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The mechanical properties and microstructure of injection molded isotactic polypropylene parts with high orientation before and after annealing are analyzed. The mechanical properties of the annealed samples are improved effectively. Through thorough analysis of various structural characterizations, a microstructural model based on the fact that the total length of long period kept constant to analyze the variation of mechanical properties is proposed. It is suggested that the increase of overall crystallinity, the recombination of crystalline phase, and the increase of amorphous phase, respectively, are beneficial for the improvements of the strength, stiffness, and toughness of annealed samples.

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A bipolar membrane (BPM) of carboxymethyl cellulose (CMC) and chitosan (CS) with superior performance was prepared based on the macromolecules containing metal elements. A carboxymethyl cellulose cation layer was modified by copper phthalocyanine 16 ) to improve its ion exchange capacity as well as cation transfer rate and promote water splitting at the intermediate layer. Chitosan was crosslinked with acetyl ferrocene to prepare the anion layer. A casting method was used to prepare the BPM which showed excellent physical and chemical properties after modification. To improve the compatibility of the anion-exchange layer and cation-exchange layer, polyethylene glycol (PEG) was blended with both the CMC and CS. Scanning electron microscopy (SEM) images illustrated a structure that consisted of an anion layer and a cation layer that were closely combined with each other. The swelling results implied a proper hydrophilic performance and good shape stability in an alkali solution ([OH − ]≤10 mol·L −1 ) of the BPM. After modification, the BPM with the metal elements exhibited good thermal stability, as shown by the thermogravimetry (TG) results. Compared with the BPM that was unmodified, both the AC impedance and the working voltage were decreased sharply. Furthermore, the modified BPM exhibited higher ion penetrability which is beneficial for its wide application.

In this work, multiwalled carbon nanotubes (MWCNTs), as reinforcing agent, were blended with linear low-density polyethylene (LLDPE), then molded by hot compression molding to prepare LLDPE/MWCNTs composites. Tensile tests indicate that the strength, Young's modulus, and toughness are all improved for LLDPE/MWCNTs composites containing 1 and 3 wt % MWCNTs. Compared with LLDPE, the Young's modulus of LLDPE/MWCNTs composites rises from 144.8 to 270.8 MPa at 1 wt % MWCNTs content. At the same time, increases of 18.5% in tensile strength and 16.6% in yield strength are achieved. Additionally, its toughness is enhanced by 26.7% than that of LLDPE. Microstructure characterizations, including differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy were performed to investigate the variations of microstructure and further to establish the relationship between microstructure and mechanical properties. Homogeneous dispersion of MWCNTs, network formation, and development of an oriented nanohybrid shish-kebab structure contribute to the enhanced strength and toughness. The increased crystallinity is beneficial to the reinforcement and increased modulus. Additionally, the thermal stability of the LLDPE/MWCNTs composites is enhanced as well. This work suggests a promising routine to optimize polymer/MWCNTs composites by tailoring the structural development.

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