Silicone Modified Water-based Polyurethane

Waterborne polyurethanes modified with organosilicones are studied in this thesis. Dihydroxyalkyl terminated polysiloxanes are used as the organosilicone, and anionic waterborne polyurethanes latexes having carboxylic groups are synthesized using acetone method. A new crosslinker for waterborne polyurethanes is also synthesized, which can react during the film formation stage.A series of dihydroxypropyl terminated polysiloxanes (PDS), with molecular weight below 4,000, are prepared through reactions between allyl alcohol, tetramethyldisiloxane and octamethylcyclotetrasiloxane (D₄). On the same time, another series of bis(3-(1-methoxy-2-hydroxypropoxy) propyl) terminated polysiloxanes (PMTS) are also synthesized using allylglycidyl ether, tetramethyldisiloxane and D4. The final and intermediate products in each process of PDS and PMTS preparations have been fully characterized for the first time using infrared (IR) and nuclear magnetic resonance (NMR). The results show that each step was proceeded as expected. Experiments show that in PDS preparation through bis(3-trimethylsilyloxy propyl)tetramethyldisiloxane (TDMS), a good practice is to first carry out the polycondensation between TDMS and D₄ , followed by trimethylsilyl removal. The molecular weights of each PDS and PMTS have been estimated for the first time simultaneously by end-group analysis, ¹HNMR and gel permeation chromatography (GPC). Good agreements between the theoretical molecular weights and those obtained from end-group analysis and ¹HNMR are obtained. However, higher values are observed for those from GPC. This might be attributed to the eventual hydrogen bond formation among molecular chains of PDS and PMTS when dissolved in the solvent tetrahydrofuran, this will increases the hydrodynamic volume of molecular chains.The anionic waterborne polyurethanes modified with PDS are prepared for the first time from toluene diisocyanate, polypropylene glycol, ethylene glycol, dimethylolpropionic acid, PDS and triethylamine through acetone method. Experiment results show that gradual addition method leads to stable PSU latexes comparatively with a process where polypropylene glycol and PDS were charged.Experiments also reveal that the viscosity of the final PSU latexes decrease rapidly when PDS is above 5% (wt), and molecular weight of PDS is about 2000. The particles morphology of latexes is investigated by transmission electron microscope (TEM). Rod shaped aggregates are observed when either PDS is below 5%, or the molecular weight of PDS is lower than 1500. In the rest of the experiments, round or atactic polygon aggregates are found. The average particle diameter is between 150nm and 600nm in both PSU and water borne polyurethanes (WPU) latexes. The particle size distributions from light scattering are quite broad for both latexes, and micron sized large particles are detected. The morphologies of fractured section of PSU films are observed using scanning electron microscope (SEM). Phase separation of incorporated PDS in PSU films seems increasing with increase in PDS content and its molecular weight. Water resistance, mechanical properties and thermal stability of PSU and WPU films are also studied. Amongst all the experiments carried out, PSU films manifested optimal properties when molecular weight of PDS is about 2000, and the content of PDS is 5%. These PDS modified PSU films outperformed their corresponding unmodified WPU films with regards to their mechanical properties and water resistance.Waterborne polyurethanes modified with PMTS (PSU-Ci) instead of PDS are also prepared. Parallel tests as for PDS modified PSU have been conducted. Different from PDS modified PSU, viscosity is always lower than in PDS modified PSU, and a continuous decrease with increase in PMTS content and the molecular weight is observed, while the surface tension in the final latex is kept relatively constant regardless of PMTS amount and its molecular weight. The particle size varies between lOOnm and 350nm in the PSU-Ci and WPU latexes, smaller than in the corresponding PDS modified PSU latexes. TEM observation reveals the formation of polygon aggregates when PMTS content is above 5%, or the molecular weight is less than 2000. SEM pictures show that phase separation in PSU-Ci films increases with the increase in PMTS content and its molecular weight. Water resistance, mechanical properties as well as thermal stability of PSU-Ci and WPU films are studied. PSU-Ci films show better performance when PMTS molecularweight is about 2600 and its content at 5%. Moreover, these properties of PSU films can exceed these properties of corresponding WPU films.A new crosslinker, N-[(l,l-dimethyl-2-acetyl)ethyl]-P-dihydroxyethylaminopropanamide (DDP), is synthesized by the Michael reaction using diethanolamine(DEA) and diacetone acryiamide (DAAM). DDP is a dihydroxyl compound withketonic moiety, which cross-links during the film formation through the reactionbetween ketone in DDP and hydrazide in water soluble bishydrazide compound. Theoptimal reactive ratio for Michael reaction, determined by gas chromatography (GC)for the first time, is at 1.05:1 expressed as n(DEA):n(DAAM);highest yields areobtained when the reaction is held at 90 °C for 12h. The separation of DDP ispredetermined through thin-layer chromatography;DDP with 97% of purity orhigher is obtained through column chromatography. The structure of DDP is fullycharacterized by IR and NMR. The composition and molecular weight of DDP aredetermined for the first time by high resolution GC/MS and liquid phasechromatography/MS, respectively. The crosslinking reaction between DDP andhydrazide can be carried out either in acidic system or in volatile alkali medium,confirmed by IR analysis. Reactive waterborne polyurethanes (RPU) and reactivewaterborne polyurethanes modified with PDS (RPSU) are thus prepared through theDDP addition into WPU and PSU, respectively. Compared with WPU latex, theviscosity and the particle size in final RPU and RPSU latexes increase slightly. TEMexperiments show that most of the particles in RPU and RPSU latexes are rodformed. SEM diagrams indicate presence of micro-domains in the fractured sectionof RPU films. Examination of SEM pictures indicates the presence of pore structuresof varying size, which is believed to be due to the micro-domain phase separation inthese RPSU films. RPU and RPSU films displayed best thermal stability with DDPcontent at 2.7% and PDS content at 5%. Mechanical properties and water resistanceof crosslinked RPU and RPSU films are improved with added hydrazide during filmformation.