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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Development of an Environmentally Friendly Solventless Process for Electronic Prepregs
The most common commercial processes for manufacturing pre-pregs for electronic boards use solvent-based resin systems. Solvents are environmentally unfriendly and contribute to voids in the pre-preg and laminate. The resin impregnation process is done in an open resin bath. This low-pressure impregnation is conducent to voids in the prepregs. Voids cause product variability, which is a major source of scrap in board shops. To eliminate the above mentioned drawbacks, a solventless process, based on the concept of injection pultrusion, is developed. The impregnation is done in a die under pressure to minimize voids.In previous work, chemo-rheological and kinetic measurements were used to identify a potential epoxy-based resin system. In addition, flow visualization using model fluids was used to establish the basic flow mechanism. Here, we use the previous results to develop a mathematical model for the B-staging process. Based on the mathematical model, three potential alternatives to produce prepreg are developed and analyzed. A prototype B-staging die is built and used to verify the mathematical model. The result shows that the model agrees well with the experimental data for low pulling speed and slightly under predicts the high pulling speed runs.
Investigation of Electron Beam Curing of Bismaleimide (BMI) and BMI/NVP Resins
Electron beam curing of a 4,4’-Bismaleimidodiphenyl-methane (BMPM) / BMI-1,3-tolyl / o,o’-diallylbisphenol A (DABPA) based BMI system, and the mixture of the above BMI resin with N-vinylpyrrolidone (NVP) is investigated to build the relationship of temperature rise, dosage and dosage rate and corresponding cure extents. The cure kinetics and effect of initiator on cure reactions are also carried out. Low intensity E-beam exposure cannot initiate BMI polymerization but high intensity E-beam exposure gives high reaction yield due to high temperature rise, which induced thermal curing. However, BMI/NVP systems can be initiated easily by low intensity E-beam exposure without thermal curing being induced. According to FT-IR measurements, 70% reaction conversion of BMI/NVP can be achieved by 200 kGy dosage exposure at 10 kGy per pass with the temperature rise no more than 50°C. The product having a Tg of 180°C can be obtained.
Numerical Simulation of the Curing Reaction during Pultrusion Processes with a Diffusion Controlled Model
A numerical simulation of the pultrusion process was developed. The material properties were determined experimentally and fitt to a numerical diffusion controlled curing model. The DiBenedetto equation was used to calculate the instantaneous glass transition temperature during the curing process. The simulation determines the expected temperatures and degrees of cure throughout the part, in response to varied processing conditions. The primary application of the simulation is the pultrusion process and part design as well as testing the effect of new unsaturated polyester resins during processing.
Developing Time-Temperature-Transformation Diagrams for Unsaturated Polyesters Using DSC Data
A general concept of time-temperature-transformation (TTT) diagrams was numerically established to portray the effects of processing conditions during the curing of unsaturated polyester resins. The isothermal curing curves and the vitrification line were constructed based on a numerical procedure to model the curing of an unsaturated polyester resin. Isothermal and dynamic DSC modes were used to obtain the experimental data. A non-linear least squares Levenberg-Marquardt algorithm was used to fit the reaction rates with an autocatalytic kinetic model with diffusion effects. The DiBenedetto equation (1987) was utilized to correlate the degree of curing and glass transition temperature to model the diffusion-limited part of the reaction. The fitted model shows a good agreement between the experimental DSC scans and the predicted reaction rates. The numerical TTT diagram can be utilized during process design and optimization, since most of the curing behavior is represented in the diagram.
A New Class of Epoxy Thermosets
SBM, PolyStyrene-block-1,4-polyButadiene-block-polyMethylMethacrylate, is a new family of block copolymers offering an original way to modify polymer materials performances. Blended with a polymer compatible with one block, SBM disperses readily and imposes a structuration to the host matrix. This organization imparts unique combinations of properties, such as impact strength, high rigidity and transparency. This stands both for thermoplastics and thermosets. Here nanostructured thermosets are presented. These supramolecular architectures yield significant toughness improvements while preserving the optical transparency of the material.
An Investigation into Fracture Toughness Testing of Dental Luting Cements Using Various Methods
Various types of luting cements are used for fixation in dentistry. Failure through fracture is a significant issue with these materials. Several fracture toughness tests have been developed to characterise dental luting cements. Among them are the Chevron-Notch Short-Rod and Mixed-Mode Sandwich tests. In this study these two techniques are applied to a dental luting cement and from the results of the testing, conclusions are drawn on what they can determine regarding a material's properties.
Characterisation of the Fracture Toughness of Acrylic Bone Cement Containing Nanoparticles using the Chevron Notch Short Rod Technique
Chevron Notch Short Rod (CNSR) bone cement samples containing silicate clay nanoparticles were prepared and mechanically tested and their fracture toughness properties determined. Acrylic bone cement samples without the nanoparticles were also tested as a control and a reduction in the derived KIC for acrylic based nanocomposite structure was found to exist. The CNSR technique has been shown to be an appropriate test method to characterise the fracture toughness of nanocomposite structures.
Mechanical and Thermal Characterization for Sterilized Medical Elastomers
We have applied thermal, mechanical, and rheological techniques in the product development for medical elastomers with success. In this presentation, examples of actual product application will be used to illustrate the utility of these techniques and to demonstrate the derived information that was used in developing successful elastomeric related medical products.
Epoxy + Montmorillonite Nanocomposite: Effects of Water, Ultrasound, and Stoichiometry on Aggregates
The effect of controlled water addition to the development of random aggregates of alkonium ion substituted montmorillonite clay in epoxy was studied based on changes to the hardener mix ratio, clay composition, and ultrasonic treatment before cure. The effects on the glass transition temperature and microhardness were determined. The introduction of water before ultrasonic mixing altered the apparent size of the treated clay aggregates observed in these mixtures after cure. The clay aggregates also appeared to change the location and the distribution of water-induced microcracks in the cured nanocomposites. This information was used to develop a technique to remove aggregates without causing microcracks.
Development of a New Solution to Vary the Thickness of the Parison over its Circumference While It Is Extracted
Complex blow molded parts afford not only a variation of the thickness of the parison in axial direction but also in circumference direction to end up in the desired optimal thickness distribution in the final part. Integrating a partial multi-walled Flex Ring into a blow molding die allows to alter the local flow channel geometry. While deforming the Flex Ring its geometry alters gradually, so no dead spots are created. As additionally the deformation of the Flex Ring keeps within its linear elastic range the deformation can be repeated for every cycle. The principle of the technology will be explained and potential solutions of the new technology will be discussed.
Preform Optimization Using Non-Linear Finite Element Simulations
Non-linear finite element simulations of the blow molding and thermoforming processes have been used to provide accurate predictions of the material thinning. However, this powerful simulation tool has provided limited assistance to the design and optimization of the wall thickness distribution of preforms used in injection blow molding. Trial-and-error methods are often used in design. This paper presents a technique that converts finite element analysis of the injection blow molding process into a design/optimization tool. A systematic optimization technique for preform design that uses an iterative series of non-linear finite element simulations will be described. The series of simulations converges on a preform wall thickness distribution that will result in a specified thickness distribution in the blow molded product. This design technique is especially effective for non-circular or irregular shaped products.
The Influence of Blowing Time and Blowing Pressure on Bottle's Labeling
Extrusion Blow Molding process is one of the only ways to produce hollow parts. This process is particularly difficult to control due to the parison swelling in the air without mould, contrary to the Injection Blow Molding in which all the different steps of the process take place in mould.There are four stages in this process. First of all the plasticising, followed to the extrusion through the die head. The next stage consists of the parison’s forming, then the transfer in the mould. The third stage is the blowing of the hollow part and finally there is the deflashing so that to obtain the final product.The purpose of this study is to show the importance of the cooling on the final quality of the product. The study has particularly been concentrated on two parameters of the forming of the hollow part. These two parameters are the blowing time and the blowing pressure. We have studied the different shapes obtained with the adjustment of these parameters and we tried to find a correlation between shape and quality of the labeling.
How to Reduce the Costs of the Rheological Simulation in Blow Molding Industry?
The aim of our study is to show that we can readily obtain a first estimate of the behavior of a tube in blow molding only using free software. From a numerical model of biaxial stretching and blowing of a parison with specific boundary conditions and thanks to a mathematical package freely available on internet : « Octave », we have studied some rheological laws of plastic materials in order to find the evolution of the radius and of the height of the tube during the blowing process. Finally, to prove that our method can be right, we check our analytical results against a complete Finite Elements simulation performed with « Polyflow ».
Thermal Characterization for Radiation Treated Medical Products
A key feature for medical products is the need to sterilize products prior to release. However, the radiation dose, which disrupts DNA sequences in bioburdens, can also damage and alter polymer properties in substantial ways. Contrary to known degradations, there are also property enhancements through irradiation. In this presentation, both property degradation and enhancement will be illustrated with actual examples.
Aspects of Micromoulding Polymers for Medical Applications
Micromoulding is maturing as a viable technology used in the manufacture of intricate, minute, 3d plastic components. There still remains a knowledge gap in understanding the effects of processing on product properties. Studies conducted within our laboratories reveal that polymer melts are exposed to extremely high shear and heat transfer rates in the process. These process conditions influence product morphology and properties.
Rapid Prototyping to Rapid Manufacturing
Since its inception, Rapid Prototyping (RP) has undergone many changes and enhancements in both materials and systems. One of these system enhancements is the Stereolithography (SLA) small beam laser, which was proposed to 3-D Systems Inc. in the summer of 1993.
Fabrication and Analysis of Plastic Hypodermic Needles
This paper presents the fabrication of plastic hypodermic needles using micro-injection molding and the analyses of their buckling behavior. As a needle cannula is a thin-walled column (here 0.7 mm outer diameter and 0.15 mm thick), it is vulnerable to buckling. The buckling behavior is characterized through numerical simulations and experiments.
Stretch Blow Molding of PET Bottle: Simulation of Blowing Process and Prediction of Bottle Propeties
This paper presents a technique for describing more accurately mechanical behaviors of a PET stretch blow molded bottle by using distributions of modulus and thickness over the bottle surface. The values of modulus and thickness at each point of surface of the bottle were predicted from deformation histories of the material during the blowing process, which were obtained in numerical simulation of the blowing process. It also needed experimental measurements and estimation of mechanical properties of a stretched material up to stretch conditions in the blowing process in order to find out dependency of the properties on stretch conditions.
Evaluating the Use of Aluminum Inserts on SL Puzzle Molds for Injection Molding of Complex Parts: A Case Study
Stereolithography is a rapid prototyping technique that is also capable to producing rapid molds with high accuracy in a short time. The mold's life expectancy is strongly dependent on the part geometry. This factor could induce weak regions in the mold that are more susceptible to collapse, like sharp corners and thin features. An alternative that could be used is to conceive the mold as a puzzle where slides are manually placed inside a main slot and drawn during the ejection. This work describes a comparison between two puzzle molds that had been made with and without aluminum inserts.
Determining, Understanding & Controlling the Morphology of Injection Moulded Parts Produced in Stereolithography Moulds
The direct use of moulds produced by stereolithography (SL) provides a rapid tooling technique, which allows low volume production by plastic injection moulding. The process’ greatest advantage is that it provides parts that are the same as those that would be produced by the conventional hard tooling in a fraction of the time and cost. However, work by the author demonstrates that the parts possess different characteristics to those produced by conventional tooling methods. These revelations defy the greatest advantages of the SL injection moulding tooling process - the moulded parts do not replicate parts that would be produced by conventional hard tooling. This work investigates the mechanisms in SL tooling that induce these different part properties and describes different approaches to modifying the process which allow the moulded parts to demonstrate characteristics closer to those produced by conventional means. The work also indicates control methods that may be unique to SL tooling.
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