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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.
Evan Mitsoulis | Thanasis Zisis | Mahmoud Ansari | Savvas G. Hatzikiriakos, November 2011
The capillary flow of a commercial LDPE melt was studied both experimentally and numerically. The excess pressure drop due to entry (Bagley correction), the compressibility, the effect of pressure on viscosity and the possible slip effects on the capillary data analysis have been examined. Using a series of capillary dies having different diameters, D and length-to-diameter L/D ratios, a full rheological characterization has been carried out, and the experimental data have been fitted both with a viscous model (Carreau-Yasuda) and a viscoelastic one (K-BKZ/PSM model). Particular emphasis has been given on the pressure-dependence of viscosity, with a pressure-dependent coefficient βp. For the viscous model, the viscosity is a function of both temperature and pressure. For the viscoelastic K-BKZ model, the time-temperature shifting concept has been used for the non-isothermal calculations, while the time-pressure shifting concept has been used to shift the relaxation moduli for the pressure-dependence effect. It was found that only the viscoelastic simulations were capable of reproducing the experimental data well, while any viscous modeling always underestimates the pressures, especially at the higher apparent shear rates and L/D ratios.
Thin wall injection moulding is a difficult process. High viscosity polymeric material is injected into a mould by high speed and high pressure. A special instrumented injection mould was designed for the investigation of the cavity filling of injection mould. Rheological measurement can be carried out with different wall thickness slit die inserts. The pressure can be measured during the filling, the packing and the cooling stages as well. The pressure drop during the filling can be used for determination the flow properties of the material. The measured cavity pressure of the injection cycle is proper for the validation if thin wall injection moulding simulation. The filling of the dies was simulated by Moldex3D software.
Composites of poly(caprolactone) (PCL) and multiwalled carbon nanotubes (MWCNTs) were produced by melt-mixing in a small scale compounder by varying the screw speed between 25 and 400 rpm at a constant mixing time of two minutes. By that, different levels of dispersions, as assessed by quantitative analysis of area ratio of remaining primary agglomerates from light microscopy, were achieved. With increasing screw speed the state of dispersion increases and levels off starting at about 100 rpm.
Melt rheological properties were measured in frequency sweeps. Interestingly, distinct differences in the complex viscosity * and the storage modulus G’ were found in dependence on the agglomerate area ratio, whereas the loss modulus G’’ was not much influenced. The storage modulus at 0.1 rad/s initially increased with decreasing area ratios, showing that especially the storage modulus is very sensitive to the nanotubes dispersion state. It increased up to a mixing speed of about 75 rpm illustrating improved dispersion followed by a decrease when further increasing the speed. As GPC investigation showed no significant differences in the degradation of the PCL matrix depending on the rotation speed, the effect of decreasing rheological parameter was assigned to nanotube shortening. Both effects improved dispersion and nanotube shortening are also reflected in the electrical resistivity values of compression molded samples. Here, up to 75 rpm a decrease in resistivity due to the better dispersion was observed, whereas above 75 rpm, where dispersion had leveled off, again an increase was found reflecting the reduction in nanotube aspect ratio.
Thus, it could be shown that rheological measurements are suitable to detect differences in the dispersion state in composites with a fixed type of CNTs and concentration but also the effect of nanotube shortening reflected in lower aspect ratios.
A fast method was develop to predict the macroscopic
properties of molded resin specimens tested in the
Underwriting Laboratories (UL®) Relative Thermal Index
(RTI) test (tensile strength retention) with microscopic
properties that can be easily measured (molecular weight).
By using higher temperatures than employed in the UL
RTI protocol, accelerated ageing can be achieved in
pellets.
Polyetherimide (PEI) resin was spiked during
extrusion with common stabilizers. The analysis focused
on melt stability, rheology and long-term heat ageing
performance. Hindered phenol stabilizers were detrimental
under accelerated thermo-oxidative ageing of PEI. The
use of new stabilizers should be carefully considered.
Polypropylene impact copolymers are widely used in
automotive applications. They are required to comply with
many criteria. Customers demand high-performance
materials which also exhibit good aesthetical properties.
The challenge is to balance properties as high impact
strength, good flow ability and absence of surface defects,
like tiger stripes.
It is known that peroxide modification whilst
increasing the flow ability of polypropylene impact
copolymers deteriorates the basic mechanical and
aesthetical properties.
Work was performed in which a PP-impact
copolymer was subjected to peroxide aided chain-scission
under simultaneous presence of the co-agent 1,4-
butanedioldimethacrylate (1,4-BDDMA). Results show
that samples made with 1,4- BDDMA exhibit superior
cold impact resistance and tiger stripe performance
compared to the materials made with only peroxide. In
addition, morphology, molecular weight distribution, and
rheological behaviour of the continuous and dispersed
phases of the modified PP impact copolymer were
studied.
Bonk-sik Kang, JongOh Park, Varij Panwar, Sukho Park, August 2011
Larger actuation displacements and blocking forces at 2.5 and 3.0 DC voltages render the new composites superior to Nafion and useful for many applications.
Amit Chaudhary, Krishnamurthy Jayaraman, July 2011
Combining clay and compatibilizer additives with linear polypropylene forms nanocomposites with a densely entangled inner structure able to produce quality foams upon extrusion.
Combining digital image correlation with the essential-work-of-fracture technique offers a plausible alternative to conventional means of measuring the robustness of soft materials.
Rheology is the science of material flow behavior, which is a very complex and multi-dimensional science. Even though it is complex, it also is quintessential to understand in order to optimize the processing of polymers. Knowing the difference between amorphous and crystalline polymers, what Melt Index really tells, and the effects of melt temperature on melt fracture are all important elements in the understanding of rheology. A simple understanding of what polymer rheology is and how shear and temperature can affect the flow characteristic of a polymer may make a big difference in the P & L of a company.
Nanocomposites of low density polyethylene (LDPE) and C18 modified multi wall carbon nanotubes (C18-CNT) were prepared by melt blending. Previous research has shown that addition of carbon nanotubes (CNTs) increase the dynamic viscosity and reduce the extensional viscosity with increasing loading. This research work shows that C-18 modification of CNTs helps to keep low values of dynamic viscosity, maintain extensional viscosity and does not increase strain hardening even at 5.0 weight % loading.
Christian Hopmann, Walter Michaeli, Moritz Grundler, Oliver Gronlund, Andreas Neuss, May 2011
The projectile injection technique is a new powerful process variant of the well established fluid injection technique for the production of hollow shaped polymer parts. For suitable part designs the PIT allows to increase the economical efficiency and process capability significantly. First research results show that it is possible to reproducibly form hollow shaped geometries independent from the rheological properties of the used polymers.
Injection moldable hydrolytically stable transparent thermoplastic Polyetherimide resin blends with high impact and thermal resistance have been developed for healthcare applications. The two-phase resin blends are capable of withstanding 2,500 autoclave cycles at 134 C and 50 ppm morpholine while maintaining clarity and ductility. Injection molding of the new steam resistant blends as well as their rheological and material properties are compared to polyetherimide.
Liquid crystalline epoxy thermosets were prepared by adding 3,3',5,5'-Tetramethylbiphenyl-4,4'-diyl bis(4-(oxiran-2-ylmethoxy)benzoate) (M1) into diglycidylether of bisphenol A (DGEBA)/ 4,4'-diaminodiphenyl methane (DDM) blends. Rheological tests with constant temperature and time tests under constant mechanical shear load conditions were performed by using rheometry instrument.
Dhwaihi Alotaibi, Ankit Patel, Horst Winter, May 2011
Long chain branched polypropylene (LCBPP) crystallizes rapidly and with high nucleation density. The origin of this fast crystallization process of is not well understood. It has been attributed to its complicated molecular architecture. In this research, we explore isothermal crystallization of LCBPP through rheological, thermal, and optical measurements. The time resolved mechanical spectroscopy technique was used to predict the liquid-to-solid transition (gel point) of LCBPP.
Kim McLoughlin Senior Research Engineer, Global Materials Science Braskem
A Resin Supplier’s Perspective on Partnerships for the Circular Economy
About the Speaker
Kim drives technology programs at Braskem to develop advanced polyolefins with improved recyclability and sustainability. As Principal Investigator on a REMADE-funded collaboration, Kim leads a diverse industry-academic team that is developing a process to recycle elastomers as secondary feedstock. Kim has a PhD in Chemical Engineering from Cornell. She is an inventor on more than 25 patents and applications for novel polyolefin technologies. Kim is on the Board of Directors of SPE’s Thermoplastic Materials & Foams Division, where she has served as Education Chair and Councilor.
A Resin Supplier’s Perspective on Partnerships for the Circular Economy
About the Speaker
Gamini has a BS and PhD from Purdue University in Materials Engineering and Sustainability. He joined Penn State as a Post Doctorate Scholar in 2020 prior to his professorship appointment. He works closely with PA plastics manufacturers to implement sustainability programs in their plants.
A Resin Supplier’s Perspective on Partnerships for the Circular Economy
About the Speaker
Tom Giovannetti holds a Degree in Mechanical Engineering from The University of Tulsa and for the last 26 years has worked for Chevron Phillips Chemical Company. Tom started his plastics career by designing various injection molded products for the chemical industry including explosion proof plugs and receptacles, panel boards and detonation arrestors for 24 inch pipelines. Tom also holds a patent for design of a polyphenylene sulfide sleeve in a nylon coolant cross-over of an air intake manifold and is a Certified Plastic Technologist through the Society of Plastic Engineers. Tom serves on the Oklahoma Section Board as Councilor, is also the past president of the local Oklahoma SPE Section, and as well serves on the SPE Injection Molding Division board.
Joseph Lawrence, Ph.D. Senior Director and Research Professor University of Toledo
A Resin Supplier’s Perspective on Partnerships for the Circular Economy
About the Speaker
Dr. Joseph Lawrence is a Research Professor and Senior Director of the Polymer Institute and the Center for Materials and Sensor Characterization at the University of Toledo. He is a Chemical Engineer by training and after working in the process industry, he has been engaged in polymers and composites research for 18+ years. In the Polymer Institute he leads research on renewably sourced polymers, plastics recycling, and additive manufacturing. He is also the lead investigator of the Polyesters and Barrier Materials Research Consortium funded by industry. Dr. Lawrence has advised 20 graduate students, mentored 8 staff scientists and several undergraduate students. He is a peer reviewer in several journals, has authored 30+ peer-reviewed publications and serves on the board of the Injection Molding Division of SPE.
Matt Hammernik Northeast Account Manager Hasco America
A Resin Supplier’s Perspective on Partnerships for the Circular Economy
About the Speaker
Matt Hammernik serves as Hasco America’s Northeast Area Account Manager covering the states Michigan, Ohio, Indiana, and Kentucky. He started with Hasco America at the beginning of March 2022. Matt started in the Injection Mold Industry roughly 10 years ago as an estimator quoting injection mold base steel, components and machining. He advanced into outside sales and has been serving molders, mold builders and mold makers for about 7 years.
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Any article that is cited in another manuscript or other work is required to use the correct reference style. Below is an example of the reference style for SPE articles:
Brown, H. L. and Jones, D. H. 2016, May.
"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers, ISBN: 123-0-1234567-8-9, pp. 000-000.
Available: www.4spe.org.
Note: if there are more than three authors you may use the first author's name and et al. EG Brown, H. L. et al.
