Latex state

This prediction is drawn according to the following model. Figure 5 illustrates that in the latex state the grafting PVA protects hydrophobic PVAc particles in water by concentrating on the surfaces of PVAc particles, but in the porous film after acetone extraction, the insoluble grafting PVAc conversely exists as an important component on the inner surface of spherical cells of PVA. 

The effect of particle size and spinning of the NMR tube were studied for the latex state 13C-NMR of natural rubber latex fractionated by particle size [134], High-resolution spectrum was obtained by measurement without sample spinning. The diffusion constant of Brownian motion was found to be a dominant factor governing the intensity and halfwidth of the signals. As the particle size decreased and temperature of measurement was raised, the intensity of signals increased and was comparable to the theoretical value, which was observed by the addition of triethylene glycol as an internal standard. 

Overdose of products containing aloe latex (stated at as little as 1.0 g per day for several days) can cause colonic perforation and bleeding diarrhea, as well as kidney damage, and, according to one reference, death (Bradley 1992 Leung and Foster 1996 List and HSrhammer 1973 Martindale and Reynolds 1996 Wichtl 2004 Williamson 2003). 

Microbial attack of raw rubber was first reported early in 1914. Thin film of NR, floating on an aqueous medium, were shown to be disintegrated by some actinomycete strains to a certain extent, that could not be ascribed to the disappearance of impurities from the rubber [8]. Spence and van Niel [9] reported that NR, in the latex state, was degraded by some actinomycete strains, and ifrat a rubber weij t loss of up to 70% was observed after a 28-day cultivation period [9]. Thin films of NR on agar plates were also found to be d raded by strains of Streptomyces and Nocardia, and the weight loss reached 52% after the cultivation period of a month and a half [10]. It was reported that thin strips of NR and S3mthetic isoprene rubbm, with a diameter of 0.5 mm, were decomposed completely by a strain of Nocardia in 56 days [11]. 

R173 S. Kawahara, Latex State and Solid-State NMR Spectroscopy of Elastomers , in ACS Symposium Series, eds. H. N. Cheng, T. Asakura and A. D. English, American Chemical Society, 2011, Vol. 1077, NMR Spectroscopy of Polymers Innovative Strategies for Complex Macromolecules, p. 475. 

Over the years, people have discovered many different ways of synthesizing IFN s. Figure 2 Illustrates the sequential IPN synthesis, top, and the simultaneous Interpenetrating network, SIN, synthesis, bottom. In the sequential synthesis, polymer network I Is swollen with monomer II plus crosslinker and activator, and polymerized In situ. The SIN synthesis begins with a mutual solution of both monomers or prepolymers and their respective crosslinkers, which are then polymerized simultaneously by noninterfering modes, such as stepwise and chain polymerizations. These methods have been used In the bulk, suspension, and latex states. Each will yield a distinguishable composition, even for the same polymer pair. 

Kawahara, S., Isono, Y, Washino, K., Morita, T., and Tanaka, Y. (2001). High-resolution latex state 13C-NMR spectroscopy Part II. Effect of particle size and temperature. Rubb. Chem. Tech-nol. 74(2), 295-302. 

Fig. 4-2. USAXS curves of SS-80 latex (stated diameter = 3000 A) and theoretical curve of a sphere (diameter = 3000 A). The peak (A) results from an interpartide interference, and maxima (B) from the shape of the latex. Curve I powder sample, cps, curve 2 disperaon (in ethanol) sample, cps x 100, curve 3 theoretical curve df a sphere. Taken from [S3], Proc. of the National Academy of Sciences. USA...

Natural mbber, the other natural hydrocarbon polymer, consisting mainly of cfr-l,4-polyisoprene is relatively resistant to microbial attack in comparison to other natural polymers. A number of micro-organisms have been reported to degrade natural rubber. An enzyme which degrades the mbber was isolated from the extracellular culture medium of Xanthomonas sp., and the erude fractions which are capable of depolymerizing natural mbber in the latex state have been reported.The same authors " reported on a Nocardia strain that used natural mbber as its sole carbon source. 

Most of the acetic acid is produced in the United States, Germany, Great Britain, Japan, France, Canada, and Mexico. Total annual production in these countries is close to four million tons. Uses include the manufacture of vinyl acetate [108-05-4] and acetic anhydride [108-24-7]. Vinyl acetate is used to make latex emulsion resins for paints, adhesives, paper coatings, and textile finishing agents. Acetic anhydride is used in making cellulose acetate fibers, cigarette filter tow, and ceUulosic plastics. 

Gut Rubber and Extruded Latex. The manufacturing technology for cut and extmded mbber thread is much older and more widely known than that for spandex fibers. Because production faciUties can be installed with relatively modest capital investment, manufacture of mbber thread is fragmented and more widely distributed with a few major and many minor producers. On a worldwide basis, Fikattice of Italy is the largest mbber thread producer with modem extmded latex plants in Italy, Spain, Malaysia, and the United States. Second in production capacity is the Globe Manufacturing Co., Fall River, Massachusettes with production operations in the United States and the UK. These firms also produce spandex fibers. 

In recent years, synthetic polymeric pigments have been promoted as fillers for paper. Pigments that ate based on polystyrene [9003-53-6] latexes and on highly cross-linked urea—formaldehyde resins have been evaluated for this appHcation. These synthetic pigments are less dense than mineral fillers and could be used to produce lightweight grades of paper, but their use has been limited in the United States. 

The Metravib Micromecanalyser is an inverted torsional pendulum, but unlike the torsional pendulums described eadier, it can be operated as a forced-vibration instmment. It is fully computerized and automatically determines G, and tan 5 as a function of temperature at low frequencies (10 1 Hz). Stress relaxation and creep measurements are also possible. The temperature range is —170 to 400°C. The Micromecanalyser probably has been used more for the characterization of glasses and metals than for polymers, but has proved useful for determining glassy-state relaxations and microstmctures of polymer blends (285) and latex films (286). 

Unvulcanized Latex and Latex Compounds. A prime consideration has to be the fluid-state stabihty of the raw latex concentrate and hquid compound made from it. For many years, the mechanical stabihty of latex has been the fundamental test of this aspect. In testing, the raw latex mbber content is adjusted to 55% and an 80 g sample placed in the test vessel. The sample is then mechanically stirred at ultrahigh speed (ca 14,000 rpm) by a rotating disk, causing shear and particle cohision. The time taken to cause creation of mbber particle agglomerates is measured, and expressed as the mechanical stabihty time (MST). 

Consumption of NR Latex. The total world consumption of natural mbber latex was 585,000 t in 1993, more than double that of 10 years earlier. The proportion of total natural mbber used as latex concentrate also increased from 7% in 1983 to 11% in 1993. Malaysia remains the dominant latex concentrate producing country in the world (Table 12). Its decline in exports during the 1980s and early 1990s has been partly compensated by an increase in consumption within the country (Table 13). Since the 1970s there has been a gradual shift in latex consumption from the traditional consumers in Europe and the United States to Asian countries. In 1994 Malaysia consumed 175,000 t of latex, more than the combined consumption of Western Europe and the United States (see Table 13). 

Future developments are likely to feature the production of more siUcone sealants that do not pick up dirt, more latex acryUc sealants that have high performance properties, urethanes that have improved uv stabiUty, and high performance polysulfides that are made in the United States. 

The largest volume commercial derivatives of 1-butanol are -butyl acrylate [141-32-2] and methacrylate [97-88-1] (10). These are used principally ia emulsion polymers for latex paints, ia textile appHcations and ia impact modifiers for rigid poly(vinyl chloride). The consumption of / -butanol ia the United States for acrylate and methacrylate esters is expected to rise to 182,000—186,000 t by 1993 (10). 

Guayule, potentially a source of natural mbber, is an unusual crop in that it has been an article of commerce in the past. Guayule grows wild in northern Mexico and the southwestern United States. When the leaves are milled in water, a latex is released that coagulates into natural mbber worms. These can easily be collected and relatively easily refined to give a product that is almost identical to the natural mbber from southeast Asia. During World War II there were several thousand acres of guayule planted in California and a small plant estabUshed to extract the mbber for military use. After the war. 

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