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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Synthesis and Properties of Telechelic Poly(Lactic Acid) Ionomers
A chemical recycling process was used to synthesize ?- and ?,?-(metal carboxylate) poly(lactic acid) (PLA) ionomers. Telechelic PLAs containing carboxylic acid groups, which were neutralized with appropriate metal acetates to produce Na-, Li-, K-, Zn-, Ca- and Y-?- and ?,?-telechelic PLA ionomers. Functionalization of the PLA was confirmed by FT-IR and 1H-NMR. In general, the Tg and Tm of the ionomers increased with molecular weight (which also lowered the ion-concentration) and ionization of the carboxylic acid. For a fixed molecular weight, the increase in Tg and Tm were linearly dependent on the ratio of q/a, where q is the cation charge and a is its ionic radius. Crystallization behavior was dependent on the ion concentration and location of the metal ions. The presence of the ionic groups increased the modulus of the polymer and the largest changes were observed with multivalent cations. The ?-(Y carboxylate) PLA even displayed a rubber-like plateau in its softening behavior.
Lexan* DMX Grade Resins – Scratch Resistant, Barrier Polycarbonates
Polycarbonates are widely used in injection molding applications because of their impact resistance, optical clarity, heat and chemical resistance. However in some applications, they lack the scratch resistance needed to maintain surface aesthetics of parts subject to constant handling. Lexan* DMX grade resins (hereinafter referred to as DMX") have been developed to offer significantly better surface hardness compared to standard polycarbonate thus potentially eliminating the need for secondary coatings operations. These transparent resins also possess oxygen and moisture barrier properties which makes them attractive for packaging applications."
Influence of Staggering Angle of Kneading Block on Phase Morphology of Immiscible Polymer Blends in Co-Rotating Extruder
The influence of kneading block configurations on the phase morphology of immiscible polymer blends (HDPE/PS) in a co-rotating twin-screw extruder had been studied. The thermal property and morphological structures of the samples were investigated by Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM), respectively. The results showed that the placement of kneading blocks in the melting zone leads to a narrow distribution of the minor phase diameter, whereas the presence of kneading blocks at the melt conveying region results in a small dispersed phase size in the blends.
Recycled Poly (Ethylene Terephthalate) (PET) Blends for Hot - Fill Bottles
Injection stretch blow moulded PET bottles offer glass like clarity, excellent gas barrier properties and good overall mechanical strength. However, PET bottles required for hot-fill (85 oC ) applications have encountered limitations due to its relatively low glass transition temperature.In this study, two virgin PET grade materials are blended with post consumer recycled PET. The heat-setting technique is used for the manufacturing of injection stretch blow moulded bottles for ‘hot-fill’ applications. The process parameters (the preform temperature, the heat-setting timing and blow mould temperature) and the blend ratios for PET bottles are optimised based on thermal and mechanical characterisation.
Hybrid FEM/FDM Approximation for Single Screw Extrusion
The hybrid FEM/FDM was employed for simulating the melting performance in a single screw extruder. The enthalpy formulation for the energy equation was used in solving the melting problem. The liquid fraction was introduced to establish the phase change between the melts and the solid bed. The simulation results were compared with the experimental results reported in the literature. Although the hybrid FEM/FDM precluded the explicit treatment of the location of the melt pool, fundamental pressure-drop flow rate relationships details of local shear rate, and macroscopic energy production seemed to provide a reasonable correlation between the predicted and experimental results.
The Effect of Interfacial Strength on the Light Refraction in Multi-Step Plastic Optical Fiber
The effect of adhesion strength at the interface of core layers on the light refraction was determined in multi-step index plastic optical fiber (MSI-POF). The multi-step refractive index profile in MSI-POF core was introduced by the combination of various methyl methacrylate (MMA)/fluoroalkyl methacrylate (FAMA) copolymers. The refraction angle at interface decreases with increasing FAMA content in copolymers and as a result, the light in MSI-POF propagated similar to the graded index plastic optical fiber (GI-POF). Adhesion strength at the interface of copolymers affects the light transmission path in MSIPOF. This might be minimized by achieving appropriate adhesion strength at the interface between core materials.
Investigation of Film Blowing Process Stability for Metallocene Based LLDPE with Different Level of Long Chain Branching
The effect of processing conditions, die design and material characteristics on the stability of the film blowing process has been investigated theoretically by the recently proposed Zatloukal-Vlcek model [Zatloukal M., Vlcek J., J. Non-Newtonian Fluid Mech. 123, p. 201-213, 2004; Zatloukal M., Vlcek J.: J. Non-Newtonian Fluid Mech. 133, p. 63-72, 2006] and the theoretical predictions were compared with the corresponding experimental data. It has been found that the model predictions are in good correspondence with the experimental reality.
Processing Fine-Celled Recyclable CBA-Based Polyolefin Foams in Compression Foam Molding
This paper focuses on understanding the technological potentials for producing recyclable polyolefin foams by using a modified technique of the conventional compression molding process, referred to as compression foam molding. A two-step compression foam molding method is being developed. The main processing feature of this method is that it allows for complete sintering of the non-foamable resin prior the activation of the CBA. First, completely sintered intermediate foamable products that have no pre-decomposed CBA particles and entrapped air bubbles are manufactured. Second, these intermediate products are used in the actual foaming process. The principal advantage of this compression foam molding method is that it produces high quality recyclable foamed structures with high volume expansion ratios by avoiding the need for cross linking.
Study of Residual Birefringence in Injection Molded Lenses
Injection-molded lenses have been widely employed for 3C products more recently. In this paper, 3D CAE flow analysis embedded with DOE methods have been adopted for studying lenses molded with cyclic-olefin-copolymers together with residual birefringence measurements. In addition, thermal annealing experiments have been performed on the relaxation effects on thermal history for further studies. Results have shown that shear stresses as birefringence are contributed by melt temperature and injection speed during filling; while, dimensional errors on optical surfaces of lenses have been influenced by melt temperature and holding pressure during the packing and cooling.
Screw Element Characterization in an In-Line LFT-D Process
Studies have been done on three different elements (mixing element and kneading blocks) to determine their influence on fibre length and wetting properties during an in-line direct compounding process using glass fibre with PP at a nearly constant specific output. Effects of individual elements could be ascertained by using only 6D length of the barrel. At 30wt% loading, the screw element geometry plays a dominant role in fibre length distribution. At 50wt% loading, fibre length is influenced mainly by the screw speed. SEM analysis results of the samples are provided. Characterization of the individual type of elements can be used as guidelines in future application.
A Compressible Model for Three-Dimensional Melt Filling and Gas Penetration in Gas-Assisted Injection Molding Processes
The numerical prediction of three-dimensional melt filling and primary gas penetration in a clip-shaped square tube is conducted using compressible models in this paper. Similar to other fully three-dimensional methods, the full Navier-Stokes equations are solved together with the front transport equation using a front capturing approach. Different from previous studies assuming incompressible fluids in the filling process, the gas compressibility is considered in the proposed compressible model. For the case of a clip-shaped square tube, the gas penetration length and gas core size are compared among numerical predictions and experimental measurements, where a 3D Hele-Shaw model is also presented. The proposed compressible model has much better prediction accuracy than the 3D Hele-Shaw model. The proposed compressible model in the present study is proven to be accurate in the three-dimensional simulations of melt filling and primary gas penetration problems.
Three-Dimesional Simulation of Injection-Compression Molding Process
A numerical model for the fully three-dimensional simulation of melt filling in an injection-compression process is proposed in this paper, where a moving grid strategy is employed. Similar to other fully threedimensional methods, the fully three-dimensional Navier-Stokes equations are solved together with the front transport equation using a front capturing approach. To avoid the difficulty in specifying gas outlet required by SIMPLE-type algorithms with incoming melt, the escape of air is modeled through source terms described by a compressible model. Filling predictions of a lens part are conducted to demonstrate the advantages of proposed scheme in simulating injection-compression processes. After conducting several computations under different processing conditions, the proposed numerical model in the present study is proven to be promising in the three-dimensional melt filling simulations of injection-compression problems.
Study on the Mixing Ability of Different Mixing Elements in Co-Rotating Twin Screw Extruder
The mixing abilities of the normal screw element, kneading disc element and rotor element were studied. Based on the molding of the 3-D isothermal non-Newtonian flow field, the speed field, shear rate field and pressure field were obtained. The residence time distribution, average shear rate and shear rate distribution of certain percent particles vs. time were acquired. The results show that the kneading disc element provide more dispersive mixing behavior, the rotor element achieves both good dispersive and distribute mixing effects and the normal screw element has the better conveying ability. And the results of experiments correspond well with the numerical analyses.
Mechanical Properties and Morphology of PMMA Grafted Silica/PMMA Injection Molded Composites
Micro- and nano-scale silica particles filled poly (methyl methacrylate) (PMMA) composites were prepared using high shear compounding and thin-wall micromolding. Mechanical performances of the composites were elucidated through tensile tests and internal structures of fractured surfaces were obtained from microscopic observations. The incorporation of silica particle has raised the tensile modulus of all specimens irrespective of processing conditions. Distribution of micro-fillers in the molded specimens was preferential towards the end side than the gate and center sides. Nano-filler particles were dispersed uniformly in most parts of the specimen while boundary separations between filler and matrix could be observed at the skin layer in micro silica filled PMMA. This led to an assumption that there was better filler-matrix adhesion in nano-filler composites than in micro-filler composites.
Numerical Simulation on Intermeshing Counter-Rotating Twin Screw Extruder with Pin-Barrel
The 3-D isothermal non-Newtonian flow field of intermeshing counter-rotating twin screw extruder with pin-barrel was researched. The pressure field, viscosity field and shear rate field were attained and analyzed. Statistic analysis are applied on the dynamic flow field simulation of intermeshing counter-rotating twin screw extruder with pin-barrel and without pin. Based on the above simulation, statistic methods have been introduced to calculate the RTD and max shear rate distribution. The results have showed intermeshing counter-rotating twin screw extruder with pin-barrel provides better distributive mixing than intermeshing counter-rotating twin screw extruder without pin.
True 3D Simulation of Flow-Induced Residual Stress in Injection Molding
Flow-induced residual stress has been one of the essential issues in plastics injection molding. It affects many physical properties of the finished parts, such as warpage behavior and optical properties. Flow-induced residual stress is caused by the high shear rate of plastics flow during filling, and can be relaxed or frozen during the post-filling process and after ejection. Furthermore, flow-induced stress of non-transparent or complicated parts can't be easily measured by experiment. In this paper, we incorporate viscoelastic models in an integrated three-dimensional numerical approach to predict flow-induced residual stress in injection molding.
A Novel Approach for Predicting Birefringence of Optical Parts
Plastic optical parts or components have been used in many industrial applications, such as optical disks, lenses, and waveguides. For the development of optical products, the control of birefringence is crucial. Basically, it is dependent on optical characteristics of material and global features given by polymer processing. However, the prediction and control of birefringence is difficult. In this study, a novel approach for the prediction of birefringence distribution of injection-molded parts is developed by the 3D simulation technology, which incorporates photoelastic analysis and viscoelastic mechanics.
High Molecular Weight (MW) Nano Sized Polyethylene (PE): Effect of Particle Size, Macro-Micro-Nano
The high MW PE with average particle size of 60 nm was synthesized using Ziegler-Natta catalyst. The AFM, SEM and TEM studies showed that PE nanoparticles were spherical in shape. Structure and crystallinity were concomitantly studied through FTIR and XRD. It shows nanospherical PE particles are more crystalline (~75%) compared to macrosized PE (~59%). The mechanical properties and surface roughness were also evaluated through AFM. At last the properties of nano sized PE were compared with micron and macro sized particles.AFM studies show the Young's modulus of nanosized PE particle varies from 1 to 1.4 GPa whereas for macro sized PE its varies from 0.6-0.7 GPa.
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.
Apatite-Poly(Ether Etherketone) Nano Composites: Prosthesis Materials: SBF-Conditioned Study
A prosthesis material using calcium phosphatespoly( ether etherketone)thermoplastic nano composite was developed. The nanosized calcium phosphates were synthesized by sol-gel technique. The biocompatibility test was carried out by SBF-conditioned study using freshly prepared simulated body fluid (SBF) at a temperature of 25-40°C and pH of 6.5-7.7. XRD was used to see the crystallinity and composition. The morphology and component distribution were performed by OM, SEM, AFM, etc. The functional groups present in composite materials were evaluated by FTIR. The growth study of SBF crystal was carried out by OM and XRD. The porous microsphere of HAp-PEEK composite was observed in SEM.
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