Abstract:A low molecular weight prepolymer with reactive end groups was annealed at temperatures between 200 and 245°C to obtain kinetic parameters for solid‐state polymerization of poly(ethylene naphthalate) (PEN). An equation was developed to describe the relationships among time, temperature, and final molecular weight for PEN. The intrinsic viscosity and melting point during polymerization were used to monitor the molecular weight and the thermal stability of the resulting resins. The effect of moisture concentrati… Show more
“…By monitoring the intrinsic viscosity as a function of time at various solid state temperatures, an empirical relation for the change of the molecular weight has been established, 27 i.e. …”
“…By monitoring the intrinsic viscosity as a function of time at various solid state temperatures, an empirical relation for the change of the molecular weight has been established, 27 i.e. …”
“…The main factors that influence the reaction rate of SSP include reaction temperature, ,,− initial end-group concentration, ,,− chip size, transport rate of byproduct (gas flow rate), − ,,,,,− crystallinity, ,,,,,− and so on.…”
Polyester industrial yarn has high
tenacity by increasing the degree
of orientation and crystallinity via the melt spinning of high-molecular-weight
(high-M
w) polymer. Solid-state polymerization
(SSP) is very important to get higher M
w; it is composed of a crystallization step, which prevents sticking
among the chips, and a polycondensation step at solid state. Spherulites
in the chip were observed using polarized optical microscopy (POM)
in the crystallization step. We studied the effect of crystallization
conditions on spherulite size by SSP and determined that the higher
the crystallization temperature, the larger the size and deviation
of the spherulite. We also observed relatively uniform sizes in the
batch process but various sizes in the continuous process. The latter
difference in the size and shape of the spherulite would cause differences
in the diffusivity of both the end-group and the byproduct, thus resulting
in large deviations in M
w and viscosity.
Thus, when the crystallization temperature in the continuous process
was reduced by 15 °C to decrease the differences of thermal and
physical impact history among chips, the sizes and shapes of spherulites
consequently became uniform and the difference of M
w decreased because of the reduced crystallization rate
difference among chips by decreased temperature deviation in the crystallization
reactor. We could get more uniform polymer with reduced variations
of M
w, intrinsic viscosity (IV), and melt
viscosity (MV). Finally, the max draw ratio, which represents the
drawability in melt spinning, increased from 6.28 to 6.71. It indicated
that fluffs in yarn could be reduced, and downstream processabilities
such as warping and weaving could be enhanced by increased drawability.
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