Transcrystallization in fiber-reinforced isotactic polypropylene composites in a temperature gradient

Abstract

Transcrystallization of isotactic polypropylene (iPP) on different fibers (carbon fiber, glass fiber, and aramid fiber) was conducted in a temperature gradient. The Ultra-High-Module carbon fiber (UHMCF), the High-Module carbon fiber, and the aramid fiber (Twaron) showed sufficient nucleation ability to form transcrystallization of iPP in certain temperature ranges. Among them, the UHMCF showed the best nucleation ability. On the contrary, the Intermediate-Module carbon fiber, the HighTenacity carbon fiber, and the E-glass fiber showed too low nucleation ability to form transcrystallization of iPP. One efficient way to induce transcrystallization on these fibers was proved by pulling the fibers in supercooled iPP melts. The interface shear between fiber and supercooled matrix melt on crystallization and the interface temperature gradient between fiber and supercooled matrix melt on crystallization are considered to be two very important factors for the formation of transcrystallization.

Fundamental studies on lignocellulose/polypropylene composites: Effects of wood treatment on the transcrystalline morphology and mechanical properties

“…[12][13][14][15][16] The exact mechanism for transcrystallinity is not fully understood. The fibers may act as heterogeneous nucleating agents and nucle-ate crystallization along the interface with sufficiently high density of nuclei.…”

The Influence of Processing and the Polymorphism of Lignocellulosic Fillers on the Structure and Properties of Composite Materials—A Review

“…Cai et al . [138] reported similar finding for the composites with glass fibres, while Thomason et al . [139] made such observations for aramid, glass and carbon fibres.…”

Crystallization of Polypropylene: Application of Differential Scanning Calorimetry Part Ii. Crystal Forms and Nucleation

“…Transcrystallization, as a nucleation controlled process, depends on thermodynamic conditions, such as crystallization temperature, T c and cooling rate. According to the literature, TCR could be initiated by several factors: topography of the substrates, shear induced crystallization, surface energy of the substrate, adsorption of small molecules, thermal gradients [83][84][85] [88], and the differences are usually related to different constants used, including T m o . TCR development of polypropylene, initiated by melt-shearing and fiber-pulling during crystallization have been followed by many authors in the presence of various crystalline/semicrystalline substrates/fibers, such as talc, PET, polyamide-6, polyamide-66, aramide, carbon, cellulose, cotton and some other polymeric fibers, which are selective α-nucleating agents [89][90][91][92].…”