Poly , latex film

The PVAc latex was cast 1.8 mm in thickness on a poly(-ethylene) plate and dried at room temperature. The latex film was dried further in a vacuum desiccator for 24 h, and extracted in Soxhlet extractor with acetone for 20... 

Many investigators have studied polymer surfaces for years [74,75] and have been successful in determining combinations of two or more valence states [76,77] by the mathematical process of deconvoluting the peak assignments [78]. It was only recently that latexes were examined by ESCA. Davies et al. [79] prepared a series of homopolymers of poly(methyl methacrylate) (PMMA) and poly(butyl methacrylate) (PBMA), and also poly[(methyl methacrylate)-co-(butyl methacrylate)] (PMMA-PBMA), by surfactant-free emulsion polymerization. It was found that the surface of the latex film was rich in PMMA, which may possibly be explained by the reactivity ratios for the MMA/BMA system (ri = 0.52 and rj = 2.11) [80], Recently, Arora et al. carried out angle-dependent ESCA studies on a series of films prepared from core-shell ionomeric latexes (with a polystyrene core and a styrene/n-butyl acrylate/ methacrylic acid copolymer shell) to determine the distribution of carboxyl groups in the films [81,82]. 

Zhao ct al. [61] used ATR-FTIR to analyse flie surface composition of coalesced poly(MMA-butyl acrylate) latex films. 

Figure 18.1 Effect of chain transfer agent, crosslinking monomer and copolymerized MMA on (a) shear modulus and (b) tan S of poly(BA) latex films...

Following a related approach, Castelvetro et al. reported the formation and properties of hybrid latex films resulting from the coalescence of low 7 poly(BA-co-MMA-co-MPTMS) terpolymer latex particles coated by a silica shell [78], The latex was synthesized at neutral pH by semi-continuous emulsion polymerization under starved-feed conditions in order to protect the MPTMS monomer from premature hydrolysis and condensation reactions. A substantial amount of free silanols were therefore available for further reaction with the silica precursor. In order to avoid the formation of a densely crosslinked silica network around the latex core, which may significantly alter film formation, the pH was kept at around 2 (at this pH, hydrolysis is promoted and condensation is significantly retarded). TEM and AFM studies of the nanocomposite film indicated that the silica shell formed a continuous percolating network throughout the polymer matrix. A porous film of interconnected hollow silica spheres was next elaborated by thermo-oxidative decomposition of the organic phase. 

Molecular interdiflfusion in a core (poly(butyl methacrylate)-shell (poly(butyl methacrylate-co-butyl acrylate) latex, which exhibits miscibility between the core and shell polymers, has been studied [93]. The volume fraction of mixing and the inter-particle penetration distance increased with annealing time [93]. In other core-shell latex films, phase separation can occur upon annealing, because of immiscibility of the core and shell phases. 

Individual Networks—Poly(urethane-urea). The polymers were self-crosslinking owing to the presence of triols already in the latex. Films were cast on glass with a doctor blade, dried for 15 min at room temperature, 15 min at 80 C (or until completely tack free), and cured for 30 min at 120°C. They were removed from the glass plate by immersion in hot, distilled water. They were dried further at 80°C under a vacuum of 2 Torr. 

Atomic force microscopy has also been used to investigate the morphology of natural rubber blended films. The natural rubber and poly(methyl methacrylate) particles in the latex films can be easily distinguished and are clearly... 

The removal of direct carbon replicas is dependent upon the polymer. Boiling xylene vapor was used to remove drawn PE from replicas [296] in work on drawn polymer morphology. Hobbs and Pratt [297] described a direct carbon replica method for replication of a PBT impact fracture surface by evaporation of platinum at 20° and PBT removal in hexafluor-oisopropanol (HFIP). Latex film coalescence in poly(vinyl acrylate) homopolymer and vinyl acrylic copolymer latexes was studied using direct replicas [298]. As the latex films have a low glass transition temperature, they were cooled by liquid nitrogen to about -150°C in the vacuum evaporator and shadowed with Pt/ Pd at 45° followed by deposition of a carbon support film at 90° to the specimen surface. The latex films were dissolved in methyl acetate/ methanol. TEM micrographs of the latex films show the difference between films aged for various times (Section 5.5.2). 

Taking poly(methyl methacrylate) as an example. Me = 10,013 g/mol (Table 10.2), Me should be equal or greater than 10,013 g/mol. Experiments by Zosel and Ley (27) on cross-linked latex films show that values of Me > Me are required for good mechanical properties, the oversimplified model above providing the minimum net size. Aspects of adhesion are discussed further in Section 12.8. 

Figure 2.102. Use of the derivative reversing heat capacity to study interfacial effects this figure shows the application of this method to poly(methylmethacrylate)-poly(vmyl acetate) (PMMA-PVAc), (50 50) latex film [from Song et al. (1999) reprinted with permission from Springer-Verlag],...

Film formation of latexes can be followed by s-NMR experiments. Three different kinds of water were found in poly(butylacrylate)/polystyrene/ poly(acrylic acid) latex films free water, mobile water bound to the polymer and immobilised water inside the polymer [750]. The effects of water and DEP plasticiser on the molecular motion of cellulose acetate (CA) have been examined by H, and CP/MAS NMR [751]. 1-NMR relaxation... 

Farinha, J.P.S. et al. (1996) Latex film formation probed by norrradiative energy transfer Effect of grafted and free poly (ethylene oxide) on a poly(n-butyl methacrylate) latex. J. Phys. Chem.,... 

A combination of methacrylates and acrylates is used on occasion to achieve needed film properties. While poly(methyl methacrylate) is commonly used for film strength and hardness, poly(methyl acrylate) will improve film flexibility. A plasticizing monomer, such as ethyl acrylate or ethylhexyl acrylate is therefore sometimes added with the methyl methacrylate monomer by the polymer manufacturer in an addition-polymerization process to produce a copolymer for use in coating formulations. The softer and more flexible polymer facilitates latex film formation. 

Here we report experimental results in which both types of phenomena are observed. These experiments involve poly(/i-butyl methacrylate) [PBMA] latex films prepared from core-shell latex particles in which PBMA is the core polymer. One set of particles has a shell containing methacrylic acid [MAA] as a comonomer [P(BMA-ct -MAA)]. Films prepared from the ion-exchanged latex have a carboxylic-acid-group-rich phase as an interparticle membrane, whereas films prepared from the same particles at high pH form an ionomer phase in the membrane. These structures retard but do not prevent interparticle polymer diffusion. A second type of PBMA, prepared from a... 

The second important observation for the data in Figure 1 is that interdiffusion occurs even at the early stages of annealing time, in the all films. This result is very different from that reported by Joanicot et al. b for a different latex film. They found that polyacrylic acid [PAA] at the surface of a poly(styrene-co-butyl acrylate) latex effectively suppressed interdiffusion until the film temperature exceeded the Tg of the PAA, at which point the polar membranes ruptured. The essential difference in... 

Mechanical Properties of the Latex Films. Figure 13.18 shows a noteworthy effect of the addition of Laponite on the mechanical properties of the nanocomposite film. A remarkable increase in the storage modulus at the rubbery plateau was observed with the addition of only 5 wt% Laponite. This improvement of the mechanical properties of the poly(styrene-co-butyl acry-late)-Laponite film was expected, considering the good dispersion of the clay platelets inside the polymeric matrix and the armored morphology of the hybrid particles. It is worth remembering here that similar results were reported by Ruggerone and co-workers" and Faucheu et al. for PS-Laponite films obtained from latexes prepared by emulsion and miniemulsion polymerization, respectively (see Sections 13.3.2.1 and 13.3.2.2). 

Acrylics. Acetone is converted via the intermediate acetone cyanohydrin to the monomer methyl methacrylate (MMA) [80-62-6]. The MMA is polymerized to poly(methyl methacrylate) (PMMA) to make the familiar clear acryUc sheet. PMMA is also used in mol ding and extmsion powders. Hydrolysis of acetone cyanohydrin gives methacrylic acid (MAA), a monomer which goes direcdy into acryUc latexes, carboxylated styrene—butadiene polymers, or ethylene—MAA ionomers. As part of the methacrylic stmcture, acetone is found in the following major end use products acryUc sheet mol ding resins, impact modifiers and processing aids, acryUc film, ABS and polyester resin modifiers, surface coatings, acryUc lacquers, emulsion polymers, petroleum chemicals, and various copolymers (see METHACRYLIC ACID AND DERIVATIVES METHACRYLIC POLYMERS). 

The adhesives (qv) used to form tube seams and bag bottoms include unborated dextrin, borated dextrin, casein, latex—casein, latex, poly(vinyl acetate), vinyl acetate copolymers, and hot-melt materials (10,27). Dextrin and casein adhesives are more commonly used in the production of grocery sacks vinyl acetate-type adhesives are commonly used in ah paper multiwah bags. The hot-melt adhesives are typicahy used to tack the phes of the multiwah bag together and to form the seam and bottom joints when polymer film phes or coated paper phes are used in bag constmction. 

Vinylidene Chloride Copolymer Latex. Vinyhdene chloride polymers are often made in emulsion, but usuaUy are isolated, dried, and used as conventional resins. Stable latices have been prepared and can be used direcdy for coatings (171—176). The principal apphcations for these materials are as barrier coatings on paper products and, more recently, on plastic films. The heat-seal characteristics of VDC copolymer coatings are equaUy valuable in many apphcations. They are also used as binders for paints and nonwoven fabrics (177). The use of special VDC copolymer latices for barrier laminating adhesives is growing, and the use of vinyhdene chloride copolymers in flame-resistant carpet backing is weU known (178—181). VDC latices can also be used to coat poly(ethylene terephthalate) (PET) bottles to retain carbon dioxide (182). 

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