Polyurethanes (PUs) are a class of materials that have continuously gained popularity in almost all industries. The chemical structure of PUs is based on the presence of urethane bonds, generated by reaction between polyalcohols and diisocyanates, which strongly influences both mechanical and chemical properties of polyurethanes. These components generate a segmented structure with hard and soft sections, that im part crystallinity or flexibility to the molecule, resulting to different physical character istics. This imparts versatility to PUs which make them suitable for different applications. In this study, the synthesis of a PU thickener is explored using a biobased diol, polypropane diol (PPD), obtained from sustainable pathways as the backbone of the structure together with isophorone diisocyanate. Dimethylol proprionic acid (DMPA) is used as a chain extender and modifier, as the ionization of the carboxylic group and subsequent neutral ization with triethylamine (TEA) enhances the products solubility in acqueous solvent. Ethylene glycol monobutyl ether was then used to terminate the PU chains, blocking isocyanate groups thus removing the hazard related to them. The synthesis pathway follows an initial pre-polymer production wherein an isocyanate terminated intermediate is obtained, the evolution of this process is monitored by devel oping an FTIR quantitative method that is cross-validated with a titration-based method. From these, diisocyanate levels are determined and it is possible the time point for the addition of the DMPA extender, and then the termination with EGBE related to a target molecular weight of around 20 [kDa] determined through gel permeation chromatography. The resulting polymer is dispersed in a solvent system consisting of ethylene glycol and water at 1:1 weight ratio, and neutralized with TEA. The viscosities of the dispersions are then measured through a Brookfield viscometer at room temperature and the effect of the different quantities of extender was observed. In particular, an increase in the ex tender resulted to relatively higher molecular weight, and an increase in viscosity, which is a typical trend in polymeric dispersions. The resulting viscosities are also on par to a similar PU thickener that used polyethylene glycol as a diol, which makes the biobased polypropane diol as a promising alternative.
I poliuretani (PU) sono una categoria di materiali in continua espansione nella maggior parte delle industrie. La struttura chimica dei PU è basata sulla presenza di legami uretanici, generati dalla reazione tra polialcoli e diisocianati, influenzando fortemente sia le proprietà fisiche che chimiche del prodotto finito. Questi due componenti generano infatti una struttura segmentata con frammenti rigidi e flessibili, che impartiscono rispettivamente cristallinità o elasticità alla molecola, rendendo i poliuretani estremamente versatili in varie applicazioni. In questo studio è stata approfondita la sintesi di un poliuretano addensante tramite utilizzo di un diolo "bio-based", ottenuto cioè da risorse rinnovabili: il polypropandiolo (PPD). Quest’ultimo risulta essere lo scheletro della catena polimerica assieme all’isoforone diisocianato (IPDI). L’acido dimetilol-propionico (DMPA) è stato utilizzato come estensore di catena e modificatore. Tramite ionizzazione del gruppo carbossilico dell’acido e successiva neutralizzazione con trietilammina (TEA), la solubilità in ambiente acquoso del poliuretano aumenta. L’etilen glicole monoetil etere (EGBE) è stato aggiunto poi per terminare le catene polimeriche, bloccando i gruppi isocianato ed eliminando in questo modo la tossicità ad essi collegata. La procedura di sintesi consiste inizialmente in una pre-polimerizzazione, il cui prodotto è un composto intermedio terminato alle estremità con gruppi isocianato. L’andamento di questo processo è monitorato tramite la configurazione di un metodo quantitativo FTIR (Fourier Transformation Infrared Spectroscopy). Quest’ultimo viene poi validato tramite il metodo di titolazione. Una volta determinati i livelli di disocianato, vengono individuati i momenti in cui è possibile aggiungere alla reazione, rispettivamente, l’estensore (DMPA) e del terminatore (EGBE). Nel terminare le catene, viene preso in considerazione un peso molecolare di circa 20 [kDa], determinato tramite Gel Permeation Chromatography (GPC). Il polimero risultante viene disperso in un sistema solvente, che consiste in una soluzione in rapporto 1:1 di acqua:etilen glicole, e neutralizzato tramite aggiunta di trietilammina (TEA). I valori di viscosità delle dispersioni ottenute sono poi misurate tramite un vis cosimetro Brookfield a temperatura ambiente, variando poi la quantità di estensore e osservandone gli effetti. In particolare, aumentando il rapporto molare di estensore incre mentano sia il peso molecolare che la viscosità, comportamento che rispecchia perfetta mente le caratteristiche di una dispersione polimerica. I valori di viscosità risultanti sono simili ad un addensante poliuretanico, il quale presenta come diolo il glicole etilenico. Il polipropan-diolo utilizzato in tesi, essendo "bio-based" e offrendo prestazioni simili all’esempio citato, risulta quindi una valida alternativa ai dioli tradizionali
Synthesis and characterization of a polyurethane rheology modifier using a biobased diol
Sartori, Sofia
2023/2024
Abstract
Polyurethanes (PUs) are a class of materials that have continuously gained popularity in almost all industries. The chemical structure of PUs is based on the presence of urethane bonds, generated by reaction between polyalcohols and diisocyanates, which strongly influences both mechanical and chemical properties of polyurethanes. These components generate a segmented structure with hard and soft sections, that im part crystallinity or flexibility to the molecule, resulting to different physical character istics. This imparts versatility to PUs which make them suitable for different applications. In this study, the synthesis of a PU thickener is explored using a biobased diol, polypropane diol (PPD), obtained from sustainable pathways as the backbone of the structure together with isophorone diisocyanate. Dimethylol proprionic acid (DMPA) is used as a chain extender and modifier, as the ionization of the carboxylic group and subsequent neutral ization with triethylamine (TEA) enhances the products solubility in acqueous solvent. Ethylene glycol monobutyl ether was then used to terminate the PU chains, blocking isocyanate groups thus removing the hazard related to them. The synthesis pathway follows an initial pre-polymer production wherein an isocyanate terminated intermediate is obtained, the evolution of this process is monitored by devel oping an FTIR quantitative method that is cross-validated with a titration-based method. From these, diisocyanate levels are determined and it is possible the time point for the addition of the DMPA extender, and then the termination with EGBE related to a target molecular weight of around 20 [kDa] determined through gel permeation chromatography. The resulting polymer is dispersed in a solvent system consisting of ethylene glycol and water at 1:1 weight ratio, and neutralized with TEA. The viscosities of the dispersions are then measured through a Brookfield viscometer at room temperature and the effect of the different quantities of extender was observed. In particular, an increase in the ex tender resulted to relatively higher molecular weight, and an increase in viscosity, which is a typical trend in polymeric dispersions. The resulting viscosities are also on par to a similar PU thickener that used polyethylene glycol as a diol, which makes the biobased polypropane diol as a promising alternative.File | Dimensione | Formato | |
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2024_10_Sartori_tesi.pdf
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2024_10_Sartori_Executive Summary.pdf
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https://hdl.handle.net/10589/227016