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In the region of thermally conductive polymer composites, forcing anisotropic fillers into the highly oriented structure is the most effective method to improve thermal conductivity and mechanical properties simultaneously. However, up to now, such highly oriented structure was mainly achieved in low viscosity polymer matrix or solutions. For the purpose of expanding the range of applications, in the present work, a new strategy, the consecutive and powerful shear flow field, was applied to introduce highly oriented boron nitride (BN) into high viscosity polymer matrix. Results indicated that BN was almost totally oriented along the extrusion plane; as a result, the anisotropic index and thermal conductivity of the composite filled with 40 wt % BN reached as high as 480% and 3.57 W/(m K), respectively. Furthermore, compared with the samples with randomly oriented BN, elongations at break were improved more than 50-fold at the same filler content. Finite element analysis was also applied to systematically investigate the effect of the orientation direction of BN on heat dissipation property of the composites, and results indicated that orienting the longitudinal direction of BN parallel to the heat source is the best way to reduce the heat source temperature to a low level. Therefore, the simple, consecutive, and environmentally friendly melt extrusion with powerful shear flow field is an outstanding method to fabricate high efficiency thermally conductive composites, and the simulative results also have important significance on designing such composites for different applications.

By combining experiments and MD simulation, the relationship between hydrogen bond evolution and damping property variation of TPU was revealed.

As a biobased and biodegradable polyester, polylactide (PLA) is widely applied in disposable products, biomedical devices, and textiles. Nevertheless, due to its inherent brittleness and inferior strength, simultaneously reinforcing and toughening of PLA without sacrificing its biodegradability is highly desirable. In this work, a robust assembly consisting of compact and well-ordered microfibrillar crystalline superstructure (FCS) surrounded by slightly oriented amorphism, is achieved by a combined external force field. Unlike the classic crystalline superstructures such as shish-kebabs, cylindrites, and lamellae, the newfound FCS with diameter of about 100 nm and length of several tens of micrometers is aggregated with well-aligned crystalline nanofibers. FCS can serve as discontinuous fiber to self-reinforce the amorphous PLA; more importantly, FCS can also act as rivets to pin the propagating fibrillar crazes leading to the formation of dense fibrillar crazes during stretching, which dissipates much energy and translates the failure of PLA from brittle to ductile. Consequently, PLA with FCS exhibits exceptionally simultaneous enhancement in ductility, strength, and stiffness, outperforming normal PLA with increments of 728, 55, and 70% in elongation at break, strength, and modulus, respectively. Therefore, FSC exhibits competitive advantages in achieving high-performance PLA even for other semicrystalline polymers. More significantly, this newfound crystalline superstructure (FCS) provides a new structural model to establish the correlation between structure and performance.

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