A study has been made of polymerization of styrene, which has little solubility in water, in aqueous solution using potassium persulfate as initiator at the polymerization temperature 70 or 80°C. The results were as follows: 1) At the early stage of polymerization, the particle size distribution is broad, but at the later stage becames narrow due to the mutual precipitation of larger or smaller particles in diameter. 2) As the initiator concentration decreases, the amount of precipitated polymer decreases, the stability of particles increases and the particles with same diameter are formed. 3) In the range of the monomer concentration investigated, the amount conversion at 28.5 hr, increases as the initial monomer concentration increases, then decreases through a maximum value. 4) The particle size and the degree of polymerization decrease as the speed of agitation increases.
From the results obtained above, it was evident that the stable particles with narrow particle size distribution were obtained at the conditions of KPS concentration 6.2×10^-4 mol/l, initial monomer concentration 0.871 mol/l, speed of agitation 250 rpm, and polymerization temperature 70°C.
On the other hand by the measurement on electrophoretic mobilities of the particles prepared above, the following results were obtained. The number of charges on a particle surface was equal to the one calculated from the degree of polymerization on the assumption that there were two strong ions at the end of a polymer molecule. From this fact, we led to the conclusions that the termination of polymerization was coupling, ·SO₄^- as the initiator could not enter into the inner part of the particle and consequently existed only on the surface of particles.

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The static and dynamic mechanical properties of the films of polypropylene fractions which encompass a wide range in molecular weight and crystallinity have been studied.
The fractionation was conducted by a conventional column elution method, utilizing kerosine as a solvent and butyl cellosolve as a nonsolvent. Two kinds of method have been used for the fractionation. One, a gradient elution fractionation at 150°C, fractionates according to molecular weight, the other, elution with one solvent at increasing temperatures, separates according to crystallinity.
In general, yield stress, tensile strength and Young's modulus of the fractions depended on the crystallinity, while elongation at break depended not only on the crystallinity but also on the molecular weight.
The temperature dependency of dynamic modulus and loss tangent of annealed fractions as well as whole polymer which had been quenched quickly from the melt, or annealed after the quenching, or cooled slowly from the melt to room temperature was measured in the temperature range from -50°C to +120°C by the vibrating reed method.
The absorption curve of tanδ in the vicinity of room temperature was studied particularly in relation to the fine structure and molecular structure of the polymer.
In the series of experiments with well-annealed fractions, it was observed that the height and width of the absorption band generally became lower and wider in accordance with the increase of crystallinity, and the temperature T_α, where tanδ went through a maximum, shifted to a higher temperature.
Furthermore, in studying the effect of thermal history on the dynamic mechanical properties of the polymer, it was found that a quenched sample without annealing had a higher value of T_α and a wider absorption band than those of well-annealed ones.
It seems that these experimental results can be well interpreted by the following assumptions; 1) the peak of tanδ in the vicinity of room temperature is attributed to microbrownian motion of the main chain segments in the amorphous region as accepted generally; 2) the value of tanδ at a temperature corresponds to the amount of segments which begin to move at the temperature; 3) T_α depends on the extent to which the motion is being restricted by the fine structure of polymers; 4) the width of the absorption band depends on the variety of the extent of the restriction.

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The viscoelastic properties of drawn semi-crystalline polypropylene films have been studied as a function of draw temperature, draw ratio and annealing time. The temperature dependency of dynamic modulus and loss tangent of the films drawn to several times under different conditions has been investigated in a wide range of temperature.
As results it was found that the maximum tan δ value in the α_a-absorption region decreased in accordance with 1) the increase of draw ratio; 2) the decrease of draw temperature; and 3) the decrease of annealing time of the drawn film.
The peak temperature T_α, in tan δ-temperature curve shifted to a higher temperature also in accordance with the above-mentioned three conditions.
The experimental results suggest that if polypropylene film is either annealed for a short time after a drawing at a lower temperature or drawn to a high ratio over 10 times even at a higher temperature, some amounts of internal stress are stored in the molecular segments of the amorphous region so that the micro-brownian motion of the segments is restricted.

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A parameter representing Barus effect, flow broadening effect, (d_max/d₀) was measured for different capillaries of same diameter (d₀=0.45mm) ranging in the length l on polypropylene melt (M_v=2.39×10⁵) at 250°C, where d_max is the maximum diameter of the extruded filaments. The apparant shear modulus obtained from Spencer-Dillon's plots depended on the die-dimension and the extrapolated shear modulus in the limit of l/d₀→0 was 5.6×10⁵ dyne/cm² Plots of {(d_max/d₀)²-1} vs. mean passing time through die (Ziabicki plot) showed the curvature contrary to his prediction. The following (d_max/d₀)-internal stress S_i relation was proposed, _??_where, E: the Young modulus, Δ: a parameter representing the contribution of the chain orientation to (d_max/d₀).(d_max/d₀) decreased with l towards an asymptotic limit at 2l/d₀=30, which was designed as Δ. The good agreement of experimental data with the above equation confirms the validity of proposed mechanism, i. e., one-dimentional elongation at die inlet and successive relaxation during passing through die, in addition to the orientation effect.Δ increased linearly with increasing shear stress. The approximate constant d log Q/d log τ=-1 was obtained, where Q, flow rate in cm³/sec, τ relaxation time of internal stress in sec.

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It is the first purpose to represent shear stress dependence of melt viscosity η(poise) as functions of intrinsic viscosity [η](100 cc/g) and absolute temperature T (°K) for polypropylene which has molecular weight distribution M_w/M_n≈3. As a fundamental equation for this purpose, Dexter's equation
_??_
was used, where η₀ (poise) is the zero shear melt viscosity, τ(dyne/cm²) is the shear stress, and n and K are the parameters.η₀ was found to be given by
_??_
and the following equations were obtained for n and K in the range τ≤10⁶ dyne/cm²:
_??_
where [η] is the value obtained in tetralin at 135°C.
Furthermore, shear stress dependence of the apparent activation energy for flow at constant shear stress ΔE_τ was investigated with these equations. The value ΔE_τ increases with increasing of τ in the range from τ≡10³ dyne/cm² to τ≡10⁵ dyne/cm², and the increasing rate for small value of [η] is greater than that for large one.

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