Interfacial crystallization and mechanical property of isotactic polypropylene based single-polymer composites
Graphical abstract
Introduction
In the past few decades, isotactic polypropylene (iPP) has been the major polymeric construction materials in the light of its impressive consumption. One outstanding advantage is its excellent comprehensive properties, including easy processing, low manufacturing cost and so on [1]. Unfortunately, the intrinsic low mechanical strength of iPP limits its further applications. Hence, considerable efforts have been made in order to further improve its mechanical properties. One of the most common methods is by embedding various fibers (carbon, clays, glass, etc.) in the iPP matrix to produce composites [2], [3], [4], [5]. However, two main problems must be avoided if the heterogeneous fibers are added in the thermoplastic matrix. The first is the interfacial residual stress due to different thermal expansion between heterogeneous fibers and polymer matrix [4]. The second is the weak interfacial adhesion owing to the incompatibility among the heterogeneous components [6]. The interfacial interaction between fiber and matrix is a crucial prerequisite for determining the mechanical property [7]. Among the various methods (including the increased specific surface area of fibers, improved chemical activity of fiber surfaces, and matched compatibility) to enhance the interfacial interaction in the iPP/fibers composites [8], [9], [10], [11], [12], [13], [14], interfacial crystallization such as transcrystallinity (TC) [15] is regarded as an efficient and economical approach [16]. Moreover, TC around the fiber, possessing better load transfer ability than amorphous layers, is believed to be of crucial significance to improve the interfacial interaction between matrix and fibers [17], [18].
On the other hand, in light of recyclability, the presence of heterogeneous additives or inclusions, such as glass fibers, clays and magnetic nanoparticles, is an inevitable obstacle for polymer based composites. Hence, the composite systems with the matrix and the fiber being from the same polymer are preferable candidates. In other words, these systems mean mono-component composites or single-polymer composites (SPCs). The concept of SPCs is not new, which was proposed for the first time by Capiati and Porter four decades ago [19]. Such self-reinforced systems have specific economic and ecological advantages. This can be understood as follows: 1) desired mechanical property can be achieved as a result of the occurrence of TC and good interfacial adhesion for the semicrystalline polymer matrix; 2) SPCs show undoubtedly advantages in terms of recyclability. Hence, up to now, many preparation methods of iPP based SPCs have been proposed [20], [21], [22] and summarized in the recent literature [23], [24], [25]. However, although the influences of crystallization temperature, fiber introduction temperature, fiber molecular weight, and matrix molecular mass on the interfacial morphology of iPP based SPCs have been investigated [26], [27], [28], [29], the effect of interfacial features on the mechanical properties of SPCs has been rarely reported up to date.
In this paper, iPP fiber was introduced into iPP film to prepare iPP based SPCs. The interfacial features of SPCs and their tensile strength as a function of introduction temperature were investigated. The underlying origin for the improved tensile strength of SPCs is discussed based on the results of polarized optical microscopy (POM), scanning electron microscope (SEM), wide-angle X-ray diffraction (WAXD).
Section snippets
Materials
The iPP (T30S) employed in this work was a commercial grade iPP, provided by Dushanzi Petroleum Chemical Co. Ltd, China. Its melt flow index (MFI) and weight-average molecular weight (Mw) were 3.0 g/10 min (230 °C, 21.6 N) and 39.93 × 104 g/mol, respectively.
Melt spinning
The iPP fibers used in this work were melt spun by using a mini co-rotating twin-screw extruder (SJSZ-10A, Wuhan Ruiming plastic and mechanical Co. Ltd) with a length-to-diameter ratio (L/D) of 16 and a die diameter of 3.0 mm. The
Influence of introduction temperature on molecular orientation of iPP fibers
The absorbance intensity difference between the parallel- and perpendicular-polarized FTIR spectra can be employed to evaluate the molecular orientation level [31], [32]. Here, to qualitatively evaluate the effect of different thermal history on the orientation level of iPP fibers, polarized FTIR test was carried out. Fig. 2 shows the polarized FTIR spectra of F-145, F-160, F-165, F-168, F-172 and F-175, respectively. It is clear to find notable difference between the absorbance intensities of
Conclusions
The iPP based SPCs have been successfully prepared by introducing iPP fibers into the molten or supercooled homogeneous matrix. The induced TC by homogeneous fiber as a function of Ti was observed by means of POM. Then the relationship between interfacial features and mechanical property of SPCs was studied. The results show that the tensile strength of SPCs firstly increases and reaches a maximum value at Ti = 160 °C, then decreases with the increase of the Ti. Based on the detailed analysis,
Acknowledgments
We express our great thanks to the National Natural Science Foundation of China (51173171, 11172271), the Major State Basic Research Projects (2012CB025904), Plan for Scientific Innovation Talent of Henan Province and Opening Project of State Key Laboratory of Polymer Materials Engineering (Sichuan University). Z. Guo appreciates the start-up funds from University of Tennessee.
References (43)
- et al.
Transcrystallization of polypropylene on carbon fibres
Polymer
(1997) - et al.
Experimental detection of a transcrystalline interphase in glass-fibre/polypropylene composites
Compos Sci. Technol.
(2000) - et al.
Release of interfacial thermal stress and accompanying improvement of interfacial adhesion in carbon fiber reinforced epoxy resin composites: induced by diblock copolymers
Compos. Part A
(2012) - et al.
Influence of alkali treatment on the interfacial and physico-mechanical properties of industrial hemp fibre reinforced polylactic acid composites
Compos. Part A
(2010) - et al.
Effect of fibre treatments on interfacial shear strength of hemp fibre reinforced polylactide and unsaturated polyester composites
Compos. Part A
(2011) - et al.
Realizing the enhancement of interfacial interaction in semicrystalline polymer/filler composites via interfacial crystallization
Prog. Polym. Sci.
(2012) - et al.
Polymer transcrystallinity induced by carbon nanotubes
Polymer
(2008) - et al.
Self-reinforced polymeric materials: a review
Prog. Polym. Sci.
(2010) - et al.
Development of self-reinforced polymer composites
Prog. Polym. Sci.
(2012) - et al.
Low velocity impact performance of recyclable all-polypropylene composites
Compos Sci. Technol.
(2006)
Tensile mechanical and perforation impact behavior of all-PP composites containing random PP copolymer as matrix and stretched PP homopolymer as reinforcement: effect of β nucleation of the matrix
Compos. Part A
Influence of crystallization temperature on the morphologies of isotactic polypropylene single-polymer composite
Polymer
Shear-induced interfacial sheath structure in isotactic polypropylene/glass fiber composites
Polymer
Polymer transcrystallinity induced by carbon nanotubes
Polymer
Interfacial crystallization enhanced interfacial interaction of poly (butylene succinate)/ramie fiber biocomposites using dopamine as a modifier
Compos Sci. Technol.
Mechanical properties of sisal fiber reinforced high density polyethylene composites: effect of fiber content, interfacial compatibilization, and manufacturing process
Compos. Part A
Effect of micromorphologic features on the interfacial strength of iPP/Kevlar fiber microcomposites
Polymer
Processing of single polymer composites using the concept of constrained fibers
Polym. Compos
Transcrystallized interphase in thermoplastic composites
J. Mater Sci.
Effects of reinforcing fibers on the crystallization of polypropylene
Polym. Eng. Sci.
The concept of one polymer composites modelled with high density polyethylene
J. Mater Sci.
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