Pure acrylates

Low temperatures can cause a phase separation in stabilized solutions in which case one phase can become deficient in stabilizer and subject to runaway reactions. Acrylic acid can crystallize out of stabilized solution, and subsequent thawing of these essentially pure acrylic acid crystals can initiate runaway reactions, often with severe consequences. Thawing of crystallized (frozen) materials needs to be accomplished using established procedures in thaw boxes or similar devices. If established procedures are not available, a safety review needs to be conducted and a procedure developed prior to thawing the material. 

Figures 1 and 2 show the corresponding conversTon curves in toluene and in methanol solutions respectively. In the latter case log-log coordinates are used to represent the data. The conversion curves are then linear and their slope B, which is the exponent of time in the relation per cent conversion = Kt, measures the extent of auto-acceleration. B is referred to as the "auto-accele-ration index". For pure acrylic acid B = 1.8 - 2.0 in non polar solvents 3 tends towards unity.

On the other hand, a good correlation was established between auto-acceleration and the type of molecular association involving the monomer in the system. Pure acrylic acid associates by hydrogen bonds to form "cyclic dimers" and "linear oligomers". The two species are in equilibrium. 

Figure 5. Ratios of optical densities at 1730 cm 1/1705 cm1 plotted in Arrhenius coordinates for pure acrylic acid (100) and acrylic acid solutions in toluene at 90, 80, and 60 volume per cent of monomer (5).

During the course of the Baylis-Hillman-reaction two stereocenters are formed, one of which remains in the Baylis-Hillman-product. An obvious concept for the development of an asymmetric version of the reaction represents the use of an enantiomerically pure acrylic acid derivative. The use of enantiomerically pure menthyl acrylates resulted, but only in certain cases, to respectable diastereomeric excesses [21]. A significant improvement was reported in 1997 by Leahy and coworkers who used the Oppolzer-sultame as a chiral auxiliary in DABCO-catalyzed Baylis-Hillman-reactions (Scheme 2) [22]. In this reaction, the... 

Floor-care polymers are based on pure acrylics or styrene acrylics, cross-linked with metals (e.g. zinc). Floor polishes formulated with acrylics have a number of advantages, as listed below ... 

These substances determine the heat and moisture resistance of the adhesives, but are also responsible for the effectiveness of the tackifying agents. Pure acrylates are among the best PSAs. 

The first PSAs consisted of rubber systems. Later, pure acrylates and acrylate copolymers, as well as polyurethane systems, were modified so as to meet higher specifications. The latest PSAs are made of polyolefinic adhesives. 

Rubber systems do stick to many plastics well, but they are relatively moisture-sensitive. There s always a risk that they may lose their adhesive strength at high humidity levels. At temperatures above about 40°C, they turn very soft and lose their inherent strength. Pure acrylates and modified acrylates are primary materials that provide PSAs with greater moisture resistance and thermal stability. Pure acrylates above all remain sufficiently adhesive up to about 150 or for short periods 200°C. Adhesive tapes of this kind are used for masking purposes in powdercoating techniques. 

Fig. 7 shows the FTIR spectra of the Si nanoparticles. Curve (a) is the spectrum of dried Si nanoparticles after hydrosily lation, while curve (b) is an experimental spectrum from pure acrylic acid for comparison. Upon comparing these spectra, peaks attributed to C=C bonds are clearly present in spectrum (b), but are almost completely absent in spectrum (a). Simultaneously, the Si-CH2 peak is observed in spectrum (a). These observations confirm that the hydrosilylation proceeds as expected and Si-C bonds replace the C=C and Si-H bonds. Although the nanoparticles were dried in air, the Si-0 peak at 1080 cm 1 is quite small. 

Acrylate-methacrylate copolymers (pure acrylates) are used in particular for house paints and other emulsion paints with high weather resistance and for waterborne industrial paints. 

Waterborne systems are formulated with pure acrylates and have a solvent content below 10%, preferably glycols. The gloss is between silk-matt and full gloss. 

Chem. Desaip. Polysiloxane resin (50%) in butyl glycol Uses Hydrophobing agent for water-based and solv.-based systems, facade impregnations based on styrene-acrylic, acrylic, and PU emulsions, wood coatings based on styrene-acr ic and pure acrylic emulsions... 

POLYMER EMULSIONS BASED ON PURE ACRYLICS FOR PRESSURE SENSITIVE ADHESIVES... 

Using various model dispersions, acrylic/styrene and pure acrylic copolymer dispersion binders for masonry paints were investigated by studying the way in which chemically different monomers affected the film properties and those of formulated paints. The test methods used were for water resistance, water vapour transmission, tensile properties, colour variation, UV transmittance, UV stability, artificial weathering and weathering-induced chalking. 12 refs. 

The choice of binder which permits the formulation of a solventless and odourless paint is discussed, with respect to performance requirements. These requirements can be achieved by reducing the minimum film forming temperature of the binder and neutralising with an odourless base. A description is given of comparative tests made on masonry paints based on acrylic emulsions having different minimum film forming temperatures and neutralisation. Differences and similarities between such acrylic emulsions are discussed. Typical commercialised products of similar particle size were used from the acrylic/styrenes and pure acrylics. The hard monomers of the binders used were methyl methacrylate or styrene, and the soft monomer in the binders was butyl acrylate. Experiments were made with mat masonry paints in the PVC range of 40-60%. 6 refs. 

PAINTS BASED ON ACRYLIC DISPERSIONS. I. COMPARATIVE STUDIES OF PURE ACRYLATE/STYRENE COPOLYMER DISPERSIONS... 

Paints Vinyl acetate/dibutyl maleate copolymers, pure acrylics, styrene/acrylic copolymers, vinyl acetate/butyl acrylate copolymers, slyrene/acrylate copolymers... 

Alkyd paints dominated the architectural coating market for a long period until the appearance of polymer dispersions or the so-called latex paints. Specifically for wall application waterborne paints based on poly(vinyl acetate) homo- and copolymers, styrene-acrylics and pure acrylic latexes almost completely took over the market from the alkyd resins for both interior and exterior application. However, for... 

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]. 

The terms pure acrylics or 100 % acrylic resin is frequently used to differentiate acrylic resins derived strictly from (meth)acrylate... 

Table 5.74 and Figure 5.302 show the stress-cracking resistances of ASA and ABS and their blends with and without prior weathering. Without prior weathering, black-pigmented ASA with pure acrylate rubber exhibits the best resistance. ASA (containing both acrylate and butadiene rubber) and ABS are decidedly more sensitive. ASA/PC exhibits behavior similar to that of ASA. 

After weathering, black-pigmented ASA with pure acrylate rubber exhibits very good resistance, while the resistance of ASA/PC is significantly reduced. In ASA equipped with acrylate and butadiene rubber and in ABS, weathering does not cause a decrease in resistance, Figure 5.302 and Table 5.74. 

ASA materials with butadiene rubber content and ABS materials are notably less resistant to stress-cracking than ASA modified with pure acrylate rubber. Polycarbonate and blends with polycarbonate exhibit lower resistance than ASA modified with pure acrylate rubber. 

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