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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STRUCTURE-PROPERTY RELATIONSHIP OF WELD-LINE IN INJECTION MOLDED POLYPROPYLENE
Coarse-grained molecular dynamics simulation of a bead-spring polymer model was conducted for two polymer flow fronts flowing parallel to one another as would be found in a weld line. The effect of a molecular orientation of the flow fronts on the structure developed at the weld-line interface was studied by changing a shear flow and chain length. It was observed that the time evolution of the interfacial thickness was suppressed by shear flow for a long chain system. According to the calculation of the orientation order parameter of the bond vector as a function of the position along the chain, it was revealed that the bonds in the central part of the long chain was kept to be oriented more strongly than in the outer part, whereas the central part of the chain was quickly relaxed for short chain. It was suggested that the relaxation of molecular orientation was closely related to the interdiffusion of polymer in the weld interface.
RHEOLOGICAL BEHAVIOR OF POLY(1-BUTENE)/WOOD COMPOSITES
The work deals with the influence of content of the untreated wood flour filler (natural pine wood) on rheological behavior of blends with poly(1-butene) matrix. Therefore the blends with 5, 10, 15, 20, 30 and 50 % of wood flour were prepared in microcompounder. The rheological behavior was studied in oscillatory shear regime. Cole-Cole plot was used for determination of differences in molecular weight and distribution. It was found that low content of the wood flour acts as a lubricant agent and decreases zero shear viscosity. On the contrary, increasing content of the wood flour has an opposite effect.
NUMERICAL SIMULATION FOR THERMAL CONTROL SYSTEM IN VARIOTHERM MOLD DESIGN
In injection molding, suitable temperature controlled in different regions within the mold is a very important issue. To manage the thermal feature in mold, various dynamical control systems, such as PID, proportional, and on-off types, are adopted. However, using those controls, the dynamic properties within the mold are still very complex. In this paper, we have conducted various control systems to manage mold temperature variation and their effects on the product by using variotherm system. Results show the dynamic behavior of the temperature distribution in the mold is strongly dependent on the control system. The optimization for those systems is also performed.
AN INVESTIGATION ON THE TEMPERATURE BEHAVIOR IN MOLD EMBEDDED WITH HEATER
Conventionally, a mold is to be cooled by cooling channels in an injection molding process. However, the demand for the high quality plastics has popularized the varied-thermo control of mold system. An electrical heater system is one of the popular heating methods used in varied-thermo type methods for its low cost and ease of use. To achieve good efficiency, the system layout and the switchover between heating and cooling have to be properly designed and optimized. In this study, a true 3D fully transient approach is proposed to simulate the temperature behavior of mold embedded with heater. Furthermore an experimental apparatus is also set up to measure and verify this transient behavior.
ADVANCED CHARACTERIZATION OF NANOFIBER BASED NONWOVENS
Polyurethane (PU) solved in dimethylformamide (DMF) was electrospun under one set of conditions by using two different supporting textiles. The mechanical properties of nanofiber mats were measured by the Sentmanat extensional rheometer and the pore size distribution was calculated by a newly proposed digital image analysis methodology applied on nanoscale SEM images taking macroscopic features of the nonwovens into account. It has been found that supporting textiles have very high effect on mechanical properties of nanofiber mats (even if their fiber diameter distributions are similar), which can be explained by different porosity of the prepared samples.
DEFECTS DURING EXTRUSION PROCESSES RECOGNIZE, ANALYZE, GRADUATE AND ERADICATE
Cutbacks, off-shoring and other cost reduction processes have led to a major loss of internal company know-how. Inefficient product and process qualities result primarily from non-aligned parameters, which are influenced by the operator. In the context of a research project conducted in collaboration with partners in industry, recognition features are established for defects in pipe extrusion lines. Products and processes can be analyzed, and defects graduated in process models, which put forward a catalog of potential measures on the basis of a self-compiled database. Reasonable variables for optimizing the products are identified, which means that defects can be eliminated by remaining within prescribed boundaries. The results are made available to all comparable production lines and validated.
SEM AND FTIR ANALYSIS OF PE PIPE FRACTURE IN ACCELERATED TEST CONDITIONS
The critical level of degradation for fracture initiation and the speed of stress corrosion crack (SCC) propagation depend on the rates of toughness deterioration and buildup of the degradation related stresses as well as on the manufacturing and service stresses. Some PE samples tested using an aggressive environment at various test conditions are investigated. SEM and FTIR analysis of PE pipes fractured in accelerated test are applied to validate the proposed model of crack initiation and propagation in PE. SEM is useful to identify the change of fracture mechanisms from chemical degradation driven crack to mechanically driven crack by the formation of visible striations. FTIR analysis enables to quantify by means of carbonyl index the chemical degradation on the crack surface.
HIGH WATER BARRIER NANOBIOCOMPOSITES FOR COATING AND LAMINATION APPLICATIONS
Polysaccharides and protein biopolymers are of increasing interest for their use as sustainable coating materials.However their main drawback in these applications is their inherent high water-permeability and low water resistance at high relative humidity conditions. In this study two specifically designed commercial fillers of different nature and aspect ratio were successfully incorporated into two polysaccharides: methyl cellulose and chitosan. The morphology study indicated that a good dispersion with intercalation of the fillers was observed in both matrices. The water barrier properties of the nanobiocomposites were found to be enhanced to a significant extent particularly for the higher aspect ratio filler as compared to the pure matrix materials while the biodegradability of the composite materials was maintained.
IMPROVEMENT OF INJECTION MOLDING MACHINE CAPACITY BY INTRUSION TECHNIQUE
In plastics molding industry, there is always a tradeoff between investment for higher capacity machine and actual capacity requirement for particular component. If capacity of molding machine is little lower than the capacity that is actually required for molding the component, the technique called intrusion can be used. Hence, intrusion is a technique that allows molding a part that has a greater volume of plastics than the maximum capacity of the machineƒ??s injection unit. Such techniques could be used when molding heavy sections or when the shooting capacity of the machine is not adequate. The paper talks about systematic study of the technique and its effect on performance of polymer blends and composites.
EXPERIMENTAL AND NUMERICAL ANALYSIS OF THE FLOW FRONTS ADVANCING IN MICRO INJECTION MOLDING WELD LINE DEVELOPING PROCESS
Understanding the weld line forming process is important for micro parts molded by injection molding technology. In this paper, the flow fronts advancing during weld line forming process of micro injection molding is investigated by both experimental and numerical methods.A glass insert flow visualization mold is devised to record the whole process of the melts flowing and weld line forming. Arburg?? 220S is chosen as the micro injection molding machine and PP is the objective material. The molding part is a micro dumbbell tensile sample, which is totally 24 mm long and has 12 mm long micro scale testarea with rectangular cross section (0.4 mm width mm depth). The numerical simulation is realized by software Comsol?? Multiphysics 3.4 taking surface tension account into. In order to find out how the processing parameters affect weld line forming in micro scale, the experiments were carried out in different processing conditions, injection pressure (25, 30, 35, 40 MPa), injection speed (15, 20cm3/s), mold temperature (120, 135 ?§C). Flow visualization experimental analyses indicate that injection pressure, injection speed and mold temperature all have effects on the flowing speed of the melts. Injection pressure and mold temperature also influence with the shape of flow fronts. Numerical simulation results give a good confirming description for the flow fronts shape which is consistent with experimental observation. In addition the characteristic prediction for the v notch size is carried out.??0.1
ENVIRONMENTAL AGEING OF MATERIALS USED FOR COLLAPSIBLE FUEL STORAGE TANKS
The purpose of this work was to perform a comparative analysis of various candidate nitrile coated fabric materials supplied by potential vendors to be used as fuel storage tanks and compare the results to the currently fielded polyurethane storage tanks. Our strategy is to utilize advanced environmental ageing methods to simulate extended weathering conditions. Our results demonstrate that the nitrile coated fabrics performed well in our evaluation. Their breaking strengths are about equal to the currently fielded urethanes and they performed comparably when subjected to environmental ageing conditions.
FINITE ELEMENT PREDICTION OF RESIDUAL STRESS FORMATION IN HOT PLATE WELDED POLYCARBONATE
During plastic welding, localized heating and coolingnear the weld results in residual stress formation due todifferences in thermal expansion between hot and coldregions. ANSYS finite element analysis was used to firstpredict the temperature fields and cooling rates for hotplate welding of polycarbonate. The temperature fieldswere then used as the input for ANSYS viscoelastic stressanalysis to predict the residual stress distribution.Similarly, the residual stress was also predicted forthrough transmission laser welding and vibration weldingof polycarbonate. The predictions were found to be ingood agreement with previously published residual stressmeasurements.
SYNTHESIS AND MECHANICAL PROPERTIES OF SULFONATED BLOCK COPOLYMERS
In this study, Dynamic mechanical analysis (DMA), and FT-IR was used to examine a series of highly sulfonated poly(styrene-isobutylene-styrene) (SIBS) block copolymers. Sulfonation levels of 53%, 64% and 97% were studied. These block copolymers were subsequently neutralized with three inorganic counter-ions, Mg2+, Ca2+ and Ba2+. Sulfonation of the base polymer maintained the glass transition temperature (Tg) of the PIB segment of the membrane at -60?øC regardless of sulfonation level. However, a new high temperature transition appears as a shoulder of the PIB Tg. The substitution of inorganic counter-ions also maintained the glass transition temperature of the membrane at -60?øC regardless of cation exchanged and increased the modulus of the rubbery plateau indicative of a crosslinking complex formation. Additional relaxations were observed above Tg for the highly sulfonated counter-ion substituted samples attributed to the Tg of the functionalized styrene segments. In addition, FT-IR results show a shifting of the IR bands attributed to the sulfonate groups when counter-ions are added, indicating chemical crosslinking occurring.
EFFECT OF THERMAL CONDUCTANCE TO MOLD ON THE TEMPERATURE RISE MEASURED BY RESIN TEMPERATURE SENSORS
In order to identify the resin state precisely the measured temperature should be closer to the actual resin temperature and sensitive to the resin temperature variation. In an absolute sense of view the measured temperature by the resin temperature sensor is a mold wall temperature. In this study we examined the effect of thermal conductance through the sensor from the resin to mold on the temperature rise measured by the sensor. In experiment we tested a thermally insulated washer and an insulation block to reduce the thermal conductance. To examine the influence of thermal conductance of mold material the temperature rise of mold wall was calculated with different thermal conductivity of the mold by transient-heat-transfer numerical simulation.
ANISOTROPIC THERMAL CONDUCTION IN POLYMERS SUBJECTED TO UNIAXIAL ELONGATIONS
Polymer processing flows involve a strong coupling of mechanical and thermal effects that have a significant impact on the final properties of the material. Simple molecular arguments suggest that Fourier's law must be generalized to allow for a tensorial thermal conductivity in polymers subjected to deformation. In our laboratory we have developed a novel, optical method to obtain quantitative measurements of anisotropic thermal diffusivity in polymers subjected to deformations. In this paper we report measurements of anisotropic thermal diffusivity and stress in both molten and solid polymers in uniaxial extension. These data are used to test the stress-thermal rule.
THE ROLE OF SHEAR BAND FORMATION ON MODE II FAILURE OF POLYMERIC GLASSES
Mode II fracture studies were performed at various rates on polymethyl methacrylate (PMMA) and polycarbonate (PC). The shear banding response of PMMA is shown to be highly sensitive to rate. As the rate increases, shear deformation becomes more localized to the point where Mode II fracture occurs. PC is much less rate dependent with lesser amounts of localization. A new theory is formulated relating orientation in a shear band to intrinsic material properties obtained from true-stress true-strain tests. A kinematic limit for orientation within a shear band is also derived based on entanglement network parameters.
GENERATING ALTERNATIVE TIME AND ENERGY SAVING PROCESSING CONCEPTS FOR ROTATIONAL FOAM MOLDING
The nature of the rotational molding process is cyclic. It requires the temperature of the rotating mold and the plastic it is charged with to be elevated from room temperature to beyond its melting temperature and then cooled back to room temperature. Consequently rotational molding cycle times are lengthy which is often considered as the fundamental drawback of this plastic fabrication process. The motivation and objectives of this paper are twofold. First the presently proposed research focuses on developing an innovative processing technology for the manufacture of integral-skin cellular composite moldings having adjacent but clearly distinct layers of non-cellular and cellular structures consisting of identical or compatible polyolefin grades. Its primary goal is to significantly reduce the processing cycle time in comparison with respective currently implemented technologies.
GENERATING ALTERNATIVE TIME AND ENERGY SAVING PROCESSING CONCEPTS FOR ROTATIONAL FOAM MOLDING
The nature of the rotational molding process is cyclic. It requires the temperature of the rotating mold and the plastic it is charged with to be elevated from room temperature to beyond its melting temperature and then cooled back to room temperature. Consequently, rotational molding cycle times are lengthy, which is often considered as the fundamental drawback of this plastic fabrication process. The motivation and objectives of this paper are twofold. First, the presently proposed research focuses on developing an innovative processing technology for the manufacture of integral-skin cellular composite moldings having adjacent, but clearly distinct, layers of non-cellular and cellular structures, consisting of identical or compatible polyolefin grades. Its primary goal is to significantly reduce the processing cycle time in comparison with respective currently implemented technologies.
CHARACTERISATION OF POLYETHYLENE POWDERS FOR ROTATIONAL MOULDING AND EFFECT OF POWDER SIZE AND SHAPE ON DENSIFICATION BEHAVIOUR
The particle size, shape and distribution of a range of rotational moulding polyethylenes (PEs) ground to powder was investigated using a novel visual data acquisition and analysis system (TP Picture??), developed by Total Petrochemicals. Differences in the individual particle shape factors of the powder samples were observed and correlations with the grinding conditions were determined. When heated, the bubble dissolution behaviour of the same powders was investigated and the shape factor correlated with densification rate, bubble size and bubble distribution.
EFFECT OF MACHINE DIRECTION ORIENTATION CONDITIONS ON STRUCTURE AND PROPERTIES OF HDPE FILMS
In this study, the effect of machine direction orientation (MDO) unit on the structure and performance of a high density polyethylene film are investigated. Both one step and two step stretching are used. The parameters studied are temperature, speed and draw ratio. Their effect on necking, row-nucleated lamellar structure, orientation as well as mechanical properties is investigated. The results showed a noticeable effect on orientation, crystalline lamellae characteristics and the mechanical properties along machine and transverse directions (MD and TD, respectively).
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