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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Melting Performance Analysis Of A Single-Screw Extruder With A NSB Screw
A recent design of a new screw referred to as the No Solid Bed (NSB) screw was introduced and the initial operation was presented . This new screw has channels in the transition section that do not allow a compacted solid bed to form. The data presented here compliments the data that was previously published.
Relative Humidity Effects on Accelerated Aging of Medical-Grade Polymers: Should ASTM F1980 be Revised to Recommend Constant RH Instead of Constant Moisture Content?
ASTM F1980 provides a methodology for accelerated aging of sterile barrier systems for medical devices, and is also widely used as the definitive guide for accelerated aging of medical devices and pharmaceutical packaging. ASTM F1980-16, as well as previous versions going back to 2007, emphasize that when increasing temperature to accelerate aging, it is preferable to decrease relative humidity so as to maintain an approximately constant moisture content. However, there is a revision under consideration by the ASTM F02.50 committee that would dramatically change this guidance to indicate a preference (although allowing for other options) to keep relative humidity approximately constant. This change is based on somewhat limited test data and literature review published recently by Thor et al. In this paper, we perform a study looking at eight resins (PP, COC, ABS, PC/PET, Copolyester, PBT, PA66gf, PUR) that have been aged at 60C and three different RH levels to evaluate the impact on aging. Our findings to date indicate that: (i) yes, it is likely that RH should be held constant when increasing temperature in order to keep moisture constant in the resins at a similar level; and (ii) for the medical-grade resins evaluated here, RH level does not significantly impact the physical aging mechanism. We also recommend that further accelerated aging studies are performed to more thoroughly evaluate the impact of moisture content on Q10 factors, corrosion rates, and other endpoints before this dramatic change is made to the ASTM F1980 standard.
Automated Optimization Of A Block-Head-Mixer With An Innovative Algorithm
CFD-Simulations are a common tool to design and optimize mixing elements. The manual evaluation and experience-based derivation of an optimized geometry is still an iterative process which is time consuming. In this paper an automated algorithm is developed and tested for a mainly distributive Block-Head-Mixer. To automatically evaluate the flow field of each geometry variant, quality criteria are introduced which enable the assessment of the mixing capability. The investigation showed that the quality criteria are suitable to evaluate the flow field and an optimized candidate compared to a starting geometry could be found automatically.
Development Of An Inline-Measurement System Of The Surface Temperature Of Square Hollow Profiles
In polymer extrusion, the die temperature is normally set to the recommended temperature in order to reach a homogeneous melt. Nevertheless, the measurement of the melt and surface temperature of the product leaving the die is not state of the art due to the difficulty of an inline - measurement. As a consequence, the product temperature leaving the die is assumed as the set die temperature. Therefore, this article aims to engineer an inline-measurement system of the surface temperature of square hollow profiles immediately after leaving the die. First, two objective quality criteria to define the thermal melt homogeneity, named weighted melt temperature and radial temperature, are introduced. After that, experimental investigations are carried out for two different types of polyolefin polymers with the variation of several process parameters such as the screw speed and the die temperature. In order not to distort the product, the developed construction is based on a contactless measurement system using infrared pyrometers to measure the average surface temperature on each side of the profile. After all, rules of behavior are derived from the process and correlations between the investigated process parameters and the melt quality as well as the surface temperature are identified.
Production Of Flexible Thermally Conductive Thermoplastic Pipes By Orientation Of Filler Particles
Pipes for heat exchanger systems are usually made of metals to achieve a high level of energy transfer. Polymers, in comparison, save weight and costs and are suitable for use in corrosive and chemically aggressive environments. However, for many applications the comparatively low thermal conductivity of polymers is a disadvantage. To overcome this, polymers are usually mixed with high amounts of fillers, which transport the heat through the pipe wall. But the use of high filler ratios influences the mechanical properties of the pipe significantly. The aim of this paper is to develop a concept for a pipe extrusion die which aligns the filler particles in radial direction, so that the anisotropic material properties of the compound can be utilized and thus the amount of filler can be reduced. Consequently, the flexible material properties can be maintained as far as possible. Several die concepts are presented and their influence on the thermal and mechanical properties of the pipe are compared.
Scale Up Optimization Of Optical Nanolayer Films: Improved Thickness & Compositional Control
A nanolayer coextruded optical film process was scaled up and optimized to show improvements in the thickness and compositional control at production level throughput rates. Adjustment of processing temperatures, implementation of online continuous gauging and automatic die lip adjusting equipment, and upgrades to the cast film pinning system led to improvements of film thickness control. A unique profile control scheme utilizing only the middle layer’s thickness instead of the total film thickness has been successfully utilized to control the critical layer’s thickness. Automation and optimization of the extruder’s feeding system provided compositional control capable of meeting tight quality specifications. With these improvements, production scale throughput rates of high-quality optical cast film capable for unique gradient refractive index (GRIN) optical applications were demonstrated.
Three Trends in Healthcare Adhesives
With an aging global population growing, the demand for new healthcare products and telehealth systems will increase. The FDA aims to advance innovation and development in digital health while ensuring patient safety and effectiveness. Adhesives are critical in the new remote monitoring products, such as the small wearable devices that stick to skin. In addition, surgical adhesives are replacing stitches, and robotic surgical systems are rising. With healthcare adhesives, there are additional challenges in safety, performance, biocompatibility ISO 10993, and cost requirements. This paper reviews three healthcare adhesive trends: (1) topical skin adhesive patches, (2) tissue adhesives, and (3) medical device assembly and equipment adhesives.
Adhesion of Overmolded TPE to FR-PC/ABS: Effect of TPE Properties and Substrate Color Recipe
Various grades of Thermoplastic Elastomer (TPE) were overmolded onto a FR-PC/ABS blend prepared with several different color recipes and tested for adhesion. All combinations prepared exhibited adhesive failure with a standardized peel test, yet showed relatively high average peak peel forces that ranged from 3.74-4.07 N/mm, which agreed well with literature values. Different color recipes for the substrate had no discernable effect on peel forces. Two-step overmolding of TPE using pre-molded (and therefore conditioned) substrates gave no significant difference to those prepared with direct 2-shot overmolding.
Effect of Molding Parameters on Orientation and Tensile Properties of Polycarbonate
The tensile properties of two different molecular weight polycarbonates were examined in relation to injection-molding conditions, such as low and high temperatures & speeds (affecting injection pressures), that were beyond those recommended by the supplier. We found conditions that prompted higher injection pressures led to decreases in tensile elongation-at-break, with more significant decreases for higher molecular weight (and high viscosity) PC. Examination of molded samples under polarized light suggested higher degrees of molded-in stress along the flow length as an important contributor to the changes in elongation at break. Additionally, corresponding to the elongation at break, the onset of strain hardening decreased under injection molding conditions that produced higher injection pressures.
Effect of Rubber Surface Treatment on the Properties of Rotomolded Thermoplastic Elastomers
Thermoplastic elastomers (TPE) are a combination of a rubber and a thermoplastic to create a recyclable blend combining the properties of both resins. The objective of this work is to produce and characterize rotomolded parts based on polyamide 6 (PA6) as the matrix and recycled ground tire rubber (GTR) as the dispersed phase. In order to improve the adhesion between PA6 and GTR, and consequently the mechanical properties of the resulting TPE, a treatment with formic acid was used on the GTR surface. All the samples were initially mixed via dry-blending using 5 and 10% wt. of GTR and then rotomolded. For these concentrations, successful rotomolded parts were produced to report on their morphological and mechanical properties. The results show that increasing the GTR content led to lower tensile modulus and tensile strength, but higher elongation at break and impact strength compared to the neat matrix.
Polypropylene/Ground Tire Rubber (PP/GTR) Composites Produced Via Rotational Molding
In this work, polypropylene (PP) was dry-blended with ground tire rubber (GTR) to produce composites by rotational molding. In particular, the effect of GTR content was investigated to modify the mechanical properties of the PP matrix. Each compound was characterized via morphology, density and mechanical properties (tensile, flexural and impact). As expected, the results showed that all the mechanical properties decreased with increasing GTR concentration due to its low modulus and strength. Also, the crosslinked structure of the GTR particles is believed to limit the interfacial PP-GTR interaction, thus also limiting mechanical stress transfer.
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.
Windows of Opportunities for Single Site Catalyst
What makes company A produce 50,000 tons/year more of the same PE or PP than company B at the same cost? Catalyst, catalyst and catalyst. Very quietly, catalyst research has brought revolution in the plastics industry. So-called single-site catalysts (many of which are metallocenes) are closely guarded secret of alpha-olefin "big guys". A single metal atom held between two carbon rings builds metallocenes. They might look naive but provide greater control over molecular chain length and structure of polyolefins. These polymers are stronger, purer, and clearer. Upon utilizing these catalysts, material suppliers can accurately design tailor-made resins for specific applications.
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