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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Evaluation of Oriented Polypropylene/Cast Polypropylene Film at the Heat-Sealing Part and the Edge
Heat-sealing process is often employed in packaging applications of polymeric films, especially for plastic bags. Often, the failure of plastic bags would initiate from a pinhole, crack, and/or the edge near the heat-sealed part. In this study, effects of heat-sealing temperature on mechanical properties of heat-sealing part and the edge of Oriented Polypropylene/Cast Polypropylene films were investigated. Fracture toughness and tear tests were conducted with the heat-sealed Oriented Polypropylene/Cast Polypropylene films. The thermal properties of the heat-sealed parts obtained by differential scanning calorimetry (DSC) were also investigated.
Long-Term Thermal Insulation Performance of Polystyrene Foam Boards with Decay of Blowing Agents
This paper studied the long-term thermal insulation performance of polystyrene foam boards with the decay of blowing agents. A transient cell-to-cell diffusion model was developed to predict the decay of blowing agents. The Mie Theory was used to quantify the radiative conductivity. A cubic-parallel-series analogy of electric circuit was employed to acquire the thermal conductivity of gaseous phase and polymer matrix. Thus, the thermal insulation performance was estimated as the blowing agents decayed. The effects of foam morphology and blowing agent type on thermal insulation capacity were examined.
Understanding Melt Rheology & Foamability of PP-Based TPO Blends
Rubber-toughened PP is an important resin for many engineering applications. By structural foaming, material cost-saving and lightweight structures can be achieved. In this study, physical blends of PP and poly(ethylene/octene) with various compositions were characterized regarding their melt strength and shear viscosity. The high pressure MuCell® foaming process was used to obtain structural foams with average cell diameters of < 50 ?m and cell densities of ~ 8 × 106 cells/cm3. This study presents key correlations between material rheology and its suitability for structural foaming and elucidates how the foaming behavior is linked to blend composition and melt temperature for an optimum system.
A Shrinkage Prediction in Rubber Compression Moulding
One of the common problems found in rubber compression moulding is the shrinkage of rubber products leading to the loss of shape. In this research, an application of artificial neural network in prediction of the rubber product shrinkage in compression moulding is presented. A back propagation neural network was developed to determine the shrinkage based on the variables of the rubber compound, processing variables such as mould temperature and mould sizing. The neural network prediction for an inside diameter shrinkage and a cross section diameter shrinkage indicate that the architectures 5-11-21-1 and 5-11-16-1 provide a good prediction within 95.9% and 96.1% accuracy, respectively.
Functionally Graded Polymer Nanocomposites (FGPNCs) Filled with Nano Sized Filler
A novel FGPNCs has been developed using polymer matrix (polyisoprene) and nanomaterials (amorphous carbon). Its performance is evaluated for structural application through storage modulus, loss tangent, tensile strength, modulus, hardness, hysteresis loss, tear strength, SEM, etc. The functionally graded nanocomposites show better properties i.e., modulus, tear strength, hysteresis loss and strain energy density compared to homogeneous composite at the same percentage of nano filler loading. As for examples, 20, 35 and 40% improvement in modulli at 50, 100 and 200% elongation with respect to homogeneous composites are observed where the average nanomaterial is 30% by weight.
Manufacture and Mechanical Characterization of a Composite Material Made of Wasted Tires and Recycled Polyethylenetherephtalate (PET)
Solid residue was obtained by two processes to reduce discarded tires: pyrolysis and thermal shock. Techniques such as X-ray, FTIR, TGA and SEM were used to characterize the samples. Two types of polyethylenetherephtalate, PET (virgin and recycled) were analysed physicochemical and mechanically to be used as matrix. A composite material was manufactured by employing a Brabender mixing chamber in order to use the granules as filler on PET at different concentrations. The mixed material was laminated and tension test were undertaken in samples to acquire the mechanical properties. Studies of fractography were performed to understand the failure mechanics.
An Optimization of Natural Rubber Injection Molding Process Using CAD/CAE: A Case Study on the Motorcycle Rubber Step
This research aims to apply Computer Aided Design/Engineering (CAD/CAE) techniques for an optimized rubber injection molding condition using a case study of rubber steps used in motorcycles. The input parameters include both physical and mechanical material properties of natural rubber and operating conditions such as gating and runner positions. The simulated variables such as temperature, pressure and velocity profiles were founded and analyzed. The numerical results are correlated well with empirical data using the vertical injection molding machine. This research provides researchers the computational tool to obtain the optimized rubber injection molding.
Shape Memory Polyurethane-Clay Nanocomposites
In this paper, we present results on shape memory behavior of polyurethane (PU)/clay nanocomposites. These nanocomposites were prepared via bulk polymerization method and contained exfoliated clay particles as revealed by transmission electron microscopy and wide angle X-ray diffraction method. The PU matrix contained a crystalline soft segment, which was responsible for shape fixity. The presence of clay decreased the crystallinity of soft segments and consequently shape fixity, but the magnitude of shape recovery stress increased, e.g., by 20% with only 1 wt% clay. The mechanism of reinforcement was studied by monitoring stress relaxation and phase separation.
Injection Molding Process Optimization Using the Process Monitoring System
To make sure the stable state of resin in the process optimization test, the process monitoring system (PMS) was applied in a wide range in this study. For each critical step of the test, the way to utilize the PMS depended upon the phenomenon in the mold and the purpose of the test. The dependent variables such as switchover point and holding time were properly set with the aid of the PMS. Based on the relationship of the state of the resin with pressure and temperature, a new PMS index was proposed. The index showed the best correlation with the part weight among various indices through the correlation analysis.
Hybrid Nanocomposites of Carbon Nanotubes (CNTs) Grown on Carbon Fiber in Polyester Matrix with Improved Thermomechanical Properties
Carbon nanotubes (CNTs) were grown on the surface of carbon fiber using thermal chemical vapor deposition (CVD) technique. Ni is used as a catalyst. The coating of catalyst on the surface of carbon fiber was done by electroless dip coating technique. By performing structural characterization of CNT coated carbon fiber using scanning electron microscope (SEM) and transmission electron microscopy (TEM), the length and diameter of CNTs were measured and found to be ~9000 nm and ~40 nm respectively. Thermo gravimetric analysis (TGA) of as received and CNT coated carbon fiber samples in nitrogen atmosphere indicates that the CNT coated carbon fiber samples are thermally more stable. The improvement in storage modulus in CNT coated carbon fiber samples is observed in dynamic mechanical analysis (DMA).
Influence of Part Thickness, Glass Fibre Content and Line Energy on Laser Transmission Welding of Polyamide mXD6
Laser transmission welding is a process used to join two thermoplastic materials based on their abilities to transmit and absorb laser energy. The influence of part thickness, glass fibre content, and line energy on the laser welding of a semi-aromatic polyamide was examined. Plaques of polyamide mXD6 were moulded at three different thicknesses (0.5 mm 1 mm, and 2 mm), a range of glass fibre contents (0, 30, 50 and 60%) in both natural and black. Lap welds were made using a Rofin Sinar diode laser in a contour welding mode over a range of line energies. The assemblies were tested in shear and the fracture surfaces examined using scanning electron microscopy.
Modeling the Rheology and Orientation Distribution of Short Glass Fibers Suspended in Polymeric Fluids: Simple Shear Flow
In this paper we present a constitutive relation for predicting the rheology of short glass fibers suspended in a polymeric matrix. The performance of the model is assessed through its ability to predict the steady-state and transient shear rheology as well as qualitatively predict the fiber orientation distribution of a short glass fiber (0.5 mm, L/D < 30) filled polypropylene. In this approach the total extra stress is equal to the sum of the contributions from the fibers (a special form of the Doi theory), the polymer and the rod-polymer interaction (multi-mode viscoelastic constitutive relation).
Ultrasound Assisted Single Screw Extrusion Process for Dispersion of Carbon Nanofibers in Polymers
A novel method for the continuous dispersion of carbon nanofibers (CNFs) in a polymer matrix for manufacturing high performance nanocomposites was developed using an ultrasonically assisted single screw extrusion process. The effect of ultrasound on die pressure, electrical conductivity, rheological, morphological and mechanical properties of polyetherimide (PEI) filled with 1-20 wt% CNFs was studied. A reduction in the die pressure, percolation threshold and an increase in the viscosity, Young's modulus and electrical conductivity along with better CNF dispersion in nanocomposites was achieved through ultrasonic treatment.
Studies on the Thermomechanical Properties of Nickelphosphorous Coated Carbon Fiber Fabric/Polyester Laminates
A systematic study was carried out to investigate the effects of nanoscaled electroless nickel-phosphorous alloy coating on the thermomechanical properties of woven carbon fiber fabric reinforced polyester matrix composites. The electroless nickel-phosphorous coated carbon fiber fabrics with different coating time interval (0, 5, 10, 15, 20, 25, 30mins) were prepared. The polyester matrix was then used to manufacture weave carbon fabric/polyester nanocomposites using wet lay-up process. Dynamic mechanical analysis (DMA) studies were carried out in bending and tensile mode. Experimental results showed Maximum improvements in modulus for 30mins coating time reinforced composites. Dynamic mechanical analysis showed enhancement in thermomechanical properties. The nickel-phosphorous coated carbon fiber fabric composites showed a considerable improvement in the glass transition temperature (Tg).
The Effect of Implementing Hybrid Mold Temperature Dependant Heat Characteristics on the Accuracy of 3D Injection Molding Simulation
When analyzing the thermal behavior of hybrid molds, normally fixed values for thermal characteristics are implemented. This paper will discuss the underestimated effect of temperature dependant heat characteristics of hybrid mold materials on the accuracy of 3D injection molding simulation via obtained results of a former PhD work and implementation of this knowledge into Moldex3D (M3D).A hybrid mold of a technical part was designed to analyze this problem. It also resulted in a better understanding of the mold design strategy and 3D simulation advantages for multiple material molds related to filling, warpage, cooling and final part quality.
Influence of Process Parameters on the Weld Lines of a Micro Injection Molded Component
The insufficient entanglement of the molecular chains and the stress amplification at the v-notch of a weld line compromise the mechanical strength of a plastic product, also in the micro scale. To investigate the influence of process parameters on the weld lines formation, a special micro cavity was designed and manufactured by ?EDM (Electro Discharge Machining). Weld lines were quantitatively characterized both in the two-dimensional (direction and position) and three-dimensional range (surface topography characterization). Results showed that shape and position of weld lines are mainly influenced by mold temperature and injection speed.
Laser Transmission Welding of Electro-Pneumatic Valves
Laser welding has proved an appropriate method for joining plastic parts. The increasing trend towards greater freedom of design, integration of ever more functions, and therefore more complex modules is putting increasing pressure on joining technology, and is thereby promoting the development and introduction of novel technologies.Laser welding of plastics is a suitable complement to established joining processes, and thereby opens up new fields of application. This has been demonstrated by numerous applications for small and even for larger components.Compared to alternative joining methods the contact free method has the advantage that hardly any flash or no flash is being produced, which means that joints with a high quality visual appearance can be produced. The laser is clearly superior to alternative processes, even for joining 3D geometries produced by coupling to a robot. The heat-affected zone is only a few #m deep and reduces the risk of surface flaws.The following paper is a case study for the introduction of the Laser welding process for electro-pneumatic valves. It describes the process development from the initial tests to the In-Line integration in mass production.
Birefringence Distribution in Gas-Assisted Tubular Injection Moldings: Simulation and Experiment
Measurements and simulation of three birefringence components and of the gas/polymer interface distribution in gas-assisted injection molding (GAIM) of a tubular geometry are presented. The governing equations of the process are derived using a nonlinear viscoelastic model and solved using a hybrid finite element/finite difference/control volume method (FEM/FD/CV). The measurements were carried out on polystyrene moldings before and after annealing. Simulation and experimental results indicate that the birefringence is high in the gas penetration region and low in the region where the gas did not penetrate.
Radiation Cross Linking Engineering Thermoplastics for Tribological Applications
Electron beam irradiation primarily leads to cross linking in the amorphous fraction of semi-crystalline thermoplastics. As a result, there is a change in morphology and an improvement in mechanical and thermo dynamical properties. This effect can be utilized for tribologically stressed parts as micro parts and gear wheels. These parts feature an unfavorable relationship of part/volume leading to a disadvantageous formation of morphology and crystallinity. Experimental work shows the potentials of radiation cross linked polyamides. Due to cross linking in particular the thermal-mechanical and tribological properties are shifted into a range, which enables the employment of this substrate for application at elevated temperatures. Furthermore, the investigations on PA6 and PA66 show that a lower crystallinity degree leads to better results of cross linking via electron beam radiation and to an improvement of abrasion resistance.
Failure Analysis and Prevention – A New European SIG
The new European Failure Analysis and Prevention Special Interest Group (FAPSIG) is creating a database with failure cases. The members share this database and contribute with their own failure investigations. The two main groups are Failure Causes and Failure Mechanisms. Failure Causes are subdivided in: Stress concentrations, low mass and/or mould temperature, highly stressed weld lines, faulty ribbing; too high stiffness of construction elements, incorrect joining, and incorrect material selection.Failure Mechanisms are subdivided in: Creep and stress relaxation, wear, fatigue, UV degradation, chemical attack, environmental stress cracking.The paper will present some examples for designers of plastic products.
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