Polyolefns Journal, Vol. 8, No. 1 (2021) IPPI DOI: 10.22063/poj.2020.2759.1164 LDPE and poly(1-butene) blends: Morphology, crystallinity and rheological properties Reza Poorghasemi Astaneh * and Yousef Jahani Department of polymer processing, Iran Polymer & Petrochemical Institute, Tehran, 14977-13115, Iran Received: 26 August 2020, Accepted: 21 November 2020 ABSTRACT I n this work, the compatibility and crystallinity of low density polyethylene (LDPE) and polybutene-1 (PB-1) blends were studied. Various blends of LDPE/PB-1 containing 5, 10 and 20 wt.% PB-1 were prepared in a co- rotating twin-screw extruder and characterized by scanning electron microscopy (SEM), shear oscillation rheology and wide-angle X-ray diffractometry (WAXD). A matrix-droplet morphology was observed in SEM images, indicating incompatibility of the two polymers in the solid state. Compared to neat LDPE, the relaxation spectra of the blends were broadened, and a slight increase in their relaxation times was observed. The relaxation time of the blends was enhanced by increasing PB-1 content, which was further proved by ftting rheological data in the Carreau-Yasuda model. Deviation of Cole-Cole diagrams from circular shape means that the blend samples were not miscible and the positive-deviation behavior of the complex viscosity and storage modulus from the mixing rule revealed the formation of strong interfacial interactions. The crystallinity of both LLDPE and PB-1 was decreased as a result of blending. The peaks attributed to the form II of PB-1 crystals were eliminated and the peaks related to LDPE were obviously weakened, suggesting to prevent crystallinity of polymers which is associated with a reduction in the total crystallinity percentage for the blend. The reduction of crystallinity was more pronounced in PB-1 phase. Polyolefns J (2021) 8: 21-30 Keywords: Blending; morphology; LDPE; crystallinity; PB-1. * Corresponding Author - E-mail: reza.poorghasemi@gmail.com ORIGINAL PAPER INTRODUCTION Low density polyethylene (LDPE) is a well-known polyolefn which is widely consumed in various in- dustrial applications, especially packaging [1,2]. Poly 1-butene (PB-1), which has received much attention in the last few decades, is a semi-crystalline linear polymer with various crystal forms that is capable of crystallization via chain-folding [3, 4] and high resis- tance against creep and stress cracking [5,6]. Gener- ally, blending is a method for changing the properties of polymers and achieving new properties not seen in single materials. PB-1 is usually incompatible with oth- er polyolefns, resulting in the formation of very weak intermolecular bonds which lead to phase separation of polymers during extrusion [7,8]. This phase separa- tion and immiscibility are necessary factors to achieve acceptable peeling properties [9] in peelable blends or