Hydroxy functionalized acrylic copolymers

Kinetic Model. All of the coatings used in this study are hydroxy functional acrylic copolymers crosslinked with melamine formaldehyde crosslinkers. The chemistry of crosslinking with melamine formaldehyde crosslinkers has been discussed in detail elsewhere (5.11). The type and rate of the reactions depend primarily on... 

Polyurethane-acrylic coatings with interpenetrating polymer networks (IPNs) were synthesized from a two-component polyurethane (PU) and an unsaturated urethane-modified acrylic copolymer. The two-component PU was prepared from hydroxyethylacrylate-butylmethacrylate copolymer with or without reacting with c-caprolactonc and cured with an aliphatic polyisocyanate. The unsaturated acrylic copolymer was made from the same hydroxy-functional acrylic copolymer modified with isocyanatoethyl methacrylate. IPNs were prepared simultaneously from the two-polymer systems at various ratios. The IPNs were characterized by their mechanical properties and glass transition temperatures. 

Figure 3. Elementary crosslinking and hydrolytic degradation reactions Involved In melamine formaldehyde ONCHjOCH.) crosslinking reactions with hydroxy functionalized acrylic copolymers (ROH).

Chem. Descrip. Hydroxy- and carobxy-functional acrylic copolymer (70%) in methoxypropanol... 

Vegetable oil-based poly(ester amide) resin has also been synthesised at a lower temperature in the absence of an organic solvent through a condensation polymerisation reaction of V,V-bis(2-hydroxyethyl) oil fatty amide and phthalic anhydride at a temperature lower than the onset of their melting points. By-products such as water were removed by a vacuum technique. Poly(ester amide) resins may also be prepared using an acid functional acrylic copolymer (butyl methacrylate and maleic anhydride) and hydroxy ethyl fatty amide of dehydrated castor oil in a 3 1 molar ratio. 

Polyols. Typical polyols used in automotive topcoats Include acrylic copolymers and polyesters which have varied number of hydroxyl groups. Acrylic copolymers ranging in number average molecular weight from 1,000 to 10,000 and containing 15-40% by weight of a hydroxy functional comonomer such as hydroxyethyl acrylate have been studied. The acrylic copolymers were prepared by conventional free radical solution polymerization. 

Block copolymers with hydroxyl segments were prepared by various ways An example utilizes the copper-catalyzed sequential copolymerizations of nBA and 2-[(trimethylsilyl)oxy]ethyl acrylate by the macroinitiator method into B-31 to B-33. The copolymers were then hydrolyzed into amphiphilic forms by deprotection of the silyl groups.313 A direct chain-extension reaction of polystyrene and PMMA with HEMA also afforded similar block copolymers with hydroxyl segments (B-34 and B-35).241-243 In block polymer B-36, a hydroxy-functionalized acrylamide provides a hydrophilic segment.117 Block copolymers of styrene and p-acetoxystyrene (B-37 to B-39), prepared by iron... 

Kubisa et al. also used hydroxy-functional PEG after reaction with 2-bromo-propionyl bromide as an ATRP macroinitiator [228]. Their goal, however, was to polymerize ferf-butyl acrylate, rather than St, then to hydrolyze the esters to acid functionality and study the cation binding properties of the doubly amphiphilic block copolymers. They utilized a CuBr/PMDETA catalyst system for the polymerization and, although the macroinitiator was completely consumed, MALDI-TOF analysis indicated that bromine was replaced with a hydrogen at... 

Ma et al. (2012b) reported compatibilized PVDF-TPU blends comprising PVDF-g-acrylic acid. Farah and Lerma (2010) prepared hydroxy-functionalized PP by reaction of PP-g-M A with 2-aminoethanol and used this fimctionalized PP in blends with TPU and unfunctionalized PP. Ethylene-octene copolymer was also used in place of PP. 

Frequently, hydroxyl functional monomers are used as part of the copolymer with the hydroxy group providing the site for crosslinking with, for example, an amino crosslinker, when the coating is stoved. Two hydroxy functional types have been shown. Hydroxyl ethyl has a terminal (primary) hydroxyl group which is more reactive than the secondary hydroxy group on the hydroxy propyl chain. It is thus possible to get more rapid cure response by incorporation of hydroxy ethyl rather than hydroxy propyl functionality in the acrylic copolymer. This, however, may not always be advantageous as frequently rapid cure can lead to poor adhesion. 

Thermosetting acrylic binder systems utilize copolymers of functional and nonfunctional acrylic (or similar) monomers. The functional monomers are incorporated for reactivity with crosslinkers. The most common functional monomer for reactions is the hydroxyl group. The hydroxyl groups on the acrylic copolymers react with melamine and urea resins (amino resins) and with polyisocyanates. These reactions are shown in Figure 11. The reaction of hydroxy functional polymers with amino resins require acid catalysis and heat. The reaction with polyisocyanates can occur at room temperature as well as at higher temperatures. A number of materials will catalyze the hydroxyl/isocyanate reaction (organotin compounds, acids, amines, metal salts, etc.)(9). 

RAFT polymerization has been used to prepare poly(ethylene oxide)-/ /wA-PS from commercially available hydroxy end-functional polyethylene oxide).4 5 449 Other block copolymers that have been prepared using similar strategies include poly(ethylene-co-butylene)-6/oci-poly(S-eo-MAH), jl poly(ethylene oxide)-block-poly(MMA),440 polyethylene oxide)-Moe -poly(N-vinyl formamide),651 poly(ethylene oxide)-Wot A-poly(NlPAM),651 polyfethylene ox de)-b ock-polyfl,1,2,2-tetrahydroperfluorodecyl acrylate),653 poly(lactic acid)-block-poly(MMA)440 and poly( actic acid)-6focA-poly(NIPAM),4 8-<>54... 

One advantage of the RAFT process is its eompatibility with a wide range of monomers, including fnnctional monomers. Thus narrow polydispersity block copolymers have been prepared with monomers containing acid (e.g., acrylic acid), hydroxy (e.g., 2-hydroxyethyl methacrylate), and tertiary amino [e.g., 2-(dimethylamino) ethyl methacrylate] functionality (Chiefari et al., 1998). Linear block copolymers are the simplest polymeric architecmres achievable via RAFT process. There are two main routes for the synthesis of block copolymers by the RAFT process, viz., (i) sequential monomer addition (chain extension) and (ii) synthesis via macro-CTAs (by R- or Z-group approaches). These are schematically shown in Fig. 11.37. Linear block copolymers are the simplest polymeric architectures achievable via RAFT process. 

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