Styrene grafting to polyethylene

Table I. Synergistic Effect of Acid and TMPTA as Additives in Grafting Styrene to Polyethylene Film Initiated by Ion is ing Radiation8 ...

Additives in Grafting Styrene to Polyethylene and Cellulose Initiated by UVa... 

Table VI. Acid Enhancement In Radiatlon Grafting Styrene to Polyethylene In Methanol...

Grafting Styrene to Polyethylene Film Initiated by Ionising Radiation... 

Fig 6. Effect of dose rate on the efficiency of grafting styrene to polyethylene film in methanol in the presence of acid (H SO, 0.2M). Total dose, 2.3 x 10 rad. 

Both Odian and Silverman models satisfactorily explain most of the observed results in all solvents (Tables I-III, VI) used in the present study, however there are some exceptions especially when solvents other than the alcohols are used (Table VI). Thus the Odian mechanism is not consistent with the DMF data nor can the Silverman model account for the acetone results. In addition, in further preliminary studies with grafting of styrene to polyethylene (10) in solvents other than those reported here both Odian and Silverman mechanisms are deficient. The problem is that possible contributions from the radiation chemistry of the components in the grafting reaction need to be considered in formulating a complete mechanism for the overall process. 

Figure 1. Effect of divinylbenzene on grafting of styrene to polyethylene film in methanol at dose rate of 4,1 X rad/h to total dose of 2,5 X 10 rad. Key O, styrene-methanol , styrene-methanol-divinylbenzene (1% v/v).

W.J. Chappas and J. Silverman, The effect of acid on the radiation-induced grafting of styrene to polyethylene, JoRad.Phys.Chemo 14 847 (1979). 

Table 4. Synergistic effect of acid with polyfunctional monomers in the radiation grafting of styrene to polyethylene, (a)... 

A theory for this acid effect has been developed essentially from the wool and cellulose work (3,4). Recently, in a brief communication, we reported analogous acid enhancement effects in the radiation grafting of monomers such as styrene in methanol to nonpolar synthetic backbone polymers like polypropylene and polyethylene (5). In the present work, detailed studies of this acid enhancement effect are discussed for the radiation grafting of styrene in various solvents to polyethylene. The results are fundamentally important since most of the experiments reported here have been performed in solvents such as the low molecular weight alcohols which, unlike cellulose and wool systems, do not swell polyethylene. 

TABLE I. Acid Effect in Radiation Grafting to Polyethylene using Styrene in Low Molecular Weight Alcohols.a... 

TABLE II. Acid Effect Styrene in in the Radiation Isomeric l Grafting to Polyethylene using Butanols.a ... 

TABLE IV. Effect of Acid Structure in Methanol to Polyethylene.a Grafting of Styrene in ... 

TABLE V. Effect of Acid on Homopolymer Formation in the Radiation Grafting of Styrene in Methanol to Polyethylene.0... 

Figure 1. Grafting of styrene in methanol to polyethylene at various dose rates total dose 0.2 X 10 rads. (V) 0.117 X 10s rad/hr, without HsSOk (Y) with 0.1 N H S04 (0)0.196 X 10s rad/hr, without HsSOi (9) with 0.1N H2SOi ( ) 0.279 X 106 rad/hr, without ( ) with 0.1N ffsS04 ( ) 0.546 X 10 rad/hr,...

TABLE VII. Effect of Dose Rate in the Presence of Acid on the Grafting of Styrene in DMF to Polyethylene. 

The parameters which predominantly influence the acid effect in radiation grafting of styrene monomer to polyethylene film are the structure of solvent, the concentration of monomer and the dose rate. Because these three variables are inter-related, it is difficult to predict, a priori, the conditions required to yield an optimum in grafting. In this respect the type of solvent used is particularly important. 

Figure 2. Grafting of styrene in DMF to polyethylene in the presence of HtSOt at various concentrations total dose 0.5 X 10s rad at dose rate 0.080 X 10s rad/hr...

Polymer radicals can also be produced by the irradiation of a polymer-monomer mixture with ionizing radiation. Thus, the interaction of ionizing radiation with polyethylene-styrene produces radical centers on polyethylene, and these initiate graft polymerization of styrene to produce poly(ethylene-gra/i-styrene) [Rabie and Odian, 1977]. 

The amount of grafted styrene is given by the increase in weight of the film. It may also be calculated quite well from the densities of polyethylene (d ), polystyrene (d2), and the graft copolymer (dj) according to the following Eq.3.31 ... 

The composition of the grafted side chain copolymer has also been determined by Sakurada (113) and found to be different from the normal copolymer formed with acrylonitrile and butadiene. With styrene the grafted copolymers were found to be richer in acrylonitrile than the normal copolymer. Similar differences were found by Resting (114) with methyl methacrylate and styrene grafted to cotton and by Odian et al. (115) with grafting mixed monomers to Teflon and to polyethylene. It is believed that one monomer may be preferentially sorbed or diffused faster than the other, leading to a different monomer ratio at the actual site of grafting. 

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