Polymerization acrylic second-stage

If polymer 1 has an active a-hydrogen in the molecular structure, such as poly(butyl acrylate), hydrogen-abstraction easily occurs in the second stage polymerization. Actually, in many cases, to improve the compatibility between two networks, a graft site is intentionally added in polymer network I to enhance the grafting of polymer 2 on polymer 1. 

Allyl methacrylate or acrylate can be prepared by alcoholysis of methacrylate acrylate by allyl alcohol in the presence of sodium methylate and a polymerization inhibitor such as hydroquinone [5]. The greater reactivity of the acrylic double bond leads to the formation of a soluble copolymer containing allyl groups that allow a second stage polymerization to form crosslinked thermoset plastics and... 

A recent study (49) of 50 50 polybutyl acrylate core-poly-styrene shell polymerization has shown the importance of the grafting reaction which occurs in the second-stage polymerization. 

Table IX gives the recipe used for these pol3nnerizations. The polybutyl acrylate seed latex was prepared by heating the ingredients for 24 hours at 70° the styrene, water, and potassium persulfate were then added and polymerized for another 8 hours at 70°. Three methods of adding the styrene monomer were used in the second-stage polymerization (i) batch polymerization (ii) equilibrium swelling of the seed latex particles followed by batch pol3nneriza-tion (iii) starved semi-continuous pol3nnerization. The particle growth was essentially stoichiometric, i.e., no new particles were initiated. All three latexes formed transparent continuous films upon drying, whereas a 50 50 mixture of polybutyl acrylate and...

ASA structural latexes have been synthesized in a two stage seeded emulsion polymerization. In the first stage, partially crosslinked poly(n-butyl acrylate) and poly( -butyl acrylate-sfaf-2-ethylhexyl acrylate) rubber cores are synthesized. In the second stage, a hard styrene acrylonitrile copolymer (SAN) shell is grafted onto the rubber seeds (16). 

In the two-step process, the second-stage reactor is similar to the first-stage reactor but is packed with an optimized catalyst for aldehyde oxidation, based on Mo V oxides, and is run under different operating conditions. Care must be exercised during the separation and purification phases to avoid conditions favouring acrylic acid polymerization, e.g., by addition of a radical polymerization inhibitor such as the hydroquinone monomethyl ether. Selectivities to acrylic acid are higher than 90% at total conversion of the aldehyde. Overall yields referred to propylene are in the range 75-85%. Most acrylic acid produced is esterified for the production of acrylate esters. 

Wu and Zhao studied LIPN systems by a two-stage emulsion polymerization technique (Wu and Zhao 1995). A latex seed (polymer 1) was synthesized first in a semicontinuous emulsion polymerization, swollen by the second-stage monomer or monomer mixture (forming polymer 2), and followed by polymerization to form IPN materials. Six kinds of monomers were used acrylonitrile (AN), vinyl acetate (VAc), n-butyl acrylate (liBA), methyl methacrylate (MMA), ethyl methacrylate (EMA), and ethyl acrylate (EA). The effect of composition, cross-linking level, feeding sequence of polymer 1 and polymer 2 on the IPN miscibility, and... 

Besides two-component LIPNs, three-component LIPNs have also been studied through three-stage emulsion polymerization processes (Zhang et al. 1991, 1994 Isao et al. 1992). These authors synthesized poly(n-butyl acrylate) cross-linked with ethylene glycol dimethacrylate as the seed latex. Styrene and divinylbenzene were added at the second stage. The third stage was linear poly(methyl methacrylate). Starved polymerization conditions resulted in more regular-shaped latex particles than batch addition of monomer. 

Core-shell latex particles prepared through two-stage semicontinuous-starved emulsion polymerization with PS as a seed and butyl acrylate as a second stage monomer were functionalized with two different acrylamides [116]. The effect of functional groups with different hydrophilicity and the locations in core-shell particles on the main colloid characteristics was investigated. 

Core-shell nanoparticles can also be fabricated using microemulsions. This was performed using a two-stage microemulsion polymerization beginning with a polystyrene seed [62]. Butyl acrylate was then added in a second step to yield a core-shell PS/PBA morphology. The small microlatex led to better mechanical properties than those of similar products produced by emulsion polymerization. Hollow polystyrene particles have also been produced by microemulsion polymerization of MMA in the core with crosslinking of styrene on the shell. After the synthesis of core-shell particles with crosslinked PS shells, the PMMA core was dissolved with methylene chloride [63]. The direct cross-... 

Another interesting three-component LIPN consists of crosslinked polyorganosiloxane (tet-raethoxysilane as crosslinker) as the first stage, swollen by butyl acrylate monomer (allyl methacrylate as crosslinker) and then polymerized to form the second component, and finally, poly(methyl methacrylate) was grafted onto the IPN core as the shell layer [Isao et al, 1992], Such kind of LIPNs are found to be a good impact modifiers in thermoplastics i.e., they are toughened by the addition of finely divided low phase. 

Thermal polymerization of MCMs (with transition metal acrylates as examples) is of interest in at least two aspects. First, the stmcture of these salts contains many dislocations, that facilitate solid-state polymerization. Second, thermal decomposition and polymerization transformations are the stages for a potential method of the synthesis of polsnner-immobilized, highly dispersed nanosize metal particles. 

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