In order to use the glass fiber reinforced polyphenylene sulfide composites (GF/PPS) in high temperature environments, thermal aging performance of two kinds of commercial grade PPS composites, reinforced by 40% glass fiber, PPS‐G40 HM and 1140L4, in thermal aging temperature of 250°C was compared by tensile strength, oxidized layer, color, crystallization and melting behavior. The results showed that tensile strength of GF/PPS composites is significantly decreased with increasing of aging time below 200 h and the tensile strength of aged PPS‐G40 HM is higher than that of aged 1140L4. The thickness of dark color area is increased with increasing of aging time. The thickness of oxidized layer of 1140L4 is thinner than that of PPS‐G40 HM. However, the color of oxidized layer of PPS‐G40 HM is lighter than that of 1140L4. The recrystallization in thermal aging results in the formation of crystal with higher melting point and increased melting temperature of GF/PPS composites. It is found that addition of epoxy resin can increase the initial mechanical property and improve the thermal aging performance of GF/PPS composites. A novel modified GF/PPS composite with higher thermal aging properties was obtained.
Polyacrylate microspheres with a hollow structure were prepared by a facile spray drying method. The effects of spray drying process parameters, including inlet temperature, atomizer rotational speed, and feed speed, on the particle size, bulk density, and morphology of the resultant polyacrylate hollow microspheres were investigated and discussed. The mechanism for the formation of the polyacrylate hollow microspheres was proposed. This facile and scalable method for preparing hollow polymer microspheres is expected to be valuable to prepare various polymer hollow structures for widespread application.
The
mechanism of regulating hydrogen bond organization
for polyamide
6,6 (PA 6,6) by nigrosine was investigated by temperature-dependent
FTIR and in situ synchrotron X-ray diffraction during
cooling/heating processes. The intermolecular interaction between
amide groups and nigrosine was verified by the FTIR spectroscopy method.
Upon melt cooling, the formation of H-bonds is promoted by nigrosine
at the initial stage (regime I) with increased enthalpy change (ΔH
1), which results from denser molecular coils
as the interaction with nigrosine increases the ability to form H-bonds
between adjacent amide groups, while at a lower temperature (regime
II), the ΔH
1 decreases with increasing
nigrosine as nigrosine restrains the mobility of PA 6,6 chains that
retards the formation of H-bonds between nonadjacent amide groups.
Moreover, the ordering arrangement of H-bonds into 2-D hydrogen bond
sheets (H-sheets) is hindered for both the regime I′/II′
stages with decreased ΔH
2 due to
the decreased mobility of chain segments, which retards the nucleation
of PA 6,6 crystallization. The crystal perfection index (CPI) was
investigated by WAXD, and it was found to decrease with the increase
of nigrosine. Combined with microstructure analysis, we proposed that
partial nigrosine can insert between H-sheets, which therefore tunes
the Brill transition behavior of PA 6,6. Overall, the regulation mechanism
of nigrosine on PA 6,6 crystallization has been established via interaction with amide groups to tune the organization
of H-sheets. The retardation effects on crystallization can improve
the flowability of PA 6,6 for high-speed injection molding applications.
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