Complex Effects of Hemp Fibers and Impact Modifiers in Multiphase Polypropylene Systems

Abstract

Natural fibers-reinforced polymer composites have progressed rapidly due to their undeniable advantages. Most of the commercial polypropylene (PP)-based materials are characterized by either high impact toughness or high stiffness, while the manufacture of PP composites with both good toughness and stiffness is challenging at present. In this work, poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) and poly(styrene-b-butadiene-b-styrene) (SBS) copolymers were used in different amounts as modifiers in PP/hemp fibers (HF) composites, with the aim to use them for electrical vehicle parts. The interface in these multiphase systems was controlled by the addition of maleated polypropylene (MAPP). SEBS and SBS showed different effects on the elongation at break of the blends and the corresponding composites due to the HF that stiffened the multiphase systems. Similarly, a different action of MAPP was observed in the composites containing SEBS or SBS: higher Young’s and storage moduli were obtained for the composite containing SBS, while greater elongation at break and impact strength values were recorded for the SEBS-containing system. In addition, a remarkable dispersion in the MAPP-containing composite and two times smaller average particle size were revealed by the SEM analysis for the SEBS particles compared to the SBS ones. The higher affinity of SEBS for PP compared to that for SBS and the different morphological characteristics of the systems containing SEBS and SBS may explain the different effects of these impact modifiers on the mechanical properties of the composites. The composites developed in this work were designed as substitutes for the fully synthetic polymeric materials or metal components used in the manufacturing of automotive parts.

The Effect of Thermoplastic Elastomer and Fly Ash on the Properties of Polypropylene Composites with Long Glass Fibers

“…To distinguish the samples, two relaxations can be seen in the loss factor vs. temperature and loss modulus vs. temperature curves of PP composites reinforced with glass fiber or a mixture of glass fiber and treated fly ash. Another relaxation can be seen in Figure 5d exclusively on the curves for composites containing elastomer, PP-25G-E and PP-25G-C-E. E peak 1 is only found in PP-25G-E and PP-25G-C-E because it corresponds to the Tg of the elastomer (olefin block) [52], whereas E peak 2 is associated with the glass transition of PP (Tg) and E peak 3 is associated with the lamellar slip and rotation in the crystalline phase of PP [53]. The tan δ curves of the samples exhibit three distinct relaxation peaks that correspond to the peaks of the loss modulus.…”

The Study Influence Analysis of the Mathematical Model Choice for Describing Polymer Behavior

“…There are different approaches to building qualitative models of composites. One of them is to describe the properties of the matrix and the inclusions or reinforcing elements separately from one another [22,23].…”

Properties of Composites Based on Recycled Polypropylene and Silico-Aluminous Industrial Waste

“…All measurements were carried out with a flow rate of 25 mL/min and under 5.0-grade helium. The melting temperature, Tm (maximum of the melting endotherm), the crystallization temperature, Tc (maximum of the crystallization exotherm), and the degree of crystallinity, Xc, calculated according to the method presented elsewhere [25], were analyzed.…”

“…However, the samples can be differentiated based on the two relaxations observed in the loss modulus vs. temperature and loss factor vs. temperature curves for the PP and PP composites (Figure 9d). The first relaxation is related to the glass transition of the PP (Tg), and the second is related to lamellar slip and rotation in the crystalline phase of the PP [25]. The highest peak of the loss modulus curve, associated with Tg, is observed at about 5 • C. The PP composites showed higher Tg values by 1-1.3 • C compared to the PP, indicating a good interaction between the components.…”