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 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.
A NEW FOCUS ON TEMPERATURE EVALUATION FOR GAS SAVING IN A ROTATIONAL MOULDING OVEN
The temperature of an oven named OPT are evaluated. Two types of moulds, an aluminium ball-like and stainless steel cube-like, were used. Finite element software was used to find a combination of hot air flow velocity and the oven internal surface geometry. The temperatures obtained in the OPT were compared with temperatures obtained in Benchmark oven. For validation purposes the OPT was compared with simulations. The agreement between the OPT and the ROT time-temperature curve behaviour is remarkable. The OPT gas consumptions are compared with in an oven named here the Kearns found in the literature.
NANOSCALE INFRARED SPECTROSCOPY OF BIOPOLYMERIC MATERIAL
Atomic Force Microscopy (AFM) and infrared (IR) spectroscopy have been combined in a single instrument capable of producing sub-micron spatial resolution IR spectra and images. This new capability enables the spectroscopic characterization of microdomain-forming polymers at levels previously impossible. Films of poly(3-hydroxybutyrate-co-3-hydroxyheanoate) were solution cast on ZnSe prisms. Dramatic differences in the IR spectra are observed in the 1200-1300 cm-1 range as a function of position on a spatial scale of less than one micron. This spectral region is particularly sensitive to the polymer crystallinity, enabling the identification of crystalline and amorphous domains within a single spherulite of this copolymer.
RHEOLOGICAL EFFECTS ON FOAM PROCESSING IN ROTATIONAL MOLDING
Rheological properties of several polypropylene polymers were measured and the foam processing of these materials using chemical blowing agent was studied. Foaming was carried out in monolayer and skin-foam layer moldings. The uniaxial extensional viscosity was quantified and the foam characterized based on bulk density, bubble size, and bubble concentration. It was found that the foam processing window is determined and bounded by melt viscosity and melt elasticity. Melt strength and strain-hardening can substantially improve the foaming performance and play significant role in determining the developed morphological structure.
STUDY ON THE PROCESS PARAMETERS TO IMPROVE STRENGTH OF WPC PREPARED BY A NOVEL COMPRESSION MOLDING SYSTEM
It was found that compression molded Wood Plastic Composites (WPC) show lower strength than the extruded WPC which could be due to lower net alignment of the reinforcing fibers and lower inter-diffusion and alignment of the polymer chains due to the smaller net flow of material during processing. To test this hypothesis, a new compression molding system was developed where materials were forced to flow in one direction. Comparative strength studies of WPC, prepared by this novel compression molding system, have been presented at varying speed and temperature of die-press. The initials results seem to validate our hypothesis.
FILLER RE-AGGREGATION AND NETWORK FORMATION TIME SCALE IN EXTRUDED HIGH DENSITY POLYETHYLENE / MULTI-WALLED CARBON NANOTUBE COMPOSITES
Multi-walled carbon nanotube (MWNT) / high density polyethylene (HDPE) composites with varying amounts of carbon nanotubes were investigated and the effect of MWNT weight fraction on their electrical conductivity, crystallinity and mechanical properties is presented here. Samples were prepared by melt dilution of a HDPE masterbatch containing 20.2 wt% MWNT with varying amounts of neat HDPE. The effect of extrusion processing on the formation of an electrically conductive MWNT network in extruded samples was assessed by the addition of a low-shear annealing zone (shear rate 1-10 s-1) before final extrusion through a die and it is also discussed here.
INVESTIGATION OF THE RELATIONSHIP BETWEEN CELLULAR AND MECHANICAL PROPERTIES OF INJECTION FOAM MOLDED POLYMER COMPOSITES
Microcellular injection foam molding technology can bring a number of advantages to the existing conventional injection molded products such as lower density, material cost reduction, reduction of residual stress, better dimensional stability, reduction of cycle time, and better dispersion of fillers. However, the technology has not been fully employed yet, especially in the automotive sector, because injection foam molded parts, in general, experience a decrease in mechanical strengths. Therefore, this research studies the relationship between cellular and mechanical properties of the two common polymer composites in the automotive industry, which are glass-fiber reinforced plastics (GFRP) and wood-fiber polymer composites (WPC).
OXIDATIVE STABILITY OF VITAMIN E INFUSED, HIGHLY CROSSLINKED POLYETHYLENE FOR ORTHOPEDIC APPLICATIONS
In this paper, highly crosslinked and vitamin E infused (VITE) ultra-high molecular weight polyethylene is evaluated for mechanical properties, oxidation resistance, and wear. Testing included small punch mechanical properties, impact strength, a fatigue study, and knee wear simulator testing. The VITE material showed no evidence of oxidation and no decrease in the mechanical properties with accelerated aging. The VITE material showed an 86% reduction in wear over the control. The combination of crosslinking and vitamin E infusion produced a polyethylene material with improved wear properties and superior oxidation resistance suitable for use in orthopedic applications.
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