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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Education for the 21st Century
Since the downturn of 2009, there have been a number of developments that have caused us to question the value of a Liberal Arts education in our country. The events of the last year including free speech on college campuses and the high level of debt of college graduates plus the personal experience of seeing college again through the eyes of our children has inspired this paper.
Manufacturing has an opportunity to grow again in this country but the level of skilled personnel is diminishing. This gap in talent threatens the revival of manufacturing in the USA. What can be done in our education system to meet this gap or need?
Novel Thermoplastic Polymer for Soft Touch Applications
Polymer Dynamix has developed a novel thermoplastic compound which combines an appealing soft, silky feel combined with flexibility. The results demonstrate that reactive modification decreases the Shore Hardness and increases the flexibility and soft, silky feel of a thermoplastic elastomer.
3D Printing Offers a Giant Step for Short Run Injection Molds
Learn how 3D printed tools for injection molding can be used to save you time and money when creating short run prototypes from production grade plastics. This paper, will discuss the business rational behind this solution, show how some of our customers are using it and provide technical tips and tricks for success. We will also touch on a few of the future developments we see for this solution.
Long Chain Branched / High Melt Strength Linear Low Density Polyethylene for Blown and Cast Film Applications
While the physical properties of LLDPE are highly desired for many blown and cast film applications, it lacks the melt strength compared with LDPE. While LDPE can be blended with LLDPE to improve melt processability, key properties are sacrificed. This paper describes a proven technique for obtaining LCB or HMS LLDPE by means of high energy electron beam modification that increases the melt strength of reactor grade LLDPE by 5-7 times without secondary compounding and without creating gels. These materials can be used as stand alone film grades or as melt strength modifiers for conventional LLDPE and other polyolefins.
When Standards Get In the Way of Innovation
Standardization is a cornerstone of modern civilization. The weathering testing industry of today exists because of the work of standards writers around the world. However, there can be too much of a good thing. Test standards in weathering sometimes get in the way of innovation. For example, the most common cycle for testing polymeric materials in xenon arc test chambers is the 102/18 cycle. That is, the test is run for 102 minutes with light only, followed by 18 minutes of light plus water spray. Users of weathering standards assume the prevalence of this test cycle must mean that it has been carefully validated for a wide variety of materials over the decades. They may also assume that this cycle was developed to provide good correlation to natural outdoor weathering, with extensive scientific research and statistical analysis to support its broad application. They assume incorrectly. The origin of this cycle dates back to the Victorian era when the first carbon arc weathering test chambers were developed. Rotating racks completed one revolution in two hours, and specimens were sprayed with water for 18 minutes as they moved past the fixed spray nozzles in the chamber. In other words, the 102/18 cycle was set in stone a century ago and has rarely been questioned since then.
Standards have also hindered innovation by overstepping their boundaries. For decades automotive OEMs bemoaned the lack of correlation between their laboratory tests and real outdoor test results. Through the development of SAE J1960 and similar standards, OEMs wrote their testing requirements around specific pieces of hardware rather than test conditions designed to simulate and accelerate natural weathering conditions. Flaws and limitations in the old technology thus became standardized, precluding any improvements to the test methods. A few of the OEMs decided to do something about it, and this was the origin of ASTM D7869, which is a true state of the art weathering test standard fo
Selecting the Best Remediation Option for Failing CPVC Piping Systems
Chlorinated polyvinylchloride (CPVC) is widely used for many piping systems including potable water, hydronic heating/cooling, corrosive liquid drains, and fire suppression systems. CPVC is popular because of its ease of installation and corrosion resistance. However, as with all plumbing products, occasionally pipes or fittings may fail. Our goal as forensic scientists is to determine the root cause of failure of the CPVC piping and to provide the client with data that will help them select the most appropriate remediation option for their building. This paper presents four unique case studies, the forensic tools we used to evaluate the CPVC piping systems, and the logic behind the remediation option selected by the client.
Impact Modeling of Single-Ply TPO Roofing Systems
A finite element model was developed to simulate dynamic stress distributions in thermoplastic polyolefin (TPO) roofing systems subjected to severe impact events, e.g., hail and hard object strikes. In order to build an integrated TPO layered composite roofing system model, separate sub-models are developed that include: the TPO membrane, polyester reinforcement scrim, low modulus closed-cell foam and fiber-glass stiffened facer sheets. A hyperelastic Mooney-Rivlin model of the TPO membrane is utilized to simulate the membrane’s large-deformation mechanical response during simple impact tests. Straightforward force-contact measurements on the TPO membrane material and low modulus foam backing, using spherical indenters, are shown to provide sufficient material properties for the impact model of interest. It is demonstrated that the local failure modes for the layered composite roofing system can be adequately characterized by using relatively simple failure criterion for each of the individual component layers in this type of roofing system. Both high-speed indentation and ice ball impact experimental tests have been performed to evaluate and verify the predicted performance of a single ply TPO roofing system. Excellent correlation is obtained between model predictions and experimental dynamic indentation tests.
Troubleshooting Extrusion Using chillWARE Computer Simulation for Sagging and Collapsing of Pipe Ends
The Extrusion process is a complex process in which a good product quality can only be achieved when all the parameters of influence (e.g. design of machinery, throughput, temperature set up, cooling situation, vacuum level, etc.) are set correctly. In everyday production on only one extrusion lines several products have to be produced (often more than 100 different products on 1 line). Following, process parameters have to be changed quite often to adjust the machine for the demands of the new product. During such a product change procedure, very often product quality problems occur.
Frequent problems like sagging, roughness on surfaces, geometric problems, deformations or a bad mechanical strengths are caused very often by the cooling situation and can often easily be reduced, if correct process parameters would be used. In this paper the use of a computational system is presented to analyze the reasons and possible solutions for such problems during extrusion. The computational system is based on finite difference method and finite element method and shows the capability to calculate the cooling process, the crystallization time and the residual stress distribution in the product.
Improved Troubleshooting and Appropriate Maintenance in Injection Molding Using Adequate Measuring Technique
Injection molding is a sensitive process. After implementing a stable process to achieve the required product quality, there are many potential external disturbances that might lead to downtimes or off-quality production. Machine manufacturers do a lot of research to adjust the process and react on external disturbances, e.g. varying residual moisture of the resin . Disturbances coming from the central cooling unit, air compressors or the nitrogen generator can also lead to low product quality or high production costs, but have not been studied sufficiently as of today.
Simulation Based Determination of the Crystallinity Distribution in Polymer Pipes
The crystallinity and density of extruded semi crystalline polymer products has an intensive influence on the mechanical, geometrical and optical properties. Basically, the final polymer morphology depends on the overall production process. For semi crystalline polymers, the crystallization process can be separated into three sequential stochastic processes: 1. Nucleation: Arising of spherulite origins 2. Growth: filling the space, starting from the origins 3. Secondary Crystallization: compilation of the final crystalline structures Thus, the overall production process has an impact on the degree and type of crystallinity. The crystallization process is very complex and is influenced by the thermal and structure-mechanical history during the production process. A unified modeling of the different phenomena is hard to realize.
The simulation system chillWARE® is utilized to calculate the degree of crystallinity in dependency of the cooling process (thermal history) for polymer pipes. It is shown, how the distribution of the degree of crystallinity and density can be influenced by using alternative cooling technologies like internal pipe air cooling.
The Melt Temperature Variation in the Barrel of Injection Molding Machine
Experimental observations on the melt temperature variation in the barrel of injection molding machine are reported in this article. To examine the temperature variation in depth, the accuracy of temperature sensor should be much higher than the sheathed thermocouple used widely in the field. A novel temperature sensor with a less heat capacity than the usual sheathed type sensors was developed in this study. The effects of some process conditions on the variation were examined. The experimental results showed that the melt temperature in the barrel was affected by the process conditions such as the screw rotation speed and the heater temperatures as well as the injection rate. Also additional conditions such as the shot volume, the dwell time after plasticizing and the length of feeding section were examined.
Investigation of Fiber Breakage Phenomena for Different Fiber Types in Injection Molding
The lightweight technologies become the driving force for people in automotives and other developments in recent years. Among those technologies, using short and long fiber-reinforced thermoplastics (FRT) to replace some metal components can reduce the weight of an automotive significantly. However, the microstructures of fiber inside plastic matrix are too complicated to manage and control during the injection molding through the screw, the runner, the gate, and then into the cavity. In this study, we have integrated the screw plastification, to injection molding for fiber microstructures investigation. Specifically, we have paid our attention on fiber breakage prediction during screw plastification. Results show that fiber breakage is strongly dependent on screw design and operation. When the screw geometry changes, the fiber breakage can be higher even if the compression ratio is lower. Moreover, the fiber breakage phenomena for two types of fibers (glass fiber and carbon fiber) are also investigated. It shows that carbon fiber is easier to be broken. Also the carbon fiber length distribution has higher peak at the exit of the screw.
Tannic Acid: A Bio-based Intumescent Char-forming Additive for Nylon 6
Intumescent and char forming additives are typically blended into certain types of commercial plastics to impart resistance to fire propagation. Intumescent compounds such as ammonium polyphosphate/ melamine/ pentaerythritol, silica gel/potassium carbonate are already used as flame retardant (FR) additives. In this work, a naturally occurring polyphenol, namely tannic acid, is explored as an intumescent and char forming additive for polyamide - Nylon 6. The tannic acid was meltblended into Nylon 6 and the compounded plastic was evaluated for thermal stability, total heat release (THR) and heat release capacity (HRC). It was found that HRC and THR of nylon blended with tannic acid decreased by 50% and 20% respectively.
Scratch Resistance of Thin polymeric Films: Effect of Orientation and Polyethylene Content
Thin films are extensively used in many industrial applications such as automotive, electronics and packaging industries. However, their properties are significantly affected by several mechanical damages like scratch. Little has been done to understand the scratch behavior of polymeric thin films. Here, we consider investigating the impact of orientation and ethylene addition on the scratch resistance of PP thin films using an ASTM/ISO standard. Experimental results show that scratch resistance has improved with higher film orientation and lower ethylene content. A comparison between machine direction and transverse direction shows that scratch performance is much better in MD. Also, an FEM simulation has been performed to support the experimental findings. It is believed that this study is beneficial to design polymeric films with better scratch resistance.
Fundamental Factors for Opacity and Tint Generated with Titanium Dioxide
Titanium dioxide is a common pigment used in plastic applications to provide opacity. The opacity derived from a particular grade of titanium dioxide results from the optimization of several factors such as refractive index differentials, particle size distribution, levels of impurities, surface coatings and crystal phase. This paper describes the relationship of these factors with the pigment volume concentrations relevant to many plastic end uses and provides a general scale of which factor provides the most opacity impact. The paper highlights the areas of opportunity to tune opacity based on scattering for titanium dioxide particles due to particle size distribution and the expected boost in opacity. The matrices employed for the evaluation of optimization are tinted systems which demonstrate the relationship of pigment volume concentration with various particle size distributions. The results compare particle size distribution of various rutile products with elevation of the L* values at constant TiO2 loadings.
Clean Enough? The Importance of a Clean Surface to Attaining Adhesion
The cleanliness of plastic surfaces has a significant impact on adhesion - the largest factor in paint, coating, ink and adhesives failures. This article examines the use of atmospheric plasma to remove organic contaminants from plastic surfaces. We examine the importance of cleanliness to adhesion, and the results of plasma cleaning from a number of applications. We also review two common direct methods for measuring surface contamination: contact angle and optically stimulated electron emission. Taken together, atmospheric plasma cleaning along with an appropriate method for monitoring the cleaning process provide a significant safeguard for avoiding adhesion related failures in plastic part manufacturing.
Fabrication and Characterization of a Honeycomb Structure Piezoelectric Foam Based on Cyclic Olefin Copolymer
This paper discussed the fabrication and characterization of a COC based pseudopiezoelectric material. A multi-layer honeycomb structure was fabricated using supercritical CO2 bonding to maintain the original structure. The disklike shape of bubble is ideal for the piezoelectric foam. The results shows that the quasi-static piezoelectric coefficient can reach up to 7000 pC/N. And thermally stimulated discharge shows that sample has a working temperature higher than 150°C. The hysteresis loop test illustrated the charge build up process inside the artificial void. The charging threshold breakdown voltage is about 5000V. Such material have applications on sensing, actuating and energy harvesting and many other fields.
Design Optimization of the Layout of the Heating/Cooling Pipes in Rapid Heat Cycle Molding of a LED TV Shell
Compared to conventional injection molding, the rapid heat cycle molding (RHCM) mold design must meet higher requirements. Taking the average temperature, the quadratic sum of the temperature deviation, the average stress, the average maximum stress, and the average life as test indexes, the orthogonal test was done. Employing the math optimizing analysis software, 1stOpt, response surface models and regression equations of different indexes were obtained by analyzing the results of the orthogonal test. The optimization model of the heating/cooling pipe layout for a LED TV shell RHCM mold was established. Finally, the optimization design of the heating/cooling pipe layout was realized by employing nonlinear programming. The heating/cooling efficiency and lifetime of the optimized RHCM mold was ensured, and the molding cycle could be done in 62 seconds.
The Ultimate Thermal Transitions and Isothermal Curing Behaviors of a Two-Part Epoxy-Amine Adhesive System: Effects of Different Mixers
Various raw mixture samples of a two-part epoxy adhesive system were prepared using different mixers, including a series of commercially-available static mixers and a dual asymmetric centrifugal mixer. The total reaction enthalpies and ultimate glass transitions of the mixtures were measured using nonisothermal differential scanning calorimetry (DSC). The isothermal cure behaviors of the mixtures at selected temperatures were kinetically monitored as the time-resolved viscoelastic material functions by means of small-amplitude oscillatory shear rheometry (SAOS) and then, the characteristic physical transformation events including gelation and vitrification were determined. Based on these DSC and SAOS studies, it has been found that the ultimate glass transition temperatures and the occurrences of physical transitions during isothermal curing for different adhesive mixture samples may exhibit strong correlations to mixing tools. Hence, to attain optimum material properties at the cured states, it is important to choose and use a proper mixer for a two-part epoxy-amine adhesive system.
Determination of Stress Concentrations in Orthotropic Composites Using Mapping Collocation Techniques
This paper demonstrates the ability to determine the individual components of stresses by processing isopharic stress (sum of the normal stresses, sometimes it is called stress invariant or the trace of the stress tensor) with a series representation of the Airy stress function in complex analysis for orthotropic materials. The present case of a loaded plate containing an elliptical hole uses simulated experimental input from exact solution. The method presented here, which is based on equilibrium and compatibility, used complex-variable formulation involving conformal mappings, analytic continuation and numerical techniques. The technique utilized complex variables and mapping, and satisfies the traction-free condition analytically at the hole. The method is applicable for both isotropic and orthotropic materials.
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