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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OBSERVATION OF BANDED SPHERULITES IN WATER-ASSISTED AND CONVENTIONAL INJECTION MOLDED LLDPE/HDPE BLENDS
Crystal morphologies of LLDPE and its miscible blends with HDPE obtained by water-assisted injection molding (WAIM) and conventional injection molding (CIM) were examined. Banded spherulites formed in both WAIM and CIM pure LLDPE parts. In CIM parts, a clear banding to non-banding morphological transition occurred for LLDPE upon blending with HDPE. However, for WAIM parts, banded spherulites of LLDPE still formed in outer and inner zones upon blending with HDPE, but the bands became irregular. In core zone of WAIM parts, a clear banding to non-banding morphological transition for LLDPE was observed when HDPE content was increased to 30 wt%.
DEVELOPING PHB/WOOD FOUR/CELL DEBRIS COMPOSITES THROUGH EXTRUSION
Polyhydroxybutyrate (PHB)-based wood plastic composites (WPCs) are superior to ordinary petroleum-based WPCs in terms of environmental protection. However, PHB is more expensive than many of the commodity petrochemical polymers because of the costly separation and purification processes, which could be avoided by directly using PHB-laden bacteria to produce PHB-based WPC. This study investigated the processing parameters, mechanical properties, and water resistance of the extruded composites with varying component ratios. The results indicate that some of the composites had outstanding properties compared with a commercial WPC. Therefore, this renewable WPC can replace petroleum-based WPCs on current markets without sacrificing product performance.
DEVELOPMENT OF THERMALLY CONDUCTIVE AND ELECTRICALLY INSULATING POLYMER COMPOSITES FOR ELECTRONIC PACKAGING APPLICATIONS
This paper discusses the development and modeling of novel polymer composites that possess multifunctional properties demanded by electronic packaging applications. In this work, a thermal conductivity analyzer was designed and implemented to measure composites effective thermal conductivity (keff). An analytical model was established to predict keff of composites filled with spherical fillers. Using this model, together with experimentally-measured keff, a semi-empirical approach was developed to study the effects of polymer-filler interfacial properties on keff.
THE EFFECT OF MELT ROTATION TECHNOLOGY ON PARTICLE DISTRIBUTION DURING INJECTION MOLDING
The melt rotation technology has been proposed to reduce the distribution variations of filler particles due to shear-induced migration in injection molded parts. The technique had been successfully employed to address the filling imbalances due to shear gradients formed during the polymer flow through runners. An experimental analysis has been carried out this time for a filled polymer. Glass-filled polypropylene has been injection molded using a multi-cavity mold system both with and without melt rotation implementations and parts have been analyzed by microscopic imaging. The preliminary results suggest that application of melt rotation results in more balanced filler concentration levels.
THE EFFECT OF CHAIN BRANCHING ON THE CRYSTALLINITY BEHAVIOR OF POLYLACTIDE WITH THE PRESENCE OF DISSOLVED CO2
This paper investigates the effect of chain extender on the crystallinity behavior of Polylactide with/without the presence of dissolved CO2 by a high-pressure differential scanning calorimeter (HPDSC). It is shown that without CO2, the crystallinity increases by decreasing the branched structure due to better chain regularity. With the presence of low-pressure (15bar) CO2, the crystallinity of PLAs significantly increased due to CO2ƒ??s great plasticization effect. However, with the increase of pressure (from 15bar to 45bar), crystallinity dramatically decreases, even though more CO2 is dissolved. However, as the pressure increases from 45bar to 60bar, the crystallinity of all PLAs dramatically increases.
ENGINEERING UP POLYPROPYLENE COMPOSITES WITH ORGANOSILANES
Modification of polypropylene resins with ñ,ý-unsaturated carboxylic functional-silanes by melt extrusion processing in presence of free radical initiator was demonstrated while preventing significantly undesired ý-scission phenomenon in comparison to prior work on vinyl- and methacryloxy-silanes. Modified PP was then used for enabling crosslinking into injected parts, showing enhanced high temperature resistance for both neat PP resin or glass-fibers-PP composites. Another improvement was water uptake in wood-fibers PP composites, which resulted in significant improvement of impact and tensile properties and stability under heat and water aging. Relevance of this work will be discussed in applications such as Automotive, Appliance, and Building.
MANIPULATION OF POLYMERIC BIODEGRADATION CHARACTERISTICS BY VIBRATION ASSISTED INJECTION MOLDING
The wide variety of biomedical applications employing biodegradable polymers requires a similarly wide range of biodegradation properties. In this study, a dynamic melt manipulation technique in injection molding has been investigated as a low cost, high volume manufacturing alternative to respond these requirements. The technique utilizes an additional oscillatory motion during injection molding to induce molecular alignment of polymer molecules in the final product. Preliminary experimental results have indicated that biodegradation process is dependent on these orientation levels and therefore polymeric medical devices with different degradation characteristics can be obtained simply by changing the manufacturing parameters.
STRUCTURE OF HIGH PRESSURE CRYSTALLIZED POLY(1-BUTENE)
Present work study the effect of high-pressure crystallization on morphology and thermal behavior of two different homopolymers of isotactic poly(1-butene). Both materials were non-isothermally crystallized under pressure in range from 20 to 200 MPa using a pvT 100 apparatus and thus prepared samples were investigated using wide-angle X-Ray scattering, differential scanning calorimetry and polarized light microscopy. Results showed significant effect of pressure on formation of metastable phases Iƒ?? and II with respect to material properties on thermal behavior and morphology in isotactic poly(1-butene).
FOAMING OF POLYMER CARBON NANOTUBE NANOCOMPOSITE FROM THE RETROGRADE PHASE
This work focuses on poly (methyl methacrylate) (PMMA) multi-walled carbon nanotubes (MWCNTs) nanocomposite foams prepared by using carbon dioxide as the foaming agent. CNTs nanocomposites were synthesized using anti-solvent process, and the foam morphology was tuned by the process design and incorporation of nanoparticles in the polymer matrix. The synergism between CNT and attractive retrograde phenomenon of PMMA in CO2 atmosphere was explored to generate foams. Thus nanocomposites were saturated with CO2 at 0 oC and 580psi followed by foaming at temperature in 70 oC. The cell morphology of nanocomposite are analyzed and compared with that of pure PMMA foam.
CHARACTERIZATION, MICROSCALE REPLICATION, AND USE OF A NOVEL BIOELASTOMER IN MESENCHYMAL STEM CELL DEVELOPMENT STUDIES
Novel materials possessing physical, mechanical, and chemical properties similar to those found in vivo provide a potential platform in building artificial microenvironments for therapeutic applications and well-defined biointerfaces for examining differentiation potential in stem cell biology. Poly(glycerol-sebacate) (PGS), a novel biocompatible and biodegradable elastomer is one such material. It provides an invaluable platform for in vitro culture studies to direct the differentiation of human mesenchymal stem cells (hMSCs) into specific lineages and functional cell types. This paper presents work in PGS material characterization, synthesis, microscale manufacturing, and investigations related to its use as a susbtrate for in vitro hMSC culture.
ENHANCED DIELECTRIC PROPERTIES OF MICRO AND NANOLAYERED FILMS FOR CAPACITOR APPLICATIONS
There is a need in electronic systems for capacitors with high energy density. Our approach to improve polymer film capacitors is to combine, through microlayer coextrusion, two polymers with complimentary properties: one with a high dielectric constant (polyvinylidene fluoride based polymers - PVDF) and one with a high breakdown strength (polycarbonate). Multilayered films with many alternating layers of polymers were produced and exhibited improved breakdown characteristics due to the development of a treeing type failure mechanism. In addition, a reduction of polarization hysteresis was observed due to layer confinement effects on the solid state structure of PVDF.
PREDICTION OF CRAZING AND BIREFRINGENCE IN ORIENTED GLASSY POLYMERS
A study has been made of prediction of crazing stress and birefringence in oriented glassy polymers. The ROLIEPOLY (RP) polymer rheological model proposed by Likhtman and Graham (2003) was employed, together with the Kramer theory of crazing (1983). Predictions were tested by comparison with results of a new experimental study of crazing and birefringence in monodisperse grades of polystyrene, following model melt-stretching histories. The RP model produced accurate predictions of birefringence, provided orientation occurred on a time-scale slower than the entanglement Rouse relaxation time. Crazing stress was predicted successfully with the model under the same conditions.
COMPARISON OF HOT PLATE, VIBRATION, INFRARED AND COMBINED INFRARED WITH VIBRATION WELDING OF ASA
Hot plate, vibration, IR, and combined IR heating with vibration welding of ASA were studied. For hot plate welding it was found that higher hot plate temperature and longer heating times improved the weld strength with the strongest welds approaching the bulk strength. For IR welding there was an optimum heating time, but even for that time the weld strength was significantly lower than for other processes. Vibration welding of ASA resulted in weld strengths that were about 72% of the bulk strength. Combined IR heating with vibration welding resulted in just a slight improvement over vibration welding alone.
NON-ISOTHERMAL CRYSTALLIZATION OF POLY(LACTIC ACID) - EFFECTS OF NUCLEATION AND COOLING RATE
The effect of nucleation and quenching on the crystallization kinetics of PLA and its blend compositions were studied. Contrary to polypropylene, the nucleation effect of talc decreased rapidly as the cooling rate increased. The effect was enhanced as the talc content increased from 0.1 to 8%. The nucleation behavior is analyzed in light of a modified Kissinger method. The lack of nucleation upon quenching was shown in a modified Kissinger plot which showed its correlation with Avrami analysis. Methods to control or enhance crystallization of PLA and some PLA blends are discussed.
MODIFYING CACO3 FILLERS WITH NANOPARTICLES USING A FLUID ENERGY MILL
A novel simultaneous milling and coating method which utilizes a fluid energy mill (FEM) is applied for the first time to prepare nanoparticle-coated CaCO3 additives for polymer composite materials. Simply milled (without coating) CaCO3 particles and as-received CaCO3 particles were used as references for comparison. The effects of the grinding pressure and the content of the coating on the particle size and flowability of CaCO3 were studied. The composite made of PP and this specially prepared CaCO3 have larger elongation at break, elastic modulus and impact strength, compared to the simply milled calcium carbonate.
NEW ENVIRONMENTALLY PROGRESSIVE POLYESTER and POLYESTER/POLYCARBONATE FR RESINS
New family of ENH flame retardant PBT (polybutylene terephthalate) and PBT/PC(polycarbonate) thermoplastic resins developed is aimed at helping electrical/electronics (E/E) manufacturers and suppliers comply with regulations restricting use and disposal of hazardous substances. The non-chlorinated, non-brominated FR PBT and PBT/PC products deliver similar mechanical, physical, thermal and flame retardant performance compared with their brominated FR based counterparts. Some of those resin properties will be discussed in this publication.
TRANSIENT MOLD COOLING SIMULATION FOR THE INJECTION MOLDING PROCESS
In recent years, injection molding technologies have been developed which use variable mold heating and cooling to increase part quality without significantly increasing cycle time. These processes are not suited for simulation with a conventional steady-state (cycle-average) mold thermal analysis. This paper presents the development of a new 3D finite element based transient mold cooling simulation capability which includes coupling the mold thermal solution with the mold filling and packing simulation. The predicted transient mold temperatures are validated against measured mold temperatures for two instrumented injection molding trials.
MORPHOLOGY AND STRENGTH OF INJECTION MOLDED PARTS WITH INTERFACES
The specific interfacial morphology and strength of paired polymers will be discussed. The focus is on two different types of interfaces during injection molding processes: (I) hot interface represents two melt streams meeting (weldline) and (II) cold interface is defined as the overmolding of a second melt to a chilled, hardened preform. A cold interface occurs during a multi-shots injection molding process. Regarding the strength amorphous and semicrystalline polymers were used, for the visual inspection of interfacial morphology by light microscopy semicrystalline POM was investigated. In conclusion, new aspects about a correlation between interfacial morphology and bonding strength are addressed.
ENVIRONMENTALLY PROGRESSIVE PBT BASED ENGINEERING THERMOPLASTICS PRODUCT PORTFOLIO FOR AUTOMOTIVE AND ELECTRICAL APPLICATIONS
This paper provides insights into a newly launched portfolio of environmentally progressive products. These molding compositions are based on a polybutylene terephthalate (PBT) that is made by chemical regeneration of post consumer recycle polyethylene terephthalate (PCR PET) and converted into PBT. These products can then be used in a variety of automotive and consumer applications. These new products' manufacturing processes require less energy and non-renewable fossil fuels as compared to the manufacturing processes of conventional fossil fuel based materials. We will present the comparison of properties results of molding compositions using this new technology and traditional PBT will be presented.
SYNTHESIS AND CHARACTERIZATION OF NOVEL POLYCARBONATE-POLYDIMETHYLSILOXANE BLOCK COPOLYMERS WITH CONTROLLED BLOCK LENGTHS AND AN ALTERNATING BLOCK ARCHITECTURE
A novel method to synthesize polycarbonate-polydimethylsiloxane block copolymers with controlled block molecular weight and an alternating block architecture was investigated. The method investigated consisted of the synthesis of polycarbonate oligomers/polymers possessing allyl-functional endgroups and the subsequent coupling of the oligomers/polymers with hydride-terminated polydimethylsiloxane oligomers/polymers using hydrosilylation. GPC and NMR were used to demonstrate successful block copolymer formation. Characterization using AFM showed nanoscale phase separation. The optical clarity of a PC-PSiO block copolymer produced with this method was significantly better than that of a commercially available PC-PSiO block copolymer, indicating smaller PDMS domains resulting from the more uniform block copolymer structure.
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