SPE Library
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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Conference Proceedings
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.
Cracking of Resin Rich Layer Joined to Tank Wall Due to Fluctuating Liquid Level
Composite laminate tanks are used in corrosive services in chemical process plants. The inner surface of tanks usually consist of a glass reinforced layer that is mostly resin and is joined to the tank structure to form a corrosion barrier. A large diameter, open top, composite laminate tank containing a hot brine solution suffered vertical cracking in the corrosion barrier during normal process operations. The process involved relatively rapid changes in the liquid level at different times during each day. Vertical cracks were discovered in the corrosion barrier by plant inspectors during a routine plant turnaround. Finite element modeling was used to demonstrate that the cracking was due to transient thermal stresses near the liquid vapor interface that resulted from the fluctuating liquid level and natural convection from the tank wall in cooler weather. In this research, the effects of the amount of glass reinforcement in the resin rich corrosion barrier were also studied. The outer surface of the tank was insulated, but the insulation does not appear to have been a factor in the cracking.
Rheological Properties of PVC/Wood-Flour Composites
Using a factorial design approach, this study examined the effect of the component materials on the viscoelastic properties of PVC/wood-flour composites. Statistical analysis was performed to determine the effects of wood flour content, acrylic modifier content and plasticizer content on the die swell ratio and viscosity of the composites measured on a conical twin screw extrusion capillary rheometer. The experimental results indicated that both the wood flour content and acrylic modifier content have significant effects on the die swell ratio and viscosity of PVC/wood-flour composites.
Reactive Blends of Poly (Vinyl Chloride) and Thermoplastic Polyurethane
In this study, a novel reactive blending technique was used to produce poly (vinyl chloride) (PVC)/thermoplastic polyurethane (TPU) blends that are otherwise difficult to produce by a conventional melt blending techniques due to degradation at elevated processing temperatures. Morphological and spectral characterization studies revealed that reactive blending process generated better mixing relative to melt blending process. The miscibility of the PVC with the polyols of the TPU and with the TPU was studied by changing in the chemical structure of the polyol.
A Study of the Processing Characteristics and Mechanical Properties of Multiple Recycled Rigid PVC
This study focuses on the ability of U-PVC to be processed a number of times. Three different types of U-PVC were investigated: virgin lead stabilised and virgin calcium/zinc stabilised material and reground, 20 year old, post-consumer windows. Each material was extruded four times and samples taken at each stage for rheological and mechanical analysis.
Fast Joining of Composite Pipes Using UV Curing FRP Composites
For this paper, twelve composite pipe joints were prepared. Among them, six were prepared using ultraviolet (UV) curing E-glass fiber reinforced vinyl ester composites and six were prepared using ambient environment curing E-glass fiber reinforced vinyl ester composites as control. Filament wound E-glass fiber reinforced vinyl ester composite pipes were used. Each section of pipe was 304.8 mm long with a 101.6 mm inner diameter. The wet lay-up technique was used to prepare the test samples. The curing time for the UV cured samples was 40 minutes, while the curing time was 24 hours for the control samples. Both internal pressure tests and four-point bending tests were conducted on the UV cured and control samples. The test results show that the UV cured FRP wrapped composite pipe joints achieved nearly the same bending strength as the control samples. However, the internal pressure rating achieved by the UV cured FRP coupled joints were lower than those achieved by the control samples. Based on the test results, the UV curing FRP can be used in joining composite truss structures and composite frame structures. Further investigation is required in order for the UV cured FRP joined pipes to be used to transport liquids or gases under pressure.
Surface Treatment of Polymers and Composites with UV Light in Air to Improve Adhesion
Ultraviolet (UV) surface treatment of polymers in air has been used to successfully modify polymer surfaces in order to enhance adhesive performance and wettability in a cost efficient manner. A wide variety of polymers including thermoplastics (TPO, PP, PC, PMMA), thermosets (Epoxy, Vinyl Ester), rubbers and composites have been successfully modified with this UV treatment. Improvements in adhesive bond strengths from 100-600% can be realized for hydrophobic polymers such as TPO and PP with treatment times on the order of 30-120 seconds. Several key process parameters for UV treatment have been identified. UV radiation in the 180nm-300nm was found to be necessary for surface modification of polymers. The extent of surface modification was found to be strongly dependent on the ozone concentration. The surface temperature during treatment was also found to be a controlling factor for some polymers and preliminary evidence points to a relationship between the optimum treatment temperature and the glass transition temperature (Tg) of the polymer substrate.
Development of Methods for Assessing the Chemical Compatibility of Thread Sealants Used with Plastic Fittings
Thread sealants have been used to help ensure a leak-tight joint and reduce friction during installation between threaded metal pipe and fittings for over 100 years. Thermoplastic fittings using the same taper thread cannot be assembled as if they were metal due to chemical compatibility and maximum material stress. However these same sealants are often used on a plastic fitting joint. This may be done either because the installer has been trained to use the same sealants on all threaded joints, or because the plastic parts are not fitted properly and are leaking under pressure. Unfortunately, sealants that work well and are compatible with metal pipe threads may contain stress-cracking agents that will cause failure in plastic fitting joints. Because it is unlikely that the industry practice of using thread sealants will change in the foreseeable future, a method is needed to evaluate these products to determine compatibility with existing fittings materials and designs. The current work develops three categories of testing using tensile, flexural, and threaded part configurations. Several variations in each of these methods are attempted, with multiple types of sealants and materials. There is a definite trade-off in test duration and complexity of the test method. The results of this testing program are provided, with analysis of the failure types and recommendations for the development of an ASTM test method.
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