Melting and nonisothermal crystallization behavior of polypropylene/hemp fiber composites

Abstract

Melting and nonisothermal crystallization behaviors of polypropylene (PP) and PP/hemp fibers (HFs) composites was investigated by differential scanning calorimetry (DSC) technique. The results show that the incorporation of HFs increases both the melting temperature (T m ) and crystallization temperature (T c ) of PP. Moreover, in comparison with PP/HF(70/30) composite, the addition of maleic anhydride-grafted PP (PP-MAH) results in a slight decrease in T m but a significant increase in T c of PP. The higher T c of PP in the composites implies that HFs could act as nucleating agents for the crystallization of PP. Nonisothermal crystallization kinetics analysis was performed using Avrami and Mo models. The values of half-time (t 1/2 ) and rate constant indicate that the crystallization rate increases with the increasing of cooling rate for all the specimens. However, the crystallization rate of PP/HF(70/30) composite is found to be lower than that of PP at a certain cooling rate. Additionally, the composite containing PP-MAH has the lowest crystallization rate. Lower overall crystallization rate of PP/HF composites compared to PP is probably due to sufficiently high density of nuclei, which hinders the transport of PP molecular chains to crystal surface during nonisothermal crystallization. The crystallization activation energies (ÁE) determined by Kissinger method are 207.4 KJ/m 2 , 218.5 KJ/m 2 , and 220.4 kJ/m 2 for PP, PP/HF(70/30), and PP/HF/PP-MAH(70/30/5), respectively.

Thermoplastic Starch-based Composites Reinforced with Rape Fibers: Water Uptake and Thermomechanical Properties

“…Studies have demonstrated that the influence of the reinforcing fibers on crystallization is not only fiber-specific but also strongly dependent upon surface conditions (Ning et al 2012). Nevertheless, it has been generally accepted that in reinforced thermoplastics, natural fibers can act as heterogenous nucleating agents (Arbelaiz et al 2006;Pengfei et al 2011). The capacity of natural fibers to act as nucleating agents might explain the slight increase in crystallinity detected when comparing composites with increasing fiber content.…”

Isothermal crystallization kinetics of polypropylene in melt‐mixed composites of polypropylene and multi‐walled carbon nanotubes

“…It is observed that rate constant k for the PP phase in unmodified MWCNTs based composite (P23Tx composite) is higher than that of P23T5L5Mx composite (see Supporting Information Table 2). It is also to be noted that though the Li‐AHA concentration is increased, however the addition of PP‐ g ‐MA in the same extent in all the modified composition has increased the melt‐viscosity of the composite (due to the melt‐interfacial interaction) that delayed the crystallization process to some extent . Moreover, Prashantha et al observed that PP‐ g ‐MA may also form a coating on the surface of nanotubes that may also decrease the nucleation rate of the MWCNTs for the PP.…”

Non-isothermal crystallization of biodegradable polymer (MaterBi)/polyolefin (PP)/hemp fibres ternary composites

“…During the crystallization of MB, F(t) decreased from 5.42 to 3.37 when the PP is added to MB, indicating that PP act as nucleating agent [35,43,44]. By other hand, when the fibre is added to MB, F(t) increased showing a retarding effect [35,45]. The same applies when the fibre is added to MB/ PP system.…”