Polyfunctional methacrylates

Small amounts of TAIC together with DAP have been used to cure unsaturated polyesters in glass-reinforced thermo sets (131). It has been used with polyfunctional methacrylate esters in anaerobic adhesives (132). TAIC and vinyl acetate are copolymerized in aqueous suspension, and vinyl alcohol copolymer gels are made from the products (133). Electron cure of poly(ethylene terephthalate) moldings containing TAIC improves heat resistance and transparency (134). 

Concrete can also be made water-repeUent by the polymerization of vinyl monomers on the surface (85). Polymerization can be initiated with peroxides, and polyfunctional methacrylates can be used as crosslinking agents. These treatments have a tendency to produce changes in color and gloss. 

In the core first process, initiator is first reacted with the polyfunctional methacrylate to make an active core. Monofunctional monomers are then added to grow arms out from the active core. This process, in general, makes stars that are larger than those from the arm first process and are more difficult to control. Stars made from this process can range from several hundred thousand to several billion in molecular weight. 

The DADC monomer has been copolymerized with small amounts of polyfunctional methacryflc or acryflc monomers. For example, 3% triethylene glycol dimethacrylate was used as a flexibiflzing, cross-linking agent with a percarbonate as initiator (26). CR-39 and diethylene glycol diacrylate containing isopropyl percarbonate were irradiated with a mercury lamp to a 92% conversion and then cured at 150°C (27). By a similar two-step process DADC was copolymerized with methyl methacrylate and tetraethylene glycol dimethacrylate (28). 

Mention may also be made here of a number of polyfunctional compounds such as allyl methacrylate and glycol dimethacrylates which have been used to produce a cross-linked sheet of enhanced heat resistance compared with conventional poly(methyl methacrylate). Some manufacturers supply the sheet in an incompletely cross-linked state which allows a limited amount of forming after which the sheet may be further heated to complete the cure. 

During mutual graft copolymerization, homopolymerization always occurs. This is one of the most important problems associated with this technique. When this technique is applied to radiation-sensitive monomers such as acrylic acid, methacrylic acid, polyfunctional acrylates, and their esters, homopolymer is formed more rapidly than the graft. With the low-molecular weight acrylate esters, particularly ethyl acrylate, the homopolymer problem is evidenced not so much by high yields as by erratic and irreproducible grafting. 

Platinum-cobalt alloy, enthalpy of formation, 144 Polarizability, of carbon, 75 of hydrogen molecule, 65, 75 and ionization potential data, 70 Polyamide, 181 Poly butadiene, 170, 181 Polydispersed systems, 183 Polyfunctional polymer, 178 Polymerization, of butadiene, 163 of solid acetaldehyde, 163 of vinyl monomers, 154 Polymers, star-shaped, 183 Polymethyl methacrylate, 180 Polystyrene, 172 Polystyril carbanions, 154 Potential barriers of internal rotation, 368, 374... 

A different approach, although stdl working with essentially non-fiinctional polymers has been exemplified [114,115], in which, a 100% solid (solvent free) hot melt has been irradiated to produce pressure-sensitive adhesives with substantially improved adhesive properties. Acrylic polymers, vinyl acetate copolymers with small amounts of A,A -dimethylaminoethyl methacrylate, diacetone acrylamide, A-vinyl pyrrohdone (NVP) or A A have been used in this study. Polyfunctional acrylates, such as trimethylolpropane trimethacrylate (TMPTMA) and thermal stabilizers can also be used. 

NR, styrene-butadiene mbber (SBR), polybutadiene rubber, nitrile mbber, acrylic copolymer, ethylene-vinyl acetate (EVA) copolymer, and A-B-A type block copolymer with conjugated dienes have been used to prepare pressure-sensitive adhesives by EB radiation [116-126]. It is not necessary to heat up the sample to join the elastomeric joints. This has only been possible due to cross-linking procedure by EB irradiation [127]. Polyfunctional acrylates, tackifier resin, and other additives have also been used to improve adhesive properties. Sasaki et al. [128] have studied the EB radiation-curable pressure-sensitive adhesives from dimer acid-based polyester urethane diacrylate with various methacrylate monomers. Acrylamide has been polymerized in the intercalation space of montmorillonite using an EB. The polymerization condition has been studied using a statistical method. The product shows a good water adsorption and retention capacity [129]. 

Allyl methacrylate and allyl acrylate are difunctional monomers, triallyl phosphate is a trifunctional monomer, and polyethylene glycol dimethacrylate is a polyfunctional monomer. All these lead to cross-linked graft copolymers. 

This group covers polymeric peroxides of indeterminate structure rather than polyfunctional macromolecules of known structure. These usually arise from autoxidation of susceptible monomers and are of very limited stability or explosive. Polymeric peroxide species described as hazardous include those derived from butadiene (highly explosive) isoprene, dimethylbutadiene (both strongly explosive) 1,5-p-menthadiene, 1,3-cyclohexadiene (both explode at 110°C) methyl methacrylate, vinyl acetate, styrene (all explode above 40°C) diethyl ether (extremely explosive even below 100°C ) and 1,1-diphenylethylene, cyclo-pentadiene (both explode on heating). 

Copolymeirization provides an unique approach to the synthesis of polyfunctional stabilizers. E.g. terpolymers of 4-isopropenyl-2,6-di-terr-butylphenol, methyl methacrylate and 2-(2-hydroxy-5-isopropenyl)-2H-benzotriazole or poly[4-(2,2,6,6-tetramethylpiperidyl) methacrylate-co-4-hydroxy-3,5-di-tert-butyl-benzyl methacrylate] (96), having M 5,400, posses properties of AO and LS [108]. 

Polyfunctional mercaptans can be used to impart some control to free-radical polymerisation. For methacrylate monomers, it has been demonstrated that polymers with polydispersities as low as 1.25 can be made. Unlike conventional radical polymerisations, this proceeds with an increase in molecular weight with time. The reason for this is that the thiol groups react sequentially as polymerisation proceeds. The polymerisation is statistically more controlled. 

It was recently shown12) that in radical polymerization the chain termination rate constant is observed to decrease with the introduction of a polyfunctional complex-ing agent into the system. An especially sharp decrease of the termination rate, up to the formation, under certain conditions, of living radical polymerization centers, was noted in the methyl methacrylate-orthophosphoric acid system. 

The most common acrylic polymer is polymethyl methacrylate, which is obtained by polymerization of methyl methacrylate (MMA). The material consists of a highway-grade aggregate and a matrix produced by cross-linking MMA with trimethylol propane trimethacrylate or other polyfunctional acrylic oligomers. 

Odian and Bernstein (1963) and Lyons (1960) have reported results of an extensive study of the crosslinking of polyethylene using gamma irradiation in the presence of polyfunctional monomers. The monomers, which included a variety of diallyl and triallyl compounds and polyfunctional acrylates, were incorporated by swelling into the polyethylene matrix until equilibrium had been attained (corresponding to monomer concentrations between 1 and 13%). Two of the most efficient monomers in terms of gel formation were allyl methacrylate (I) and allyl acrylate (II). 

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