Grafting products

The graft products are usually characterized by different methods. The first method is the calculation of graft parameters known as the grafting percentage (GP), grafting efficiency (GE), and weight conversion percentage (WC). These parameters can be calculated as follows ... 

Figure 9.2 Size exclusion chromatography traces for raw grafting products formed in the coupling reaction of chloromethylated polystyrene with polysty-ryllithium (a) without 1,1-diphenylethylene capping, and (b) with capped polystyryl anions (adapted from ref. [4])...

About 10 drops of solution A and B, respectively, are added dropwise to 30 ml of an ace-tone/ethanol mixture (2 1). While the ungrafted mixture causes a visible clouding, the graft product is fully soluble. 

Many reactions have been performed in the presence of a solvent. However, the solvent must be chosen carefully to avoid reaction with polymer. For example, the low yield for grafts of acrylonitrile on polyamides in the presence of methanol has been shown to be due to the methanolysis (18,31). Generally speaking, the grafted products are principally obtained however minor amounts and homopolymers can also result. The homopolymerization proceeds by an intramolecular transfer reaction between macroradicals and monomers. The amount of homopolymer depends on the system. Details on systems already investigated will be described in the next section. 

Also, acrylonitrile may be grafted by radiation to lignosulfonates with grafting yields of about 20%. However, the compatibility of the grafted product as a filler in SBR seems to be inferior to that of the original lignosulfonate (57). 

Daniel, Moore, and Segro (49) further investigated the graft polymerization of acrylonitrile to paper. They found that in grafted products having add-ons up to 53% neither cellulose nor polyacrylonitrile could be extracted with respective solvents. 

Kamogawa, and Sekiya (54) studied the graft polymerization of acrylamide onto cotton fabric using ceric ammonium nitrate as the catalyst. Similarly to Kulkarni et al. (35) the authors performed subsequent cross-linking with formaldehyde amd methylol compounds. From precipitation studies by acidification of cuprammonium solutions on mixtures of polyacrylamide and cellulose on the one hand and polyacrylamide-cellulose grafts on the other the authors conclude that chemical bonds must exist between the two polymers in the grafted product. 

Crude grafted product (poly (St-co-6), poly (St-g-MAN), PMAN)... 

A more complete fractionation, which also allows the isolation of some fractions forming the graft product, may be carried out according to the scheme described in Table VI. 

Notwithstanding the excess monomer with respect to the free rubber representing 40% of the total amount of elastomer present in the crude product, at the end of the reaction the amount of PVC in the grafted product increases from 30 to 40% however, no significant variations in... 

The PVC content in the graft copolymers increases considerably when the reaction temperature decreases. This is shown by the case of crude products prepared at 50° and at 70 °C which yield grafted product containing 46 and 29% of PVC. 

As may be deduced from the data reported, the amount of monomer converted into graft copolymer is very low—about 3% of the mass the grafted product on the average contains 30% PVC divided into fractions with PVC contents varying from 15 to 70%. 

A comparison was accomplished with a conventional poly (vinyl chloride) (Table VII) having a molecular weight comparable with that of the homopolymer present in the crude grafting product. 

Morphological or supermolecular structure is the most easily changed property of cellulosic fibers. Interactions of selected monomer solutions with fibers can yield grafted products... 

Cotton cellulose (1 g) was allowed to stand with 1 % aqueous solution of ammonium persulfate (0.5 g) for 30 min at room temperature Methyl methacrylate (MMA) (20 ml) and methanol (20 ml) were added to the mixture. After degassed, the flask was sealed and shaken at 60 °C for 1 to 4 h. The graft product was isolated by pouring into a large excess acetone followed by Soxhlet extraction with acetone for 48 - 72 h. 

Although an appreciable thermoplasticization was realized by the decrystallization treatment, the treatment did not give cellulose graft products which melt upon heating. This lack of melting was confirmed by microscopic observations of films prepared with the decrystallized composites. 

More recently, the second survey used the results obtained from the Company Ciba Geigy on the addition of thiols onto insaturated compounds. The authors showed that the addition of thiols onto dienes by ADIB led to highly grafted products since they may contain 45% by weight of fluorine (70% grafting), but such products are only soluble in freon or hexafluoroxylene. 

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