produced the best morphology, indicating that there is an optimum fiber content to get well-distributed fibers in the matrix.
Processing MICA Based Pigment Masterbatch
Many effect pigments used in thermoplastics such as those used for pearlescent appearance are comprised of coated mica crystalline platelets. For effective coloration of thermoplastics the mica structure should not be altered. If the mica platelet is reduced in size while being compounded into the plastic it will alter the appearance of the plastic. It is desirable to maintain the mica structure in order to produce the best possible appearance of such pigments. To avoid attrition of the platelet structure exposure to shear during processing should be avoided, particularly when compounding high concentrations of pigment for masterbatch production. Co-rotating twin screw extruders are used for the compounding pigments into thermoplastics. Typical kneading blocks have predominantly been used with this equipment for the compounding of pigments for many decades. The mixing properties of this element include compression and simple shear which causes damage to the mica structure. Avoiding compression through the use of elongational mixing can significantly reduce damage to the crystalline structure of mica and enhance the appearance of mica based pigments. New mixing alternatives are available today that eliminate the shear peaks that are characteristic of typical kneading blocks, and utilize highly effective and efficient elongational mixing for the dispersion and distribution of mica based pigments while preserving the platelet structure.
Rotational Molding of Linear Low Density Polyethylene with Different Concentrations of Ground Tire Rubber
In this work, ground tire rubber (GTR) was dryblended with linear low density polyethylene (LLDPE) to produce thermoplastic elastomer parts by rotational molding. In particular, different GTR concentrations (0, 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50% wt.) were incorporated to determine the effect of the rubber phase on the processability and overall properties of the parts. Each composition was characterized in terms of morphology and mechanical properties (tensile, flexural and impact). The results show that the addition of the rubber phase decreased the tensile and flexural moduli and strengths, but the tensile elongation at break was always above 100%. This good elasticity produced impact strengths higher than the neat matrix with an optimum GTR content around 20% wt.
Low Density Open Cell Flexible Foams with High Tortuosities and Mechanical Properties Highly Dependent on the Strain Rate
This paper describes the mechanical behavior in compression, at both low and high strain rates, of several low density open cell polyolefin cellular materials with different gas phase tortuosity of the cellular structure. Due to the high tortuosity of some of the polyolefin foams under study they have a mechanical behavior similar to that of open cell polyurethane foams at low strain rates (i.e. they could be used for comfort applications) and they have a similar mechanical behavior to that of closed cell polyolefin foams at high strain rates (i.e. they could be used in body protection applications). Therefore, these new materials with high tortuosities have an unique mechanical performance strongly influence by the strain rate.
Analyzing the Viscous Dissipation of a Two-Dimensional Flow of Non-Newtonian Fluids in Single Screw Extruders
For modeling the flow of non-Newtonian polymer melts in single screw extruders numerical methods are required in general. In this study the viscous dissipation and the conveying characteristics in the melt channel of single screw extruders are analyzed for a two-dimensional, fully developed flow of power law fluids. Therefore three different numerical methods are presented and the results are compared. Furthermore, a comprehensive parametric design study is shown, analyzing the viscous dissipation depending on three independent parameters: (i) pitch to diameter ratio, (ii) power law exponent, and (iii) dimensionless pressure gradient. The derived results for the viscous dissipation can be used to calculate the mean melt temperature profile more precisely.
In-Situ Visualization and Cell Growth Modeling in a Polymeric Foaming Process
In this paper, we consider a two-dimensional model of the foam nucleation process of CO2 in polystyrene (PS) matrix by random initiation of growing bubbles in time and space. The model was extended to account for the simultaneous cell nucleation, growth, and collapse processes of the foaming bubbles at two different viscosities of PS resins. By means of connection among neighboring bubbles, secondary nucleation behaviors emerged from a multi-bubble system were attempted in simulations. The resulting cell size distribution (CSD) of bubbles shows power law behaviors for both simulations and experiments. The cell size distribution and morphologies obtained from the numerical simulation agreed with the snapshot pictures of the experiments qualitatively and quantitatively. Finally, different nucleation and growing rates were investigated to understand the relationship between the bubble nucleation /growth and final morphology of the foam structure. Potential applications lie in the analysis of the resulting micro-/nano-cellular structures due to secondary nucleation and the foam stabilization.
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