The relation of the molecular weight, the number of branches, the blending ratio, the crystallization conditions and the crystallinity to the crystallite sizes of the various types of polyethylenes were studied. The crystallite sizes normal to the (110) and the (200) planes were measured by the X-ray diffraction method, and the crystallite sizes along the c-axis were obtained by the melting temperature method. The crystallite sizes along the c-axis increase with increases of the molecular weight and crystallinity of linear polyethylenes, and the crystallite sizes normal to the (110) and the (200) planes slightly decrease with increases of the molecular weight, and increase with increases of the crystallinity. It appears that the dependency of the molecular weight on the crystallite sizes is less than that of the number of branches in polyethylenes.
The crystallite sizes decrease with increases of the number of branches, and the effect of the cooling rate on the crystallite sizes decreases with increases of the number of branches in polyethylenes. It is shown for the blends of linear and branched polyethylenes by the measurements of the changes in the crystallinity and the crystallite sizes along the c-axis, that in the blends, there are both types of crystallites consist of linear and branched polymers respectively. The excellent linear relations were found between the crystallite sizes along the c-axis and the blendirg ratios or crystallinity, and the cubic relations between the crystallite sizes normal to the (110) or the (200) planes and the blending ratios or crystallinity in the blended polyethylenes, were also observed. The branched polyethylene can be considered as a plasticizer, facilitating the crystallization of the linear polyethylene above the crystallization temperature of branched polyethylene in the blends.

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Radiation-induced graft-copolymerization onto film of polypropylene was investigated by the method described in the first report. A characteristic effect of alpha-ray for the graftcopolymerization was confirmed from these experimental results. It was found that addition of organic acid to the grafting system make to increase the percentage of grafting and reduce the production of homo-polymers.

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By use of the similar method as shown in the former papers, graft-copolymerization of several monomers on polypropylene fibers was investigated. The fibers were irradiated with neutron in the form dipped in boric acid solution or in pure water. The effect of irradiation on the degree of grafting was found to be much larger than those in the case of films, suggesting that the degree of grafting depends on the surface area of the substance to be grafted. The effect of the changes was also shown by dyeability, tensile strength, and elongation of the samples thus grafted.

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The dilute aqueous solution of partially saponified polyvinyl acetate (PVAc) obtained by ordinary alkali method colored to red as PVAc did by treating with iodine, but that of partially acetylated polyvinyl alcohol prepared from acetic acid and polyvinyl alcohol in homogeneous system did not turn to red with iodine, even if both were equal in acetyl contents.
The investigation of reaction was carried out along with infrared absorption spectrum and the water solubility of partially saponified PVAc films, and it was found that the coloring was caused by maldistributed groups of residual acetyl in a polymer chain. The relation between conditions of saponification and groups of residual acetyl in partially saponified PVAc was made clear by the study.

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Solution polymerization of vinyl acetate with the initiator of hydrogen peroxide-l·ascorbic acid was performed at 30°C to examine the effects of atmosphere, monomer concentration and the nature of solvents on inhibition period, rate of polymerization and degrees of polymerization. Polymerization was inhibited by oxygen. The rate of polymerization and initiator decomposition became maximum at a certain monomer concentration. These rates were affected by addition of water, and decreased with the decrease of dielectric constant of solvents. The degree of polymerization became higher as the both concentrations of monomer and water increased. The polymers having degree of polymerization lower than 1700 showed no degradation by saponification.

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Polymerization of vinyl acetate with the initiator of hydrogen peroxide-l·ascorbic acid was performed in methanol, to examine the effects of initiator concentration and addition of ferrous ion on the rate and degree of polymerization. The rate of polymerization became maximum when the initiator concentration or the concentration ratio of both components be came to a particular value.
Degree of polymerization increased with decreasing of initiator concentration. At both 30°C and 3°C, initial polymerization rate increased but maximum conversion and degree of polymerization decreased with increasing of concentration of ferrous ion. It seemed that the difference of iron compounds had no effect on polymerization, and the acceralating effect of ferrous ion was greater when polymerization rate without this ion was lower. When benzoyl peroxide or azo-bis-isobutylonitrile was used instead of hydrogen peroxide, polymerization rate was low and no acceralation was found by the addition of ferrous ion.

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Kinetic considerations are given for the relationship between polymerization conditions and degree of polymerization (P₀) of initial products based on the results of the previous papers. It was found that the following equation considering the chain termination (containing chain transfer) by the both components of initiator could quantitatively explain the experimental results.
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where C_H and C_A are the chain transfer constants of hydrogen peroxide and l·ascorbic acid respectively.

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