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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Vibration-Assisted Liquid Composite Molding
By oscillating the injected resin stream in liquid composite molding, the mold filling time can be significantly reduced. Flow enhancement is achieved because of the shear-thinning characteristics of typical polymer resins, as the effective shear rate of the resin is increased by oscillation of the resin within the fiber preform and the viscosity of the resin is correspondingly reduced. An experimental apparatus has been developed which consists of one-dimensional flow within a fiber preform and a vibrating piston which forces the inlet resin stream to oscillate. Experiments have been conducted using a polyacrylamide/water solution to simulate the polymer resin, and effects of oscillation amplitude, frequency and fiber volume fraction have been investigated. A simple analytical model has also been developed, and experimental results confirm the predicted trends in the amplitude, frequency and volume fraction effects on flow enhancement.
Rapid Surface Treatment of Reinforcing Fibers Using Ultraviolet Light Processing
A fast, inexpensive and environmentally benign process requiring only UV light and air for the surface treatment (oxidation) of reinforcing fibers has been developed that represents a substantial improvement over existing methods. In this new method, fibers are subjected to short wavelength ultraviolet (UV) light producing ozone from atmospheric oxygen. UV photons can also react with ozone to create monatomic oxygen, a highly reactive chemical species which is available to oxidize the fibers. Additionally, the UV photons can break chemical bonds on the fiber surface creating favorable conditions for reaction with ozone and monatomic oxygen. The result of this two-fold process is the rapid oxidation of the fiber surface that is essential to promote favorable interactions with the matrix in polymer composites. The effect of UVO treatment on the surface chemistry, tensile strength, and interfacial adhesion of a PAN based carbon fiber and an aramid fiber is reported.
Water Diffusion Based Non-Destructive Evaluation (NDE) of PMR-II-50/M60J 4HS Weave Carbon Fabric Composite Materials under Stress-Thermal Cycling
Due to the geometric complexity of woven fabric composite materials, conventional Non-Destructive Evaluation (NDE) methods such as x-radiography and acoustic emission (AE) do not show microcracks well inside the materials. In this study, a simple and cost effective water uptake test as a NDE methodology for PMR-II-50/M60J (polyimide/carbon fiber) 4HS weave fabric composites is suggested. The short term water uptake test for 24 hours at 80°C has been performed before and after stress-thermal cycling experiments with the TAMU developed conduction heated stress-thermal cycling apparatus. The woven composite materials’ non-Fickian model during short term water uptake, that is, the rate of uptake initially increases rapidly followed by quick slow down associated with diffusion in cure-induced voids and cracks was modified by the effective diffusivity depending on crack densities. The suggested crack densities dependent diffusion model was compared with the experimental data. The application of the water absorption induced NDE was also re-evaluated by comparing to the results of the literatures in terms of crack closure by swelling and unloading of the existing load and matrix dissolution by hot water.
Nanocomposite Polyetherimide with High Thermo Oxidative Stability
Selected fillers were incorporated to prepare polyetherimide composite. The influence of fillers on the thermo-oxidative stability of the composite was studied by thermogravimetric analysis. The results showed that at optical filler loading and characteristics, the polymer composite became superior in its thermo-oxidative stability that is very promising in widening the window of service temperature of polyimides for extremely high temperature conditions where most polymeric composites fail. The findings should prove useful in developing high-temperature polymer composites for aerospace and electronics applications.
Low Cost Processing of Carbon Fabric Reinforced Nylon Composites
This manuscript describes the processing techniques and processing windows used to produce carbon fiber reinforced nylon matrix composite panels. Preliminary mechanical property measurements were also made. Anionic polyamide 6 resin (casting grade) was polymerized in situ after infusion. Careful time and temperature control were necessary to obtain total fiber impregnation with subsequent complete polymerization. These advances will permit the use of affordable thermoset manufacturing processes such as Vacuum Assisted Resin Transfer molding (VARTM) or Resin Transfer Molding (RTM) to produce thermoplastic-matrix composite structures.
Processing and Mechanical Properties of Continuous Fiber Reinforced Thermoplastics
In this study, multi-axial warp knitted thermoplastic composites were fabricated by our-developed Micro-braiding technique. Cross-sectional observation, tensile test and 3 point bending test were performed. The composite with good impregnation state was obtained under appropriate molding conditions, consequently high mechanical properties were achieved. The multi-axial warp knitted fabric composite without unimpregnated region had the equivalent mechanical properties with unidirectional composite laminates. Moreover, new concept of continuative fabrication method was proposed.
Measurement System Analysis for Viscosity Measurement of Highly Filled Biofiber Composites
A comprehensive measurement system analysis (MSA) on measurement of apparent viscosity using the slit die method was conducted. Nine materials and three operators with three repeats were used. P/T (precision to tolerance) and P/P (precision to process) ratios were estimated from gage R&R analysis. Repeatability was found to be greater than reproducibility. Slip analysis on the wood fiber composites indicated that these composites essentially flow by slip mechanism. Six Sigma methodologies with rigorous method development resulted in establishing control materials and implementing SPC in a manufacturing plant.
Injection Molded Biocomposites from Natural Fibers and Modified Polyamide
This paper focuses on the development of a new technology and process in order to manufacture natural fiber reinforced engineering thermoplastics like nylon 6. Natural fibers are not suitable reinforcements when high temperature melting (above 200°C) engineering thermoplastics is used as matrix materials because natural fibers start to degrade thermally at above 200°C. Small quantities of inorganic salts like lithium chloride were added to the nylon 6 during melt extrusion processing to depress its melting temperature. The final composites are injection molded into test specimen at the reduced processing temperatures of nylon 6. The molded plastics and composites are tested for mechanical and thermal properties. Natural fiber reinforced nylon 6 composites show improved tensile and flexural properties. The morphology of the fracture surfaces is observed using Environmental Scanning Electron Microscopy.
Processing/Structure/Property Relationships for Artificial Wood Made from Stretched PP/Wood-Fiber Composites
This paper presents the processing/structure/property relationships for artificial wood made from stretched PP/wood-fiber (WF) composites that have required strength and density. The die drawing of PP/WF composites causes a unidirectional orientation of the polymer molecules and enhances the mechanical properties significantly along the stretched direction. The drawing of the composites also lowers the density of artificial wood by generating voids at the WF and polymer matrix interface. The critical processing and materials parameters are identified. The effects of these parameters on the structure and the properties are also investigated.
Effect of Processing Conditions on the Physico-Mechanical Properties of Cellulose Fiber Reinforced Poly (Lactic Acid)
Green composites were made from poly (lactic acid) (PLA) and cellulose fibers by extrusion followed by injection molding processing and their physico-mechanical properties were evaluated. The properties of PLA reinforced with varying amounts of wood pulp-based cellulose materials were studied. These composites possess superior thermal and mechanical properties based on the strong interaction between the PLA matrix and the cellulose fibers. It was found that the wood pulp-based cellulose fiber could be a good reinforcement candidate for the high performance biodegradable polymer composites.
Biobased Composites Manufactured through a Reactive Extrusion of Maleated Wood Particles
Biocomposites such as particleboard and medium density fiberboard are currently made with formaldehyde-containing adhesives. Since the government is continuously developing and implementing very stringent regulations to eliminate formaldehyde emissions into the environment, alternative approaches must be developed to replace these adhesives. This study examined the concept of using a reactive extrusion process as a means of developing a new, formaldehyde-free binding system for wood composite products. The surfaces of wood particles were modified by grafting maleated polyethylene through a continuous reactive extrusion process. Chemical changes resulting from this treatment were followed by studying the FTIR and XPS spectra. The modified wood particles were compression-molded into panels, which were tested for bending properties. Both FTIR and XPS data revealed that the chemical reactions have taken place between the hydroxyl groups of wood particles and maleated polyethylene. The modulus of rupture (MOR) results showed that the composite panels compared favorably with current standard requirements for particleboard.
Coupling Efficiency of Maleated Polyethylene Copolymers in Wood Fiber-High Density Polyethylene Composites
Coupling efficiency of several maleated polyethylene (MAPE) copolymers was investigated in this study. Interfacial bonding strength, flexural modulus, and other mechanical properties of wood fiber-high density polyethylene (HDPE) composites were related to coupling agent type, molecular weight, acid number, and concentration. Acid number and molecular weight were two important indexes for interfacial adhesion. Acid number had negative influence on interfacial bonding strength at high concentration, whereas molecular weight had positive effects. Backbone structure of coupling agents also affected interfacial bonding strength. MAPEs with linear low-density polyethylene (LLDPE) backbone were better than those with HDPE and low-density polyethylene (LDPE) structure. Compared with untreated composites, modified composites with 50% of wood fiber were improved in interfacial bonding strength by 140% on maximum and flexural modulus by 29%. According to experimental results, coupling agent 100D, 226 D, and C16 were the best coupling agents. Therefore, coupling agents with larger molecular weight, moderate acid number, and low concentration were preferred to improve the interfacial bonding of the resultant composites.
Mechanical Properties of Carbonized Bamboo Fiber Reinforced Biodegradable Polymer Composite
The mechanical properties of biodegradable polymer composite with carbonized bamboo fibers were evaluated. Poly (butylene succinate) (PBS) was used as the biodegradable plastic matrix while the condition of carbonization was varied. By increasing fiber content, tensile modulus was confirmed to increase. In particular, the tensile modulus of composite filled with semi-carbonized bamboo displayed higher values than the uncarbonized bamboo fibers composite. The values of tensile strength decreased according to the increase of fiber content; however, the carbonized bamboo fiber composites experienced less decrease than the uncarbonized ones. The surface resistivity of carbonized bamboo fiber composites was lower than that of bamboo fibers and also decreased with the increase in fiber content in each case.
Development of Thermoplastic Electrolytes and their Ionic Conductivity
The ionic conductivity of polyethylene oxide film complexed with copper acrylic acid salt (PEO-Cu(AA)2) as well as copper and copper chloride were studied. The effects of the interaction between PEO and salts on their conductivities are discussed with the help of thermal analysis and vibration spectroscopy. Bulk conductivity values were evaluated from the alternating current measurement by constructing impedance plots. PEO-Cu and PEO-Cu(AA)2 complexes exhibited the typical ionic conductive behavior of polymer electrolytes. The ionic conductivity of PEO-Cu(AA)2 complex at room temperature yielded the magnitude of conductivity at 10-6 Seimen/cm.
Electrical Properties of Carbon Nanofiber-Modified Thermotropic Liquid Crystalline Polymers
Vapor-grown carbon nanofibers (CNFs) were incorporated into a thermotropic liquid crystalline polymer (TLCP, Vectran V400P) to investigate the electrical and mechanical properties of the composite. The percolation threshold was observed in composite films at 5 wt% CNF. With increasing CNF content (up to 5 wt%), the longitudinal tensile strength decreased, whereas the transverse strength increased. Thus, with increasing CNFs, the composite films became not only more electrically conducting but also displayed more balanced longitudibal/transverse properties. The morphological features of CNF-modified TLCP were analyzed by X-ray diffraction. Results suggest that the CNFs lead to the disruption of the TLCP orientation, and may help produce TLCP-based films that have balanced in-plane properties.
Application of Radiation Cross-Linking for the Improvement of the Short-Time Thermo-Mechanical Properties of 3D-MID's
Materials with compounded cross-linking additives, e.g. PA6, PA66 and PBT, were developed to improve the heat resistance of engineering thermoplastics during high short-time temperature-loads. Cross-linking of plastics is a process, with which the individual plastic molecules are chemically bonded together. This process is released through, e.g. electron beam irradiation. The temperature-dependent irreversible mobility of the molecules decreases through cross-linking. Therefore, the softening range is shifted to higher temperatures depending on the degree of cross-linking. This behaviour is considerably interesting for the development of MID-assembles, which will be processed in continuative processes of the electronic production, e.g. soldering. The following paper offers an overview of the potentials of iradiation cross-linked PA for MID-applications.
A Novel CNTs/Polymer/PE Composite with High Electromagnetic Shielding
A sandwich structure composite employing polyethylene and multi-walled carbon nanotubes/polymer, which is synthesized by in-situ polymerization on well aligned carbon nanotubes, is demonstrated with high electromagnetic shielding effectness. The shielding effectness of composites related with the orientation of carbon nanotubes embedded in the polyethylene was studied systematically. The shielding effectness of composites with parallel with the normal of polyethylene matrix were measured to be higher than those with carbon nanotubes perpendicularly to the composite surface or randomly oriented with frequency ranging from 0.3 GHz to 3.0 GHz.
Distribution of a Minor Solid Constituent in a Transfer Molded Leadframe Microcircuit Package
This study investigates the spatial distribution of a minor particulate constituent in a transfer molded leadframe microcircuit package. The package has been polished at three levels parallel to its top surface. Levels 1 and 2 are above the die and leadframe while level 3 is just below the top surface of the die and leadframe. The distributions of area fraction and size of the particulate were analyzed for each level using micro-photography. Comparisons were made at different levels as well as different positions within each level. Both size and spatial distributions of the particulate material are evidently non-uniform, and its relations with gate, die and leadframe are interpreted. ANOVA tests were conducted to assess the statistical significance of the variations.
Three-Dimensional CAE of Wire-Sweep in Microchip Encapsulation
Wire Sweep is a common molding problem encountered in microchip encapsulation. The resin melt flow will exert drag force on wires and hence causes deformation of wires. In this paper, an integrated CAE of wire sweep is proposed to help engineer to evaluate and optimize the encapsulation process. The resin flow is calculated by a true 3D thermal flow solver based on a highly flexible prismatic element generation technique. Thanks to the efficiency of the proposed methodology in terms of CPU time and memory requirement, the industrial packages with complex geometry and high pin count can be analyzed with minimum model simplification. Furthermore, a user-friendly integrated environment is also developed to link the flow analysis with structure analysis to provide the total solution for wire sweep assessment. The developed approach proved from numerical experiments to be a cost-effective method for true 3D simulation of wire sweep in microchip encapsulation
Three-Dimensional Dynamic Simulation of Paddle Shift during Semiconductor-Chip Encapsulation
In this paper, the movement of the paddle during the semiconductor-chip encapsulation process is simulated dynamically. The non-uniform pressure distribution across the paddle will cause the paddle to shift during filling. The movement of the paddle will in turn cause a change in cavity thickness, and thus will affect the flow. This interaction between paddle shift and flow has been simulated. A three-dimensional finite-element method is used for the flow analysis. The simulation results are evaluated using an example case. The effects of mold temperature and filling time have also been examined.
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