SPE Library
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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Rheology
SPE Library content related to rheology
HYDROLYTIC DEPOLYMERIZATION OF PET DURING EXTRUSION
Depolymerization of PET to high molecular weight oligomers could introduce opportunities to re-use PET waste via chemical recycling. Hydrolysis of PET in the presence of water/steam was carried out in a twin screw extruder, at barrel temperatures of 265°C and 300°C with screw speeds of 20, 60 and 200 rpm. The extruded products were characterized to determine intrinsic viscosity (IV) of samples as well as thermal properties (DSC) and rheological behavior. Proton nuclear magnetic resonance (HNMR) analysis was used to estimate carboxyl end group content. The results showed that the average molecular weight (Mw) of extruded polymer was reduced to less than 10,000 g/mol
THE EFFECT OF NANOCLAY ON THE RHEOLOGICAL PROPERTY AND MELT STRENGTH OF POLYPROPYLENE/POLYAMIDE-6 BLEND
Polypropylene (PP) and polyamide-6 (PA6) blend and nanocomposite were prepared using melt intercalation technique by blending PP and PA6 by the incorporation of nanoclay. The melt intercalation of PP and PA6 blend was carried out in the presence of a compatibilizer maleic anhydride grafted polyolyaltha olfin. The rheological property, melt strength and the morphology of PP/PA6 blend and PP/PA6/CN nanocomposite were studied. It was found that the incorporation of nanoclay has positive influence on the rheological property and the melt strength of PP/PA6 blend.
TRANSIENT PARTICLE FLUX DURING INJECTION OF COMPOSITE POLYMER COMPOUNDS AND THE RELEVANCE OF SUBSEQUENT MANIFESTATIONS IN MULTI-CAVITY TOOLING
An experimental analysis of the degree of particle diffusion is conducted and analyzed, focusing on multi-cavity tooling. Highly reinforced composite resins are injected into multi-cavity tooling and subsequently analyzed by thermal and mechanical approaches to uncover the degree of shear-induced particle diffusion manifesting under varying injection velocities, mold temperatures, and primary runner aspect ratios. Results indicate that shear induced diffusion is occurring in the length and time scales employed, yet the imposed environments, favorable to particle diffusion, show relatively low influence on cavity-to-cavity gradients in particle concentrations with net migrations occurring opposite to theoretical notions under molding environments. A significant local migration is found to occur radially within the melt delivery. Mechanical properties exhibit a dependence on the rheological history of the polymer in.
EFFECTS OF COMPONENT VISCOSITIES AND DISPERSED PHASE VOLUME FRACTION ON RELAXATION BEHAVIOR FOR POLYMER BLENDS
The influences of the viscosities of the matrix and dispersed phase, and the volume fraction of the dispersed phase on the relaxation behavior reflected on the Cole-Cole plot and the imaginary part of complex viscosity curve are analyzed using the Maxwell and the Palierne models and experimental data. It is found that these three parameters have a great impact on the radii of the circular arcs of the Cole-Cole plot. Moreover, the total relaxation time of the deformed droplets increases with the increase of the viscosity and volume fraction of the dispersed phase, especially the increase of the viscosity of the matrix. In addition, it is important to found that the Cole-Cole plot is invalid to analyze the miscibility of the polymer blend when the droplets of the dispersed phase have not enough time to relax during dynamic frequency sweep test.
IN SITU GENERATED BICONTINUOUS REINFORCEMENTS
The principle subject discussed in the current study is a method to form bicontinuous reinforcement within a polyether ether ketone (PEEK) polymer matrix by using metal stearates as fillers. X-ray scattering, differential scanning calorimeter, dynamic mechanical analysis (DMA) and melt rheology were used to investigate the dynamics of the material and the structure of the components. Metal stearates affect the packing of PEEK molecules and reduce the total crystallinity by slightly changing the crystal growth of PEEK with no change in unit cell of PEEK. Melt rheology and DMA results suggest that PEEK is a dominant phase in the composites and the metal stearates form a secondary continuous phase in the polymer resin. The reinforcing effect of the metal stearates at low temperatures is maintained up to their softening temperature around 100°C beyond which PEEK begins to dominate the mechanical behavior. Effective moduli of metal stearates in composites suggest that the secondary metal stearate phase forms bicontinuous morphology.
DETECTING POLYMER LONG CHAIN BRANCHING STRUCTURES BY USING ANALYTICAL RHEOLOGY
Polymer rheology is a very sensitive indicator of polymer long chain branching, and therefore can be used as a tool to determine polymer structures. This paper is thus focused on the study of the relationship between polymer linear viscoelastic properties and polymer structures using both rheological experiments as well as theoretical modeling methods applied to both model polymers and commercial polymers. In this work, the “hierarchical model” was employed to predict their rheological behaviors as well as to identify the impurities in the materials using the “analytical rheology” concept. After validating the tube model theory successfully on the model polymer melts, we tried to access the validity of the modeling predictions for commercial polyolefins.
RHEOLOGY AND MELT FRACTURE OF POLY(LACTIDES)
The wall slip and melt fracture behaviour of several commercial polylactides (PLAs) have been investigated. PLAs with molecular weights greater than a certain value were found to slip, with the slip velocity to increase with decrease of molecular weight. The onset of melt fracture for the high molecular weight PLAs was found to occur at around 0.2 to 0.3 MPa, depending on the geometrical characteristics of the dies. Addition of 0.5wt% of a poly(?- caprolactone) (PCL) into the PLA that exhibits melt fracture was found to be effective in eliminating and delaying the onset of melt fracture to higher shear rates.
Particle motion dynamics in rotating molds
Simple image analysis techniques are used to follow free-flowing particle motion and detect phenomena such as mixing.
Characterization of metallocene polyethylenes for sealing layer applications
Molecular weight, molecular weight distribution, chain branching, and melting behavior of metallocene polyethylenes play a crucial role in the sealability and hot tack properties of their films.
Toward better treatment for clogged arteries
Bioresorbable composites prepared for mechanical performance are promising candidates as cardiovascular stent material.
Achieving robust thermoplastic vibration welds: insights from numerical simulations
Accounting for resin flow behavior in a process model can offer important guidelines for maximizing weld strength by tailoring resin properties and optimizing welding conditions.
Hindering crack growth in natural rubber and nanocomposites
Nanodispersed clay can greatly improve crack growth resistance by enhancing tensile strength under static conditions and improving flex-fatigue properties under dynamic conditions.
Biaxial deformation of PET in stretch blow molding
A series of experiments help to understand the effects of temperature, strain rate, and mode of deformation on the biaxial stress-strain behavior of a common industrial plastic.
Specific nonlinear viscoelasticity in reinforced natural rubber
Natural rubber reinforced with zinc dimethacrylate shows specific nonlinear viscoelasticity behavior due to ionic cross-links.
Improved vacuum thermoforming of polyamide
Irradiating semicrystalline polyamide 12 film stiffens it by promoting crosslinking and broadens the forming temperature window.
Stronger and faster-flowing plastics for miniaturizing personal electronics
An innovative technique promises to minimize trade-offs between the processability and mechanical performance of engineering plastics.
New dual-functional liquid crystalline photocrosslinkable polymers
Polymers are prepared from stilbene-based precursors for use in photolithography and optical data storage, among other applications.
SEQUENTIAL INJECTION MOLDING: DESIGN CONSIDERATIONS
New injection processes have been developed last decades, improving the designer freedom in order to launch attractive functionalities. All these procedures should be carefully analysed before to decide their use, because it is necessary to understand their natural restrictions, cost and operation requirements and rheological implications in the tools construction. This contribution presents a wide study made in the T.I.I.P., research group from the University of Zaragoza, which gives simulation results and experimental values about sequential injection moulding, and some practical considerations for designers and toolmakers, in order to get successfully results.
REACTIVE EXTRUSION OF POLY(LACTIC ACID) WITH STYRENE-ACRYLICGLYCIDIL
METHACRYLATE
In this paper are discussed the rheological changes
observed in PLA by one-step reactive extrusioncalandering
(REX) using as a chain extender (CE) an
oligomeric copolymer styrene-acrylic multifunctional
expoxide. Dymamic rheological experiments and gel
permeation chromatography tests were used to
characterize the architectural modifications of two grades
of PLA, with different D-enantiomer content. According
to the results, an increase on D-enantiomer content seems
to reduce the CE coupling reactions. At the extrusion
conditions used high level of chain modification is
obtained as could be revealed by the increase on low
frequency complex viscosity as well as in the storage
modulus (G’) (associated to the melt elasticity).
The Effect of Carbon Nanotubes on the Rheology and Electrical Resistivity
of Polymer Blends
Different mixing protocols were used to incorporate
Carbon Nanotubes (CNT) into Polyamide 12 (PA)/ High
Density Polyethylene (PE) blends. At a composition of
75PA/25PE/0.75wt.% CNT, interface localization of CNT
promoted by predispersing CNT in the PE phase, resulted
in five decades lower resistivty compared to other mixing
protocols. Melt storgae modulus (G’) was also found to be
affected by interface localization in this case with over
20% higher G’ compared to the other protocols. Specific
CNT localization is explained in terms of preferential
interaction between PA and CNT on the one hand, and
kinetic restrictions arrising from the mixing protocol on
the other.
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