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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THERMALLY-EXPANDABLE MICROCAPSULES FOR POLYMER FOAMING – ITS EXPANDABILITY AND VISCOELASTICITY
The thermally expandable microcapsule is a new type of blowing agent for polymer foaming. It has a core and shell structure. A low boiling point hydrocarbon liquid is encapsulated by the shell of acrylonitrile co-polymer. Mixing the microcapsules with the thermoplastic polymer and letting them thermally expand in the polymer can foam the polymer. In this study we developed a new microcapsule so that it can be used at high operating temperatures over 200 oC for foaming polypropylene (PP) by injection molding and extrusion. We investigated the effect of viscoelasticity of the shell polymer on the expandability of the microcapsule as well as on the surface appearance. The visual observation of batch foaming the rheological measurement and the experiments of foam injection molding and extrusion elucidated the existence of the optimal degree of cross-linking of the shell polymer that could realize the superior expandability and appearance at PP foam injection molding and extrusion.
THERMALLY-EXPANDABLE MICROCAPSULES FOR POLYMER FOAMING – ITS EXPANDABILITY AND VISCOELASTICITY
The thermally expandable microcapsule is a new type of blowing agent for polymer foaming. It has a core and shell structure. A low boiling point hydrocarbon liquid is encapsulated by the shell of acrylonitrile co-polymer. Mixing the microcapsules with the thermoplastic polymer and letting them thermally expand in the polymer can foam the polymer. In this study, we developed a new microcapsule so that it can be used at high operating temperatures over 200 oC for foaming polypropylene (PP) by injection molding and extrusion. We investigated the effect of viscoelasticity of the shell polymer on the expandability of the microcapsule as well as on the surface appearance. The visual observation of batch foaming, the rheological measurement and the experiments of foam injection molding and extrusion elucidated the existence of the optimal degree of cross-linking of the shell polymer that could realize the superior expandability and appearance at PP foam injection molding and extrusion.
THE EFFECTS OF RESIDUAL STRESS AND CRYSTALLINITY ON RCP RESISTANCE IN PE-100 POLYETHYLENES
PE-100 pipe materials owe their excellent impact and brittle rapid crack propagation (RCP) resistance to ductile regions adjoining the inside and outside pipe surfaces. Slow cooling after extrusion seems to further toughen these regions by increasing crystallinity, but slow cooling also changes the distribution and magnitude of residual strain in the pipe wall and this may reduce the RCP driving force. This paper describes an experimental technique, which decouples these two effects and shows that crystallinity has less effect than expected. The effect of residual strain, meanwhile, is analysed using a semianalytical model of RCP, which indicates that its role may have been underestimated.
STUDY OF THE THERMAL ENDURANCE AND THE THERMAL DEGRADATION KINETICS OF A POLYPROPYLENE WOOD COMPOSITE
The thermal endurance and the thermal degradation kinetics of a Polypropylene wood composite are studied. The study is done by using several kinetics analysis methodologies including the following: conventional TGA, modulated TGA, Flynn-Wall-Ozawa isoconversional analysis (ASTM E1641-07), thermal endurance (ASTM E1877-05) and Friedmad isoconvertional method. The thermal degradation of the Polypropylene wood composite is compared with the thermal degradation of pure Polypropylene and wood powder. Despite of a discoloration process, the temperature peaks of wood decomposition for the composite and for the wood power are coincident. On the other hand, the temperature peak of Polypropylene decomposition for the composite is shifted to higher temperatures.
NOVEL AROMATIC POLYKETONE BLENDS WITH A NEW SILOXANE POLYETHERIMIDE COPOLYMER
New siloxane polyetherimide copolymers (SILTEM* resin) and aromatic polyketones form compatible blends across the composition range and exhibit superior mechanical, thermal and flame resistance properties. The exceptional properties of these blends make them suitable candidates for a wide range of applications including injection molded articles and electrical wire insulation. In particular, wire coatings made from these blends show excellent tensile elongation to break, high softening temperature, flexibility and good processibility and show promise for use in high temperature, halogen-free wire coatings and tubings.
FIBER JAMMING AND FIBER-MATRIX SEPARATION DURING KNITLINE FORMATION OF FIBER REINFORCED COMPOSITES
Knitline formation in the compression molding of sheet molding compound (SMC), a defect highly influenced by Fiber-Matrix separation, was studied through experiments and computer simulations.Square plates with meeting flow fronts where compression molded varying the initial mold coverage. In order to evaluate the influence of mold coverage on knitline development, tensile and three point bending tests of specimens taken from the meeting point of the flow fronts where performed.Mechanistic computer simulations of fiber suspensions where used to validate the experiments.
INTERFACIAL STRENGTH AND SCRATCH RESISTANCE OF METALLOCENE PE FILM INSERTED PP INJECTION MOLDED PARTS
Interfacial strength of Metallocene PE film-inserted PP injection molded parts (mPE/PP FIMs) was evaluated by micro-cutting method. Scratch properties of the FIMs were also characterized by progressive load scratch tests in comparison with Ziglear-Natta PE film-inserted PP injection molded parts (zPE /PP FIMs). It was found that interfacial strength of mPE2/PP FIMs increased with the increase of film thickness as well as the critical normal load for onset of film fracture obtained by scratch tests. TEM observation showed the penetration of PP lamella crystal into mPE film.
ENHANCED WATER STABILITY OF SOY PROTEIN PLASTICS USING ACID ANHYDRIDES.
Protein based plastics were processed using anhydride chemistries in conjunction with glycerol to obtain modified soy protein polymers that were water stable. Formulations processed with chemistries such as maleic anhydride (MA) and phthalic anhydride (PTA) produced relatively water stable soy protein based plastics. Various formulations were produced by varying the anhydride content (3-10% w/w) in the final plastic mass. The respective mixtures were extruded and injection molded to form the samples for characterization. Formulations with 10% PTA were observed to have water absorption of only 19% after 24 hrs of water submersion as compared to 250% for the control formulation.
DUAL AE TRANSDUCER METHODOLOGY FOR FRACTURE PROCESS MONITORING IN SHORT FIBER REINFORCED COMPOSITES
This study dealt with application of acoustic emission (AE) to characterize fracture process of short glass fiber reinforced thermoplastic composites. Generally, only one type of AE transducer with resonant frequency of 100- 200kHz is adopted to evaluate fracture process of composites by AE. However, the authors clarified AE transducer with resonant frequency of 1MHz was sensitive to detect fiber dominant fracture. From this background we propose dual AE transducer system with different resonant frequency (140kHz and 1MHz) to characterize fracture process of composites by AE monitoring. This methodology is applied to evaluate fracture process during tensile loading for various composites.
HALOGEN-FREE FLAME RETARDANT THERMOPLASTIC POLYESTERS WITH ENHANCED PROCESSABILITY
Many phosphorus containing additives and nitrogen synergists are available for use as flame retardant systems in engineering plastics, to develop halogen-free products for the electrical & electronics industry. However, many issues such as blooming, mold deposits, short-shots, and tool corrosion are associated with the use of such additives in polyesters. We illustrate typical issues encountered with the use of halogen-free systems in PBT and demonstrate how the Celanex?? XFR?? series from Ticona overcomes those issues and can be used as a viable alternate to halogenated compounds. We also highlight the unique advantages of our halogen-free PBT products over conventional halogenated PBT products.
FRACTURE BEHAVIOR OF GLASS FIBER/UNSATURATED POLYESTER RESIN LAMINATE BY DUAL AE TRANSDUCER MONITORING SYSTEM
AE was applied to evaluate fracture mechanism of glass fabric reinforced unsaturated polyester laminates with different fiber surface treatment. For AE monitoring dual transducer monitoring system was adopted to discuss dominant fracture under tensile loading. AE transducers with resonant frequency of 140kHz and 1MHz were applied to monitor matrix and fiber dominant fracture, respectively. By this system, effect of fiber surface treatment on fracture was discussed. Cumulative AE counts from fiber dominant fracture were constant independent of fiber surface treatment and loading pattern.This result suggested laminate strength was determined by accumulation of fiber related fracture.
ACOUSTIC EMISSION CHARACTERISTICS OF SHORT AND LONG FIBER REINFORCED PP INJECTION MOLDINGS
This study dealt with effect of fiber length on AE characteristics of glass fiber reinforced PP injection moldings. Short and long fiber reinforced PP was molded by injection molding, and static tensile tests were conducted with AE monitoring. In AE monitoring, dual transducer system with resonant frequency of 140kHz and 1MHz was adopted. Effect of fiber length on fracture was discussed by AE initiation stress and maximum amplitude.From these parameters fracture process was divided into two phases; interfacial fracture dominated by fibers oriented perpendicular to loading and fiber breakage and following matrix cracking by fibers oriented parallel to loading.
FAILURE ANALYSIS OF A LARGE DIAMETER HEAT-FUSIBLE PVC PIPE IN A HORIZONTAL DIRECTIONAL DRILLING INSTALLATION
Many times it is assumed that the material is at fault when there is a large-scale failure in a piping system. In this case a 30- inch fusible PVC pipe approximately 1100 feet in length failed during a pressure test. A careful analysis of the failed pipe and an assessment of the pipe properties revealed that the material was not at fault and that improper test procedures were to blame. The analysis includes fracture toughness measurements and calculations that show that the propagation of the crack was directly related to the pressure test procedures that were used including the attachment of end-caps and entrapment of air in the system.
ANALYSIS OF NON-COVALENT FILLER-MATRIX INTERACTIONS IN SHAPE MEMORY POLYURETHANE NANOCOMPOSITES USING FLUORESCENCE EMISSION SPECTROSCOPY
This work established the utility of fluorescence emission spectroscopy as a tool for analysis of filler-matrix interactions in nanocomposites. The non-covalent filler-matrix interactions and their influence on properties of shape memory polyurethane (SMPU) composites of Cloisite??30B organoclay, carbon nanofiber (CNF), oxidized carbon nanofiber, silicon carbide (SiC), and carbon black (CB) were analyzed using fluorescence emission spectroscopy. Strong interactions in SMPU composites of organoclay and CB were determined, whereby only weak interactions were observed in the cases of CNF and SiC. Thus, a direct correlation between the extent of filler-matrix interactions and the degree of crystallinity was determined.
COMPARISON OF VIBRATION, INFRARED AND COMBINED INFRARED WITH VIBRATION WELDING OF PMMA TO ABS
Vibration welding is one of the most popular techniques for joining thermoplastics. For vibration welding, irregular flash formation results in poor aesthetics while infrared (IR) welding has more desirable flash aesthetics. In this work, we compare vibration, IR, and combined IR with vibration welding of PMMA to ABS. Vibration welding had the shortest cycle time with strong joints of 89% of the bulk strength of the weaker ABS. IR welding had much longer cycle times, nicer flash aesthetics but weaker welds with maximum joint strength that was 71% of the bulk strength of ABS. Combined IR with vibration welding had intermediate cycle times, with the same joint strengths (91% of bulk strength of ABS) as just vibration welding and with nearly the same flash aesthetics as just IR welding.
EFFECTS OF INFRARED PREHEATING ON ANGULAR DISTORTION OF VIBRATION WELDED TPO
Thermoplastic polyolefins (TPO) are frequently used in automotive applications. Vibration welding is often used to join parts together, resulting in joints that are not as strong as the bulk and in angular distortion in Tee-joints. In this study, we evaluated the effects of infrared (IR) preheating of the web plate prior to vibration welding on weld strength and angular distortion of Tee-joints. It was found that angular distortion could be significantly reduced by as much as 50% for IR preheating times of 10 or 15 sec. Strength on the other hand increased for lower IR preheating times of 8 and 10 sec. compared to vibration welding only.
DESIGN OF EXPERIMENTS ON THE EFFECTS OF PROCESSING PARAMETERS FOR LEUCO DYES
The purpose of this experiment is to determine what processing variables can alter the initial color of leuco dyes. A Design of Experiments (DOE) was performed in order to test what effect the different processing parameters had on the samples initially. The samples were made using an impact disc mold and an injection molding machine with a copolymer polypropylene base material. After the parts sufficiently cooled a reading was taken to determine the color of the impact discs. At the conclusion of the experiment it was found that barrel temperature had the greatest impact on the initial color of the part.
THE EFFECTS OF THE PROCESSING PARAMETERS OF INJECTION FOAM MOLDING ON GLASS-FIBER REINFORCED POLYPROPYLENE
Automotive manufacturers have been actively searching for lighter and stronger materials to improve fuel efficiency and to possibly reduce material costs. Glass-fiber reinforced polymer parts have been replacing some of their metal counterparts for the last few decades for these purposes. Efforts continue to focus on further reducing weight and cost without a major compromise to the required properties of the parts. It is well known that foaming technology can provide a significant weight reduction, but their effects on glass-fiber composites have not been fully explored yet. In this context, this research has utilized injection foam molding technology to develop a glass-fiber reinforced polypropylene and has analyzed the effects of its processing parameters on a wide range of properties of the structures produced.
THE EFFECT OF CASTING CONDITION ON HEAT SEAL PROPERTY OF HIGH DENSITY POLYETHYLENE FILM
Film cast condition in T-die extruding processing affects molecular structure development. Relationship between the molecular structure development and the external form, width and thickness in T-die extruding of high-density polyethylene (HDPE) was studied. The film width and thickness distribution changed proportional to cast conditions, chilled roll speed, chilled roll surface temperature, mass throughput rate. On the other hand, molecular orientation, crystalline orientation and other factors did not develop proportionally to the cast conditions. The cast conditions are important factors to affect molecular structure. Molecular structure is also an important for heat seal properties. Heat seal strength changed depending on cast conditions. In low chilled roll speed heat seal strength was low. The failure mode was peeling. In high chilled roll speed heat seal strength was high. The failure mode was changed to tearing. To discuss major factor to decide heat seal properties, the effects of molecular orientation and film thickness were studied. The film thickness was not major factor to decide heat seal properties in this study. Both peeling and tearing were observed for film thickness from 10 to 30 ?¬m. However film thickness is also important factor to affect the heat conductive rate directly. Crystallinity was important factor to affect heat seal properties. Molecular orientation was also a major factor to decide heat seal properties in this study. The failure mode of peel test was changed drastically at 0.025 birefringence. Molecular orientation was an important factor to decide heat seal properties as well as crystallinity.
EPOXY THERMOSET TOUGHENED WITH AMPHIPHILIC BLOCK COPOLYMERS
In order to take full advantage of the properties of epoxy thermosets it is sometimes necessary to improve their toughness. Usually this is done by adding toughening agents. Typical toughening agents such as thermoplastics or elastomers can do a good job of improving toughness but often this improvement comes at the expense of desirable mechanical properties such as modulus, thermal properties such as the glass transition temperature (Tg) and/or ease of processibility of the uncured formulation (undesirable changes in viscosity). This paper focuses on the use of an amphiphilic block copolymer that gives a better balance of improved toughness without tradeoffs to other key performance properties and processibility.
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