Polyurethane-acrylic hybrids

Chem. Descrip. Aliphatic polyurethane/acrylic hybrid disp. with n-methyl pyrrolidone cosolv. 

Thus, in alkyd-acrylic systems, the final product contains free acrylic polymer, grafted acrylic-alkyd polymer, and free alkyd resin [95]. Polyurethane-acrylic hybrids present a polymer network formed by acrylic chains linked by both polyurethane chains and pure acrylic connections [76]. 

Lopez A, Degrandi E, Cretan C, Canetta E, Keddie JL, Asua JM. Waterborne polyurethane-acrylic hybrid nanoparticles by miniemulsion polymerization applications in pressure-sensitive adhesives. Langmuir 2011 27 3878-3888. 

The adhesives can have open times varying from a few seconds up to about 10 minutes to match application requirements. Improvements related to adhesives that have long open times and/or high green strength via the use of urethane diols or polyurethane-acrylic hybrid systems has been reported [42]. 

MAA) and the resultant polymerization gave a urethane/acrylate hybrid dispersion [568]. The urethane/acrylic hybrid had markedly improved water resistance over the physical blend of the components. Polyurethane/acrylic hybrids were compared with polyurethane/acrylic waterborne blends, with increased phase mixing in the hybrids observed, resulting in improved mechanical properties [569]. 

Other than the hydrocarbon elastomers and acrylics, and to a smaller degree silicones, little success commercially has attended efforts to utilize other polymers for PSAs. The patent literature describes a number of water solubles, suitably crosslinked, as the base ingredient for repulpable adhesives on paper backings used to splice rolls during papermaking operations. The patent literature also reveals efforts to utilize polyurethanes, polyurethane-acrylic hybrids, ionomers, and polyester block elastomers, among others, but only repulpable adhesives have reached the marketplace. Two systems that have achieved mentionable commercial success are described below. 

For printing inks that require specific properties not obtainable by conventional styrene acrylic emulsions, an aqueous dispersion of an add functional polyurethane-epoxy acrylate hybrid (self crosslinking for improved chemical resistance) [9] patented by Air Products and Chemicals, Inc. or a self crossHnking styrene acrylic emulsion which reacts upon evaporation of water [10] patented by Akzo Nobel Resins BV, may be used. The Air Products novel dispersion contains a quaternary ammonium polyurethane acrylic hybrid carboxylate salt and pendant acrylate epoxide that selfcrosslink upon evaporation of water and ammonia. Akzo s novel polymer contains a diacetone acrylamide reactive monomer and a bishydrazide. The crossHnking reaction between ketone groups and a bishydrazide proceeds rapidly at room temperature, after evaporation of water from the ink. 

Among the countless number of applications of polymers, the construction industry is one which utilises several polymeric materials. In this book I cover those polymeric materials which are single or bicomponent systems and are cured at ambient temperature either with the aid of curing agents or atmospheric moisture. The various polymers used in manufacturing such products include epoxies, polyurethanes, acrylics, silicones, polysulphides, alkyds and polyesters. As a result of innovation, new technologies exist which utilise more than one polymer in a single product. Such systems are discussed in Chapter 10, on hybrid polymers. 

Property Epoxy Polyurethane Polyester Hybrid Acrylic s... 

Most work has been with free-radical systems but other chemistries can be used. Begishev etal. studied frontal anionic polymerization of e-caprolactam [18, 19], and epoxy chemistry has been used as well [20-23]. Mariani ctal. demonstrated frontal ring-opening metathesis polymerization [17]. Fiori et al. produced polyacrylate-poly(dicydopentadiene) networks frontally [24], and Pojman etal. studied epoxy-acrylate binary systems [25]. Polyurethanes have been prepared frontally [13,14, 26]. Frontal atom transfer radical polymerization has been achieved [16] as well as FP with thiol-ene systems [27]. Recent work has been done using FP to prepare microporous polymers [28-30], polyurethane-nanosilica hybrid nanocomposites [31], and segmented polyurethanes [32]. 

However, the implementation of miniemulsion polymerization in industry is challenging because industry will only adopt this method provided that new and improved materials can be produced and that the technology required to mn the process is available at a reasonable cost. The former is tme because hybrid alkyd-actylic coatings and polyurethane-acrylic adhesives with... 

Different polymer-nano-ZnO hybrid systems based on epoxyl2 [42], poly(styrene-co-acrylic acid) [43], polyurethane [44], etc. have been reported by several other researchers. 

Wang et al. [183] carried out hybrid mini emulsion polymerization of acrylates in the presence of polyurethane. The polyurethane was used as the costabilizer, and SLS as the surfactant. When MMA was used as the monomer, some homogenous nucleation was observed. This is in agreement with Tsavalas [179] who reported evidence of homogenous nucleation in the hybrid miniemulsion of MMA in the presence of alkyd. 

Barrere and Landfester [184] prepared a hybrid miniemulsion in which isophorone diisocyanate was condensation polymerized with dodecanediol to form polyurethane at the same time that the polystyrene or polyBA was free radical polymerized. Unlike previous work, the polyurethane was not prepared in organic solvent in advance. Therefore, in this one-pot synthesis, polyaddition and free radical polymerization both take place in the same particle. HD was used as the costabihzer. After miniemulsification, the polycondensation was allowed to take place, and then a free radical initiator was added to polymerize the styrenic or acrylic monomer. Molecular weight distributions were bimodal the PU had a substantially lower molecular weight than the polyacrylate. Neither intra- nor interparticle phase separation could be detected by TEM the particles appeared to be homogeneous. No measurements of grafting were made, but since there was no unsaturation in the PU, none was expected. 

In this book I have confined discussion to those polymeric materials which are cured by chemical reaction and which have found widespread application in the construction industry. As such, the book covers materials based on epoxies, polyurethanes, silicones, polysulphides, alkyds and polyesters. In addition, there is a chapter on hybrid polymer systems and one on acrylics. It is true that acrylic emulsions are not strictly thermosetting polymer systems, but their widespread use and importance made their exclusion difficult. These materials find use as coatings, sealants, adhesives, grouts, flooring compounds, repair compounds and waterproofing agents. 

Several other polymers such as polyurethanes, alkyds, acrylics, polyesters, silicones, etc. can be hybridised to improve the performance or to obtain desired end-results. The growth of hybrid polymer technology is giving rise to considerable improvements, and many hybrid systems have been introduced to the market. Most of the work reported in this field is for coatings, but at the same time it is useful for other products used in the construction industry. Research is under way by many polymer manufacturers and universities, and innovations are continuously being reported. In this chapter we shall be dealing with those combinations which are useful, or may be useful, for the construction industry. 

Lu, Y., Xia, Y, Larock, R. C. (2011). Surfactant-free core-shell hybrid latexes from soybean oil-based waterborne polyurethanes and poly(styrene-butyl acrylate). Proa. Ora. Coat. 71, 336-342. 

Uses Defoamer for water-based industrial coatings, emulsion paints (pigmented acrylate/polyurethane, baking enamels, hybrid systems), inks Properties Colorless liq. faint hydrocarbon odor sp.gr. 0.99 g/cc dens. 8.28 Ib/gal flash pt. (Seta) > 100 C ref. index 1.451 > 97% NV Toxicology TSCA listed... 

Kukanja, D., Golob, J., Zupancic-Valant, A., and Krajnc, M. 2000. The structure and properties of acrylic-polyurethane hybrid emulsions and comparison with physical blends. Journal of Applied Polymer Science 78(l) 67-80. 

Synthesis and Characterisation of Aqueous Hybrid Polyurethane-Urea-Acrylic/Styrene Polymer Dispersions... 

After addition of prepolymer-ionomer and crosslinking it with polyamine some of these particles may remain untouched, but both new hybrid core-shell particles where acrylic/ styrene polymer will constitute the core and polyurethane-urea will form the shell ... 

Hybrid polyurethane-urea-acrylic/styrene polymer dispersions were prepared according to methods la , lb , 2 and 3 described in Section 6.3.2. Dispersions designated as MDPUR-ASD were made by polymerisation of monomers in DPU according to the methods la, lb and 2 while dispersions designated as MDPUR were made by synthesis of DPUR in ASD according to method 3. In all syntheses the ratio of polyurethane-urea to acrylic/styrene polymer in the hybrid was 2 1. 

The results of investigations of the effect of method of hybrid dispersion synthesis (la, lb, 2 or 3 - see Section 3.2) on the properties of dispersions as well as of films and coatings made from them are presented in Tables 6.9 to 6.11 (dispersions prepared using water-soluble initiator) and in Tables 6.12 to 6.14 (dispersions prepared using redox initiating system). In all dispersions the chemical structure of the polyurethane-urea and acrylic/styrene polymer component was the same (see relevant tables in Section 6.5.2). All the dispersions contained a similar low level (2-3.6%) of NMP. 

Figure 6.17 Particle size distribution for a typical polyurethane-urea-acrylic/styrene hybrid dispersion synthesised in this study (MDPUR-ASD 97 from Table 6.7 prepared according to method 2 using a water-soluble initiator).

Properties of hybrid dispersions prepared according to the different methods (la, lb and 2 - see Section 6.3.2) and based on the same polyol (PTMG 2000), but differing in the presence or absence of double bonds in the polyurethane-urea part of the hybrid, as well as of films and coatings made of them, are presented in Tables 6.21 and 6.22. All dispersions have a similar low level (2.0-3.3%) of coalescent and have the same structure of the acrylic/styrene part of the hybrid. Redox initiator was used in the synthesis of dispersions according to the method 2, and in all other dispersions presented in these tables a water-soluble initiator was applied. 

Figure 6.23 Particles of hybrid polyurethane-urea-acrylic/styrene dispersion prepared according to method la using less hydrophobic monomer and water-soluble initiator (MDPUR-ASD 22). Photograph was taken using TEM.

The morphology of dispersion particles was investigated using the method described in Section 6.4.1. Examples of different morphologies of particles of hybrid dispersions synthesised in this study according to methods la, lb and 3 are presented in Figure 6.31 in comparison with particles of the starting dispersion of BA/MM/S copolymer. The contrast was selected so that in pictures d and c white colour represents the polyurethane-urea part of the hybrid and in picture b the same colour represents the acrylic/styrene part of the hybrid. 

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