Latex blending

Hyperbranched polyurethanes are constmcted using phenol-blocked trifunctional monomers in combination with 4-methylbenzyl alcohol for end capping (11). Polyurethane interpenetrating polymer networks (IPNs) are mixtures of two cross-linked polymer networks, prepared by latex blending, sequential polymerization, or simultaneous polymerization. IPNs have improved mechanical properties, as weU as thermal stabiHties, compared to the single cross-linked polymers. In pseudo-IPNs, only one of the involved polymers is cross-linked. Numerous polymers are involved in the formation of polyurethane-derived IPNs (12). 

Compounding and palletizing of the latex blended material is sometimes done by melt mixing. In such cases precautions must be taken to avoid thermal and shear degradation of the blended polymer. 

One of the most important solution blend polymers is high-styrene resin, which is manufactured by several companies worldwide. This is a latex blend of high-styrene rubber and normal styrene butadiene rubber. The different high-styrene master batches are available in the world as ... 

Impact-resistant polystyrene from latex blends. 

Figure 7 shows the representative bright field HRTEM images of nanocomposites of NR and unmodified montmorillonite (NR/NA) prepared by different processing and curing techniques. It is apparent that the methodology followed to prepare the nanocomposites by latex blending facilitates the formation of exfoliated clay structure, even with unmodified nanoclays. It has been reported in the literature that hydration of montmorillonite clay leads to extensive delamination and breakdown of silicate layers [94, 95]. It has also been shown that NA disperses fully into the individual layers in its dilute aqueous dispersion (clay concentration <10%)... 

This is truly reflected in the morphology of the uncured clay preexfoliated rubber nanocomposite films (NLu NA) prepared by the latex blending method (Fig. 7a). Curing the NR/NA nanocomposites in situ prevulcanization (No>NA) does not alter the arrangements of dispersed clay layers greatly, as seen from the... 

Morphology evolution is thus found to be dependent on the processing technique applied to disperse the nanoparticles. The latex-blended and prevulcanized nanocomposites show predominant exfoliation with some intercalation, especially in uncured and prevulcanized samples. In conventionally cured but latex-blended nanocomposites, realignment of NA particles is visible, with a greater tendency of NA platelets towards agglomeration. In solid state mixing, the dispersion is still poorer. XRD studies also corroborate the above observations. 

Fig. 6 Latex blending of NBR-layered silicate composites (reprinted from [10], with the permission from Elsevier)...

These prepared latex blends were then measured using the HDC technique. 

The simplest mixture of two kinds of polymer molcules, polymer 1 and polymer 2, which can be achieved by mechanical blending, latex blending, or solvent cast blending, involves no chemical bonds between the two types of molecules (see Figure 1). Occasionally such blends may be described chemically as poly(l-m-2), where the m denotes "mechani-... 

We prepared a 360-A polymer with a low degree of grafting by blending latexes. The 360-A latex blended with the copolymer latex gave a 15% rubber content with no graft. The resultant latex blend was freeze-coagulated and was treated the same as the previous specimens. 

Material. Optically clear films (about 5 mils thick) of three SA (saturated acrylic) plastics (3) that contained 25, 33, and 50% of an acrylic graft rubber (referred to as SA-1, SA-2, and SA-3) were compression molded. The acrylic graft rubber latices were latex blended with a resin latex composed primarily of methyl methacrylate, and the blend was coagulated. The compositions of these three polymers are as follows SA-1, 79/17/4 wt %—methyl methacrylate/butyl acrylate/styrene SA-2, 72/23/5 wt %—methyl methacrylate/butyl acrylate/styrene SA-3, 59/34/7 wt %—methyl methacrylate/butyl acrylate/styrene. All three graft rubbers contained low levels of a crosslinking comonomer (less than 1.0 wt %). 

Varkey, J.T. Augustine, S. Groeninckx, G. Bhagawan, S.S. Rao, S.S. Thomas, S. Morphology and mechanical and viscoelastic properties of natural rubber and styrene butadiene rubber latex blends. J. Polym. Sci. B Polym. Phys. 2000,38 (16), 2189-2211. 

PRI-Reference Paint MMA/nBA Latex blended with 8/MMA/nBA Latex ... 

A standard Paint Research Institute latex paint, provided by J. F. Matthews of DuPont, was the reference sample to which the biocidal latex polymers were compared. After two months both the unweathered and weathered samples showed moderate or moderate to heavy growth on the paint surface. The unweathered samples showed severe stain intensities on basswood. The weathered samples showed medium stain intensities on both. When coatings of an MMA/nBA latex blended with a MMA/nBA/8 terpolymer latex were tested, only trace growth of Aureobasidlum pullulans on the coatings was observed using pine or basswood substrates. 

Most early thermoplastics, e.g., PVC or PS, were obtained in the free radical polymerization, initiated either by heat or by sunlight. The first systematic studies of the free radical chemistry commenced 80 years later [Ostromislensky, 1911, 1915, 1916]. Fikentscher empirically determined which one of the 30-or-so monomers liked or disliked to copolymerize with each other. The advantage of latex-blending was also established. The theory of the free radical copolymerization was finally developed in the 1940 s [Alfrey et al, 1952]. 

The first patented PVC alloys were prepared by latex blending with PVAc, and poly(vinylchloride-co-vinylacetate) (PVCAc) [Voss, and Dickhauser, 1930, 1933, 1935, 1936]. I. G. Farbenindustrie commercialized PVC extruder-blended with polyacrylic ester — the so called rigid formulation [Fikentscher and Heuce, 1930 Fikentscher, and Wolff, 1931]. Troluloid and Astralon were the first commercial thermoplastic polymer blends. 

Various vinyl latexes, previously polymerized, were mixed with natural rubber latex, both still in aqueous dispersion, and then coagulated. Thus, core-shell latex and latex blend materials were known very early. 

Latex Blends. These are combinations of two or more kinds of latexes, differing in chemical... 

Pre-crosslinked Latex Blends. In these materials the individual latexes are crosslinked during synthesis, then blended, and a film is formed. Because of limited deformation and/or interdiffusion capabilities, such films tend to be weak, and only used for special purposes [Zosel and Lay, 1993 Lesko and Sperry, 1997], However, light crosslinking, as occurs in SBR latexes, may be tolerated. Pre-crosslinked latex blends materials are actually not IPNs, because the definition requires that at least one of the polymers be polymerized and/or crosslinked in the immediate presence of the other. An application of pre-crosslinked suspension-polymerized blends, in anionic and cationic form, is as ion-exchange resins. In suspensions, the particles are larger, usually of the order of 10-200 pm. 

The early research on core-shell and latex blend materials has already been mentioned, see Table... 

While no crosslinker is mentioned in the patent, poly (ethyl acrylate) usually gels. That it was readily soluble suggests a low molecular weight. These early patents set the stage for today s latex blends and IPNs. 

Selected Patents in Latex Blends and Crosslinked Systems... 

The field of latex blends and their crosslinked counterparts has been especially active, see Tables... 

Table 6.4. Selected patents in latex blend applications... 

It was observed that intermediate compositions dried slower than the unblended constituents. The mechanical properties of latex blends comprising low and high particles, the film formation ability, and the comparison of results to classical theory of polymer blends containing hard particles have been reported by Lepizzera et al. [1997], This is one of the few studies in the literature that has attempted to correlate emulsion blend properties with empirical/theoretical relationships previously available in the open literature. 

Langmuir-Blodgett teehnique Latex blending Latex blends Latex IPN (LIPN)... 

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