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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.
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.
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.
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.
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.
Gas clathrate hydrates are inclusion compounds formed of hydrogen-bonded H2O cages, encapsulating small molecules such as methane, hydrogen or carbon dioxide. In the search for viable gas storage media, clathrates may offer an alternative to micro-porous materials such as zeolites, active carbons and metal-organic frameworks. However, a barrier must first be overcome: Slow kinetics of enclathration (diffusion of gas into bulk systems can be of the order of days). Here we present a general strategy to greatly increase the rate of enclathration by means of trapping water in hydrophobic nanoparticle cage, gel, or porous polymer.
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.
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.
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%.
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.
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.
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.
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.
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.
Three-dimensional(3D) warpage simulation of polymer injection molded components is well developed and widely used in industry. Although a simple linear analysis is a good representation of reality for most warpage cases, it can lead to totally wrong warpage predictions in some special cases. In this paper, we extend the 3D warpage solution to account for geometric nonlinearity. Two typical large deflection examples are presented: one is the post-buckling of a tray model, and the other is the large deflection warpage of a two-shot over-molded part.
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.
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.
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.
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.
In this study, hot gas is used for heating the cavity surface. Different mold gap sizes were designed. Mold surface temperature was heated to above glass transition temperature, then, the mold will closed for melt injection. The cavity surface can be heat to 130oC for assisted the melt filling at micro feature. Hot gas heating can improve the filling process and achieve 91% the high aspect ratio micro groove (about 640.38 m of the maximum of 700 m). It was found that the mold gap size can affect the heating speed and heating uniformity.
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Brown, H. L. and Jones, D. H. 2016, May.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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