Grafting experiments

Polyethylene (PE) was a commercial LD type (without additives) with a density of 0.92 and polypropylene (PP) was also a commercial material with a density of 0.91. The polvolefin samples were melt pressed to 1 mm thick sheets (plates) which were wiped clean with acetone and used directly for the grafting experiments with the vapor-phase process. 

Nasmyth What happens with grafting experiments with chicks, in which a little chick wing is grafted onto a bigger chick What do those experiments tell... 

Independently the Mn"5 pyrophosphate complexes were developed as efficient initiators at very low concentrations (1 to 3 mmole/1) for grafting of vinyl monomers to starch. High yields of polymer (over 90%) and very high grafting efficiencies (98-99%) were obtained by reactions for 1 to 3 h at room temperature ( 30°C) in moderately acidic aqueous media (pH = 1.5 to 2.0). Co rresponding grafting experiments have later been carried... 

Grafting Procedures. In the grafting experiments, two procedures were followed. 

Effect of Air. The comparatively small effect of air on the Van de Graaff grafting experiments led to a few similar experiments with cobalt-60 radiation (Table II). In all cases substantial grafting took place in the presence of air. In many cases there was no difference within the... 

By substituting a-methyl styrene for styrene, true grafting conditions can be closely simulated without actual grafting since the radical affinity and other features of the two monomers are rather similar. In this way an approximate measure of the chain scission accompanying the grafting reaction can be made. This has been carried out (102) for the same conditions as the grafting experiments and the results are included in Table 2. It can be clearly seen that considerable chain scission occurs... 

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. 

Cellulose is a partly crystalline and highly hydrogen-bonded substrate. Consequently it is much less accessible to grafting than starch (2). The present paper describes grafting experiments with the Mn -initiator applied to never-dried pulp fibers from wood and to fibers from cellulose derivatives of low degrees of substitution, i.e. cellulosic substrates known to be more accessible to chemical reactions than other cellulose fibers after drying. 

Grafting experiments where an induced scion (sunflower or a day-neutral- or short-day-induced Jerusalem artichoke) is grafted on a short-day stock enhancing tuberization (Daniel, 1934 Schiebe and Muller, 1955 Sibija, 1937 van de Sande Bakhuyzen and Wittenrood, 1951 Wagner, 1932). 

Table VI shows the grafting experiments made with 360-A latices. Grafting runs (32 and 33) which were made from latex 8B (360 A) again showed that the initiator system has a significant part in the properties of the grafted polymer. The persulfate system produced a polymer with almost twice the tensile impact as the pentamine/peroxide system. Run 33 was scaled-up in the pilot plant.

In one series of experiments, collagen films (0.0013 cm and 0.005 cm thick) made from collagen fibrils of about 99% purity were substituted for the collagen powders in the standard grafting experiment. Although it was not possible to measure weight increase in the thinner film specimens, the IR spectra of the treated and solvent-extracted films indicated that polymer was probably grafted onto the substrate. 

Grafting Methods. The procedures used for the grafting runs were modifications of previously reported methods (11, 12, 13). All grafting experiments were performed in quadruplicate in pyrex tubes (15 X 2.5 cm) with styrene/ethanol/additive solutions at The backbone polymer films (4 x 2.5 cm) were fully... 

In order to make use of the dual nature of the growing sites of living polyacetals we have carried out grafting experiments by reacting the latter onto phenyl containing backbones such as polystyrene. One thus expects a Friedel and Crafts type reaction to proceed which will produce the desired graft copolymers. 

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