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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Simulation of an Industrial High Capacity Blown Film Extrusion Process
One of the most important production processes for manufacturing plastic films is the blown film extrusion. The conventional way to improve the output of a production line can be achieved by a substitution or a modification of the limiting air cooling ring. In order to verify an output intensification, typically the trial and error method is being used. For reducing the experimental costs, a numerical procedure called Process Model has been developed for simulating the formation of the bubble with regard to changing process conditions and rheological behavior. The applicability of the Process Model has been proven for small production lines with a maximum output of approximately 100 kg/h (LDPE).
According to industrial concerns, the Process Model has to be verified for higher mass flow rates (> 750 kg/h). Therefore, the numerical procedure has to be adapted. Besides a modification of the simulation domain and the integration of an internal bubble cooling device (IBC), an adaption of the material model has to be done. For the consideration of the material behavior from each layer of the multilayer film, a specific approach has been developed and used. In this paper, the simulation results of the first application of the Process Model for an industrial blown film line including an internal bubble cooling system will be presented. This device intensifies the heat exchange and enhances the bubble stability with regard to higher air volume flow rates . The resulting heat exchange and the flow phenomena will be discussed.
Influences of Processing Parameters, Material, and Mold Geometry on the Shape of Caverns as a Quality Parameter for Electroplating on Plastics
For automotive application processing technical polymers like acrylonitrile butadiene styrene (ABS) or polycarbonate blends (PC/ABS) with injection molding and refining them by electroplating is state of the art. The surface quality and processing parameters during the injection molding mandatorily influence the resulting part quality. Besides the electroplating parameters, the surface of the injection molded part is responsible for the conjunction of the polymer and the metal layer system. The surface and adhesion of the hybrid material combination is defined by etching butadiene in the part surface to a cavern structure.
An objective evaluation method for quantifying the two-dimensional shape of caverns is developed by using image analysis. The analysis is based on scanning electron microscope (SEM) images of chemical etched polymer part surfaces (ABS, PC/ABS). For quantifying the surface, meaningful key figures (e.g. roundness, degree of orientation, caverns/?m², and area of caverns) are emerged. Finally, different materials, etching times, and processing parameters are compared to results of climate change tests and the analytical valuation of the surface structure.
Microstructure-Property Relationship for Impact Energy Absorption of Functionally Graded Porous Structures of Acrylonitrile Butadiene Styrene (ABS)
Functionally graded (FG) structures are advanced class of composite materials where the microstructure is gradually continuous. This continuity eliminates problems like stress jumps and delamination that are encountered with conventional composite materials. FG porous structures have the added advantage of high strength-toweight ratio compared to the solid FG materials. Strengthto- weight ratio can be tailored with controlled fabrication processes to satisfy certain design requirements. Microstructure-property relations help in selecting the appropriate microstructure for required strength and provide a guide to fabrication procedures. In this work, FG porous structures of ABS are fabricated with thermally activated microspheres and compression moulding with a special mould design. Gradient in the porous structure is created by inducing thermal gradient across the thickness. SEM images of the porous structure were analyzed by locally adaptive thershoulding technique which is based on minimizing an energy functional of the thresholding surface through a variational Minimax algorithm. The purpose of local threshoulding is to extract accurate information about the microstructure like pores’ diameters and porosity. This information is then utilized to run correlation analysis between microstructure to processing and microstructure to impact energy absorption. The results showed the potential to control microstructure and hence tailor impact energy absorption. Impact energy is shown to be more correlated to pores’ average diameter than to porosity.
Evaluation of Liquid Crystal Polymers (LCP) as an Additive for Polybutylene Terephthalate (PBT) to Improve Melt Processing and Properties
Liquid Crystal Polymers (LCP) are partially crystalline aromatic polymers based on p-hydroxybenzoic acid and related monomers. LCP’s offer numerous benefits such as higher melt flow during molding, low warpage, good dimensional stability, better moldability, superior mechanical and thermal properties, excellent chemical resistance, flame resistance, and weatherability and are used in thin walled and optical applications. This paper evaluates the use of LCP as an additive to improve the properties and performance of Polybutylene Terephthalate (PBT). Unfilled PBT formulations with different loadings of LCP (0.25wt% to 5wt%) were compounded and tested. Rheological analysis was performed using a capillary rheometer to quantify the influence of LCP in melt flow of unfilled PBT. Thermal analysis through DSC was performed to measure the influence of LCP on crystallization phenomenon of PBT. Mechanical properties and heat deflection temperature were measured to estimate the differences in performance between the various formulations.
Ultrasonic Sealing Tool Design for Thin Film Plastics
Thin film packaging is used for a wide range of products including packaging of food, medical tools, electronics, and toys. Each of these applications requires a different type of film, from thin and brittle, to composite film including a foil layer, to biodegradable films. These films can be adhesively bonded, heat sealed, impulse welded, and increasingly, ultrasonically welded. Ultrasonic welding offers many benefits to thin film sealing such as faster cycle times, reduction in film usage due to narrower bond widths, elimination of adhesive layers, improved hermeticity for increased shelf life, and less sensitivity to contaminants in the seal area.
However, tool design can have a significant effect on weld strength. Optimum tool design depends not just on the thickness of the material to be welded, but also the type of polymer to be joined, and seal requirements (such as hermeticity and peel strength). In this study, we seek to provide starting guidelines with the goal of lowering the cost and duration of the tooling development process by investigating the achievable peel strength of a wide variety of film types with twenty-five horn and anvil design combinations.
Comparative Analysis of Energy Director Styles on Polybutylene Terephthalate (PBT) with Servo-Driven Ultrasonic Welder
In ultrasonic welding of plastics, the design of the energy director can be crucial to achieving an optimal weld, especially for semi-crystalline plastics like polybutylene terephthalate (PBT). However, it can be difficult and expensive to maintain a sharp energy director on molded parts. Consequently, there is significant interest in determining if an alternative joint design can be used to produce comparable strength to the traditional 60-degree triangular energy director used for semi-crystalline materials. In this study, four different joint styles are compared using the Dukane 30 kHz iQ Servo ultrasonic welder. A shear joint, round, 60- and 90-degree energy directors were analyzed in terms of both tensile strength and weld characterization, which was determined by microscopic inspection of cross sections.
To achieve a baseline for testing, velocity profile calculations were made by finite difference analysis (FDA). During welding, plots were made of force and displacement over time. Several weld setups were used to weld all four joint designs. The primary parameter investigated was weld velocity magnitude and profile. The resulting force profiles were analyzed for trends as well.
Evaluation of Branched Polypropylene Degradation by Using Different Constitutive Equations
In this work, virgin as well as thermally degraded branched polypropylenes were investigated by using rotational and Sentmanat extensional rheometers. Based on the shear and extensional rheology data it was deduced that both chain scission and chain branching takes place during thermal degradation of the tested polypropylene. It was found that simple constitutive equations such as Generalized Newtonian law, modified White-Metzner model and Yao model can be used to describe the measured steady state shear and uniaxial extensional viscosity data. It was revealed that Yao and Generalized Newtonian models have capability to quantify level of extensional strain hardening (i.e. the maximum steady state uniaxial extensional viscosity divided by 3 times Newtonian viscosity) as a function of degradation time via their parameters not only quantitatively but also qualitatively.
Analytical Solutions of Nonlinear Constitutive Equations for Large Amplitude Oscillatory Shear (LAOS) Flow
Nonlinear viscoelastic models have been studies to elucidate the nonlinear behavior of viscoelastic materials. It is axiomatic that the analytical solutions of these constitutive equations are helpful to investigate various viscoelastic flows. For this reason, studies on calculating the analytical solutions of viscoelastic models have been spotlighted. However, various studies rely on power series approximations and it cannot overcome the inherent limitation of convergence radius. In this study, new approach is suggested to calculate analytical solutions of the Giesekus model. This approach provides systematic way to calculate not only shear stress but also normal stress under large amplitude oscillatory shear (LAOS) flow.
Properties of Poly(Ethylene Glycol) Methyl Ether Acrylategrafted Polylactide
Polyethylene glycol (PEG) is known to plasticize PLA but can exhibit migration over time. In order to reduce migration, reactive extrusion was used to chemically graft polylactide (PLA) with low molecular weight poly(ethylene glycol) methyl ether acrylate (APEG). APEG was added in various concentrations (0, 15 and 30 wt%) in the presence of an organic peroxide as a radical initiator. The covalent grafting of APEG on the PLA was evidenced by ATR-FTIR, 1H NMR. The physical effects of APEG in terms of thermal and flow properties were also investigated. The melt-state viscoelastic properties were characterized by oscillatory shear measurements. The glass transition temperature of the modified PLA was measured using differential scanning calorimetry. As expected, storage modulus decreased with APEG content and the glass transition temperature of the APEG-modified PLA was decreased by approximately 14°C compared to that of pure PLA.
In-Situ-Pultrusion – Structural Thermoplastic FRP-Parts
Fiber reinforced plastics, produced by In-Situ-Pultrusion are supposed to be used as local reinforcement of injection molded plastic parts. For this purpose, the pultruded parts are overmolded after being inserted into the injection mold. From process technologies reasons, the parts made by In-Situ-Pultrusion consist of cast Polyamide 6 (PA6). This cast PA6 differs from standard injection molding PA6. In previous studies, it was shown that a good bonding between the partners can be reached. In this work, a new bending girder made of PA6GF30 and In-Situ-pultruded PA6 is presented. Some mechanical properties were tested and compared with an equal bending girder, made of pure PA6GF30.
Interfacial Fracture Behavior of Injection Molded Parts
The formation of interfaces cannot be avoided in joining processes of thermoplastics. Generated by injection molding, they could be mainly divided into “cold” and “hot” interfaces. Cold interfaces occur during assembly injection molding (AIM) and “hot” interfaces or well known as weld lines represents the meeting of two melt streams. A new tensile test coupled with transmitted light microscope (TLM) was developed to classify the interfaces in terms of morphology and strength and analyze the failure behavior of thin sections. The objective is to improve the injection molding process by understanding the failure behavior.
Evaluation of Consumption Process on Antioxidants in Polyethylene by Chemiluminescence Measurement Method
In recent years, plastic pipes have been increasingly used for hot water supplies and heating systems and these require materials with long-term durability. In this paper, we report the preparation of polyethylene samples containing different amounts of antioxidants. Furthermore, we conducted accelerated degradation tests on these samples, and we evaluated the degradation of the polyethylene samples by chemiluminescence. We found that non-isothermal chemiluminescence measurements are more suitable for both the qualitative monitoring of the deactivation of antioxidants and the degradation of polyethylene resin samples as compared to isothermal measurements. The process of antioxidant consumption is discussed on the basis of the chemiluminescence measurements.
Non-Destructive Testing of Composites by Robot Supported Aircoupled Ultrasound
Air-coupled ultrasound is used as a non-destructive testing method for fiber reinforced plastics. By using reemission measurements only one sided access is needed. In order to make a complete scanning of components with a curved surface, a six-axis industrial robot is used. The problem here is to relate each ultrasonic measurement point to the right point on the examined part. In this work, two different procedures are studied and presented with several examples to solve this problem. One possibility is to determine the position by knowing the exact velocity of the robot arm. In the other method, the position will be sent from the robot system to the ultrasound system via incremental displacement signals. To validate the method, multiaxial curved components were investigated, like a carbon fiber car roof with impact damages.
Non-destructive Testing of CFR-Tapes with Thermoplastic Matrix using Air-coupled Ultrasound
For analysis of CFR-Tapes with thermoplastic matrix, air-coupled ultrasound is evaluated as a non-destructive testing method for detecting material defects, mechanical defects and incorrect fiber volume ratio. The inspection performance is determined by means of specially prepared specimen and applying further investigation based on Matlab. It is shown that air-coupled ultrasound testing is not only capable of detecting a variety of defects, but has the potential of being applied as an inline testing system for the production of CFR-Tapes.
Foam Injection Molding of Polylactide with in-Situ Fibrillated Polytetrafluoroethylene
Manufacturing polymeric foams with high cell densities with injection molding is of great interest to industry, primarily because of the flexibility and costeffectiveness of the technology. Yet, there is still limited research work on foam injection molding of polylactide (PLA), an emerging bio-derived bio-degradable thermoplastic. The manufacture of PLA foam of high cell density and void fraction with injection molding remains challenging due the low melt-strength property of the resin. In this work, we examined processing of PLA foams with in-situ fibrillated polytetrafluoroethylene (PTFE) through injection molding. The prepared PLA/PTFE foams possessed void fractions of 50% and above.
Tensile Properties Modification of Ductile Polyoxymethylene/ Poly (Lactic Acid) Blend by Annealing Technique
This research aimed to improve tensile property of polyoxymethylene/poly (lactic acid) blend (POM/PLA) by annealing process. POM/PLA at ratio of 60/40 was injection molded to dumbell specimens. The blend was annealed at 80 C and 100 °C for 10-30 min. The effect of annealing on crystallinity, mechanical performance and fracture behavior was investigated. Crystallinity of PLA in the blend increased with increasing annealing times, which resulted in the increment of tensile strength and tensile modulus of POM/PLA blend. However, higher crystallinity of PLA in the blends after annealing yielded higher notch sensitivity and lower fracture toughness as compared to unannealed blend. The optimum condition of POM/PLA (60/40) was found at annealing temperature of 80 °C for 10 min, which obtained good in tensile strength and tensile modulus of the blend. It can be noted that notch sensitivity factor of neat polymer was improved in unannealed POM/PLA blend.
Polystyrene Foam Insulation: Implementation of Alternate Sustainable Flame Retardant
Sustainable solutions are being increasingly demanded in the construction product market place. Polystyrene insulation is an increasingly important component of green construction. The benefits of insulation in residential and commercial buildings include lower energy consumptions, improved thermal comfort, reductions in the first costs of the heating and cooling equipment and reductions in CO2 emissions from the burning of fossil fuels across the United States.
As with all foam insulations, polystyrene foam insulation is combustible and must comply with stringent building and fire codes, which have been in place since 1976. The basic requirement in codes is a flame spread index of 75 or less and a smoke developed index of 450 or less when tested in accordance with ASTM E84, in addition to separation of the foam insulation from building occupants through use of a thermal barrier, typically ½” gypsum board. Additional requirements are in place depending upon the particular application.
Like many other building products – from electrical wires to structural and decorative wood products to paint – foam insulation uses flame retardants to protect people and property from the hazards of fire. Flame retardants used in foam insulation meet current regulations and their history of safe use is supported by scientific research.1 Manufacturers are committed to product safety and the effectiveness of flame retardants, and support research and development efforts to continually advance and improve these materials.
A recent announcement by the Design for the Environment program of the U.S. EPA detailed a suitable polymeric flame retardant for use in polystyrene foam insulation. The chemistry is a brominated polymeric flame retardant to replace Hexabromocyclododecane (HBCD)2. HBCD has recently been listed as a persistent organic pollutant (POP) under the UNEP Stockholm convention and is on the Authorisation List (Annex XIV) under the European Union REACH (Regi
Flow of Molten Plastics: Puzzles and Problems
When high-molecular weight polyolefins and vinyl polymers are melted and formed into commercial products, the melts show themselves to be not just viscous liquids but complex fluids that exhibit a range of peculiar flow behaviors that cause problems for processors. Extrudate swell, shark skin, and wall slip are among the phenomena that complicate life for the plastics engineer. These arise from the elasticity of melts, their very high viscosities and the large normal stress differences generated in shear. Normal stress differences generate flow in a direction orthogonal to the principal flow and are the cause of the well-known rod-climbing or Weissenberg effect, which is shown in Fig. 1 in a polymer solution. It has also been observed in molten polymers.
Multicomponent Injection Molding of Thermoplastics and Liquid Silicone Rubber (LSR) – Either Cured by Heat or UV Light
For processing thermally curing liquid silicone rubber (LSR) as well as UV light curing LSR for multicomponent injection molding with thermoplastics in an comparable way a processing center was designed and set into operation.
For the production of the multicomponent specimens a modular tool was designed. In there a thermoplastic plate gets molded on the one side, then gets transferred automatically by a robot system and gets overmolded by the silicone on the other side. The complete silicone side of the tool is easily changeable from a heated cavity, which is more or less state of the art, to a transparent cavity, wherein the UV LSR gets cured by according LEDs.
In first studies tests have been carried out concerning the adhesion between several thermoplastic materials and different LSR types, cured by heat as well as by UV light. The adhesion has been tested according to VDI 2019.
The used injection molding technique makes an intermediate treatment like surface activation of the thermoplastic plate possible before it gets overmolded. Therefore exemplarily different surface treatments and their effects on the adhesion strength of the material composite were evaluated.
New Materials Bring New Testing Challenges
Polymers have been utilized in automotive applications for many years. However as OEM’s strive for affordable lightweight vehicles, suppliers are discovering what may have been acceptable yesterday is today’s opportunity for improvement. One such opportunity involves utilizing new materials to differentiate automotive interiors. Faced with the challenge of setting new trends, interior design engineers must also satisfy customer expectations that the materials used will withstand the rigors of everyday use. This paper reviews the recent development of piano-black; high-gloss components that eliminate the need for secondary processes such as painting, and how one OEM discovered during field tests their initial screening tests were inadequate. Scratch and mar testing solutions are discussed for a better understanding of how to compare and select the finishing option that offers the most durable outcome.
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