Peroxides lauryl

Chain transfer also occurs to the emulsifying agents, leading to their permanent iacorporation iato the product. Chain transfer to aldehydes, which may be formed as a result of the hydrolysis of the vinyl acetate monomer, tends to lower the molecular weight and slow the polymerisation rate because of the lower activity of the radical that is formed. Thus, the presence of acetaldehyde condensates as a poly(vinyl alcohol) impurity strongly retards polymerisation (91). Some of the initiators such as lauryl peroxide are also chain-transfer agents and lower the molecular weight of the product. 

Lauryl peroxide (dodecyl peroxide) [105-74-8] M 398.6, m 53-54°. Crystd from n-hexane or benzene and stored below 0°. Potentially EXPLOSIVE. 

There has also been a trend in recent years to the use of free-radical initiators that decompose more rapidly than the traditional initiators such as caproyl and lauryl peroxides. Currently used initiators include peroxydicarbonates, t-butylperpiva-late, azobis-(2,4-dimethylvaleronitrile) and acetyl cyclohexylsulphonyl peroxide. 

Initiators commonly used include dibenzoyl peroxide, lauryl peroxide, 2, 2 -azobis isobutyronitrile, and others that are suitable for use in the temperature range of approximately 60-90°C. 

Organic peroxides acyl peroxides (benzoyl, acetyl, lauryl peroxides, etc), alkyl peroxides, hydroperoxides, etc. are used as polymerization initiators. Azocompounds (for example, redox systems, etc. are also widely used as initiators. In... 

Dechlorination of poly (vinyl chloride) (PVC) prepared by polymerisation of vinyl chloride (VC) with butyllithium (BuLi) was investigated under the conditions of high pressure and high temperature water. Dechlorination was induced completely and polyene product was formed from PVC under high pressure and high temperature. The polymers obtained from polymerisation of VC with the BuLi revealed different decomposition behaviour from that obtained with radical initiator such as lauryl peroxide. This was attributed to the different chemical structure of the sample PVC. Complete dechlorination of PVC could be achieved in hot water under the conditions of 19.3 MPa and 300 deg.C. 3 refs. 

Zard has developed the use of N-amidyl radicals. The precursors of the radical intermediates are 0-benzoyl hydroxyamines such as 37. Addition of a tributylstannyl radical to the carbonyl group of the benzoate moiety is followed by the cleavage of the weak N - O bond. A subsequent 5-exol6-endo tandem cyclization takes place to yield the skeleton of the natural product deoxyserratine (Scheme 12) [49]. Later, the same group disclosed a tin-free source of amidyl radicals that relies on the use of M-(0-ethyl thiocarbonyl-sulfanyl) amides and lauryl peroxide as initiator. Examples of polycyclization were also given [50]. On the occasion of a model study toward the synthesis of kirkine, the use of thiosemicarbazide precursors gave access to the tetracyclic structure of the natural product [51]. 

The generation of amidyl radicals from N-allylsulfonamides and their subsequent cyclization was probed by Moutrille and Zard [130]. This strategy allowed the preparation of lactams such as 140 by treatment of acylsulfon-amide 138 with lauryl peroxide and a xanthate in DCE (Scheme 44). However, when the stability of the generated amidyl radical (as with 137) was not high enough, the extrusion of sulfur dioxide turned to be too slow, and premature cyclization of the N-amidosulfonyl radical intermediate took place, leading to 139. 

Azonitriles have generally been considered to be cleaner initiators in the sense of being devoid of chain transfer however, recent research w ork indicates this is not true. Other initiators/chain-transfer agents include /-butyl peroxide, cumyl peroxide, lauryl peroxide, benzoyl peroxide, /-butyl hydroperoxide, cumyl hydroperoxide, dicumyl peroxide, and persulfate the half-lives of these initiators are given in Table 4.2 [185],... 

Solvents and Initiators. All polymerization solvents, ethyl acetate (EA),1,2-dichloroethane (DCE), methyl ethyl ketone (MEK), cyclohexanone (CH), toluene and tetrahydrofuran (THF) were purified by standard procedures (12) and stored under N2 or over molecular sieves. All other solvents used, N,N-dimethylformamide (DMF), di-methylsulfoxide (DMSO), y-butyrolactone, hexane, diethyl ether, acetone, etc., were AR grade materials. Initiators, azobisiso-butyronitrile (AIBN), di-t-butylperoxide (DTBP), lauryl peroxide (LP) and benzoyl peroxide (BPO) were recrystallized (AIBN and BPO) or used as received from suppliers. 

Thermal decomposition of sulfonyl azides produces variable amounts of alkylazides presumably through a radical mechanism [75, 76]. The first preparative and attractive tin-free procedure for the azidation of radicals was recently reported. Secondary and tertiary alkyl iodides and dithiocabonates are easily transformed into the corresponding azides by reaction with ethanesulfonylazide in the presence of di-lauryl peroxide (DLP) as radical initiator (Scheme 27, Eq. 27.2). Interestingly, this... 

Bouchard [161] developed a poly(vinyl acetate) adhesive formulation using hydrogen peroxide-zinc formaldehyde sulfoxylate as the initiator system, poly-(vinyl alcohol) and sodium decylbenzene sulfonate as the emulsification system, and lauryl peroxide dissolved in the seed monomer to reduce the viscosity of the final latex (see Table XVIII). To this, from separate streams, a hydrogen peroxide solution, a sodium bicarbonate solution, and vinyl acetate are added. The final latex had a pH of 4.5 and a viscosity of 7 cP at 25°C. 

There are various additives in PVC plastics, such as antioxidants, light stabilizers, initiators, plasticizers, flame retardants, pigments and others. As initiators, potassium persulfate, benzoyl peroxide, lauryl peroxide, percarbonate and some azo-compounds can be used. The presence of chlorine in the hydrocarbon backbone gives rigidity and toughness to the polymer, but PVC liberates hydrogen chloride when exposed to high temperatures. To prevent this, stabilizers are added to the polymer. There are several kinds of stabilizers on the market. The most important contain lead, tin, calcium and zinc and... 

GC/mass spectrometry has also been used to determine diols, adipic acid and cyclomonodiol adipates in aliphatic polymers [138], isobutyronitile, benzoyl peroxide, lauryl peroxide and tetramethyl succinonitrile in polystyrene [139] additives in polypropylene [140] crosslinked rubbers [141] and other polymers [142,143]. 

---