Structure of blown films of polyethylene/polybutene-1 blends

Interfacial structure and properties of isotactic polybutene-1/polyethylene blends

Polymer blending is one of the most economical and effective techniques for achieving products with high comprehensive performances. However, the immiscibility between polymers results in a weak interface, which is typically the position where material failure starts when an external force is applied. Therefore, understanding and controlling the interfacial structure are important for controlling the failure behavior of polymer blends and achieving advanced materials. In this study, the related work was performed on a crystal/crystal blend of isotactic polybutene-1 and polyethylene (iPB-1/PE). The results indicated that iPB-1 and PE were partially miscible in a wide temperature window (140–220°C), and the phase separation of iPB-1/PE blends was retarded at 180°C, resulting in an increase in the interfacial thickness and interfacial adhesive strength when iPB-1/PE crystallized at a low temperature. In addition, the iPB-1/high-density PE (HDPE) samples exhibited higher interfacial adhesive strength than the iPB-1/linear low-density PE, which was attributed to the relative streamline chain structure and the wide molecular weight distribution of HDPE and improved the interpenetration, crystallization, and miscibility of iPB-1 and HDPE at the interface. During storage at room temperature, the interfacial adhesive strength of iPB-1/PE decreased because of the spontaneous crystal transition of iPB-1.

Crystal structures, crystallization and II-I transition behaviors of iPB-1 in iPB-1/UHMWPE blends - Part 1. Crystal structures and crystallization behaviors

Isotactic polybutene-1 (iPB-1) is of particular commercial interest due to its excellent mechanical performances. The form I polymorph is preferred in most industrial applications, while the form II is kinetically...

The Three-Phase Structure of Random Butene-1/Ethylene Copolymers

The three-phase arrangement of random copolymers of butene-1 with ethylene was investigated and compared with isotactic poly(butene-1) homopolymer (iPB-1). In all the analyzed compositions, isothermal crystallization leads to a three-phase structure, made of one crystal phase and two amorphous fractions that differ in mobility: the mobile amorphous fraction (MAF), made of the polymer chains that relax at the glass transition, and a rigid amorphous fraction (RAF) made of the amorphous segments coupled with the crystal phase. Copolymerization with ethylene leads to a drop in crystal fraction and to a sizable increase of both the RAF, and of the specific RAF, i.e. of the RAF normalized to crystallinity. Analysis of crystal growth rate allowed quantifying the fold surface free energy, which increases of about 50 to 100% in the copolymers, compared to iPB-1 homopolymer. In the butene-1/ethylene random copolymers, ethylene units are mostly excluded from the crystals and accumulate at the crystal/amorphous interphase, thus affecting the rigid amorphous area. The varied composition and higher mobility of the rigid amorphous fraction of the copolymers affects also the Form II to Form I transformation of poly(butene-1) crystals, which occurs with enhanced kinetics in the copolymers, compared to iPB-1 homopolymer.