PVAc, additives

The polymerization of vinyl monomers in liquid and supercritical CO2 has been studied extensively. Patents were issued in 1968 to the Sumitomo Chemical Company [81] and in 1970 to Fukui et al. [82] for the preparation of homopolymers of polystyrene, poly(vinyl chloride), poly(acrylonitrile) (PAN), poly-(acrylic acid) (PAA), and poly(vinyl acetate) (PVAc), as well as the random copolymers PS-co-PMMA and PVC-co-PVAc. Additionally, a patent was issued in 1995 to Bayer AG [83] for the preparation of styrene/acrylonitrile copolymers in SCCO2. In 1986, the BASF Corporation was issued a Canadian patent for the precipitation polymerization of 2-hydroxyethylacrylate and various N-vinylcarboxamides in compressed carbon dioxide [84]. In 1988, Terry et al. attempted to homopolymerize ethylene, 1-octene, and 1-decene in SCCO2 for the purpose of increasing the viscosity of CO2 for enhanced oil recovery [85]. These reactions utilized free-radical initiation with benzoyl peroxide and r-butylperoctoate at 71 °C and 100-130 bar for 24-48 h. Although the resulting polymers were not well characterized, they were found to be relatively... 

Poly(vinyl acetate). The dielectric and mechanical spectra of hybrids produced by mixing a poly(vinyl acetate)—THE solution with TEOS, followed by the addition of HCl have been investigated (45). Mixtures were made which were beheved to be 0, 5, 10, 15, and 20 wt % Si02, respectively. These composites were transparent and Eourier transform infrared spectroscopy (ftir) revealed hydrogen bonding between the siUcate network and carbonyl units of the poly(vinyl acetate) (PVAc). No shift in the T of the composites from that of the pure PVAc was observed. Similarly, the activation... 

In contrast to other polymers the resistance to water permeation is low due to the hydrolysis of the poly(vinyl acetate) (163,164). Ethylene copolymers have been developed which have improved water resistance and waterproofness. The polymer can be used in the latex form or in a spray-dried form which can be preblended in with the cement (qv) in the proper proportion. The compressive and tensile strength of concrete is improved by addition of PVAc emulsions to the water before mixing. A polymer-soHds-to-total-soHds ratio of ca 10 90 is best. The emulsions also aid adhesion between new and old concrete when patching or resurfacing. 

Depending on the formulations various grades of water resistance can be achieved according to EN 204 (D1-D4) [172], For the two-component PVAc adhesives crosslinking and hence a duroplastic behavior is effectuated by addition of hardening resins (e.g. on basis of formaldehyde), complex forming salts (based... 

The addition of comonomers during the polymerization enables a higher flexibility compared to PVAc-homopolymerizates. This results in a lower glass transition temperature and a lower minimum temperature of the film formation. Possible comonomers are acrylic acid esters (butylacrylate, 2-ethylhexylacrylate), dialkylfumarates, ethylene and others. 

Fillers (calcium carbonate, calcium sulfate, aluminum oxide, bentonites, wood flour) increase the solid content of the dispersion. They are added up to 50%, based on PVAc. The purpose of the addition is the reduction of the penetration depth, provision of thixotropic behavior of the adhesive, gap filling properties and the reduction of the costs. Disadvantage can be the increase of the white point and a possible higher tool wear. 

There are three important processes for preparing PVAc latexes in the presence of PVA as a protective colloid batch, semi-continuous, and delayed addition of monomer [10]. In this Chapter, the effects of the addition of VAc and initiators on the properties of PVAc latexes are discussed using the three methods under the same charge of ingredients for polymerization as shown in Fig. 1 [1,11]. 

The classic method for establishing the proportion of head addition occurring in VAc polymerization involves a two step process.5 The PVAc is converted to PVA by exhaustive hydrolysis and the number of 1,2-glycol units is determined by periodate cleavage. 

I-. - also head r.t rail addition definition 4. If) lail-to-tail linkages in PVAc 324... 

Poly(vinyl acetate) (PVAc), 13 735 25 557 adhesives, 25 578-583 applications of, 10 514-517 chemical properties of, 25 565 colloidal suspensions, 7 275 commercial manufacture of, 25 606-608 as a concrete additive, 25 585-586 conversion to poly (vinyl alcohol), 25 608-610... 

Lastly PVC/PVAc are the most-used copolymers for some speciality application niches. They are appreciated for their lower melt viscosities, higher tolerance to additive fillers, and better cold-draw properties than homopolymers. 

Li Y, Shimizu H (2009) Compatibilization by homopolymer significant improvements in the modulus and tensile strength of PPC/PMMA blends by addition of a small amount of PVAc. ACS Appl Mater Interfaces 1(8) 1650-1655... 

Because PVAc is approved by the FDA it has also several uses in the food industry. PVAc can also be found in just about every chewing gum. It is a major component in the so called gumbase, a mixture of different polymers that in combination with sugar, sweeteners, flavours, and other additives make up a chewing gum. 

As pointed out above, PVAc is frequently not used as a hompolymer but rather as the major component of a copolymer (VAE, terpolymers, vinylacrylics, etc.). Additionally, in the applications mentioned above PVAc and the related polymers are usually not used alone but as a part of a more or less complex mixture with other components. These components can be, for example, fillers, plasticisers, impact modifiers, compatibilisers, or other polymers. These components need to be taken into account when discussing biodegradabUity. They influence the biodegradability of the mixture as a whole but they may in particular influence the biodegradability of the PVAc moiety by altering the physical circumstances under which degradation reactions can take place. 

It can be seen that these are U(l) equations, but with the addition of the vacuum charge density pvac and the vacuum current density 7vac. On the 0(3) level, the Lehnert charge density becomes... 

TP polymer typically low-shrinkage additive (PE, PS, etc.) or low-profile additive (PVAc, etc.) 20 parts... 

The dismutation rate constant includes in it the fraction of H-H additions.) Here Xn depends on monomer concentration which is contrary to fact. There are about 1-2% H-H additions along the PVAc backbone (31), so it does not dismute as soon as one monomer adds backward. 

Tg of either polymer components. In addition to the two distinguishable Tg signals, the melting endotherm and cold-crystallization exotherm of CA are both detectable for every blend at almost the same temperature positions as those for the CA (DS = 2.95) alone, with a proportional reduction of the respective peak areas. In contrast to the result, the thermograms compiled in Fig. 9a for the pair of CA (DS = 2.70) and P(VP-co-VAc) (VP/VAc = 0.51/0.49) (combination A) indicate a definitely single Tg that shifts to the higher temperature side with increasing CA content. As summarized in Fig. 8, CA/PVAc blends are immiscible irrespective of the DS of the CA component, while PVP forms a miscible monophase with CAs unless the acetyl DS exceeds a value of... 

Turning to the viscoelastic properties of these binary monolayers, a simple trend is confirmed. The larger is the content of PVP, the more viscous becomes the monolayer, starting from the nearly elastic monolayer of PVAc. We show the trend by means of the polar plots at two compositions, 27 mol % and 72 mol % but not an intermediate third composition the latter case is shown only for results obtained with the successive addition method. They are shown in Figs. 20 and 21. Although the plots appear to resemble that of PVAc, Figs. 14A and 16D, several key differences emerge. For the... 

Fig. 19 n-< A > isotherms for 72 mol % PVP/PVAc mixed monolayers on water at 25 °C by stepwise addition and compression. Surface pressure 77 for 72 mol % polyfvinyl palmitate)/poly(vinyl acetate) binary mixture as a function of area per monomer. The surface concentration was controlled as noted in the plot. For the stepwise-addition technique, lens formation was observed in the region where the two techniques differ for 77 lOmNm-1. For the plot, the mixture required stabilization times considerably longer than the 1-2 hours allowed between points to form equilibrium films. < A > = average area per monomer... 

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