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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Joining of Plastics and Composites
Analysis of Parameters for Heat Sealing and Ultrasonic Sealing of PET/PE Films.
Sealing of laminated polymer films is done by applying/generating heat in the seal area. Heat causes the low melting point inner layer to melt and intermolecularly diffuse with a matching layer, creating a joint. Two common processes for sealing are heat sealing and ultrasonic sealing. Different process parameters for both heat sealing and ultrasonic sealing were evaluated individually in order to find a relationship with peel strength. For this experiment a two ply film of PET/PE was used. In heat sealing, increasing the sealing temperature and sealing time caused an increase in peel strength. Increasing heat sealing pressure decreased peel strength. However, this was shown to be due to excessive pressures, which resulted in PE squeeze. In ultrasonic sealing, the effects of weld time and weld force on peel strength were evaluated. For ultrasonic weld time, initial increases caused large changes in peel strength with subsequent changes being less pronounced. Similarly, for ultrasonic weld force, initial increases in weld force caused increases in peel strength. However, at higher weld forces, peel strength decreased due PE squeeze out.
A Method for Cross-Sectional Analysis of Polymer Welds
A fundamental aspect of a polymer weld is the presence of intermolecular diffusion between the two joint surfaces. Without the movement of polymer chains across the melt interface, then the bond achieved is merely adhesive, and not a true weld. Therefore, it is essential to be able to determine where diffusion has occurred in order to properly evaluate weld quality. One of the simplest methods to do so is via cross section and heat treating of a weld section. The scientific basis for this process and the experimental method to complete it is presented here.
Durable Bond of Originally Incompatible Materials by Using the InMould-Plasma Process
Continuously increasing demands on the component functionality as well as the demand for efficient production processes are causing a change of multi-component injection molding from a special process to a key technology in plastics processing. However, the possibilities of the process are limited due to the complex interactions in adhesion. Innovative product solution ideas are limited by limiting material factors or by excessive process costs due to necessary process steps. The use of the atmospheric pressure (AP) plasma process can extend the compatibility of polymer materials. Nevertheless, a complete integration into the injection molding process has not yet been achieved. With the development of the InMould-Plasma treatment a process has been developed which integrates the plasma activation of plastic surfaces into the injection molding cycle. In this study it is shown that original incompatible materials, like polypropylene (PP) and thermoplastic polyurethane (TPU), have a long-term stable bond under different aging conditions, by using the InMould-Plasma technology. Due to their relevance in the automotive sector, the aging conditions are based on test standards of German car manufacturers. These include aging in an oven up to 120 °C, cold storage down to minus 40 °C, water storage and climate change tests. For testing the bond strength, the samples were peeled apart according to the standard VDI 2019. The influence of the aging of the individual components was supplemented by tensile tests. The test specimen are tensile rods according to DIN EN ISO 3167 and were subjected to the same conditions as the composite. It is shown that the InMould-Plasma process enables a long-term stable bond between originally incompatible materials and withstands the aging conditions in accordance with test standards of German car manufacturers.
Chemical Resistance Testing of Polycarbonates and Blends With Hospital Disinfectants and Cleaners
We tested an array of hospital surface disinfectants and cleaners for compatibility with several polycarbonate-based thermoplastic materials commonly used in healthcare equipment. To assess compatibility, we exposed tensile specimens to cleaners while under flexural strain, and then checked for cracking and tensile property retention. The results illustrate which cleaners are the harshest and which materials are the most chemically resistant. We also observed that periodic wiping and drying is frequently more damaging than the traditional test method of continuous wet exposure.
Development of Innovative Biocidal Nanoparticles For Use In Plastics Technology
Increased demands on high-end materials focus the development on new functionalities such as biocidal effects, which are made possible by property changes in the nanoscale range of existing materials or by a combination of different material classes. Therefore nanoparticles, based on transition metal oxides have been synthesized in order to reach biocidal properties on plastic part surfaces. The influence of the nanoparticles on the thermal and mechanical properties have been characterized as well as the biocidal properties of the plastic part surfaces and of the nanoparticles itself.
Effect of Photoinitiator Concentration and Curing Time on Soybean Polyethylene Glycol Resins
Bioprinting, a subset of additive manufacturing, utilizes bioinks, which is a combination of biomaterials and live cells, to produce functional tissue. Soybean oil is a plant polymer with promising biomaterial properties for development as a bioink. Soybean oil is low cost, has excellent biodegradation, biocompatibility and low immunogenicity.Additionally, suboptimal soybean properties such as mechanical and bioactive properties can be altered and improved when combined with other polymers. The curing of resins formulated from a combination of soybean oil epoxidized acrylate and poly(ethylene glycol) diacrylate was investigated with different concentrations of the photoinitiator diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide/2-hydroxy-2-methylpropiophenone, blend (DPH) and at different curing times. Visual observations of the cured resins indicated that as the photoinitiator concentration and curing time were varied, the resins exhibited changes in flexibility and rigidity / brittleness.
Long- and Short-Term Tensile Strength and Morphology of Joined Beta-Nucleated Polypropylene Parts
This paper presents the results of static short-term and long-term tensile tests for beta-nucleated joined polypropylene samples by the hot plate welding process. In the present study different dimensionless joining displacements are accounted for. The results show that high short-term tensile strength does not directly transfer to high long-term tensile strength. The morphology of the weld seam in the joined samples is examined by means of transmitted and reflected light microscopy. For the dimensionless joining displacements of 0.75 and 0.95, stretched spherulites are obtained. X-Ray diffraction can be used as a tool for qualitative and quantitative analysis and eventually for differentiation of samples of various joining displacements.
Modeling of Heat Generation in Spin Welding
Spin welding is a common joining process for plastic parts with circular joints such as insulated cups and bowls, filter housings, and valves. In this process, heat is developed from surface friction as one part is revolved about the axis of the joint, resulting in a high linear speed. Finite element analysis (FEA) of the process can provide insight into potential mechanical deformation or failure under load that may compromise the weld, as well as aid in determining proper process parameters to achieve sufficient heating for a good weld. In this work, an approach to predict the weld temperature has been investigated and compared to measured results.
The Effect of Argon Plasma Irradiation On 3D Scaffolds For Bone Tissue Engineering
Tissue engineering using 3D scaffolds is an alternative to bone repair techniques that are currently used, such as autografts or allografts for bone non-union. Plasma irradiation is used as a sterilization method and can alter the surface topography of the scaffolds. We have prepared 3D scaffolds composed of poly(lactic-co-glycolic)acid (PLGA) and nanohydroxyapatite (nHA) using thermally– induced phase separation (TIPS) and 3D-plotting (3DP) techniques. We have also performed experiments to study murine stem cell adhesion to scaffolds that have been plasma irradiated. The scaffolds that were plasma irradiated with argon gas had ~140% more cell adhesion compared to untreated scaffolds.
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