The batch emulsion copolymerization of vinyl acetate with different vinyl silane functional monomers (vinyl trimethoxysilane [VTMS], vinyl triethoxysilane [VTES], and vinyl silanetriol [VSTO]) is studied. The nature of the silane strongly affects the development of the microstructure and crosslinking ability of the latexes. A combination of techniques (Soxhlet extraction, centrifugation, assymetric‐flow field flow fractionation AF4/MALS/RI) shows that the factor controlling the molar mass and crosslinking density is the degree of hydrolysis of the alkoxysilane, producing higher molar masses and degrees of crosslinking when the degree of hydrolysis is high. Thus, the copolymer containing VSTO produced a very crosslinked latex, the one with VTMS produced a latex with a low degree of crosslinking in the wet state that can yield high degrees of crosslinking upon drying, and the latex with VTES do not produce significant amounts of crosslinking neither before nor after drying. 相似文献
The semicontinuous emulsion copolymerization of vinyl acetate and butyl acrylate (VAc/BuA) (85:15) initiated by thermal initiators ammonium persulfate (APS) and potassium persulfate (PPS) at 70°C in the presence of nonylphenol ethoxylates of varying chain lengths (NP-n) and acrylamide partially polymerized (Amol) was investigated. VAc-BuA copolymer latexes were synthesized as two different series in the glass reactor, in the first serie was initiated by APS and PPS was used as initiator in the second serie. The influence of the counterions or initiators and chain lenghts of non-ionic emulsifier on the properties of VAc-BuA copolymer latexes were determined by measuring Brookfield viscosities, weight average molecular weights (M̄w), number average molecular weights (M̄w), molecular weight distribution and surface tension of latexes to air. The results of copolymer latexes indicated that their physicochemical properties increased with the increasing chain length of nonionic emulsifier for two initiators. 相似文献
An aqueous solution of the hydrophilic monomer such as acrylic acid is dispersed in a continuous lipophilic medium using surfactants, which promote the formation of a water- in-oil (W/O) emulsion. The water-in-oil (W/O) emulsion polymerization process has shown superior characteristics1 such as the low viscosity of the dispersion, easy removal of the reaction heat2 and the high molecular weight of the obtained polymer3 etc. And it is attractive to investigate the reaction system because the… 相似文献
The emulsion copolymerization of methyl methacrylate and octyl acrylate was studied using a reactive surfactant ammonium sulfate allyloxy nonylphenoxy poly(ethyleneoxy) (10) ether (DNS‐86), and a conventional surfactant sodium dodecylbenzene sulfonate (DBS) with a similar structure as a comparison sample. A series of latex samples have been prepared with two kinds of surfactants, and their properties have been characterized and compared. 1H‐NMR proves that the reactive surfactant has been incorporated into the resulting copolymers. The atomic force microscopy (AFM) proves that the reactive surfactant DNS‐86 migrate to the surface of the latex film to a much less degree than the conventional surfactant DBS. Transmission electron microscopy (TEM) demonstrates that there are some differences in the particle morphologies. The stability and water‐resistance of the latex films prepared by reactive surfactant DNS‐86 are better than those prepared by the conventional surfactant DBS. 相似文献
Acrylonitrile/methyl acrylate copolymers were synthesized by suspended emulsion polymerization with water as dispersed phase and monomers as continuous phase, potassium peroxydisulphate (KPS) as initiator, Span-80 as emulsifier, and poly(vinyl alcohol) (PVA) as suspending agent. Effects of reaction parameters such as water/monomer mass ratio, concentration of initiator, polymerization temperature and agitation rate on polymerization conversion and the particle size distribution of acrylonitrile/methyl acrylate copolymers were studied. It was found that polymerization conversion increased with an increase of water/monomer mass ratio, concentration of initiator and polymerization temperature, while the agitation rate had no significant effect on the polymerization conversion. Particle size distribution became narrower with an increase of water/monomer mass ratio and agitation rate. Under the same initiator concentration and polymerization temperature, particle size distribution became wider along with polymerization time. The differential scanning calorimetry (DSC) results indicated that the peak temperature of the copolymers decreased with increasing MA content. 相似文献
In this work, vinyl acetate/butyl acrylate emulsion copolymerizations carried out in a continuous tubular reactor (pulsed sieve plate column, PSPC) were compared to those conducted in a semibatch stirred tank reactor under similar operational conditions. In order to minimize the compositional drift along the PSPC, reactions were carried out with different numbers (2, 3 and 4) of lateral feed streams of the more reactive monomer (butyl acrylate). For comparison, fed batch reactions were conducted with the same number of intermittent shot additions of butyl acrylate, at the corresponding batch times. Both systems (tubular and semibatch) with distributed feeding of more reactive monomer are able to reduce composition drift thus providing more uniformity in copolymer composition. In addition, the tubular reactor presents much better control of temperature than the tank reactor, which is important to achieve higher productivity. 相似文献
Complete parameter sensitivity analyses using the numerical fractionation technique are presented for the cases of homopolymerization with chain transfer to polymer and termination by combination. Also, using reported values for the kinetic rate constants associated with the linear and non‐linear homopolymerizations of styrene, vinyl acetate, methyl methacrylate and butyl acrylate, overall molecular weight distributions and averages of the MWD were calculated using the NFT. Good agreement with the expected behavior, with MMA and STY not gelling while BA and VAc do, was obtained. It is concluded that the NFT produces coherent and reliable performance for known polymerization systems, whether linear or non‐linear.
