The statistically designed experiments were carried out to study the effects of molding conditions, molecular weights and synthesis methods on the residual stress detected bytetrachloromethane and Rockwell hardness of the injection molded polycarbonate disks.These properties were strongly affected by the mold temperature and the holding pressure.The high resistance to solvent crack was obtained at high mold temperature and at lowholding pressure. High mold temperature and high holding pressure resulted in high Rockwell hardness. The stock temperature and the injection rate did not affect theseproperties. The treatment of the specimen at 120°C not only increased the resistance tosolvent crack and Rockwell hardness, but also extinguished the effect of mold temperatureand holding pressure on these properties. The properties of the specimen molded at highmold temperature were similar to those of the specimen treated at 120°C No correlationbetween the residual stress and the frozen orientation was found.

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The reaction product between isotactic polypropylene and maleic anhydride was crosslinked with zinc acetate, and physical properties of the ionically crosslinked product were studied.The results obtained were as follows:
1) The crosslinking effect was remarkably observed in the melt index of the polymer.This effect was strongly displayed by the reaction product in solvent than that in moltenstate.
2) The ionically crosslinked product showed elevated softening temperature and improvedthermal stability.
3) Crosslinking effects on dynamic viscoelasticity and tensile stress-strain propertieswere hardly observed.Some other interesting properties observed were as follows:
i) Maleic anhydride introduced into isotactic polypropylene was effective in increasingthe oxidative stability of the reaction product.
ii) When isotactic polypropylene was treated with benzoyl peroxide, the spherulites formedin the product were very small.

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Viscoelastic behaviors of crystalline α-olefin copolymers were studied using the ultrasonic wave method. The samples studied here include ethylene-propylene block or random copolymer prepared by using Ziegler catalyst and some polyethylene-polypropylene blends.The ultrasonic wave absorptions and the sound velocities were measured at frequencies of 5 and 9 Mc/s and in a temperature range of 218353°K.
It was found that mechanical properties studied by ultrasonics for ethylene-propylene block copolymers were different from those of random copolymers and blends, and changed distinctively with the propylene content and with the number of repeated units in copolymers.
It is believed that the characteristics of block copolymers are associated with the mobility of molecular segments containing ethylene-propylene junctions.

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In order to obtain further information on the solid state post-polymerization of trioxane induced by γ-rays, the fractionation of polyoxymethylene is carried out by stirring the p-chlorophenol solution.
The polymer obtained at a low conversion contains a small amount of high polymer fraction and the amount of high polymer increases with increasing the conversion. This can be explained qualitatively on the assumption that the rate of propagation is smaller than that of the initiation reaction and that the life-time of the propagating species is rather long.
It is found that the molecular weight distribution shows two peaks, of which the distribution in the low molecular weight range is somewhat broad. These results in the molecular weight distribution may be explained because the rates of initiation, propagation and termination can be expected to fairly differ appreciably in different crystal environment.

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Melt polycondensation of aliphatic mixed diamine and terephtalic acid results in the gel formation during the course of polycondensation, which causes disadvantage for themelt spinnability of the polyamide (MED-T nylon). The gelation may relate with theimino linkage formation between two amino groups (-CH₂NH₂+-CH₂NH₂→-CH₂NHCH₂) during polycondensation. Therefore, imino group content in the polymer wasdetermined by titrating secondary amine in the hydrolysis product of the polyamide.Paperchromatographic analysis could also serve to find the presence of a linear triamine.
A considerable amount of imino group was found in the polyamide from terephthalic acid, while the polyamide from adipic acid had a lower content of imino group. This differentbehavior may relate with either the acidity and the rate of amide formation of dicarboxylicacid. A model reaction of carboxylic acid with hexamethylenediamine led to the conclusionthat aromatic dicarboxylic acids have essential disadvantage for the preparation oflinear polyamides by means of melt polycondensation.

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Polyvinyl alcohol (PVA) was partially acetalized with ο-benzaldehyde-, ρ-benzaldehyde-, α-cinnamaldehyde- or β-butyraldehyde- sulfonic acid. The residual hydroxyl groups in thesemodified PVA molecules were acetalized with aldehydes such as acetaldehyde in water orwater-organic solvent mixtures using their own sulfonic acid groups as catalysts. Rateconstants of the selfcatalytic acetalization (k_s) were compared with those of acetalizationof unmodified PVA carried out under the same condition using external catalysts such ashydrochloric acid (k_e). As a second example of the selfcatalytic reactions of polymers, PVAwas partially acetylated and simultaneously acetalized with β-butyraldehyde sulfonic acid, the acetyl groups of the thus obtained modified PVA's were hydrolyzed in water usingtheir own sulfonic acid groups as catalysts. Rate constants of the selfcatalytic hydrolysis (k_s) were compared with those of hydrolysis of partially acetylated PVA's carried out under thesame condition with hydrochloric acid (k_e). Ratios of the rate constants (k_s/k_e) of theboth reactions were generally greater than unity and increased with decreasing concentrationof the polymers. These self-catalytic reactions are a strong support for our argumentthat local concentrations of functional and catalyst groups on a polymer molecule is effectivefor the enhancement of the reaction rates under conditions that the bulk concentrations offunctional and catalyst groups are kept constant.

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