Addition polymers halogens

FIRE RETARDANT FILLERS. The next major fire retardant development resulted from the need for an acceptable fire retardant system for such new thermoplastics as polyethylene, polypropylene and nylon. The plasticizer approach of CP or the use of a reactive monomer were not applicable to these polymers because the crystallinity upon which their desirable properties were dependent were reduced or destroyed in the process of adding the fire retardant. Additionally, most halogen additives, such as CP, were thermally unstable at the high molding temperatures required. The introduction of inert fire retardant fillers in 1965 defined two novel approaches to fire retardant polymers. 

The resistance of polymers to flame may be increased by the addition of halogenated compounds and antimony oxide. Organic phosphate additives inhibit the glow of the char formed in burning polymers. Polymers with chlorine pendant groups, such as PVC, and those with halogen-substituted phenyl groups, such as polyesters produced from tetrabromophthalic anhydride, are more flame-resistant than hydrocarbon polymers. 

J.L. Bolland and G. Gee, Trans. A review of the role of basic iron(IH) oxide acting as a char forming/ smoke suppressing/flame retarding additive in halogenated polymers and halogenated polymer blends. Faraday Soc., 42, 236 (1946). 

In this important class of additives, the halogen contributes to some extent to the flame retardancy although this contribution is offset by the lower phosphorus content. The halogens generally reduce vapor pressure and water solubility, thus aiding retention of these additives. Thus, more efficient and effective blending/manufacturing processes involved usually lead to a favorable economics of polymer flame retardation.26... 

Atlanta, Ga., 26th-30th April 1998, p.3310-2. 012 NOVEL ZINC HYDROXYSTANNATE-COATED FILLERS AS FIRE RETARDANT AND SMOKE SUPPRESSANT ADDITIVES FOR HALOGENATED POLYMERS Hornsby P R Cusack P A... 

Among the classical (summarized in [11]) reactions of cyanoacetylenes (salt and n-complex formation, nucleophilic addition of, inter alia, amines and alcohols, Diels-Alder additions with 2 (see Section 2.22.2), addition of halogens and hydrogen halides, etc.) their polymerization might deserve a second look since the products formed - polyacetylenes - have attracted much attention during the last two decades. Thus 1, several of its derivatives, and 2 have been polymerized with anionic initiators (triethylamine, sodiiun cyanide, butyllithium) to give black, low-molecular-weight polymers claimed to have structures like 33 [38-40], which is obtained from 2 by treatment with butyllithium. 

Polyacetylene reacts with chlorine rapidly to give a white polymer that is equivalent to poly(l,2-dichloroethylene) and no stereospecificity has been reported on the chlorinated polymer. The addition of halogens is an important general reaction of carbon-carbon double bonds in a stereospecific and regiospecific sense. For instance, the electrophilic additions of chlorine to ethylene, buta-1,3-diene and hexa-l,3,5-triene have been shown to proceed by 1,2-trans (anti), 1,4-cis (syn) and 1,6-trans (anti) attack, respectively. This stereospecificity has been rationalized with a mixing rule of a-n orbital interaction. The reaction of a long conjugated polyene like polyacetylene with chlorine may produce an atactic chlorinated polyene, because random l,2n additions occur to result in a random addition product. ... 

Besides the addition of halogens and hydrohalogens across the double bond just covered, there are many other reagents that will react similarly with unsaturated polymers by free radical, ionic, or radical-ion mechanisms. Of prime importance is the addition of ethylene derivatives to polydienes. One of the earliest reactions of natural rubber to be studied in detail was the combination with maleic anhydride (Cunneen and Porter, 1965). Depending on the reaction conditions and the presence or absence of free radical initiators, one or more of four basic reactions may take place, with the products shown (the arrows indicate where the addition has taken place and the new bonds formed). 

Italmatch introduces low-halogen flame retardant for polyolefins. Addit Polym [trade journal—Elsevier] Febmary 2007. 

After the rope has been drawn, stir the remaining reaction mixture thoroughly until no more polymer forms. Isolate any additional polymer and, after thoroughly washing it with water, put it in the container for nonhazardous organic solids. Separate the dichloromethane and aqueous layers of the reaction mixture. Pour the dichloromethane into the container for halogenated organic liquids. Flush the aqueous layer and all aqueous solutions down the drain. 

Rieke calcium and copper, which are highly soluble reactive metals, undergo direct oxidative addition to halogenated cross-linked polystyrene resins as shown in Schemes 9.2 and 9.3 [33]. The resulting insoluble polymeric aryl-calcium or aryl-copper reagents can be used to carry out a number of usefiil transformations on the polymers by reacting them with various electrophiles as shown in Table 9.5 and Table 9.6 [22]. 

General - From the above it can be seen that substitution in the ortho positions of a bisphenol A polyester gives rise to an increase in Tg. There is roughly a 25 C increase in temperature between the two series of polymers APE = 215 C, CAPE = 240°C, BRAPE = 275 C (Fig. 5). In addition the halogenated derivatives yield polyesters which show a greater degree of crystallinity over a broader range of compositions than do the APE polyesters. This may also help to explain some of the solubility differences in compositions which will now be addressed. 

Halogen-substimted alkenes can also polymerize. These molecules are polar, so the resulting polymer has dipole attractions in addition to induced dipole forces. A familiar example of such a polymer is Saran, the food wrap that clings to itself. Saran is a copolymer because it is made from two monomers, CH2=CHC1 and CH2=CCl2. The attractive forces between Saran polymer films come from the dipoles caused by the carbon-chlorine bonds. Table 21.6 lists more ethylene-based monomers that give addition polymers. 

Tin compound Inorganic additive/filler Halogen source Polymer... 

For most vinyl polymers, head-to-tail addition is the dominant mode of addition. Variations from this generalization become more common for polymerizations which are carried out at higher temperatures. Head-to-head addition is also somewhat more abundant in the case of halogenated monomers such as vinyl chloride. The preponderance of head-to-tail additions is understood to arise from a combination of resonance and steric effects. In many cases the ionic or free-radical reaction center occurs at the substituted carbon due to the possibility of resonance stabilization or electron delocalization through the substituent group. Head-to-tail attachment is also sterically favored, since the substituent groups on successive repeat units are separated by a methylene... 

Alumina trihydtate is also used as a secondary flame retardant and smoke suppressant for flexible poly(vinyl chloride) and polyolefin formulations in which antimony and a halogen ate used. The addition of minor amounts of either zinc borate or phosphoms results in the formation of glasses which insulate the unbumed polymer from the flame (21). 

Olefin Polymers. The flame resistance of polyethylene can be increased by the addition of either a halogen synergist system or hydrated fillers. Similar flame-retarder packages are used for polypropylene (see Olefin polymers). Typical formulations of the halogen synergist type are shown in Table 15 the fiUer-type formulations are in Table 16. 

Reactive Flame Retardants. Reactive flame retardants become a part of the polymer by either becoming a part of the backbone or by grafting onto the backbone. Choice of reactive flame retardant is more complex than choice of an additive type. The reactive flame retardant can exert an enormous effect on the final properties of the polymer. There are also reactive halogenated compounds used as iatermediates to other flame retardants. Tables 8 and 9 Hst the commercially avaHable reactive flame retardants and iatermediates. 

In polymers such as polystyrene that do not readily undergo charring, phosphoms-based flame retardants tend to be less effective, and such polymers are often flame retarded by antimony—halogen combinations (see Styrene). However, even in such noncharring polymers, phosphoms additives exhibit some activity that suggests at least one other mode of action. Phosphoms compounds may produce a barrier layer of polyphosphoric acid on the burning polymer (4,5). Phosphoms-based flame retardants are more effective in styrenic polymers blended with a char-forming polymer such as polyphenylene oxide or polycarbonate. 

The discussion centers on heat stabilizers for PVC because this polymer is the most important class of halogenated polymers requiring these chemical additives. PVC of ideal chemical stmcture (1) should be a relatively stable compound as predicted from model studies using 2,4,6-trichloroheptane [13049-21-3] (2) (1). 

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