Polymer Engineering and Science articles from March 2004

Polymer Engineering and Science archives from March 2004

A study on the effects of chaotic mixer design and operating conditions on morphology development in immiscible polymer systems.
March 1, 2004... INTRODUCTION Microstructures of immiscible polymer blends and filled polymer systems strongly influence the rheological behavior, mechanical integrity, chemical resistance, and optical and electrical properties of enduse articles....

Heat transfer behavior of melting polymers in laminar flow field.
March 1, 2004... INTRODUCTION As is well known, the three basic modes of heat transfer are conduction, convection, and radiation. When heat is applied to a material, it is transmitted by one or more of these basic modes, and the total heat quantity that is...

A micromechanical model for the elastic properties of semicrystalline thermoplastic polymers.
March 1, 2004... INTRODUCTION Elastic moduli of semicrystalline thermoplastics are important properties that remain difficult to predict because of their complicated dependence on many factors. These factors. which arise from the polymer synthesis and the...

Model filled polymers: the effect of particle size on the rheology of filled poly(methyl methacrylate) composites.
March 1, 2004... INTRODUCTION Plastics and rubbers are usually filled with inert particles to enhance the mechanical properties and reduce cost (1). The inclusion of filler, however, makes the processing of polymers more difficult. The flow behavior of...

A phenomenological constitutive model for foams under large deformations.
March 1, 2004... INTRODUCTION Naturally occurring low-density cellular or porous materials such as wood, honeycomb and bone have long provided inspiration to designers of novel engineering micro-structures. Honeycomb sandwich structures made from either...

Monitoring the evolution of PET branching through chemorheology.
March 1, 2004... INTRODUCTION Melt modification of low molecular weight (MW) and narrow molecular weight distribution (MWD) polyethylene terephthalate (PET) in order to alter its structural and rheological properties by chain extension and/or branching has...

Structural changes of PVC in PVC/LDPE melt-blends: effects of LDPE content and number of extrusions.
March 1, 2004... INTRODUCTION Polyvinyl chloride (PVC) is widely used in the construction, automotive and consumer products industries. This plastic accounts for 64% of all plastic pipe consumption, dominating sewage applications by 80%, and piped water by...

Effect of molecular structure on the rotational molding characteristics of ultra-low-density ethylene-[alpha]-olefin copolymers.
March 1, 2004... INTRODUCTION Rotational molding is unique among plastics molding processes because it does not involve application of external stresses (1). Instead, the plastic particles coalesce in a pressure-free environment to form a homogenous melt...

Microstructural modifications in uniaxially hot-drawn polycyclohexylene terephthalate films.
March 1, 2004... INTRODUCTION Among semicrystalline polymers, poly(ethylene terephthalate) is one of the most studied because recrystallization can be obtained either by thermal treatment (isotropic structure) or by drawing (anisotropic structure). During...

Curing kinetics and chemorheological analysis of polyurethane formation.
March 1, 2004... INTRODUCTION Much has been written on the chemistry leading to polyurethanes (1). Varying the type and the reactants ratio of the formulation components achieves various degrees of cross-linking and. Therefore, obtains a large class of...

Electrical conductivity of polymer blends containing liquid crystalline polymer and carbon black.
March 1, 2004... INTRODUCTION Carbon black (CB)-loaded immiscible polymer blends tend to exhibit a higher conductivity level than either polymer components at the same CB content. This phenomenon is due to the preferential CB location within one of the...

Improvement of the processability of poly(ether ketone ketone) by the addition of a thermotropic liquid crystalline polymer.
March 1, 2004... INTRODUCTION Poly(ether ketone ketone) (PEKK) is a high-temperature thermoplastic that has high stiffness and strength and excellent chemical resistance (1-5). The term PEKK actually represents a variety of copolymers with different ratios...

Constitutive equations for the viscoplastic response of isotactic polypropylene in cyclic tests: the effect of strain rate.
March 1, 2004... INTRODUCTION This paper concerns the effect of strain rate on the viscoplastic behavior of injection-molded isotactic polypropylene (iPP) in isothermal uniaxial cyclic tests with small strains. The influence of strain rate on yielding...

Experimental characterization of fill length behavior in extruders.
March 1, 2004... INTRODUCTION Twin screw extruders are usually operated at a specific throughput that is less than 50% of the maximum. Therefore, portions of the extruder are completely filled, while other locations are partially filled. Filled regions are...

Production and analysis of injection molded micro-optic components.
March 1, 2004... INTRODUCTION Injection molding is a manufacturing technique that, through filling of a mold cavity (typically made from steel or aluminum alloys) with molten polymer, produces plastic parts. The geometry of the mold cavity is identical to...

Essential work of fracture (EWF) analysis for compression molded alternating poly(propylene carbonate).
March 1, 2004... INTRODUCTION With the increasing environmental concern in modern society, there are various efforts to produce materials from renewable or recycled resources. In relation to the former approach, the use of sawdust (1) or natural fibers (2,...

Polymeric composites for use in electronic and microwave devices.
March 1, 2004... INTRODUCTION The telecommunications industry is looking for high dielectric constant and low loss microwave substrates (1). Electromagnetic (EM) crystals have been studied and created in response to these needs (2). Advances in high-speed...

Uniaxial tensile behavior and thermoforming characteristics of high barrier EVOH-based blends of interest in food packaging.
March 1, 2004... INTRODUCTION Ethylene-vinyl alcohol random copolymers are a family of semicrystalline materials with excellent barrier properties to gases, solvents and aromas, and with outstanding chemical resistance (1): Since they began to be...

Micromechanical properties on the surface of PVC/SBR blends spatially resolved by a nanoindentation technique.
March 1, 2004... INTRODUCTION Characterization of mechanical properties in fine spatial resolutions is becoming increasingly important in a number of heterogeneous materials (1-8). Heterogeneous microscopic properties on the surface or through the...