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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Effect of Polypropylene Rheology on the Vibration Welding Process
Vibration welding is a joining technique to assembly thermoplastic components. Meltdown-time profiles and assessment of weld microstructure are commonly used to characterize the behavior of polymers during vibration welding. The aim of this work is to establish relationships between the rheological properties of molten polymers and their meltdown rate during vibration welding. Two polypropylene homopolymers with different molecular weights resulting in different rheological properties were studied. Vibration welding was carried out using a butt-weld geometry and meltdown-time profiles were measured. Significant discrepancies between experimental results and theoretical predictions based on the simple model developed by Stokes suggest the presence of significant elastic effects.
Real Time Temperature Measurement of Nylon 66 Butt-Joints during Vibration Welding
Modeling the vibration welding process requires accurate knowledge of the melt temperature at the interface. Due to technical difficulties related to the very small molten film thickness, little work has been done to date on measuring the weld temperature under real time conditions. This paper presents a novel technique for measuring the weld temperature in real time. It involves inserting a 25 ?m thermocouple into one of the welding parts in close proximity to the weld zone. During vibration welding, the thermocouple works its way to the weld interface and records the melt temperature. The experimental data from vibration welding nylon 66 butt joints indicate that the melt temperature at the weld interface is within 15°C of the onset of polymer melting. The temperatures measured in the solid phase prior to entering the melt film are consistent with theoretical models for heat conduction into solid plates.
Heated Tool Welding of Thermoplastic Polyolefin (TPO)
This study focused on the weldability of two specific thermoplastic polyolefins (TPO-A and TPO-B) using heated tool welding. A three-factor (heating temperature, heating time, and welding pressure) and three-level design matrix was used to perform the welding. Two statistical methods, three-factor two-level design of experiments (DOE) and Box Behnken method, were used to analyze the weld results. In addition, vibration welding of these TPOs was also used to compare the weldability. For heated tool welding, the maximum joint strength was 88% of the bulk strength for TPO-A and 76% of the bulk strength for TPOB. For vibration welding, the maximum joint strength was 65% for TPO-A and 56% for TPO-B. While heated tool welding provided stronger joints compared to vibration welding, it had a longer cycle time. The two statistical methods provided similar results indicating that the simple three-factor two-level design of experiments was a valid screening method for heated tool welding of TPO.
The Effects of Weld Geometry and Glass-Fiber Orientation on the Mechanical Performance of Joints – Part II: Kinetics of Glass-Fiber Orientation and Mechanical Performance
The mechanical performance of injection molded short glass-fiber reinforced thermoplastic components is anisotropic and is highly dependent on the fiber orientation and distribution. Similarly, the bulk and short and long-term mechanical performance at the weld is influenced by these fibers and the specific welding technology used as related to melt-pool formation.The purpose of this analysis is to show:the short-fiber orientation (analytical and simulation data) and distribution at the pre-welded bead, ribs and wall areas;advantages of SigmaSoft injection molding simulation software, which utilizes full three dimensional fiber representation of any molded part;the mechanical performance of welds with optimized geometry (US Patent 6,447,866).Findings on the mechanical performance of butt-joints with different designs and localized geometry will help designers and technicians with plastic part design optimization. In a previous ANTEC paper (Part I), we related these findings to the kinetics of welds and part design issues for straight and T-type butt-joints.
Optimized Rheology and Density of Polyolefin Elastomers for Clarified Polypropylene Applications
Polyolefin elastomers based on metallocene technology are excellent impact modifiers for polypropylene. This study looks at how density and melt rheology of polyolefin elastomers affect clarity and impact performance of clarified polypropylenes with 2, 10, and 35 MFR. Optimum clarity and improved impact performance are achieved by matching rheology and density of polyolefin elastomers with polypropylene.
New Product Development: Benchmarking, Prototyping, & FEA Modeling
Increasing demand for smaller products at lower costs has encouraged a rubber products company to develop a new product line made exclusively from plastic. Firestone Industrial Products Company approached new product development by benchmarking industry standards, prototyping duo-durometer polyurethane weld joints, and finite element analysis (FEA) modeling of a flex-member component.
Plastics Standards - A Great Benefit
Suppliers, manufacturers, and consumers receive significant value from plastics standards. Standards are important in the marketplace because of their educational value, effects on research, product development and production. Improved electrical performance and evolving fire standards requirements necessitate changes to improve how wire and cable standards are developed. Technical people from materials suppliers, manufacturers, and users are needed to support these efforts. As plastic materials improve, the need to develop performance-based standards more rapidly is necessary.
Feasibility of Selected Methods for Embossing Micro-Features in Thermoplastics
During the last few decades the use of MEMS (Micro-Electro-Mechanical-Systems) has been steadily increasing in a number of industries, and especially in the medical industry. One application for MEMS is in micro-fluidic devices that rely on micro-channels (10 to 200 ?m wide and deep) to direct and analyze fluids for medical diagnostics. Current methods for producing these features, including hot embossing and micro-injection molding, can be slow (1 to 10 minutes cycle time), are only amendable to batch processing and expensive. Fast surface heating embossing methods have the potential of producing micro-channels rapidly and inexpensively. Three embossing methods were studied: ultrasonic, infrared radiation (IR) heating and hot gas heating. For IR and hot gas heating, a cold tool with the micro-features was pressed onto the surface immediately following heating. Similarly, for ultrasonic embossing the micro-features were machined on the surface of the horn. It was found that cycle times as short as a few seconds were achieved and the quality of the features was similar to those seen in injection molding. In addition FEA studies were conducted to simulate polymer flow during embossing.
3D-Laser Transmission Welding
Contour welding is a variant of the laser transmission welding that offers the highest flexibility relative to the weld geometry. In this process the laser beam is translated along the weld line using a robot. This paper reviews the results of welding experiments using a proprietary box geometry with a three-dimensional weld line. It was found that low leakages and high burst pressures can be achieved with optimized process parameters for Polyamide or Polyacetale. In addition, short welding times (a few seconds) were demonstrated. Thus, this process is well suited for mass production of complex plastics parts. It was also seen that the process is relatively robust and weld quality is relatively independent of parameter settings (over the ranges evaluated).
Through Transmission Laser Welding of Polycarbonate and High-Density Polyethylene
Through Transmission Laser Welding (TTLW) of thermoplastics is a relatively new joining process with many advantages for design and manufacturing of various components in electronic, medical and automotive industries. The use of high power diode laser systems has made TTLW a cost effective process in welding of many amorphous and semicrystalline polymers. In this work, a laser welding system, comprised of a power supply and a diode laser with a Branson proprietary fiber bundle, was used to experimentally study TTLW of polycarbonate (PC) and high-density polyethylene (HDPE). The effects of welding power (measured laser power at the interface), heating time, and welding pressure on joint strength were studied. Maximum weld strength of about 95% the bulk strength of PC and HDPE were achieved.
Overlap Welding of Thermoplastic Parts without Causing Surface Thermal Damage by Using a CO2 Laser
This paper deals with the principle and applications of a novel infrared laser welding procedure for overlapped thermoplastic parts. Features of experiment, using a CO2 laser as a radiation heat source and numerical simulation of heat transfer phenomena combined with radiation and conduction in the welding process, are demonstrated. Not only high weld strength but also excellent surface quality of welded regions is essential for overlap welding of plastics in industrial applications.The current welding procedure was developed using a combination of penetration infrared radiation heating process and thermal diffusion cooling process by a solid material which is transparent to infrared radiation as a heatsink. The solid heatsink placed in contact with an irradiated surface of overlapped thermoplastic parts during radiation heating. This welding procedure is able to achieve both high weld strength and excellent surface appearance without causing surface thermal damage, as is often suffered in conventional direct infrared radiation welding process without a solid heatsink. In addition, the pigmentation of the welding material to increase absorption of radiation is unnecessary for this procedure.
Evaluation of Electrospun Polymer Coatings on 316 Stainless Steel Meshes
Electrospinning is an advantageous technique for applying porous coatings onto porous substrates, particularly those used for biomedical applications. This paper explores the feasibility of electrospinning polystyrene coatings onto stainless steel meshes with varying conditions. The effect of pore size and surface treatment on the morphology, thickness, and adhesion of the coatings obtained were examined.
Effects of the Molecular Characteristics of Polymers on the Electrospinning of Polystyrene
The influence of Mw and concentration on the electrospinning of polystyrene in ? and non-? solvents was studied. The jet breakdown phenomena were visually recorded for different molecular weights. The splitting and splaying of the jet is affected strongly by the molecular characteristics and is analyzed in terms of the dimensionless concentration [?]c.
The Effects of Blow-Up Ratio on Bi-Directional Tensile Properties of an Ethylene Acrylic Acid Copolymer
The orientation of blown films corresponds to the blow-up ratio utilized to process the films. Ethylene acrylic acid copolymer was used to produce films with various blow-up ratios and thicknesses. Tensile testing these films in the machine and transverse direction will illustrate the correlation between blow-up ratio and tensile properties.
Formulation of Optimally Stabilized Poly(vinyl chloride) Systems with the Aid of the Chemiluminescnce Technique. Part I.
The aspects of thermal stabilization of flexible PVC compounds are analyzed with the chemiluminescence technique. The intensity of the CL emitted during the degradation of PVC was found to be proportional to the concentration of build up polyenes. Ba/Zn carboxylates are differentiated by their polyene blocking ability.
Thermal Stabilization of PVC-Wood Composites
The rate of PVC-Wood composites discoloration was used to estimate the effect of PVC heat stabilizers. The mechanical properties of these composites were strongly dependent on stabilizer efficiency and were improved by more effective stabilizers.
Technical Review of the Four Major Thermal Press Applications: Staking/Swaging, Inserting, Degating, Part Marking
Thermal presses are used primarily in four applications with regard to assembly (decorating) of thermoplastic parts: staking/swaging, inserting, degating and part marking. Thermal staking/swaging and inserting are generally thought of as competitor processes to ultrasonic, while degating operations with heated tooling are thought of as an augmentation to degating by force alone. Part marking such as date- or lot-coding and serializing is another area where these machines can be applied. This paper discusses these four applications areas and references competing processes to highlight the strengths and weaknesses of utilizing modern thermal presses for these applications.
Optical Correction for Heat Buildup in the Center of TTIr Plastics Welds
Through Transmission Infrared (TTIr) laser welding of plastics often results in voids forming in the center of the weld. These voids can lead to weak and unattractive welds. Their formation is due to non-uniform temperature distributions within the weld zone and out gassing of volatiles (such as moisture). This non-uniform temperature distribution has been demonstrated not only by a Gaussian laser light distribution but also by an even light distribution depending on the joint/part design. This paper reviews the development of tailored optics that re-shape the distribution of typical light/laser sources in order to promote uniform temperature distributions. It was seen in FEA models that by using uniform heat distributions, uniform temperature fields were produced in butt joint configurations. In addition it was seen that a distribution with high heat input on the outer edges produced uniform heating in lap shear joint configurations. Laboratory experiments verified these FEA predictions, and strong and attractive welds were generated.
Laser Welding of Polypropylene to Thermoplastic Polyolefins
Polypropylene (PP) and thermoplastic polyolefin (TPO) are currently used in many automotive applications. However, the weldability of these two materials using through transmission scanning laser welding has not yet been reported. This study focused on the effects of color and welding parameters on lap shear joint strength. Three colors, black, blue and tan, as well as three welding parameters, laser power, weld time and scanning speed, were used to evaluate the weldability. The samples were welded using a 200 W flashlamp-pumped Nd:YAG laser. For the 1.06 ?m wavelength, it was found that 3.2 mm thick natural PP has a transmission rate of 29%. It was also found that the black TPO had the most laser absorption, followed by the blue TPO and then the tan TPO. Therefore, the black TPO required the least amount of welding time to reach the maximum joint strength. In addition, as the scanning speed was reduced, the time required to reach maximum joint strength was also reduced.
Modeling the Bond Formation Development between Polymer Filaments in FDM Prototypes
Fused Deposition Modeling (FDM) processes have the capability to fabricate parts with locally controlled properties by changing deposition density and deposition orientation. The integrity and mechanical properties of parts are largely determined by the bonding quality realized among polymer filaments. This paper reports a theoretical study of the mechanical properties of FDM prototypes, heat transfer analysis of the FDM process and modeling of the bond formation among ABS filaments. Thermal analysis of the FDM process resulted in an estimation of cooling profile of the extruded filaments. Quantitative predictions of the degree of bonding achieved during the filament deposition process were made. The model was used to estimate the effects of different manufacturing parameters in the FDM process.
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