Wool graft polymer

Another application in macromolecular chemistry is radiation-induced graft polymerization, by which favourable properties of two polymers can be combined. In this process, copolymers of A and B are produced by irradiation of the polymer A in the presence of the monomer B. Examples are graft polymers of polyethylene and acrylic acid or of polyvinyl chloride and styrene. The properties of textiles (cellulose, wool, natural silk, polyamides, polyesters) can also be modified by graft polymerization, for example for the production of weatherproof products. 

However, when proteins or amino acids are present in such monomer solutions, photoinitiation proceeded well. Fibrous proteins such as wool keratin and silk fibroin showed grafted polymer uptakes despite their lack of solubility 20>. 

J.L. Garnett and R.S. Kenyon, Acid Effects in the styrene comonomer technique for radiation grafting to wool, J.Polym. Sci.Polym.Lett.Edo 15 421 (1977). 

As far as no diffusion-controlled system of methyl methacrylate (MMA) is used to synthesize the wool graft copolymer, deposition of polymer occurs preferentially in the orthocortex regions rather than in the para-type cortex regions2>5 a marked difference in the... 

Fig. 8. Electron micrograph of a thin longitudinal section of the 73.0% MMA-grafted fiber (Lincoln wool), showing polymer occurring parallel to the direction of the fiber axis in the paracortex (P), and cuticle (cu), nuclear remnant (nr), and cell membrane complex (cm).

The variation of E and E with temperature for the wool grafted with methyl acrylate (MA) is shown in Fig. 12. With increasing add-on of the polymer, the amount of a-crystallites is decreased. 

It is worthwhile to note that as pointed out in preceding discussion, absorption at around -50 C is totally independent of the contents of the a- and the 3-materials, and also of the grafted polymer. However, some intensity difference is observed among the samples. This seems to be due to the difference in the average cross-sectional area occupied by the wool components in each test sample which consists of exactly 35 single fibers, since the diameter of the wool and longitudinal uniformity is somewhat different from fiber to fiber. 

Radiation grafting is an extremely valuable one-step method for directly modifying the properties of polymers (y,2). The technique has been used with a wide variety of naturally occurring macromolecules such as wool (3) and cellulose (4) and also with many synthetic polymers, particularly the polyolefins (2, 5, 6) ... 

The inclusion of mineral acid in the grafting solution has recently been shown to increase the radiation copolymerisation yield, particularly when styrene is grafted to trunk polymers like wool (3) and cellulose (4) i.e. polymers which readily swell in polar solvents such as methanol. This acid effect is important since for many copolymerisation reactions, relatively low radiation doses are required to yield finite graft. The process is particularly valuable for monomers and/or polymers that are either radiation sensitive or require high doses of radiation to achieve the required graft. 

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. 

In the middle range of styrene concentrations, a compromise is attained where there is sufficient styrene to scavenge all excess methanol radicals not involved in activation of the trunk polymer, yet an excess of monomer remains for grafting by the charge-transfer mechanism proposed by Dilli and Garnett (12) originally for copolymerisation to cellulose (4) and subsequently extended to wool (3), polyolefin (2,5) and PVC (13) systems. The data in Table V are consistent with this interpretation. 

Similar grafting experiments by the emulsion technique were described (34) in the system vinyl chloride/copolymer butyl methacrylate-methacrylic acid and in the reverse system, and also in the system styrene/polyvinyl chloride. In this last case again as in homogenous medium, the inverse process failed (vinyl chloride on polystyrene). Grafted acrylonitrile copolymers were also prepared in order to improve their dyeability, by polymerizing acrylonitrile in emulsion in the presence of many different polymers as polyvinyl alcohol, polymethacrylamide and polyvinylpyrrolidone (119, 120, 121), polyvinyl acetate and polyacrylic acid (115), wool (224,225), proteins (136), etc. 

Properties of fibers can be altered by carrying out interfacial polymerizations on their surfaces. Thus the shrink resistance of wool can be improved by immersing the fiber first in a solution containing one component of a condensation polymer and then immersing it in another solution containing theother component. Polyamides, polyurethanes, polyureas, and other polymers and copolymers may be grafted on wool in this manner. 

The dielectric strength of polyethylene has been measured as a function of additive concentration while in stabilised polymers the depth of degradation was found to be uniform . HALS have been found to be effective stabilisers for UV cured coatings and do not influence the cure rate . Bleached wood pulps can be effectively stabilised by ascorbic acid and wool by hydroxy-benzotriazoles and HALS . Hydroxybenzotriazole stabilisers also protect wood pulp and polyurethanes by co-reaction . The spectroscopic properties of monomeric and polymeric benzotriazoles have also been compared . UV absorbers are effective in clear coats and when grafted to wood . Dihydroxybenzophenone stabilisers inhibit the chain scission in the photodegradation of poly(methoxyacrylophenone) while tin stabilisers have also been found to photostabilise PVC . 

The use of plasma grafting of synthetic polymers on wool for shrink-proofing has also been extensively investigated (97,98). 

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