An Overview of the Potential of UV Modification of Polypropylene

This is the peer reviewed version of the following article: Amintowlieh, Y., Tzoganakis, C., & Penlidis, A. (2016). An Overview of the Potential of UV Modification of Polypropylene. Macromolecular Symposia, 360(1), 96–107, which has been published in final form at https://doi.org/10.1002/masy.201500110. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.UV radiation with a photoinitiator has been utilized to modify polypropylene (PP). Factors affecting solid state photomodification were studied and the optimal processing conditions for formation of three different structures (degraded, long chain branched and crosslinked) in PP were determined. A long radiation time (more than 5 minutes) is required to form long chain branched PP (LCBPP) and this exposure time is even higher for production of crosslinked PP (XPP). Trimethylolpropane triacrylate (TMPTA) was utilized to decrease UV radiation duration. Optimal concentrations of TMPTA and photoinitiator for formation of long chain branched and crosslinked PP were determined. Finally, a setup was suggested for continuous photomodification of PP using a twin screw extruder. In this design, PP strands are irradiated directly after the die. Optimal photoinitiator (benzophenone) concentration, coagent (TMPTA) concentration and radiation time required to form controlled rheology (CRPP) or long chain branched PP or crosslinked PP were identified.Natural Sciences and Engineering Research Council (NSERC) of Canada Canada Research Chair (CRC) progra

On the role of extensional rheology and Deborah number on the neck-in phenomenon during flat film casting

In this work, viscoelastic, isothermal extrusion film casting simulations have been performed utilizing a 1D membrane model and the viscoelastic modified Leonov model as the constitutive equation in order to elucidate the role of planar to uniaxial extensional viscosity ratio, extensional strain hardening and Deborah number on the neck-in phenomenon. Based on the performed theoretical parametric study, it has been found that neck-in can be correlated to all the above mentioned variables via a simple dimensionless analytical equation. This correlation can provide detailed view into the complicated relationship between polymer melt rheology, die design, process conditions and undesirable neck-in phenomenon. Obtained results have been validated against literature experimental data for different polyethylene melts and processing conditions. © 2017 Elsevier Ltd16-05886S, GACR, Grantová Agentura České RepublikyGrant Agency of the Czech Republic [16-05886S

Continuous Modification of Polypropylene Via Photoinitiation

This is the peer reviewed version of the following article: Amintowlieh, Y., Tzoganakis, C., & Penlidis, A. (n.d.). Continuous modification of polypropylene via photoinitiation. Polymer Engineering & Science, 55(10), 2423–2432 which has been published in final form at https://doi.org/10.1002/pen.24133 This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.A twin screw extruder was used for continuous modification of polypropylene (PP) via UV radiation. Long chain branches were incorporated in the PP backbone to modify its rheological properties. Benzophenone (BPH) as photoinitiator and trimethylolpropane triacrylate (TMPTA) as coagent were utilized during PP photomodification. Radiation was carried out after mixing in the extruder on solid stretched strands with approximately 0.3 mm thickness. The effects of photoinitiator concentration, radiation time and coagent presence were studied via a replicated two-level full factorial design of experiments. It was shown that photomodification of PP can be done continuously. Formation of long chain branches (LCBs) in the experimental runs was confirmed via rheological measurements. Gel content of the samples was also measured. It was found that long chain branches can be formed in PP with and without TMPTA at certain processing conditions. The amount of gel in the samples prepared with TMPTA was higher; however, the gel content could be controlled by manipulating BPH concentration and radiation time.Natural Sciences and Engineering Research Council (NSERC) of Canada Canada Research Chair (CRC) progra

Effect of Temperature and Pressure on Surface Tension of Polystyrene in Supercritical Carbon Dioxide

This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry B., 111, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/jp065851tThe surface tension of polymers in a supercritical fluid is one of the most important physicochemical parameters in many engineering processes, such as microcellular foaming where the surface tension between a polymer melt and a fluid is a principal factor in determining cell nucleation and growth. This paper presents experimental results of the surface tension of polystyrene in supercritical carbon dioxide, together with theoretical calculations for a corresponding system. The surface tension is determined by Axisymmetric Drop Shape Analysis-Profile (ADSA-P), where a high pressure and temperature cell is designed and constructed to facilitate the formation of a pendant drop of polystyrene melt. Self-consistent field theory (SCFT) calculations are applied to simulate the surface tension of a corresponding system, and good qualitative agreement with experiment is obtained. The physical mechanisms for three main experimental trends are explained using SCFT, and none of the explanations quantitatively depend on the configurational entropy of the polymer constituents. These calculations therefore rationalize the use of simple liquid models for the quantitative prediction of surface tensions of polymers. As pressure and temperature increase, the surface tension of polystyrene decreases. A linear relationship is found between surface tension and temperature, and between surface tension and pressure; the slope of surface tension change with temperature is dependent on pressure.Natural Sciences and Engineering Research Council of Canada (NSERC) Canadian Foundation for Innovation (CFI) Canada Research Chairs (CRC) Progra

Constructing pristine and modified cellulose nanocrystals based cured polychloroprene nanocomposite films for dipped goods application

In this work, polychloroprene rubber (CR) nanocomposite films reinforced with native and modified cellulose nanocrystals (CNCs) were evaluated for dipped goods applications. The CNC modification, with a goal of enhancing the interaction between the CNC and CR, was conducted by surface graft polymerization of lactic acid. The films were then prepared by latex blending, casting, and curing (with ZnO/MgO). TEM studies displayed that the CNCs formed a partially structured network while modified CNCs (mCNCs) tend to disperse mostly individually in the polychloroprene and show percolation at 3 wt%. Tensile tests of the films showed a substantial increase in the modulus, tensile strength, and tear resistance for both CNC, and mCNC reinforced films while the elongation at break remained above 600%. The films made with CNCs and mCNCs exhibited similar acetone vapor permeability at different loadings of the filler. However, their permeability towards water and 2-propanol vapor increased steadily with an increase in CNCs loading. In contrast, the mCNC-based films displayed steady permeability and a surge at 3 wt%, which could be attributed to percolation. Overall, the fabrication of CNC and mCNC reinforced CR films demonstrated appealing physical properties for a range of dipped goods applications.Natural Resources Canada || CelluForce Inc

Operational maps between molecular properties and environmental stress cracking resistance (ESCR)

This is the peer reviewed version of the following article: Sardashti, P., Stewart, K. M. E., Polak, M., Tzoganakis, C., & Penlidis, A. (2019). Operational maps between molecular properties and environmental stress cracking resistance. Journal of Applied Polymer Science, 136(4), 47006. https://doi.org/10.1002/app.47006, which has been published in final form at https://doi.org/10.1002/app.47006. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.Environmental stress cracking (ESC) is one of the main failure mechanisms involved in polymer fractures. This paper focusses on the environmental stress cracking resistance (ESCR) of polyethylene (PE) in which ESC occurs through a slow crack growth mechanism. In order to predict the ESCR of PE, it is necessary to fully understand the molecular structure of the resin. This paper demonstrates the relationships between molecular structure characteristics and material responses based on experimental characterization and published literature trends. Relationships between ESCR, molecular weight (MW), percentage crystallinity, and density were used to create ESCR and molecular structure maps, which can be used to improve the development of PE resins with a desirable (better/higher) ESCR. These maps along with a logical flow chart offer practical prescriptions and describe pathways towards the development of PE with a desirable ESCR. In addition, this paper presents case studies that demonstrate the effectiveness of this approach.The authors gratefully acknowledge financial support from the Natural Sciences and Engineering Research Council (NSERC) of Canada, the Canada Research Chair (CRC) program, and the Ontario Graduate Scholarship (OGS) program. Many thanks also go to Imperial Oil Limited, Sarnia, ON, Canada, for financial support and for providing resins for the study over many years

A Low-Cost and Lithium-Free Hole Transport Layer for Efficient and Stable Normal Perovskite Solar Cells

The most widely used material as a hole-transport layer (HTL) for effective normal perovskite solar cells (PSCs) is still 2,2′,7,7′-Tetrakis[N, N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (Spiro-OMeTAD), which requires heavy doping with the hydroscopic Lithium bis(trifluoromethanesulfonyl)imide (Li-ΤFSI). However, the long-term stability and performance of PCSs are frequently hampered by the residual insoluble dopants in the HTL, Li+ diffusion throughout the device, dopant by-products, and the hygroscopic nature of Li-TFSI. Due to the high cost of Spiro-OMeTAD, alternative efficient low-cost HTLs, such as octakis(4-methoxyphenyl)spiro[fluorene-9,9′-xanthene]-2,2′,7,7′-tetraamine) (X60), have attracted attention. However, they require doping with Li-TFSI, and the devices develop the same Li-TFSI-derived problems. Here, we propose Li-free 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI) as an efficient p-type dopant of X60, resulting in a high-quality HTL with enhanced conductivity and deeper energy levels The optimized X60:EMIM-TFSI-enabled devices exhibit a higher efficiency of 21.85% and improved stability, compared to the Li-TFSI-doped X60 devices. The stability of the optimized EMIM-TFSI-doped PSCs is greatly improved, and after 1200 hr of storage under ambient conditions, the resulting PSCs maintain 85% of the initial PCE. These findings offer a fresh method for doping the cost effective X60 as the HTL with a Li-free alternative dopant for efficient, cheaper, and reliable planar PSCs