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PREVENTING CRACKING FAILURES IN PC, ABS, AND PC/ABS BLENDS IN MEDICAL, PHARMACEUTICAL, AND CONSUMER DEVICE APPLICATIONS
Polycarbonate and Acrylonitrile Butadiene Styrene are materials of choice for many medical, pharmaceutical, and consumer products because of their durability, stability, and high-quality surface finish. As these materials become widely used, failures are occurring more frequently and in situations where generally accepted design approaches and validation testing suggests the materials should perform quite well. This paper will discuss reasons why these failures occur as well as design methodology and life prediction techniques for preventing future failures.
MECHANICAL AND THERMAL PROPERTIES OF AN EPOXY RESIN REINFORCED WITH DIFFERENT NANOCLAYS
High intensive mixing techniques and/or long ultrasonication periods of time are normally used to prepare epopy clay nanocomposites. However this approach is not practical. In this work epoxy clay nanocomposites were prepared using a combination of short times of ultrasonication and hand mixing, therefore making clay chemistry to govern over possible differences in the composite properties. Several types of nanoclay were used in order to investigate clay chemistry on thermal and mechanical properties of the nanocomposites. Flexural test proved to be more sensitive than tensile testing in determining the effect of type and clay content.
PRECISE, HIGH-SPEED, HOT-PLATE WELDING; CONTROL TO THE THIRD POWER
In general, conventional hot-plate welding has not kept pace with technology advancements that other widely used plastics joining technologies have experienced. Extol will describe recent advancements in the hot-plate welding process which provide the capability for high-speed welding with precise force, heat and speed control. Each of these key variables (force, heat, and speed) will be discussed with respect to advances in machine design that facilitated precision control resulting in improving the process. These improvements also contributed to more efficient tool design, process setup, cycle time improvements and process innovations allowing for flexibility in product design and material selection.
A STUDY ON THE MEASUREMENT OF RHEO-OPTICAL BEHAVIOR IN AMORPHOUS TRANSPARENT POLYMERS
In the present study, rheo-optical and mechanical properties of amorphous polymers (PS, PC and COC) widely used in engineering field have been investigated. The storage stress-optical coefficient of polystyrene(PS) showed the sign change as the frequency increased. On the other hand, the sign of stress-optical coefficient over the whole frequency region is always positive with respect to polycarbonate(PC). For COC's of different composition, even though the glass transition temperature can vary, the stress-optical coefficient of COCƒ??s with different composition stays almost constant at two extremes.
THE EFFECT OF ELECTRON BEAM IRRADIATION ON HDPE/EPDM BLENDS WITH TRIALLYL CYANURATE
Blends formed of 80 wt% of high-density polyethylene (HDPE) and 20 wt% of ethylene-propylene diene monomer (EPDM) have been added with 3 wt% of triallyl cyanurate (TAC). The thermal and mechanical properties were followed up as a function of e-beam irradiation dose. The results obtained that the values of gel contents, decomposition temperature, tensile strength, and impact strength increase with increasing irradiation dose up to 100 or 150 kGy and then decreased. Additionally, the effect of cross-linking agent of TAC was observed in upgrading of various properties.
PRESTRESSED DOUBLE NETWORK HYDROGELS
A new method to prepare and characterize hydrogels is presented. A polyacrylamide-co-bisacrylamide based crosslinked hydrogel is prepared using thermal curing, without use of a catalyst. This paper discusses the kinetic study of these systems and the effect of curing temperature on the mechanical properties. Finally the concept of prestressed double network hydrogels is introduced where the hydrogel is formed by crosslinking in two steps. The first step is in an unstrained state while the second is in a strained state. The formation of these prestressed double networks along with final mechanical behavior as compared to a single network is discussed.
INVESTIGATION OF TEAR PROPERTIES OF POLYETHYLENE BLOWN AND COMPRESSION MOLDED FILMS
In this paper, eleven (11) blown (two sampling angles, i.e. MD and CD) and compression molded polyethylene films were prepared and tested by tensile tests and the Elmendorf tear tests. Tear values were analyzed statistically and the variation of the tear data was investigated based on the observation of the tear samples. The effect of tensile properties in a given direction on tear properties in the opposite direction was investigated. The relationship between tear properties obtained from the compression molded film and the blown film were compared and modeled using the geometric mean of tear values.
BIODEGRADATION OF THERMOPLASTIC STARCH AND ITS BLENDS WITH POLY(LACTIC ACID) AND POLYETHYLENE: INFLUENCE OF MORPHOLOGY
The room temperature mineralization of thermoplastic starch (TPS) with a high glycerol content and its blends with low-density polyethylene (LDPE) and polylactic acid (PLA) were examined under controlled degradation conditions. The biodegradation of native granular starch was also carried out as a reference. These results are correlated with the respective morphologies and continuity behavior of the various blend systems. CO2 evolution was measured to evaluate biodegradation properties during the test. As a whole, these results indicate a good relationship between morphology, phase continuity and biodegradation behaviour.
A NOVEL POLY (LACTIC ACID) BASED WATERBORNE POLYURETHANE
In the past few decades, Bio-plastics of plant origin and biodegradable plastics, and emulsions containing no organic solvent have drawn growing attentions as general environmentally friendly materials. Poly (lactic acid) based polyurethanes self-emulsified in 100% water were synthesized. The particle sizes of some of the emulsions were fine (less than 100nm) and they were stable for 6 months under 5oC storage condition. The low Tg sample showed good biodegradability. In this report, result of the polymerization and the emulsification, and the characteristic of the obtained emulsions were described.
AN EVALUTION OF MIXING QUALITY OF THREE DIFFERENT TYPES OF MIXING ELEMENTS
One of the most important, yet problematic, issues in the extrusion process is achieving good mixing. Considerable prior efforts have been made to understand different types of mixing elements for single-screw and twin-screw extrusion. However, there is still a lack of good process values or criteria that can be used for design purposes. The focus of this work is to better quantify the mixing behavior, using 3D FEM analysis and in-line melt camera, to develop some design criteria. This study will focus on the Maddock mixer and Stratablend II mixer, comparing design variations on mixing performance.
DESIGN OF INDUCTION HEATING MODULE FOR UNIFORM CAVITY SURFACE HEATING
Previous studies using electromagnetic induction heating for rapid tool heating indicate that the temperature uniformity on cavity surface is not easy to be achieved no matter with surface or insert type induction heating. In this paper, a series of experiments were conducted to study the effectiveness of temperature uniformity on tool cavity surface for different induction heating coil. According to the results of heating experiments, the surface temperature of 10 mm thickness hot work die steel could rise from 50oC to 150oC in 15 seconds and the temperature uniformity of the heated zone reached 94%~95%.
EFFECTS OF ELECTRONIC CONDUCTIVITY ON PHASE INVERSION OF A WATERBORNE NOVOLAC EPOXY IMPREGNATED EMULSION FOR FILTER PAPER
A novel cationic waterborne epoxy emulsion for oil filter paper was synthesized. Hydrophilic groups are introduced into a multifunctional bisphenol-A novolac epoxy resin (NEP) by chemical modification, while maintaining the epoxy groups as much as possible, which is neutralized to form the equably water dispersed epoxy resin. The structure of modified NEP in different rate of ring-opening is characterized by Fourier Transform Infrared Spectroscopy (FTIR). The emulsion phase inversion process of waterborne bisphenol-A novolac epoxy resin (WNEP) is detected by measuring the electrical conductivity in different ring-opening rates and different neutralization rates.
AN IMPROVED FOLGAR TUCKER MODEL FOR TRANSIENT BEHAVIOR OF ORIENTATION KINETICS IN FIBER SUSPENSION
The famous Folgar-Tucker (FT) mathematic model has been habitually used to determine the evolution of the orientation state of fiber suspension. A critical problem with the practical processing flow of fibers is, however, that the predicted transient rate of orientation with respect to time is quicker than the experimental observed one. Therefore, it is reasonable to propose an improved FT model by using two time-dependent factors to effectively slow down the rate. Furthermore, this improved model is well applied to simulate the injection molding process of a rectangular plate.
SIMULATION AND VERIFICATION OF GAS-ASSISTED INJECTION MOLDING ON HOLLOWED CORE RATIO OF SPIRAL TUBE
The hollowed core of the part is a very important property for understanding gas-assisted injection molding. In this study, the spiral tube mold was utilized to investigate thickness ratio of the hollowed core. The process parameter effects are explored on thickness ratio of the hollowed core. Both the experiments and simulations were compared for verification. The results indicate that the thickness ratio of the hollowed core increases with the increased melt temperature and gas pressure. However, the increase in delay time reduces the thickness ratio of the hollowed core. The experimental results are in good agreements with those in simulations.
CHARACTERIZATION OF CRACK INITIATION AND SLOW CRACK GROWTH IN POLYETHYLENE WITH CYCLIC CRACKED ROUND BAR TESTS
With the purpose of an accelerated material ranking cyclic test with cracked round bar (CRB) specimens at ambient temperatures of 23C were carried out with eight high density polyethylene materials. Although testing times of only about one week per material were needed, a ranking of the results was in good correlation to Pennsylvania Notch Test (PENT) data. Additional measurements of the crack opening displacement provide further options for investigating the resistance of the materials against crack initiation.
EFFECTS OF THE PROCESSING HISTORY ON THE CRACK KINETICS IN A POLYETHYLENE PIPE GRADE
A PE 80 pipe grade was investigated in order to analyze the impact of morphological variations related to the process history of a material. Specimens were manufactured from a compression molded plate as well as from an extruded pipe. Morphological characterizations were carried out by Differential Scanning Calorimetry and by Dynamic Mechanical Analysis. A measurement of the crack kinetics for a lifetime assessment based on concepts of Linear Elastic Fracture Mechanics was conducted with cyclic tests on Cracked Round Bar specimens at different R-ratios (min. load/max load). The results of the cyclic tests reflected the morphological influence on the lifetime.
STUDY ON RHEOLOGICAL BEHAVIOR OF ULTRA HIGH SPEED INJECTION MOLDING
In this study, the high-speed experiment was conducted to verify moldex3D simulation technology. Mold and melt temperature were kept at 200, 215 and 230 C in the maximum injection pressure condition. The experimental method changed the injection speed from 100 to 1500 mm/s and obtained the pressure drop and flow rate. The experimental results were calculated using some equations and compared with Moldex3D simulation results. Both simulation and experimental results demonstrated that the second Newton area appears starting from 1000 mm/s injection speed. With the increase of melt and mold temperature, the shear rate increases and the viscosity value decreases.
MECHANICAL PROPERTIES OF FUSED DEPOSITION MODELING PARTS MANUFACTURED WITH ULTEM*9085
In this work the influence of the orientation and the toolpath generation of manufactured parts based on the mechanical data are analyzed. Tensile Specimen are generated with the given parameters as well as with changing parameters of the native software based upon the CAD data. The parts then are built up with the Fortus 400mc from Stratasys. First tensile tests show different strength and strain characteristics that depend on the given structure and as a result of the build direction. The influence of the parameters was analyzed with a statistic test method by using the software Design Expert.
NOVEL NANOCOMPOSITES OF MOISTURE SENSITIVE POLYMERS AND BIOPOLYMERS WITH ENHANCED PERFORMANCE FOR FLEXIBLE PACKAGING APPLICATIONS
EVOH, PA, PVOH and, since more recently, some biopolymers are materials with broad application in high barrier packaging due to transparency and superior oxygen barrier. However, these materials suffer from strong plasticization in properties due to sorption of moisture, which handicaps their application under high moisture conditions such as those applied in many packaging cases. This paper shows the development of novel nanocomposites based on a kaolinite grade, commercially marketed as O2Block‹Ÿ?, which exhibit enhanced UV and gas barrier and decreased water permeability and sensitivity.
IMPROVEMENT ON THE MECHANICAL PROPERTIES OF CORK COMPOSITES USING SUBERIN AS COUPLING AGENT THROUGH A REACTIVE EXTRUSION PROCESS
New functionalized composite structures were prepared using low-density polyethylene (LDPE), cork powder and different suberins extracted from cork and birch outer bark as coupling agents to promote interfacial adhesion. The compounding was performed under reactive extrusion and samples processed by compression moulding. The morphology of the functionalized composites showed good adhesion between cork and the polymeric phase. The mechanical results confirm that the addition of suberin acts as coupling agent improving the strength and leads to cork-polymer composite materials with improved strain and lower modulus. When the suberin was added to the composition a slight increase on composite density occurred.
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