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Cellulose nanocrystals (CNCs) are naturally-sourced nanoparticles that can be used to modify polymers and provide exceptional mechanical properties to nanocomposite materials. In this study, CNCs were incorporated into water-based pressure sensitive adhesives (PSAs) via in situ semi-batch emulsion polymerization to improve PSA properties. A sequential design approach was used to improve CNC/poly(n-butyl acrylate/vinyl acetate) nanocomposite PSAs. In the first part of the design, the effects of acrylic acid (AA) and anionic surfactant sodium dodecyl sulfate (SDS) were examined in the presence of 0.5 wt% CNCs (based on polymer mass). While the SDS was crucial to maintaining latex stability, its excessive addition led to a decrease in PSA performance, namely tack and peel strength. The AA comonomer was pivotal in improving the shear strength of the PSAs, especially in the presence of CNCs. In all cases, the addition of CNCs led to improved PSA shear strength. In the second part of the design, the addition of 1-dodecanethiol (NDM) as a chain transfer agent (CTA) with CNC levels up to 1 wt% led to an improvement in tack and peel strength but at the cost of diminishing the shear strength. Generally, the addition of CNCs improved PSA performance. Thus, to maximize the impact of CNCs on PSA properties, a careful balance of SDS (for latex stability), AA (to improve shear strength) and NDM (to improve tack and peel strength) are needed.

A series of epoxy-polyamide based nanocomposites is developed utilizing hyperbranched polymer (HBP)-modified nanoclay particles. To this aim, the pristine nanoclay is surface modified by a polyester-amide hyperbranched polymer (HBP) at various polymer to clay (P/C) ratios of 0.5, 1, 2.5, 5 and 10. The microstructure of the modified clays is investigated by X-ray diffraction (XRD) analysis. The results demonstrate that HBP adsorbs on the clay lamellae and the interlayer distance becomes larger due to interfacial interactions. The greater the P/C ratio is, the better intercalated morphology is obtained. In the next step, 1 wt.% of the pristine and modified nanoclay particles is introduced into a bisphenol-A based epoxy resin and the mixture is then cured by an amido polyamine based hardener to obtain nanocomposite specimens. Prior to curing process, the resulting dispersions undergo rheological measurements. The rheological behavior clarifies that HBP-modified nanoclay particles have reached to some extent to an exfoliated morphology. The inferred nanocomposites are then analyzed by XRD, thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA), tensile test and eventually scanning electron microscope (SEM) analyses. It is concluded by the outcomes that intercalated and/or exfoliated morphologies become more probable when the clays are modified by HBP and due to such nanostructure of the nanocomposites, the physical-mechanical characteristics are meaningfully enhanced.

This is the peer reviewed version of the following article: Saeb, M. R., Mohammadi, Y., Pakdel, A. S., & Penlidis, A. (2016). Molecular Architecture Manipulation in Free Radical Copolymerization: An Advanced Monte Carlo Approach to Screening Copolymer Chains with Various Comonomer Sequence Arrangements. Macromolecular Theory and Simulations, 25(4), 369–382, which has been published in final form at https://doi.org/10.1002/mats.201500096. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

Cellulose nanocrystals (CNCs), a sustainable nanomaterial, are in situ incorporated into emulsion-based pressure-sensitive adhesives (PSAs). Commercially available CNCs with different surface hydrophilicity and surface charge (CNC101 and CNC103 from CelluForce) are used to explore their role in PSA property modification. Viscosity measurements and atomic force microscopy reveal differences in degree of association between the CNCs and the latex particles depending on the surface properties of the CNCs. The more hydrophilic and higher surface charge CNCs (CNC101) show less association with the latex particles. Dynamic strain sweep tests are used to analyze the strain-softening of the nanocomposites based on CNC type and loading. The CNC101 nanocomposites soften at lower strains than their CNC103 counterparts. This behavior is confirmed via dynamic frequency tests and modeling of the nanocomposites' storage moduli, which suggest the formation of CNC aggregates of, on average, 3.8 CNC101 and 1.3 CNC103 nanoparticles. Finally, PSA properties, i.e., tack, peel strength, and shear strength, simultaneously increase upon addition of both CNC types, although to different extents. The relationship between the PSA properties and CNC surface properties confirms that the less hydrophilic CNCs lead to improved CNC dispersion in the PSA films and therefore, enhance PSA properties.

This paper reports on the reinforcing effects of different types of fillers, namely, nanoclay (NC), micron size calcium carbonate (MCC), and micron size recycled powder coating waste (MPCW), on the ultimate properties of acrylonitrile butadiene rubber (NBR) compounds. The microcomposites and nanocomposites were characterized by X-ray diffraction and scanning electron microscopy, implying enlargement of d-spacing of NC or intercalation of NBR chains and formation of exfoliated structure, while some agglomerates of MCC were detected. Curing characteristics of the studied composites showed that incorporation of the fillers into the NBR, in particular the NC, causes an increase in the torque, indicating a higher degree of crosslinking. Furthermore, different from micron size MPCW and MCC, the NC accelerated the vulcanization reaction. It was also found that the use of NC and MPCW results in a remarkable increase in the mechanical and rheological properties compared with pure NBR. All in all, variations in the aforementioned criteria were attributable to the extent of matrix/filler interaction reflected by scanning electron micrographs. The correlation established between the microstructure and characteristics of the prepared NBR composites can shed some light on how to develop composites with enhanced properties by incorporating waste materials into the polymers. J. VINYL ADDIT. TECHNOL., 00:000–000, 2015. V C 2015 Society of Plastics Engineers

Surface modification of nanoclay particles was carried out by various amounts of polyester-amide hyperbranched polymer (HBP). Thermal gravimetric analysis and X-ray diffraction analysis were performed to estimate the efficiency of the HPB grafting on the clay particles. Epoxy/clay nanocomposites were prepared by addition of 1 wt.% unmodified and modified clays. The corrosion protection properties of the nanocomposites were evaluated by electrochemical impedance spectroscopy (EIS). Results revealed that surface modification of the clay particles by HBP caused significant enhancement of the epoxy coating corrosion resistance especially when the ‘polymer/clay’ ratios were 10/1 and 5/1.

This work is aimed to undertake the simultaneous effect of chain extension (chemical modification) and solid-state polymerization (SSP) on the structural properties of recycled poly(ethylene terephthalate) to compensate the molecular weight (MW) losses caused by thermal degradation. This hybrid technique was qualified by tracking changes in the MW, intrinsic viscosity (IV), and concentrations of hydroxyl and carboxylic groups of various samples containing different concentrations of chain extender that experienced different residence times (2, 4, 6, 8, and 10 h) and different SSP process temperatures (190, 200, and 210 C). It was found that at high concentrations of chain extender, thermal degradation is facilitated owing to the lack of functional groups, as witnessed by a sharp drop in the MW and IV. The re-recycled poly(ethylene terephthalates) experienced chemical modification followed by SSP physical treatment and revealed a rise in MW and IV. Accordingly, the synergistic effect of hybrid modification in comparison with the individual chemical modification was highlighted. J. VINYL ADDIT. TECHNOL., 00:000– 000, 2014. VC 2014 Society of Plastics Engineers

The thermo-mechanical properties of a series of epoxy-silica hybrid composites prepared through sol–gel process are evaluated in a manner that the effect of organic solvent on the formation of silica domains is highlighted. By means of infrared spectroscopy, small-angle X-ray scattering, scanning electron microscope, dynamic mechanical thermal analysis, and thermo-gravimetric analyzer, the specimens were morphologically studied varying the type of organic solvent. Among polar and nonpolar solvents incorporated by the organic–inorganic hybrid system, a mixture of xylene and ethanol (3:1) was properly comparable with tetrahydrofuran (THF) solvent regarding appearance and thermo-mechanical characteristics. Enhanced thermal stability and modulus was observed upon increasing solvent content. Also, a proper dispersion of silica domains throughout the epoxy was seen in the case that the xylene/ethanol mixture or THF served as solvent. It is to be emphasized that the assigned mixture is environmentally better than that of THF. J. VINYL ADDIT. TECHNOL., 2014. © 2014 Society of Plastics Engineers

This work is targeted to study emulsion polymerization of vinyl chloride monomer (VCM) using experimental and mathematical methods. To fulfill this goal, a computer code was developed on the basis of zero–one population balance by which the effects of initiator and emulsifier concentration on the evolution of VCM conversion were investigated in the course of polymerization. The model was also trained to capture the coagulation of the particles. This enabled to adopt a reliable way of evaluating the particle size distribution (PSD). In particular, the rates of homogeneous and micellar nucleation mechanisms were simulated and reasonably predicted alterations in the PSD and the number of polymer particles under the influence of aforementioned parameters. The results from modeling were satisfactorily consistent with the experimental outputs and obviously visualized the impact of initiator and surfactant concentration on the PSD of the prepared PVC latexes.

We report on modeling of free-radical polymerization of styrene in a stirred tank reactor–spinning disc reactor (STR–SDR) arrangement using Kinetic Monte Carlo (KMC) simulation algorithm. The prepolymer from batch reactor was transferred to SDR and simulation results were validated comparing conversion and molecular weight of the generated molecules in the batch reactor and SDR with corresponding values from experimental data. The developed model was also applied to simulate SDR under a range of different operating conditions to accurately predict the resulting polymer properties. In this way, different prepolymer conversions were theoretically adapted to probe the evolution in chain microstructure until polymerization terminated on the rotating disc. The developed computer code based on KMC approach enables precise monitoring of molecular-level events in the reactor like variations in molar concentration of macroradicals and molecular weight distribution with time, and provides a greater insight into the STR–SDR cascade polymerization of styrene monomer.

Utilizing response surface methodology, the conversion of vinyl chloride monomer (VCM) was monitored when the polymerization temperature, the type of surfactant, and the weight ratio of water-to-monomer (W/M) were taken as the emulsion polymerization variables. Because the homogeneous nucleation was found to be the dominant mechanism in VCM emulsion polymerization, irrespective of the surfactant concentration, the whole experiments have been carried out below critical micelle concentration of the used surfactants. Among all the studied variables, the polymerization temperature appeared as the most effective parameter; moreover, its interactive effect with W/M caused different trends in the alteration of final conversion being observed. Also, depending on the reaction temperature, the VCM conversion would be affected by the type of the surfactant used. Contrarily, simultaneous change in the type of surfactant and W/M revealed an insignificant effect on the evolution of VCM conversion. The optimization of final conversion of VCM was also accessible through contour plots of response surface methodology. It is worth noting that, taking a conventional approach into consideration, the alteration of VCM conversion seemed to be a monotonic function of temperature. J. VINYL ADDIT. TECHNOL., 21:157–165, 2015. © 2014 Society of Plastics Engineers

Polypropylene, as a thermoplastic polyolefin, possesses advantageous physical, mechanical and thermal characteristics, but also suffers from disapproving lesser properties such as poor dye- and coat-ability. Herein, nanoclay particles and a polyester-amide-based hyperbranched polymer are utilized to improve paint-ability along with mechanical properties. XRD and SEM results rationalize the idea that maleic anhydride-modified polypropylene and hyperbranched polymer together improve the nanoclay dispersion. The corresponding idea of “molecular skateboards” is also developed via rheology measurements. DMA data demonstrate that mechanical characteristics of the hyperbranched polymer-modified samples remain intact or even improved comparing neat polypropylene and contact angle measurements reveal reduction in θ values.

A one-pot emulsion polymerization process to produce silica nanoparticles fi xed on polymer particles is presented. Simultaneous nanoparticle formation/monomer emulsifi cation and later polymerization of monomers prevent the agglomeration of silica particles and result in hybrid organic–inorganic, core–shell latexes. The emulsion polymerization of methyl methacrylate is performed using nascent silica nanoparticles, cetyltrimethylammonium bromide, and ammonium persulfate as Pickering surfactant, cosurfactant, and initiator, respectively. The effects of parameters like temperature, initiator type and concentration, and cosurfactant and silica precursor amounts on the polymerization, coagulation percentage, and morphology of hybrid particles are determined using SEM and TEM.