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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Changing the Game in Thermoplastic Polyolefins (TPO) for Cut Sheet Thermoforming
Thermoplastic polyolefins (TPO's) based on polypropylene (PP) are desired for cut sheet thermoforming applications for their superior physical properties, weathering performance, and chemical resistance. However, their acceptance has been limited due to poor processing performance. A new generation of thermoformable TPO's was developed that extends the processing window and physical properties over currently available products. High gloss, thermoformed parts, incorporating a co-extruded gloss layer on the TPO substrate, was also demonstrated.
A Study on the Heating and Cooling Cycle System via Vapor Chamber in Injection Molding Process
The objective of this work is to develop a vapor chamber based heating and cooling cycle system.. Two injection molds incorporated with the system were produced to evaluate its effect on the products, the test material is ABS.One of the products was a 2 opposite gates tensile test part. The tensile strength of the part was found increasing by 6.8% compared with the conventional one. The other product was a plate with 8 holes, the depth of the weld line is decreased from 12?m to 0.5?m. The results showed that the system can reduce the defect of the weld lines. Furthermore, adding a vertex tube cooling system will decrease the cycle time resulted from the rise of the mold temperature.
Microstructure and Biostability of Biomedical Polyurethane Block Copolymers with Different Soft Segment Chemistries
We present a comparative study of the biostability and structural organization of polyurethanes (PU) having chemistries of those of commercial biomedical interest. The soft segments are poly(carbonate)diol (PC), poly(tetramethylenoxide)diol (PTMO) and a mixed macrodiol composed of poly(hexamethylenoxide)diol (PHMO) and poly(dimethylsiloxane) (PDMS). In PDMS based PU, PDMS units are completely phase separated from the hard segments due to their highly non-polar character. However, ‘interphase’ mixing is achieved for the PDMS end group segments and the PHMO component. PTMO and PC-based PU present a much lower degree of phase separation and larger interdomain spacings than PDMS based PU. The mechanical properties and biostability of the samples will also be compared.
Thermal Properties and Structure of Injection Molded Thin-Wall Products of Polypropylene/Boron-Nitride Composites
Thin-wall injection molding of hexagonal boron nitride (h-BN) / polypropylene (PP) composites with different h-BN contents were performed to improve heat conductivity. Effects of h-BN content and process parameters on processability were evaluated. Furthermore high-order and internal structures, thermal and mechanical properties of molded products were also analyzed by wide X-ray diffraction, density, SEM, thermal diffusivity and DSC measurements and tensile testing. Flow length of molded products increased with increasing injection speed and h-BN content. Molecular orientation and crystallization of matrix PP were suppressed by compounding h-BN. The thermal conductivity increased with increasing h-BN content and varied at the position of molded products. They were influenced by not only h-BN content but also polymer orientation.
Preparation and Properties of Nanoparticle and Long Fiber Reinforced Thermoset Composites
In this study, a novel approach is applied to prepare polymer composites reinforced by both nanoparticles and long fibers. Carbon nanofibers were pre-bound onto glass fiber mats, and then unsaturated polyester composites were synthesized through vacuum assisted resin transfer molding. These composites were compared with those synthesized by pre-mixing carbon nanofibers into the polymer resin. Mechanical and thermal properties of composites were measured. Flexural strength and modulus of composites were improved with the incorporation of nanoparticles. It was also found that carbon nanofibers increased the glass transition temperature and reduced the thermal expansion coefficients of unsaturated polyester resin.
Numercial Simulations of Residual Stresses in Polycarbonate Injection Mold Parts
The present study attempted to numerically predict residual stress and birefringence in injection molded PC specimens with different thickness, 2.0mm and 6.5mm. Numerical simulations have been done based on a viscoelastic fluid model and commercial software MOLDFLOW by three dimensional finite element methods. The former is used to compute flow-induced residual stress, while the latter for combined residual stresses, including thermal-induced and flow-induced stresses. Effects of processing conditions on the residual are considered by the numerical simulations. As for 2.0mm PC injection molded parts, the predicted residual stresses of viscoelastic model show quite precise in accordance with experimental results. But for 6.5mm PC specimen, Moldflow simulated results have less error.
Surface Replication Property and Higher-Order Structure Development of Molded Parts with Ultrastructural Patterns Prepared by Micro/Nanomolding
Injection molding of thin-wall parts with micro/nanoscale patterns using various polymers was performed to clarify the processability and surface replication of molded parts. Effects of process conditions on processability, higher-order structure and surface properties of molded parts were evaluated. The optical anisotropy in the vicinity of the gate became higher at any other positions. Height replication ratio of surface patterns increased with increasing injection speed, holding pressure, injection temperature and mold temperature. In the case of nanomolding, negative birefringence toward flow direction appeared higher than at the skin-shear region from the observation of skinshear- core structure inside molded parts. Thus molecular orientation axis oriented along the thickness direction because of deformation during de-molding process. Thermal stability of nano-surface patterns was influenced by the size of surface features and internal higher-order structure.
New Flex Ring Dies Improve the Thickness Tolerances of Pipes and Thus save Money
Conventional pipe dies consist of a solid mandrel and a solid outer ring. With such dies the thickness distribution in pipes can only be influenced by centring the die. Two thick regions situated opposite each other can not be fought. This is possible when you retrofit a multi-walled Flex Ring sleeve into the outer ring of a pipe die. Similar to the well proved flex lip technique in flat film production the Flex Ring technology allows for a locally limited adjustment of the flow channel gap. Even the thickness distribution of single layers in coextruded pipes can be fine tuned. The new technology which overcomes by far existing limitations to the pipe production process will be explained and results obtained with the new generation of pipe dies will be presented.
Composites of Single-Wall Carbon Nanotubes and Styreneisoprene Copolymers
Single-wall carbon nanotubes (SWNTs) were dispersed in water using the surfactant sodium dodecylbenzenesulfonate to facilitate dispersion. Styrene-isoprene copolymer (S-I copolymer) and SWNT composites were prepared by mixing the dispersed SWNTs with S-I copolymer latex after polymerization. The polymer composite had an electrical percolation threshold of 0.2% indicating good dispersion of the nanotubes in the polymer. Mechanical properties of the copolymer significantly improved at SWNT weight fractions as low as 0.1%. Dynamic mechanical analysis of film samples in tension showed that the composites had a measurable modulus above the glass transition temperature (Tg) and that the modulus increased with increasing nanotube content, indicating that entanglements had formed giving mechanical stability to the composite.
Design of Thermoplastic Matrix Hybrid Composite Gas Cylinders for Domestic Applications
Continuous glass/polypropylene (GF/PP) commingled fiber tapes were used to produce wrapped pressure gas vessels for domestic applications. The vessel structural-wall was built using a hybrid solution consisting in a very thin steel liner over-wrapped by the filament wounded GF/PP commingled fiber tape layers. FEM analysis was used to evaluate if the composite gas pressure vessel based on the hybrid solution is able to withstand the pressure requirements defined in European standards. Finally, vessel prototypes were submitted to burst pressure tests. As result domestic composite gas cylinders are already being successfully commercialized at large scale in Portugal.
Study of Damage in Filament Wound Thermoplastic Matrix Composite Pipes
Reinforced thermoplastic matrix pipes may be subjected to different types of loading conditions as well as different environmental conditions. However, they may suffer damage due to unexpected working conditions (low velocity impact, such as stones, tools, etc). This paper describes a methodology based upon fracture mechanics to evaluate possible pipe damages. It reports a set of tests made to characterize materials and pipes. Fracture Mechanics tests were made in samples subjected to low velocity impact. The study of damage evolution was done by using the ESPI (Electronic Speckle Pattern Interferometry) technique in order to determine the delamination area.
Advanced Technologies for Laser Marking of Plastics
The newest generation of laser material science and hardware/software is driving strong industry demand for indelible, high speed laser marking processes to replace conventional ink printing. This paper presents a total solutions" methodology for achieving unprecedented marking contrast quality and color laser marking of plastics via concomitant engineering of: 1) laser additive material science 2) primary molding operations 3) laser/software technology and 4) systems integration. The first of its kind laser pigment to receive U.S. Food and Drug Administration (FDA) approval for use in laser processes is introduced as well as techniques to achieve high speed vector marking of alphanumeric text graphics and product security codes."
Elimination of Flash –A Novel Micro-Embossing Technique
Micro-electro-mechanical systems (MEMs) with fluidic devices rely on micro features typically ranging from 10 to 200 ?m in size. To produce these features on polymer substrates with high quality and fidelity, existing techniques typically have long cycle times and are relatively expensive. It has been shown that localized heating with ultrasonic embossing has short cycle times but generates flash. This paper reviews the elimination of this flash by using micro-cellular foamed polystyrene substrates, that self absorb the generated flash. Standard dog bone shaped features were embossed with various parameters and the resulting features characterized by optical end electron beam microscopy.
Influence of Particle Size on Melting and Energy Consumption during Compounding: Does the Effect Hold at Scaled-Up Conditions?
A number of studies have shown that differences exist in the melting behavior of polymers in twin screw extruders (and continuous mixers) when the feed is in a granular form as opposed to a pelletized form. Specifically, small particle melting is influenced by frictional heating while larger particles undergo extensive plastic deformation before melting. These differences also have an impact on energy consumption and melt temperature. The data reported in previous studies were generated on small scale laboratory equipment and it is not clear if and how the reported differences in melting behavior, energy consumption and melt temperature would vary as equipment size increases to those used in commercial scale polymerization facilities.This paper presents results of experiments conducted on a twin rotor continuous mixer (Kobe LCM-100G) using a high density polyethylene resin in a granular form and in a pelletized form. We have also investigated the impact of adding granular material to the pellet feed at various concentrations. Results include temperature profiles in the melting section of the continuous mixer as recorded by strategically located thermocouples as well as overall impact on key process parameters such as energy consumption and melt temperature.
Shrinkage Study of Textile Roller Molded by the Microcellular Injection Process
There are several advantages of the microcellular injection molding process. One of the advantages is that the shrinkage of the part can be reduced. This project investigated the effect of the process parameters on the shrinkage of the textile roller. Polybutyleneterephthalate (PBT) materials with 30 wt% glass and Wollastonite fiber were used. The results showed that the shrinkage by microcellular injection molding is less than that of conventional injection molding. Glass fiber filled PBT has more shrinkage than Wollastonite fiber filled PBT due to the non-uniform cell size of the glass fiber filled PBT.
Stress Induced Mixing in Rotor Elements of a Counter-Rotating Continuous Mixier
The numerical approaches we originally developed were applied to the rotor element of a counter-rotating continuous mixer in order to evaluate the mixing performance. Our approaches include the combination of the 3-D FEM based flow analysis and the marker-particle tracking method. The kneading block of a co-rotating twin screw extruder was also investigated in order to contrast the mixing behavior with the rotor.The numerical results showed that the stress induced mixing in rotor elements totally depends upon the process conditions and high rotational speed achieved the uniform mixing. The uniform mixing was expected when the polymer melt underwent narrow stress distribution in the flow channel.The numerical approaches are the effective method to design the process conditions in order to improve the stress induced mixing.
Dynamic Mold Surface Temperature Control for Assisting Injection Molding of Light-Guide Plate and Improving Optical Performance
During the light guide plate (LGP) injection process, there are challenges in filling the polymer melt completely into a micro-featured geometry. Although a high mold temperature can solve this issue, it also significantly increases the cycle time. Dynamic mold surface temperature control may be implemented to assist LGP injection molding. It was found that when the mold temperature exceeds 140 degrees centigrade, a reasonable accuracy figure can be achieved in micro-feature replication (about 94.66% to 98.22 %). Residual stresses were also reduced and luminance values increased by approximately 33.50% near the light source and by 49.40% further from the source.
Effect of High Mold Temperature and Layout of Gate Position on Conductivity of Composite Polymer Bipolar Plate
In this study, the feasibility of an injection molded fuel cell bipolar plate for the purposes of lowering costs is evaluated. PC was blended with 4%wt carbon fiber to observe the fiber condition in grooves, and then using PPS blended with carbon fiber as high as 50%wt molded samples. But high contents fiber may have been blocked by the groove and thus led to non-uniform density distribution of fiber and surface conductance. It was found that both gate locations (one being that melt flow parallels the groove (Pa), another being that melt flow is perpendicular to the groove (Pe)) influence conductance. Further, variable mold temperatures were required to assist the melt flow with a high content of fiber and to reduce the fiber-blocking, resulting in better conductivity performance. This improved the resistance by about 60% in PA and 48.89% in PE when using higher mold temperature.
Effect of Injection Molding Parameters on the Electrical Conductivity of Polycarbonate/Carbon Nanotube Nanocomposites
Polycarbonate (PC) was compounded with carbon nanotubes (CNT) using a co-rotating twin screw extruder followed by injection molding. Two 1.8 wt% C/CNT nanocomposites produced from the direct compounding and solution masterbatch approach were injection molded into ASTM D638 standard tensile bars and underwent electrical conductivity measurement in accordance with the ASTM D4496 standard along the flow directions of the tensile bars. It was found that the resulting electrical conductivity was sensitive to injection speed and melt temperature, as well as the location of the injection molded specimens. High electrical conductivities were achieved at high melt temperatures, but high injection speeds resulted in a non-uniform distribution of conductivities across the specimen width. Finally, higher electrical conductivities were found at locations farther away from the gate.
Study on the Optical Performance of Light Guide Plate with Double-Side Micro Feature Design
The objective of this study is to manufacture a two-sided micro-feature light guide plate to replace a diffusion plate. First, Trace Pro optical simulation software was used to simulate the micro-feature of the two-sided light guide plate. Then the micro-molding was manufactured, and precision injection experiments were run. Finally, the results of the simulation and the experiments were compared, and the optical simulation results showed that the rightness and uniformity of the light guide plate related to the size and density of the micro-feature. Further, the larger the distance from the sided light source, the closer the size increase and density became. However, the size decreased and the density loosened when the distance from the side light source was decreased. The uniformity achieved 88%. Molding transformation results were the most important factor which influenced the simulation error.
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