Inspired by the oriented, gradient, and heterogeneous characters of natural materials, an oriented and gradient cocontinuous structure is designed to obtain excellent mechanical performance via a gradient shear stress and temperature during melt processing. The investigation of hierarchical structure containing phase morphology, crystalline morphology, and lamellae in the cocontinuous structure can clarify the role of gradient shear stress and temperature in promoting gradient and oriented features. Given such oriented and gradient features in the cocontinuous structure, a notable enhancement in the tensile strength, tensile modulus, elongation at break, and impact strength is achieved in the model poly(butylene adipate‐ran‐terephthalate)/poly(butylene succinate) biodegradable cocontinuous blends. Compared with the isotropic cocontinuous structure, homogenous structure and discrete phase structure, oriented and gradient cocontinuous structure provides a promising balance of strength, hardness, and toughness. Local reinforcement is achieved by highly oriented cocontinuous phase, crystal, and lamellae in skin layer. Meanwhile, the toughness is achieved by weakly oriented cocontinuous phase. The tuning of cocontinuous structure with gradient and oriented features is suggested as a new pathway toward the development of “materials systems” with unprecedented mechanical performance.
To increase
the maximum internal pressure that a polyethylene (PE) pipe can withstand,
a novel rotational shear system (RSS) was constructed in this study
to fabricate PE pipes with enhanced hoop strength by applying hoop
shear on the pipes using a rotational mandrel. The microstructure
and morphology with the influences of melt plasticizing temperature
on PE pipes processing under rotational shear were investigated indirectly
using small-angle X-ray scattering and wide-angle X-ray diffraction
(SAXS/WAXD) measurements. In the SAXS patterns, equatorial streaks
and meridional scattering peaks were clearly observed in all three
samples prepared at different melt plasticizing temperatures, 215,
235, and 255 °C. Their presence indicated that shish–kebab
crystals form in rotational shear. Compared to those at
the low melt temperature, the increase in the melt temperature enhanced
the amount and the dimensions of shish formed. However, the shish
also relaxed faster at the high melt temperature. This behavior was
attributed to the enhancement of the molecular chain’s athletic
ability. The hoop tensile strength and the heat resistance of the
pipes peaked at the melt plasticizing temperature of
235 °C, 75.2 MPa, 102.4 °C, up 1 MPa, 0.2 °C (compared
to the 215 °C) and 7.8 MPa, 3.2 °C (compared to the 255
°C). The axial strength increased with an increase
of melt plasticizing temperature. However, the increase of melt plasticizing
temperature worsens the inherent good tensile toughness of PE100 pipes
as the
axial elongation at break decreases.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.