Anhydrides epoxides

It is possible to react an organic moiety to the hydroxyl groups on ceU waU components. This type of treatment also bulks the ceU with a permanently bonded chemical (68). Many compounds modify wood chemically. The best results are obtained by the hydroxyl groups of wood reacting under neutral or mildly alkaline conditions below 120°C. The chemical system used should be simple and must be capable of swelling the wood stmcture to facUitate penetration. The complete molecule must react quickly with wood components to yield stable chemical bonds while the treated wood retains the desirable properties of untreated wood. Anhydrides, epoxides, and isocyanates have ASE values of 60—75% at chemical weight gains of 20—30%. 

Matsuda, H., Murakami, K. and Ueda, M. (1988a). Oligoesterifed woods based upon anhydride and epoxide III. Preparation and dimensional stability of ohgoesterified woods by heating wood impregnated with anhydride-epoxide solution. Mokuzai Gakkaishi, 34(10), 844—850. 

Table 3. Least-Squares Analysis 2000-1400 cm 1 of 1 1 Stoichiometry Anhydride Epoxide Mixtures (0.5% wt BDMA Catalyst) Crosslinked at 90 °C...

Fig. 4. Zeroth-order graph of a stoichiometric anhydride/epoxide tertiary amine-catalyzed copolymerization at 80 °C...

Table 2.25 Anhydride-epoxide copolymerization initiated by tertiary amines... 

Reactive chemicals such as acid anhydrides, epoxides, strong acids and bases, acyl chlorides, and... 

Sodium aluminohydride (NaAlH4, SAH) in THF is somewhat less reactive than LAH toward carboxylic acids, anhydrides, epoxides, amides, and nitro compounds [CBS], and it can be used for selective reductions. However, it is as sensitive to moisture as LAH so similar precautions must be taken. 

For Lewis base and Lewis base salt catalyzed anhydride cured epoxy reactions, Fischer (7) proposed that the initial step of an anhydride, epoxide, and tertiary amine system was the activation of the anhydride (reaction 1) ... 

Recently, Crandall and Mlh (12) studied the anhydride curing mechanism using near and middle IR and DSC. Their findings supported the anhydride-epoxide curing mechanism that most experts essentially agree upon. 

Base-catalyzed anhydride-epoxide reactions have been found to have greater selectivity toward diester formation. Shechter and Wynstra (8) showed that equal molar amounts of acetic anhydride and phenyl glycidyl ether with either potassium acetate or tertiary amines as a catalyst reacted very selectively. They proposed the following reaction mechanism for the acetate ion catalyzed reaction ... 

The anhydride-epoxide reaction is complex because of the possibility of several reactions occurring simultaneously. Thus, appreciable etherification can result in undesirable amounts of unreacted anhydride and half-acid ester in the cured resin. On the basis of experimental results, Arnold (11) has suggested that for optimum properties anhydride to epoxide ratios of 1 1 are needed for tertiary amine catalysts, and 0.85 1 for no catalyst. 

Plasticizers include esters of aromatic and aliphatic acids and anhydrides, epoxidized oil, phosphate esters, hydrocarbon oils and polymeric materials. PVC is the polymer most in need of plasticizers, but polyvinyl acetate, epoxies, cellulose nitrate and acetates also require these additives. 

With regard to reactively compatibilized TPU blends, Lu et al. (2002) determined the relative reactivity of various functionalities toward TPU using model compounds. The ranking of relative reactivity was found to be primary amine (most reactive) > seccmdaiy amine >> hydroxyl carboxylic acid anhydride >> epoxide (least reactive). 

Plasticizers are typically di- and triesters of aromatic or aliphatic acids and anhydrides. Epoxidized oil, phosphate esters, hydrocarbon oils, and some other materials also function as plasticizers. In some cases, it is difficult to discern if a particular polymer additive functions as a plasticizer, a lubricant, or a flame retardant. 

Most plasticizers are used with polyvinyl chloride (PVC). Some go into such plastics as cellulosics, nylon, polyolefins, and styrenics. Plasticizers are typically di- and tri-esters of aromatic or aliphatic acids and anhydrides. Epoxidized oil, phosphate esters, hydrocarbon oils, and some other materials also function as plasticizers. In some cases, it is difficult to discern whether a particular polymer additive functions as a plasticizer, lubricant, or flame retardant. The most popular plasticizers are the phthalates, followed by the epoxies, adipates, azelates, trimeflitates, phosphates, polyesters, and others. There are a number of discrete chemical compounds within each of these categories. As a result, the total number of plasticizers available is substantial. 

Resins obtained using alternative means to phenyl isocyanate for blocking the hydroxyl functionality of a sucrose "penta" ester, e.g. reaction with aluminium diisopropoxide monoacetylacetonate or cyclic anhydride/ epoxide also show promise. 

In summary, the reactivity of various functional groups toward Li 9-BBNH is classified into four broad categories [18] (1) rapid- or fast-reduction aldehyde, ketone, ester, lactone, acylchloride, acid anhydride, epoxide, disulfide, -alkyli-odide, and tosylate (2) slow-reduction tertiary amide, alkylbromide, and aromatic nitrile (3) sluggish-reduction carboxylic acid, aliphatic nitrile, primary amide, nitro and azoxy compounds, and secondary alkylbromide and tosylate (4) inert olefin, oxime, alkylchloride, sulfoxide, azo-compound, sulfide, sulfone, and sulfonic acid. 

It has been found that tertiary amines are catalysts that not only affect the rate of the anhydride-epoxide reaction, but its course as well [82,83]. Dearborn and coworkers [84], for example, report that the highest crosslinking in amine-catalyzed anhydride-epoxide resin cures was obtained at a 1 1 anhydride expoxide ratio. This implies that the amine largely or wholly suppresses the undesirable side reaction of epoxide polymerization. This method of curing is potentially a powerful tool in polymer chemistry, since in its broadest sense it enables one to prepare a linear polyester containing at regular intervals along the chain various substituents available for further reactions. 

---