The β-nucleated polypropylene (β-PP) and polypropylene (PP) were coextruded to form the alternating layered structure with different layer number. During the isothermal crystallization of layered samples at 130°C, the high-density β-nuclei at the two-dimensional layered interfaces between β-PP and PP layers grew asymmetrically. In the β-PP layer, the growth of β-lamellae was quickly terminated by other β-spherulites. In the PP layer, because the formation of α-crystals delayed, all β-lamellae could freely grow perpendicular to the interface and finally form the β-transcrystallinity (β-TC) layer with about 25 μm thickness. If the thickness of PP layer was lower than 50 μm, PP layer would be almost occupied by β-TC. The ordered arrangement of β-TC led to an orientation of molecular chains of β-TC layer parallel to the interface. With the increase of layer number, the content of β-TC and orientation degree of layered samples increased. This paper provided a simple and effective method to prepare continuous, highly ordered and content-controlled β-TC. As a result, the sample with high content of β-TC exhibited good mechanical properties.

Continuous and orderly αor β-transcrystallinity plays a significant role in achieving excellent performance for isotactic polypropylene (iPP). However, this special structure is difficult to obtain through conventional methods.Here, continuous and orderly αor β-transcrystallinity was constructed in an iPP layer of an eight-layer iPP/α-iPP sample using a layered design and temperature control. The crystalline structure and morphology of the iPP layer were greatly influenced by the cooling rate. The iPP layer contained a large amount of β-transcrystallinity and a small amount of αtranscrystallinity when the sample was cooled to 130 °C for isothermal crystallization at a cooling rate of 50 °C/min. However, only α-transcrystallinity was formed in the iPP layer when the cooling rate was 1 °C/min. The different crystallization mechanisms are discussed in this paper. In addition, the experimental results showed that β-transcrystallinity could simultaneously improve both the tensile and impact properties.

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The high demand for fresh-like characteristics of vegetables and fruits (V&F) boosts the industrial implementation of high hydrostatic pressure (HHP), due to its capability to simultaneously maintain original organoleptic characteristics and to achieve preservative effect of the food. However, there remains great challenges for assuring complete microbial inactivation only relying on individual HHP treatments, including pressure-resistant strains and regrowth of injured microbes during the storage process. Traditional HHP-assisted thermal processing may compromise the nutrition and functionalities due to accelerated chemical kinetics under high pressure conditions. This work summarizes the recent advances in HHP-based combination strategies for microbial safety, as exemplified by several emerging non-thermally combined patterns with high inactivation efficiencies. Considerations and requirements about future process design and development of HHP-based combination technologies are also given.