Water-borne coatings have increased in popularity due to the recent environmental regulations being placed on coating formulation. The most readily available coatings without volatile organic compounds are thermoplastic polymer dispersions that rely on interdiffusion to form a film. These dispersions are reliant on toxic crosslinking chemistries to achieve adequate coating mechanical properties, but still have significantly inferior properties when compared with current thermosetting industrial coatings that contain volatile organic compounds. As a result, waterborne coatings made with conventional emulsion polymers cannot be considered for high-performance coatings. Polyurethane dispersions have been developed that can meet these demands, but require several lengthy coating applications and are therefore incredibly costly. A water-based acrylic emulsion polymer coating that could self-stratify and apply multiple crosslinkable layers simultaneously, has the potential to revolutionize current coating formulations. Recent advances in anisotropic polymer colloid synthesis offer a potential pathway to make such a high-performance coating. Incorporating unique functionality into each of the lobes of a bilobal particle would enable the formation of a new class of water-based, self-stratifying, high-performance, acrylic coatings. The primary goal of this thesis was to show proof of concept for a bilobal platform that could be used to form water-based self-stratifying coatings. The approach was adapted from recent advances in pigment-associating emulsion polymers used to improve coating pigment dispersion. Butyl acrylate and methyl methacrylate seed particles ~90 nm in size were formed and subsequently used to synthesize preliminary ~130 nm acrylic bilobal particles, within the target size range of water based coating dispersions. Control over the seed particle glass transition temperature, size, and morphology, and synthesis of promising preliminary bilobal particles was demonstrated; this was accomplished using a systematic analysis of various reaction conditions, namely, pre-emulsification, reaction duration, and the concentrations of the monomers. Expanding upon the chemical versatility would enable these particles to be used in a wide variety of applications, but this thesis represents a promising start for the bilobal platform within the coating industry.

Emulsion polymerizations of vinyl acetate (VAc) were performed by fully or partially replacing poly(vinyl alcohol) (PVA) with renewable materials as protective colloids or by adding renewable materials, as additives or fillers, to the emulsions during or after polymerization. The purpose of the study was to increase the amount of renewable materials in the emulsion. A total of 19 emulsions were synthesized. Different recipes were used for the synthesis. The following renewable materials were studied; hydroxyethyl cellulose (HEC) with different molecular weights, starch and proteins. HEC and starch were used as protective colloids. Proteins were used as additives or fillers. Cross-linking agent A and Cross-linking agent B were used as cross-linking agents. A total of 26 formulations were pressed, either cold or hot. The synthesized emulsions were evaluated with respect to pH, solids content, viscosity, minimum film formation temperature (MFFT), glass transition temperature (Tg), particle size and molecular weight (Mw). The tensile shear strengths of the emulsions were evaluated according to EN 204 and WATT 91. It was possible to fully, or partially, replace PVA as protective colloid with renewable materials. It was also possible to use renewable materials as additives or fillers in the emulsions. The emulsions obtained properties that differed from the reference. Generally, emulsions with HEC as protective colloid showed lower viscosity and slightly higher MFFT, Tg and molecular weight than emulsions with PVA as protective colloid. Larger particle sizes than the reference were obtained for emulsions containing PVA combined with renewable materials. The emulsion with starch as protective colloid exhibited the largest particle size. 10 formulations passed the criteria for D2. The emulsions where PVA was fully or partially replaced with HEC or starch showed a water resistance similar to the reference (around D2). The addition of protein did not decrease the water and heat resistance compared to the reference. Addition of protein after polymerization increased the water resistance (D2) compared to addition during polymerization. Addition of cross-linking agents did not increase the water resistance further. Two formulations passed the criteria for D3. The emulsion in the first formulation had PVA as protective colloid and protein B was added during polymerization. The emulsion in the second formulation had HEC as protective colloid. To both of these emulsions, protein A was added after polymerization, as a filler, combined with Cross-linking agent B as cross-linking agent before hot pressing. The first formulation also showed a good heat resistance (passed the criteria for WATT 91).

Improvement properties of building materials are essential. In this dissertation thesis, the main concern had been on synthesizing a new resin to improve the properties of concrete and brick. Solvent-based polymers have been used for many years to improve the quality of building materials. In contrast to solvent-based polymers, water-based emulsion polymers are one of the available solutions that have been used to improve the quality of building materials. Several advantages can be enumerated for water-based emulsion polymers such as lower volatile organic compounds (VOC), easier application, lower carbon dioxide emissions in the production, and fossil resource preservation. Water-based emulsion polymers are synthesized from simple homopolymers to copolymers with various monomers and additives. In this research, the synthesis and characterization of water-based acrylic styrene emulsion copolymer had been the main concern. Acrylic monomers could develop the qualities such as thermoplasticity, water solubility, and a longer lifespan of the polymer, while styrene monomers will impart water resistance and stiffness properties. In this research, the first step had been the synthesis of a water-based emulsion copolymer. Furthermore, considering the importance of biodegradability of the synthesized copolymer, the research followed by the replacement of ingredients such as emulsifiers with higher biodegradability characteristics with eco-friendly by-products, i.e. reducing the microplastic hazards. As a result, the copolymer could be decomposed better, and consequently, problems with the release of microplastics will be reduced. The synthesized water-based acrylic styrene emulsion copolymer was characterized by FTIR, DSC, and TGA. The FTIR results confirmed successful emulsion polymerization of acrylic styrene copolymer. DSC results confirmed the formation of an amorphous thermoplastic type of copolymer with a single glass transition temperature. The TGA result also confirms a single decomposition temperature. The film formation was carried out using a film applicator to evaluate the film formation properties. The substitution of the superseded emulsifiers (both anionic and nonionic) did not alter the characteristics of the synthesized copolymer, while some of the qualities such as water absorbance of the dried copolymer are improved (a water absorption test was carried out). To improve the quality of both synthesized emulsion copolymers (with conventional and superseded emulsifiers), the nanocomposite of the emulsion copolymer was prepared (Cloisite 30B at a concentration of 0.2 to 1 %). The synthesized nanocomposite showed better water resistance in the coating application in contrast with emulsion copolymer. The next stage of the research has been concentrated on the application of the synthesized water-based emulsion copolymer to building materials (concrete and brick). The synthesis copolymer has been applied as a coating on the surface of the concrete and bricks. Moreover, the synthesis copolymer was used as one of the ingredients in the mixture of the concrete. The promising results for the coating improved when the synthesis polymer was modified with nanoparticles (Cloisite 30B at a concentration of 1 % weight of the latex). Incorporating the synthesized copolymer in the mixture of concrete caused decreasing in the density of concrete by 4 % ( via air voids formation mechanism). However, water absorption was improved when synthesized copolymer was mixed with the concrete. The synthesized copolymer and the nanocomposite is a suitable coating for the concrete and brick. Furthermore, this copolymer is a suitable water-based coating with improved properties in building materials.

This thesis investigates the effect of reaction media on the efficiency of grafting hydrophobic polymers from cellulose nanocrystals (CNCs) via surface-initiated atom transfer radical polymerization (SI-ATRP), with the goal of producing highly-modified CNCs for incorporation into latex-based pressure sensitive adhesives (PSAs). A latex is a dispersion of polymer particles in water made by emulsion polymerization; latexes are commonly used in paints, coatings, elastomers, inks/toners, household products, cosmetics, and adhesives. However, latex-based PSAs often underperform compared to their organic solvent-polymerized counterparts due to a lack of cohesive strength in the cast latex films. The environmental benefit of using latex-based PSAs synthesized in water is significant, but the development of strategies to improve their performance are required. CNCs are hydrophilic rod-shaped nanoparticles with high mechanical strength. Adding CNCs to latex-based PSAs has been shown to improve both adhesive (i.e., tack and peel strength) and cohesive (i.e., shear strength) properties and offers a degree of sustainability because CNCs are derived from natural cellulose sources such as wood pulp. However, their hydrophilicity, particularly relative to the hydrophobic polymers used in PSAs, has constrained CNCs to the continuous (i.e., water) phase of the latex. To improve CNC compatibility with the dispersed (i.e., polymer) phase and improve their distribution in cast latex films, hydrophobic polymers can be grafted from CNCs. However, CNCs with a high polymer graft density are required to ensure their compatibility with monomers/polymers during latex synthesis. To begin, grafting poly(butyl acrylate) (PBA) from CNCs using SI-ATRP in polar dimethylformamide (DMF) versus non-polar toluene was directly compared. The enhanced colloidal stability of initiator-modified CNCs in DMF led to improved accessibility to surface initiator groups during polymer grafting. As such, PBA-grafted CNCs produced in DMF had up to 30 times more grafted polymer chains than PBA-grafted CNCs produced in toluene. The PBA-grafted CNCs produced in DMF showed high contact angles when cast in a film and formed stable suspensions in toluene. This work highlights that optimizing CNC colloidal stability in a given solvent prior to polymer grafting is a more crucial consideration than solvent–polymer compatibility in the context of obtaining high graft densities and thus hydrophobic CNCs via SI-ATRP. The improved polymer grafting method in DMF was then used to produce PBA and poly(methyl methacrylate) (PMMA)-grafted CNCs at two polymer chain lengths. Polymer grafted CNCs were incorporated in situ during a seeded semi-batch emulsion polymerization to produce PBA latex nanocomposite PSAs. Viscosity measurements revealed significant differences between latexes prepared with CNCs versus polymer-grafted CNCs, with the lower viscosities of the latter suggesting their incorporation inside the polymer particles. When CNCs with short polymer grafts were introduced into PSAs at 1 wt. % loading, they exhibited comparable tack and improved peel strength compared to unmodified CNCs (and all properties improved relative to the base latex without any CNCs). This is attributed to their improved distribution throughout the PSA, the enhanced wettability of the substrate with the CNC containing latex, and the increased polymer chain mobility achieved based on the low molecular weight of the grafts. CNCs with long polymer grafts aggregated in the latex and did not improve PSA properties. PMMA-grafted CNCs slightly outperformed PBA-grafted CNCs likely due to the higher glass transition temperature of PMMA. These results provide insight into future optimization of more sustainable latex-based PSA formulations as well as new commercial CNC-latex products, where the presence of low molecular weight grafts on CNC surfaces could improve polymer mobility and tack and peel strength. / Thesis / Master of Applied Science (MASc) / When the adhesives used in tapes, labels or sticky notes are produced using water-based reactions, they normally underperform compared to conventional adhesives produced using toxic solvents. To improve such water-based adhesives, adding nanocellulose (tiny particles derived from wood pulp) during synthesis has been shown to be an asset. Nanocellulose can be chemically modified to improve its compatibility with adhesive ingredients, and thus change the role of nanocellulose during adhesive manufacturing. In this thesis, modified nanocelluloses were added to water-based adhesives to evaluate their effect on performance (i.e., strength and stickiness). It was found that the reaction conditions during nanocellulose modification were crucial for obtaining highly modified particles that are compatible with adhesive ingredients. This work aims to provide insight for future production of less environmentally taxing adhesives made in water and expand the use of nanocellulose in new commercial products.

No description available.

This thesis has as its principal goal the development of sustainable pressure-sensitive adhesives (PSAs). To that end, we examined polymer reaction engineering practices and polymer formulations through the lens of the 12 Principles of Green Chemistry. To begin with, we employed emulsion polymerization as our polymer synthesis method because of its use of water instead of hazardous solvents. We also replaced various petroleum-based components with bio-based alternatives (e.g., starch, cellulose nanocrystals), thereby reducing synthesis hazards, increasing product safety and increasing the amount of sustainably sourced raw materials in the PSA. However, changing the synthetic method as well as key components in the formulation presented significant challenges to maintaining PSA performance. This thesis illustrates the challenging path taken towards developing a fully renewable PSA. PSAs should display a specific balance of adhesion and cohesion. Typically, petroleum-based additives (which are often hazardous/toxic) such as tackifiers, cross-linkers, chain transfer agents and rheology modifiers are added to tailor latex properties to fit the intended application. However, because of their inherently opposing effects, an additive used to increase adhesion will weaken the cohesive forces of the polymer, and vice versa. Cellulose nanocrystals (CNCs) are sustainable nanomaterials that have been shown to be effective to resolve the adhesion/cohesion conundrum. In the first part of this project, we developed a new technique to increase CNC loading in emulsion-based PSA formulations beyond the 1-2% limits previously encountered due to high latex viscosity, colloidal instability, and poor film properties. The higher CNC loadings were shown to continuously improve shear strength but resulted in eventual decreases to tack and peel strength. In the second part of this project, we replaced the sulfated CNCs with carboxylated CNCs (cCNCs), which are produced by a process using a “greener” catalyst (i.e., hydrogen peroxide instead of sulfuric acid). The cCNCs’ carboxylate surface groups interacted strongly with the polymer matrix, ultimately leading to catastrophic coagulation. The interactions between cCNCs and other standard latex components were studied and through the creative manipulation of the emulsion polymerization process, a reproducible method to incorporate the cCNCs in a seeded semi-batch reaction yielded stable, high-quality latexes. In the third part of this project, the effect of the cCNCs on the adhesive properties of the nanocomposite latex films was studied and compared to the effects of the sulfated CNCs. AFM imaging revealed that cCNCs interact with latex particles and each other; thus, omitting ultrasonication at the preparation stage was shown to preserve these interactions and lead to greater property enhancements. In the fourth part of this project, starch nanoparticles (SNPs) were used to displace some of the petroleum-based monomer in the production of core-shell (SNP cores, acrylic shell) latexes. SNPs are renewably sourced, inexpensive, and biodegradable. The challenge of locating the SNPs into the particle cores was overcome by crosslinking the SNPs using a food grade cross-linker (sodium trimetaphosphate) and functionalizing them using a sugar-based monomer (EcoMer™). To tune the PSA properties to rival a range of commercial tapes, a method to incorporate CNCs to the SNP-latexes in situ was developed. In addition, because monomers such as 2-octyl acrylate (2OA), styrene, and acrylic acid can be bio-sourced, they were selected as the acrylic shell monomers to encapsulate the SNPs in the nanocomposite latexes. Due to supply chain challenges, n-octyl acrylate was used as a model monomer for 2OA to produce latexes with ~80% bio-content that rivaled commercial Post-It™ notes, masking tapes, and duct tapes. After addressing the sustainability of the polymerization method and polymer components, we posed the question: what are the effects of using renewably sourced and bio-sourced materials on the end-of-life of the PSAs? Because the infrastructure for biodegradation studies at the lab scale via composting does not exist in Canada (to our knowledge), we designed an in-house aerobic composting set-up consisting of a series of bioreactors and sensors capable of measuring the aerobic biodegradability of our polymers in a simulated composting environment. Although not fully tested, the composting setup was designed, and its construction was begun. Steps to complete the construction and validate its operation are detailed. The path towards sustainability is often long and complex. In this four-year study, the re-design of an adhesive synthesis process using a more sustainable approach, emulsion polymerization, along with an 80% bio-sourced formulation required significant corrective measures. Overcoming the technical challenges required mustering all the polymer reaction engineering tools at our disposal. Despite the time and effort required, achieving a more sustainable process is indeed within our grasp.

This thesis aims to improve the performance of latex-based pressure-sensitive adhesives (PSAs). PSA performance is usually evaluated by tack, peel strength and shear strength. Tack and peel strength characterize a PSA’s bonding strength to a substrate while shear strength reflects a PSA’s capability to resist shear deformation. In general, increasing shear strength leads to a decrease in tack and peel strength. While there are several commercial PSA synthesis methods, the two most important methods consist of either solvent-based or latex-based techniques. While latex-based PSAs are more environmentally compliant than solvent-based PSAs, they tend to have much lower shear strength, at similar tack and peel strength levels. Therefore, the goal in this thesis was to greatly improve the shear strength of latex-based PSAs at little to no sacrifice to tack and peel strength. In this study, controlling the polymer microstructure of latexes or their corresponding PSA films was used as the main method for improving the PSA performance. The research was sub-divided into four parts. First, the influence of chain transfer agent (CTA) and cross-linker on latex polymer microstructure was studied via seeded semi-batch emulsion polymerization of butyl acrylate (BA) and methyl methacrylate (MMA). Three techniques were used to produce the latexes: (1) adding CTA only, (2) adding cross-linker only, and (3) adding both CTA and cross-linker. It was found that using CTA and cross-linker simultaneously allows one to expand the range of latex microstructural possibilities. For example, latexes with similar gel contents but different Mc (molecular weight between cross-links) and Mw (molecular weight of sol polymers) could be produced if CTA and cross-linker concentration are both increased. However, for the corresponding PSAs with similar gel contents, the relationship between their polymer microstructure and performance was difficult to establish as almost all of the medium and high gel content PSAs showed very low tack and peel strength as well as extremely large shear strength readings. In the second part of this thesis, in order to improve the tack and peel strength of medium and high gel content PSAs, the monomer composition and emulsifier concentration were varied. It was found that changing the monomer mixture from BA/MMA to BA/acrylic acid (AA)/2-hydroxyethyl methacrylate (HEMA) while simultaneously decreasing emulsifier concentration dramatically improved the corresponding PSAs’ shear strength as well as tack and peel strength. The addition of polar groups to the PSA increased its cohesive strength due to the presence of strong hydrogen bonding; meanwhile, PSA films’ surface tension increased. In the third part, two series of BA/AA/HEMA latexes were generated by varying the amounts of CTA either in the absence or presence of cross-linker. The latexes produced in the absence of cross-linker exhibited significantly larger Mc and Mw compared to their counterparts with similar gel contents prepared with cross-linker. The PSAs with the larger Mc and Mw showed much larger shear strengths due to improved entanglements between the polymer chains. In the final part of the thesis, the performance of the BA/AA/HEMA PSAs was further improved by post-heating. Compared with original latex-based PSAs with similar gel contents, heat-treated PSAs showed not only significantly improved shear strengths, but also much larger tack and peel strengths. The different shear strengths were related to the PSAs’ gel structures, which were discrete in the original PSAs but continuous in the heat-treated PSAs. The improved tack and peel strengths were related to the PSA films’ surface smoothness. During the post-heating process, the PSA polymer flowed, resulting in much smoother surfaces than the original PSA films. In addition, the effect of post-heating was related to the polymer microstructure of the untreated PSAs. Decreasing the amount of very small or very big polymers or simultaneously increasing Mc and Mw could lead to post-treated PSAs with significantly better performance. Moreover, it was found that by optimizing the polymer microstructure of the original latex-based PSAs, it was possible to obtain a treated PSA with similar or even better performance than a solvent-based PSA with similar polymer microstructure. Our original objective was surpassed: in two cases, not only was shear strength greatly improved, but so were tack and peel strength due to the simultaneous modification of PSA bulk and surface properties.

No description available.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23930号 / 工博第5017号 / 新制||工||1783(附属図書館) / 京都大学大学院工学研究科化学工学専攻 / (主査)教授 大嶋 正裕, 教授 山子 茂, 教授 佐野 紀彰 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24814号 / 工博第5157号 / 新制||工||1985(附属図書館) / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 山子 茂, 教授 辻井 敬亘, 教授 大内 誠 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM