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A STUDY OF THE FREEZING PHENOMENA IN PVC AND CPVC PIPE SYSTEMS
Residential and commercial piping systems often experience complex failures from freeze events. In this paper the freezing failures are studied by replicating pipe freezing conditions in a laboratory setting. Testing was performed on ?« inch (12.5mm) PVC and CPVC pipes. Pressure and temperature during the freeze event were monitored and the fracture modes of failed pipes were examined. Freeze events result in excessively high pressures. It has been shown that during a freeze event, the properties of plastic pipes are advantageous over other more rigid piping systems. In this study, it was observed that PVC and CPVC pipes were able to sustain over thirty times the typical household water pressure before bursting occurred.
VALIDATION OF IN-MOLD SHRINKAGE SENSOR FOR DIFFERENT CAVITY THICKNESSES
An in-mold shrinkage sensor having a deflectable diaphragm under melt pressure, instrumented with strain gages connected in a full bridge circuit is designed and validated for conventional and thin wall parts. Molded part shrinkage is then measured as the polymer melt solidifies, shrinks, and retracts from the mold wall. The DOE was conducted using HIPS to validate the sensor performance for the thickness of 2.5 mm and 1.5 mm. With a 2.5 mm and 1.5 mm cavity thickness, the coefficient of correlation, R2, to the final part thickness was 0.939 and with 0.966 respectively for the in-mold shrinkage sensor.
DILUENT EFFECT OF THE POLY(ETHYLENE-alt-PROPYLENE) (PEP) BLOCK UPON THE POLYETHYLENE (PE) THERMAL FRACTIONATION OF PE-block-PEP DIBLOCK COPOLYMERS
The diluent effect of the amorphous (rubbery) PEP block upon the SSA thermal fractionation of the PE component as compared with the PE homopolymer was evaluated. The shape and distribution of the melting peaks obtained after applying the SSA protocol is notably different in the PE-b-PEP diblock copolymers. It has been established how the presence of a diluent blended with the amorphous zones of this semicrystalline polymer trends to increase the molecular mobility of PE chains in such a way that fractions closer to thermodynamic equilibrium can be generated.
MICROCELLULAR EXTRUSION FOAMING FOR LINEAR AND LONG-CHAIN-BRANCHED POLYLACTIDE
In this work, microcellular extrusion foaming for both linear and long-chain-branched (LCB) polylactide (PLA) was processed on a single-screw extrusion system with CO2 as a blowing agent. The rheological experiments were conducted on an advanced rheometric expansion system (ARES) rheometer to compare the rheological properties among linear and LCB-PLAs without blowing agent. The characterization for foamed samples shows that in comparison to the linear PLA, the LCB-PLA foams have larger volume expansion ratios, decreased cell-opening, smaller average cell sizes and higher cell densities, due to the higher viscosity, higher melt strength and higher crystallinity derived from long-chain branching.
USE OF COMPOSITE MATERIALS IN A HYDROFOIL ON A HIGH-SPEED ULTRA LOW-WAKE PASSENGER FERRY
High-speed passenger ferry service is attractive in many communities due to its convenience and expedience but has in certain instances caused problems related to pollution and shoreline erosion. One approach to mitigating these problems is to switch from widely used metals to lighter composite materials in vessel construction. This shift in materials would increase efficiency and decrease wake generation. This research addresses several challenges that have been faced when incorporating composite materials into a hydrofoil for a passenger ferry and describes a potential solution.
USE OF COMPOSITE MATERIALS IN A HYDROFOIL ON A HIGH-SPEED, ULTRA LOW-WAKE PASSENGER FERRY
High-speed passenger ferry service is attractive in many communities due to its convenience and expedience, but has, in certain instances, caused problems related to pollution and shoreline erosion. One approach to mitigating these problems is to switch from widely used metals to lighter composite materials in vessel construction. This shift in materials would increase efficiency and decrease wake generation. This research addresses several challenges that have been faced when incorporating composite materials into a hydrofoil for a passenger ferry and describes a potential solution.
IDENTIFICATION OF THERMOFORMABILITY INDICATORS FOR MULTILAYER FILMS
To identify dimensional thermoformability indicators, high-temperature tensile and differential scanning calorimetry (DSC) methods were studied. It was found that a new indicator ADR(TD) minus ADR(MD), i.e., the differential of the area draw ratios (ADR) between transverse direction (TD) and machine direction (MD) of a multilayer film can rank or predict thermoformability of the multilayer films with good resolution. This new indicator and a derived dimensional thermoformability index (DTI) can differentiate between different nylons, polyethylenes and multilayer structures. The ranking correlates well with the overall first-heat of fusion of the multilayer films. Thus, these indicators can be used as tools to help design multilayer structures.
ADVANCED MATERIALS FROM NOVEL BIO-BASED RESINS
Cereplast Hybrid ResinsTM also known asBIOPOLYOLEFINSƒ?› are bio-based plastic resins replacing 50 percent or more of the petroleum content in traditional plastic products with renewable source materials such as starches from corn tapioca wheat and potatoes. The addition of CereplastHybrid Resins TM to the existing line of CompostableResins TM further establishes Cereplast as the leadingsolutions provider in environmental and sustainable plastics. The first product from the Cereplast HybridResins TM family is BiopropyleneTM a 50 percent biobasedresin that can replace traditional polypropylenein many applications. Cereplast Hybrid Resins TM canbe processed at the same cycle time as traditional plastics on conventional equipment but requires less energy in the production process by using significantly lower processing temperatures. Inaddition Cereplast Hybrid Resins TM meet therequirements for toxicity set by ASTM D 6400-04specifications making Cereplast Hybrid Resins TMsafe for all applications. This paper further discusses mechanical properties and potential applications ofBiopropyleneTM.
MORPHOLOGY DEVELOPMENT WITH TENSILE STRAIN IN GLASS FLAKE FILLED POLYPROPYLENE
The object of this study was to understand the phenomenon of voiding around particles in stretching filled polymers below the melting temperature with plate shaped fillers. Injection molded tensile bars of glass flake filled polypropylene with 20 vol% of glass flakes were subjected to axial strains ranging from 0.1% to 1.0% at130?øC to 150?øC in a tensile frame. The onset ofdebonding in glass flake filled polypropylene at these temperatures was readily identified from stress-strain curves in tensile tests. Substantial void growth was observed around the flakes at strains as low as 0.5% and 1%. Furthermore voids were seen to develop all around the glass flakes rather than just at the ends along the stretch direction.
THERMAL FRACTIONATION BY SSA AS AN APPROACH FOR THE INDENTIFICATION OF BINARY PE BLENDS
Thermal fractionation by Successive Self Nucleation and Annealing (SSA) technique has been used as qualitative method for characterization of the branch distribution in polyethylenes. Low Density and Linear Low Density Polyethylenes differentiate at molecular level by the quantity, distribution and type of branches, and both are widely used in blends, especially for film blowing. In some cases, it is necessary to identify if a film has been produced with a blend, which is difficult if one PE is used in low proportion (less than 30%). By applying modifications to the regular SSA protocol, it was possible to segregate cristallizable fractions of each PE, in proportions as low as 10% in the blend
FINITE ELEMENT SIMULATION OF 3D UNSTEADY VISCOELASTIC FREE SURFACE FLOW WITH LEVEL SET METHOD
The simulation of free surface flow is of great engineering significance in polymer processing like injection, blow molding and extrusion. However, its key technology for practical application remains to be difficult in Computation Fluid Dynamics (CFD). In this work, the finite element formulation of level set method for three dimensional free surface flow of a viscoelastic fluid is presented based on the unstructured mesh. The free surface is captured by using the level set approach and the Streamline-Upwind/Petrov-Galerkin (SUPG) scheme is introduced to minimize the numerical diffusion present in the discretized level set equations. A penalty method is employed to solve the flow equation and the constitutive equation with a decoupled algorithm. The computation stability is improved by using the Discrete Elastic-Viscous Split Stress (DEVSS) algorithm with the inconsistent Streamline-Upwind (SU) scheme. The performances of the formulations are demonstrated on a three-dimensional viscoelastic mold-filling flow problem and reasonable results are achieved.
NANO-ASSEMBLED BIAXIALLY ORIENTED POLYPROPYLENE FILMS WITH HIGH OXYGEN BARRIER
Biaxially oriented polypropylene (BOPP) films with high oxygen barrier and high clarity were produced through the layer-multiplying, forced assembly process technique. 15-mil thick sheets with 33 alternating polypropylene (PP) / poly(ethylene oxide) (PEO) layers were coextruded and subsequently biaxial oriented at 135-150 ?§C. The biaxial orientation resulted in a layer thickness reduction from the microscale to the nanoscale. Crystallization of PEO was confined in the nano-layers where lamellae could only grow within a two dimensional plane. Highly in-plane oriented PEO lamellae improved the oxygen barrier by an order of magnitude. On the other hand, the films retained the high clarity.
SILICA AEROGELS CROSSLINKED BY FLEXIBLE POLYURETHANES: EFFECTS OF SILANE PRECURSORS ON STRUCTURE-PROPERTY RELATIONSHIPS
Although they have only recently become a hot field of interest, aerogels were first developed by Kistler1 in the 1930's by supercritically drying a low solids suspension of colloidal particles. The resulting material was highly porous and possessed low thermal conductivity and low density. It is unsurprising then that aerogels have been used as thermal insulation, in applications ranging from personal footwear2 to battery pack insulation for a Mars rover3. The 'pearl necklace' nanostructure of aerogels, however, is inherently weak as demonstrated by their friability and brittleness. Only about 31 kPa4 of stress is required to completely shatter a native silica aerogel.
IMPROVED DESIGN FOR POLYMER DISTRIBUTION IN FLAT FILM & SHEET EXTRUSION DIES
A design methodology has been developed for creating an improved flow passage in a flat die that distributes polymer extrudate across the width under a condition of uniform shear rate. This type of flow passage will spread any and all molten polymer materials uniformly regardless of the power law exponent value. This also results in a uniform residence time inside the die which allows for reduced changeover time and material waste. The new method achieves these results in a more compact fashion with reduced wetted area expanding the applications to wider widths than previous constant shear designs.
NANOPARTICLE FILM REINFORCEMENTS FOR HIGH PERFORMANCE AEROSPACE STRUCTURAL PREPREG COMPOSITES
Prepreg composites offer many advantages over other types of composite materials such as low void content, control of fiber volume fraction, control of laminate thickness, and others. Nanoparticles have shown to improve mechanical properties when incorporated into composite materials. Incorporation of nanoparticles into prepreg materials can be very challenging if not done at the prepreg fabrication stage. In this study, a novel method of incorporating nanoparticles into prepreg composite materials was explored. This new method allows for selective reinforcement of the prepreg material at critical areas such as stress concentration locations. Surface abrasion and open hole tensile properties of the composites were measured.
EFFECT OF FILLERS SHAPE FACTOR ON THE PERFORMANCE OF THERMALLY CONDUCTIVE POLYMER COMPOSITES
As electronic devices tend to slimmer and more integrated management of heat transfer in devices become a big task for device design. Metallic materials are widely used for heat dissipation materials but there are many attempts to replace the metallic materials with highly thermal conductive thermoplastic composites due to their lightweight and economic manufacturing cost. Intrinsically polymers are thermally and electrically insulator but they can turn into thermally conductive material by compounding with thermally conductive fillers such as graphite ceramic filler carbon black carbon fiber or carbon nanotube (CNT). In this research strong correlation of shape of graphite on thermal conductivity was investigated in polymer/graphite composites.
EFFECT OF FILLERS SHAPE FACTOR ON THE PERFORMANCE OF THERMALLY CONDUCTIVE POLYMER COMPOSITES
As electronic devices tend to slimmer and more integrated, management of heat transfer in devices become a big task for device design. Metallic materials are widely used for heat dissipation materials, but, there re many attempts to replace the metallic materials with highly thermal conductive thermoplastic composites due to their lightweight and economic manufacturing cost. Intrinsically polymers are thermally and electrically insulator, but they can turn into thermally conductive material by compounding with thermally conductive fillers such as graphite, ceramic filler, carbon black, carbon fiber, or carbon nanotube (CNT). In this research, strong correlation of shape of graphite on thermal conductivity was investigated in polymer/graphite composites.
THE MICROSTRUCTURE OF MICRO-INJECTION MOLDED HIGH DENSITY POLYETHYLENE
Micro-injection moldings were obtained for high density polyethylene (HDPE), to study the effects of processing conditions on the microstructural characteristics and mechanical properties of the moldings. Various microstructural features, such as skin-core structure, skin layer thickness fraction, and distribution of crystalline shape and size, were observed under different processing conditions and analyzed and compared to observations made with poly(oxymethylene) (POM). Process-structure-Youngƒ??s modulus relationships were analyzed by considering the effects of skin layer thickness, average plunger velocity. Suggestions for mold design were proposed on the basis of polymer melt flow behaviour.
HIGH FLOW PP/EPR BLENDS FOR THE AUTOMOTIVE INDUSTRY: BASIC CORRELATIONS BETWEEN EPR COMPOSITIONAND APPLICATION PROPERTIES
Injection molded automotive parts usually feature high flow length to wall thickness ratios. In order to ensure low cycle times, tooling costs and scrap rates, the respective material formulations should have a high flowability. Reducing the viscosity, however, also affects the materials' morphology and mechanical properties, especially the impact strength. To quantify this effect high impact reactor-thermoplastic polyolefins (rTPOs) consisting of polypropylene (PP) blended with in-reactor made ethylene-propylene rubber (EPR) were prepared and tested. Particular attention was paid to the influence of the ethylene-propylene rubber's composition, i.e. comonomer ratio and molecular weight, on application properties of such rTPOs like toughness, surface gloss and scratch resistance.
PT CONTROL METHOD BY CAVITY TEMPERATURE FOR INJECTION MOLDING
It would be of great value to develop dependable strategies for the control of part weight. Based on the Pƒ??Vƒ??T (pressureƒ??volumeƒ??temperature) behavior of the polymer, a Pƒ??T (pressureƒ??temperature) control method by cavity temperature was presented in this study. In the present control method, the total injection time is controlled by cavity temperature instead of time, the relationship between pressure and temperature can be controlled. The experimental results revealed that the Pƒ??T control method by cavity temperature yields a much better part quality and uniform part weight than conventional control method.
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