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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Comparative Study of Contact and Non-Contact Hot Plate Welding of HDPE
Hot plate welding is one of the most popular plastics joining methods and it is employed in most industries. Traditionally, the hot plate is coated with a non-stick" surface usually polytetrafluoroethylene (PTFE) which is usable to temperatures not exceeding 260°C. To avoid sticking to the hot plate and to accommodate higher hot plate temperatures non-contact hot plate is used. This paper is concerned with determining the optimum process parameters for non-contact hot plate welding of high-density polyethylene. For a given welding pressure the melt layer thickness weld displacement and their ratios were used as control or reduced parameters. During heating the melt layer thickness of the high-density polyethylene samples was measured. An empirical relationship between melt layer thickness and hot plate temperature and heating time was developed and used to predict the melt layer thickness in future experiments. The effects of the reduced welding parameters on joint quality are presented and compared with contact hot plate welding. For both processes the maximum attainable joint strength is 100% of the bulk material strength with the optimum melt layer thickness of 3.5 mm (1.75 mm for each part). The energy at break was more dependent on the ratio of weld displacement to melt layer thickness. For non-contact hot plate the optimum weld displacement melt layer thickness ratio was 0.75 compared to a ratio of 0.4 for contact hot plate welding.
Non Destructive Evaluation of Plastic Parts Using 3D Computed Tomography
During the production of plastic parts the presence of voids, inclusions, fiber reinforcement and fillers can play a critical role in the structural integrity of the product. Although in recent years tremendous improvements have been made in the field of analysis and design software to predict such factors, their physical detection is more difficult to accomplish. Certainly, when considering quality assurance and quality control, the ability to accurately and efficiently determine internal structure in a non-destructive manner is beneficial. This paper presents a novel method of using Computed Tomography (CT) to detect and visualize internal structure in polymer articles.
Biodegradable Polymer Blends for Medical Applications
Biodegradable polymers are used in medical applications, among many reasons, because of their history of biocompatibility. In this report an attempt has been made to establish the structure created by reactive processing of poly (caprolactone) and Easter 14766 with dicumyl peroxide (DCP). Results showed that PCL quantitatively formed tetra-functional branches while the Easter 14766 formed a combination of tri and tetra-functional branch points. The Easter 14766 was also shown to be more reactive than the PCL, with half as much DCP being required to achieve equivalent amounts of branching. Both Easter 14766 and PCL displayed typical branching behavior with increase in melt elasticity and zero shear viscosity. Easter 14766 showed a little improvement in mechanical properties. However, studies showed PCL to be insensitive to branching.
Practical Risk Analysis as a Tool for Minimizing Plastic Product Failures
Risk analysis techniques have become increasingly popular in the industrial sector, especially with the increasing number of mandated quality programs worldwide. Methods such as Failure Modes and Effects Analysis (FMEA), Fault Tree Analysis (FTA) and others are gaining wide recognition for their utility in product design. This paper discusses the practical use of risk analysis in plastic product systems as an up-front tool for design and product evaluation. Simplified techniques are presented which minimize the cumbersome nature of the risk analysis process and allow for more effective and efficient design and testing programs.
Avoiding the GIGO Syndrome - Combining the Real and Virtual Worlds in Analysis of Polymer Product Failures
In recent years, the advance of high speed processors in personal computers has placed the capability of sophisticated analytical methods on nearly every desktop. In the plastics industry, codes are readily available to model, among other things, stresses, thermal characteristics and flow. Without proper input, however, such analyses are subjected to the Garbage In, Garbage Out (GIGO) syndrome and can produce misleading results. This paper discusses an approach to analytical modeling that includes experimentation for model input and constitutive model development, as well as the use of experimentation for verification of numerical modeling results.
Ternary Composites: An Innovative Form to Improve Final Properties of Polypropylene
The incorporation of glass fibers in a thermoplastic matrix improves its tensile properties but decreases the impact strength. The addition of a third component such as an elastomer generates a new material with improved impact resistance but poor mechanical properties. In this work, a rubber phase was added to a glass short fiber reinforced polypropylenes to obtain a material with balanced tensile and impact properties. Two different types of rubber was used and analyzed. Some composites with different concentration rubber/FV/PP was prepared and molded by injection. Its mechanical an impact behavior was studied and the processing window was analyzed.
Municipal Plastic Waste: Alternatives for Recycling with Profit
The recovery and recycling with profit of municipal plastic waste (MPW) is still an unsolved problem. Only in the developed countries a small portion of their MPW is used with profit. The major part of the plastic residue is disposed of landfilling. This work analyses the existing methodologies for recycling and assesses their potential application to MPW. Also, a comparative study of incineration, in terms of energy saving and contamination risks, is performed. The energy required for recycling and the energy obtained for controlled incineration is calculated, and the maximum energy opportunity is obtained. On the other hand, the energy needed to recycle either commingled or separated plastic residues was compared, taking into account the final properties obtained and the compatibilization step.
Poly(vinyl alcohol)/Sodium Montmorillonite Nanocomposites
Poly(vinyl alcohol) / Sodium Montmorillonite hybrids of various compositions formed from water solution have been characterized utilizing X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC). Compositions with polymer concentration lower than 60 wt% formed intercalated hybrids predominantly, whereas higher concentrations of poly(vinyl alcohol) resulted in exfoliation of the clay layers in the polymer matrix. Furthermore, montmorillonite acted as a nucleating agent resulting in polymer crystallizing at higher temperatures for the hybrids compared to bulk polymer. It has also been observed that the presence of clay seems to induce a change in the polymer structure that is normally obtained through the annealing of poly(vinyl alcohol).
Determination of Solvent Independent Interaction Parameters for the HDPE/LDPE Blend by an Improved Inverse Gas Chromatographic Approach
The technique of inverse gas chromatography has been used to investigate the thermodynamics of blend of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) at three different concentrations and four elevated temperatures. The measured polymer-polymer Flory-Huggins interaction parameters, c23, suggest that the well-known probe dependence problem cannot be solved by simply satisfying the zero Dc criterion. The problem is mainly attributed to the use of different reference volumes in the calculations of c12, c13, and c1(23) for different solvents. By selecting a common reference volume, probe independent c23 values were obtained.
A Miscibility Study of LDPE/LLDPE Blends at Elevated Temperatures Using IGC
The technique of inverse gas chromatography (IGC) has been used to study the miscibility of low-density polyethylene (LDPE) with six linear low-density polyethylene (LLDPE) with different solid state density, molecular weight averages, and molecular weight distribution. In particular, the Hildebrand solubility parameters of the pure polymers were measured and used to calculate the corresponding interaction parameters ?LDPE-LLDPE at four elevated temperatures. Our results suggest that the two types of polyethylene are thermodynamically miscible in the chosen temperature range. And the miscibility behavior of LDPE/LLDPE blends seems to be insensitive to the properties of LLDPE.
Shear-Induced Crystallization in Injection Moldings of Ziegler-Natta and Metallocene Based Isotactic Polypropylenes
A comparative analysis of the shear-induced crystallization of metallocene and Ziegler-Natta based isotactic polypropylenes (i-PP's) was carried out. Numerous injection molding runs were performed and the effect of the shear-induced crystallization on the moldings was elucidated. The simulation of the injection molding process was performed using our unified crystallization model proposed earlier. The gapwise distributions of birefringence, crystallinity, spherulite size and thickness of the shear-induced crystallization layer in moldings were measured along with the mechanical properties of the moldings. The effects of processing conditions on these properties were determined. The measured values of crystallinity, spherulite size and thickness of the shear-induced crystallization layer were compared with the results obtained from the simulation of the injection molding process.
Electromagnetic Shielding and Protection against ESD by Using Stainless Steel Fibres
Non-conductive plastics are transparent for electromagnetic radiation. This can prevent the use of plastics in housings for electronic devices. A solution to this problem is to apply a conductive coating, or to make the plastic itself conductive by adding conductive fillers. We have proven that stainless steel fibres are an excellent means to make plastic conductive for EMI (Electro Magnetic Interference) shielding purposes. Electrically insulating polymers can cause electrostatic charging/discharging (ESD) problems in some applications. Integration of stainless steel fibres in the polymer can overcome these problems by preventing charge build-up and/or by providing a safe path for discharge currents. Stainless steel fibres can be mixed in thermoplastics (injection moulding), epoxy and poly-urethane (conductive floors), paint, elastomer, rubber, ...
Computer Aided Engineering Simulation versus Actual Performance of an Automotive Structural Component
Computer Aided Engineering (CAE) tools are able to provide powerful solutions to complex product design issues. A certain level of confidence in these solutions is assumed. However, the solutions provided are a function of several parameters: • Solver algorithm • Boundary conditions • Material properties • Fabrication process • Mesh size and type. How confident can we be in solutions from software that is performing an approximation of a real world condition based on all these variables? This paper will examine the effects of mesh size and solver method on the analysis accuracy when compared to the physical testing. To increase our confidence in these solutions, we wanted to understand the relationship between the key parameters and physical testing results. We compared various Finite Element meshing methodologies and analysis codes (structural and moldfilling) to lab tests of a Ford Ranger Pickup truck tailgate handle. Lab tests consisted of a tensile machine pulling directly on the back face of the ranger handle, which was injection molded in Nylon 6 polymer with 15% glass and 25% mineral fillings. Since material properties change with water absorption for nylon resins, all tests were conducted on dry as molded samples. Displacements and load values were documented for each test. The solutions provided from the analysis codes (while modifying element type and mesh size) were compared to the physical test results. Additional analytical lab testing was completed on the molded samples to confirm part composition, physical properties and glass orientation. Conclusions and recommendations were based on how closely the solutions matched the physical tests.
Increased Speed to Market Using CAE Simulation for Injection Molded Plastics Parts
The ability to cut time and cost from a molding program is a significant advantage for injection molders operating in an increasingly competitive marketplace. Warpage and other defects that show up in molded plastics parts, as well as inefficiencies in production are unacceptable. Innovation, productivity, and dedication to quality are crucial for suppliers of injection molded parts. CAE simulation software offers a competitive advantage to those who wish to eliminate inefficiencies in their operations - advantages such as shortened time to market, efficiency improvements in the use of raw materials, reduced cycle times, and optimized production efficiency and product quality.
Chemo-Rheology and Structure Development of a Solventless System for Manufacturing Electronic Pre-Pregs
Current processes used to manufacture electronic pre-pregs and laminates use solvent based systems. Solvents are environmentally unfriendly and add no value to the final product. We are developing a new solventless process, based on the concept of continuous Resin Transfer Molding or Injection Pultrusion. The first step in designing the process is to select a suitable chemical system. The viscosity of the system should be such that it allows proper impregnation at a temperature at which not much reaction takes place. To predict the required pulling force, the friction at the wall as the material solidifies needs to be truly understood. A potential resin system has been identified and its chemo-rheology and structure formation will be discussed.
Gas Absorption with Filled Polymer Systems
This paper deals with the gas absorption behavior of polymer systems. The emphasis is on the difference between filled and unfilled polymers to explain heterogeneous nucleation in filled polymers. A Foaming process simulator has been built to study the gas absorption. It consists of a test chamber that holds the polymer samples. The chamber can be pressurized with gas up to 5,000 psi and heated up to 450°F. The gas pressure is monitored by a high-accuracy pressure transducer and recorded by a data acquisition. The amount of gas absorbed by a polymer is determined from the pressure change. A rotor applies shear to the polymer melt to investigate the shear effects. Two polymer systems were tested, HDPE with/without talc, and PVC with/without calcium carbonate. It was found that the filled polymers absorbed more gas compared to the unfilled ones. It is suggested that there is a certain amount of gas accumulated in the filler-polymer interface. This accumulated gas helps to create nucleation sites during the foaming process.
Trimellitates-Versatile Plasticizers for the Vinyl Compounder
Since the introduction of Trimellitic Anhydride by Amoco Chemicals in the late 1960s trimellitates have found their place in applications requiring greater permanence than what commercial phthalate plasticizers could bring. Trimellitate plasticizers offer today's vinyl compounder a unique combination of properties not attainable with polymeric or other monomeric plasticizers1,2. Phthalate plasticizers, long the workhorse of the industry, are efficient, process easily, impart good low temperature properties, and are well-suited for general use. Unfortunately, the phthalates can be volatile and lack the permanence needed for high temperature applications. The polymerics, which have the permanence necessary for high temperature applications, are often inefficient, difficult to process, have poor low temperature properties, and are expensive. The data presented here will demonstrate how trimellitate plasticizers bridge the performance gap between the phthalate and the polymeric plasticizers, combining the easy processing and low temperature properties of the phthalates with the low volatility and permanence of the polymerics. Compounds directed at two markets will be looked at: UL 105 °C Wire and refrigerator gasketing compound.
The Role of a Heat Affected Zone (HAZ) on Mechanical Properties in Thermally Welded Low Density Polyethylene Blown Film
Low density polyethylene (LDPE) thin films are produced by blown film extrusion. The control of key variables during processing is important in the development of optimized microstructure and mechanical properties. Joining several extruded film pieces by thermal welding is common in industry to produce finished products. It has been reported in the literature that the welding process impacts the cold brittleness temperature of a film and weld system. This observation is confirmed in this work. There have also been reports in the literature of changes in polymer microstructure and properties adjacent to thermal welds in non-film applications such as pipe welding. This Heat Affected Zone (HAZ) has been observed here for the first time in the thin films. The size of the HAZ is shown to scale with welding temperature. Evidence correlating the size of the observed HAZ to the degree of change in cold brittleness temperature is also presented.
The Plastics Resources for Educators Program (PREP)
The Plastics Resources for Educators Program (PREP) was developed as part of the National Science Foundation's Advanced Technology Education (ATE) project. The funded project was entitled, Advanced Technological Education in Plastics Engineering Technology". The PREP program aims to help establish the educational infrastructure necessary to insure the U.S. plastics industry remains internationally competitive. There are three major outcomes associated with PREP. The first outcome is the development of instructional materials including plastic processing simulators virtual laboratory instruments and an electronic textbook. The second outcome is the development of the summer plastics educators institute at UMass-Lowell. The third outcome is establishing a communication forum that will facilitate exchange between plastics and polymer educators nationally. An overview of PREP and the structure of the program will be discussed. Examples of materials available to plastics and polymer educators via the PREP Internet WebPages will also be demonstrated."
Blends of Ethylene/Styrene Interpolymers and Other Polymers: Rheology and Morphology during Processing
Ethylene/styrene Interpolymers produced via INSITE* Technology exhibit compatibility with a wide range of polymers due to their inherent combination of olefinic and styrenic functionality. Blends of Interpolymers with polyethylene and polystyrene are discussed in terms of rheology, morphology, and observations from injection molded products. Dispersion of the minor phase is predicted by a rheological model, and these predictions are compared with the morphology of the blends.
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