Maliang Zhang

Exfoliated graphite as a filler to improve poly(phenylene sulfide) electrical conductivity and mechanical properties

Electrical conductive poly(phenylene sulfide) (PPS)/exfoliated graphite (EG) composites were prepared by a 1-chlornaphthalene blending method, and the interface effects of EG and PPS on PPS/EG properties were characterized. EG was an excellent nanofiller for enhancing composite conductivity, and PPS/reduced exfoliated graphite oxide (REGO) composite displayed better conductivities in the range from 3.42 × 10−3 to 1.17 × 10−2 S cm−1 as REGO loading increased from 0.5 to 5 wt%. However, PPS/exfoliated graphite oxide (EGO) exhibits a much lower conductivity than composite reinforced with REGO. EGO can be well dispersed into PPS matrix, but the oxygen-containing carbons introduce structural defects on the EGO surface that disrupt the electronic continuum medium and reduce electrical conductivity. However, the incorporated EGO can effectively improve the mechanical properties of PPS, but REGO displays very poor capacity to enhance PPS mechanical performance. When EGO concentration reached 1 wt%, the breaking strength of PPS/EGO achieved the maximum 1.3 × 103 MPa, and this value was 109.5 times that of PPS. The excellent mechanical properties of PPS/EGO were mainly attributed to the heterogeneous nucleation of EGO and the formation of a large number of covalent bonds by EG–thiol adducts.

Effects of hydrogen bonding between MWCNT and PPS on the properties of PPS/MWCNT composites

PPS/MWCNT composites were prepared from polyphenylene sulfide (PPS) and hydroxyl multi-walled carbon nanotubes (MWCNT-OH) or carboxyl multi-walled carbon nanotubes (MWCNT-COOH) by the 1-chloronaphthalene blending method, and the effects of noncovalent interaction between PPS and fillers on the properties of the composites were studied. It was found that MWCNT-COOH could be easily dispersed into PPS, which effectively improved the electrical conductivity and mechanical properties of PPS. With the increase of MWCNT-COOH content from 0.5 to 5 wt%, the conductivity of the PPS/MWCNT-COOH composite rose from 8.8 × 10−3 to 0.35 S cm−1, and the breaking strength and tensile modulus achieved the maximum values of 2189.5 MPa and 294.3 MPa, respectively, when the MWCNT-COOH content was 2 wt%. However, the dispersion of MWCNT-OH into PPS was relatively difficult, and the PPS/MWCNT-OH composite displayed low electrical conductivity and weak mechanical strength. It was concluded that the excellent mechanical properties and electrical conductivity of PPS/MWCNT-COOH were mainly attributed to the strong hydrogen bonding interaction between the carboxyl and sulfide.

Higher UV-shielding ability and lower photocatalytic activity of TiO2@SiO2/APTES and its excellent performance in enhancing the photostability of poly(p-phenylene sulfide)

U–TiO2 is successfully coated with SiO2 and subsequently well modified by APTES, and the core–shell structure exists on TiO2@SiO2 and TiO2@SiO2/APTES, which greatly reduces aggregation of the TiO2 nanoparticles. The photocatalytic activities of U–TiO2, TiO2@SiO2, and TiO2@SiO2/APTES are evaluated using MB decomposition. Nearly 50% of the MB is degraded after 15 min in the presence of the U–TiO2 under UV radiation (300 W), and only 17.44% and 4.18% of the MB is degraded in the presence of the TiO2@SiO2-0.6 and TiO2@SiO2/APTES-1. However, TiO2@SiO2/APTES-0.6 and TiO2@SiO2-0.2 exhibit excellent UV absorbance capacities, and the TiO2@SiO2/APTES-0.6 achieves 80% of the UV-shielding ability of U–TiO2. Poly(p-phenylene sulfide) (PPS) is an easily photodegraded material and TiO2/PPS is more seriously photodegraded than PPS, however, the TiO2@SiO2/APTES nanoparticles can effectively protect the PPS from UV degradation, owing to their lower photocatalytic activities, higher UV-shielding abilities and easy dispersion in the PPS matrix. The breaking strength retention rate of the 1 wt% TiO2@SiO2/APTES/PPS film shows a maximum increase of 38.26%, and the breaking elongation retention rate increased by 41.64% at 2 wt% TiO2@SiO2/APTES loading. These results reveal that the incorporation of the TiO2@SiO2/APTES nanoparticles into the PPS matrix imparts excellent anti-UV properties to the PPS matrix, leading to a mechanical performance improvement.

C 60 as fine fillers to improve poly(phenylene sulfide) electrical conductivity and mechanical property

Electrical conductive poly(phenylene sulfide) (PPS)/fullerene (C60) composites were prepared by 1-chlornaphthalene blending method, and the interface effects of C60 and PPS on PPS/C60 properties were characterized. C60 is an excellent nanofiller for PPS, and 2 wt% PPS/C60 composite displayed the optimal conductivity which achieved 1.67 × 10−2 S/cm. However, when C60 concentration reached 2 wt%, the breaking strength and tensile modulus of PPS/C60 fiber achieved maximum 290 MPa and 605 MPa, and those values were 7.72 and 11.2 times as that of pure PPS. The excellent conductive and mechanical properties of PPS/C60 were attributed to the heterogeneous nucleation of C60 during PPS crystallization, formation of a large number of covalent bond by main C60-thiol adducts and minor C60-ArCl alkylation between C60 outer surface and PPS matrix. At same time, PPS/C60 thermal properties were also investigated.

SiC-fixed organophilic montmorillonite hybrids for poly(phenylene sulfide) composites with enhanced oxidation resistance

SiC-fixed organophilic montmorillonite (OMMT@SiC) hybrid particles, with various proportions of SiC, were fabricated by electrostatic self-assembly in the presence of CTAB. Then, their PPS composites were prepared by melt-compounding. The results showed that the oxidation resistance and mechanical properties of PPS/OMMT@SiC composites was enhanced. When SiC content reached 5 wt%, the oxidation induction temperature of the PPS/OMMT@SiC composite achieved its maximum 513.1 °C, which was 40.9 °C higher than that of pure PPS. Meanwhile, the oxidation induction time of the obtained composite achieved a maximum of 25.2 min. These enhancements were attributed to the existence of the SiC, which prevented the aggregation of OMMT and facilitated OMMT to be further exfoliated in the PPS matrix. The sulfur atoms of PPS formed chemical bonds with SiC, meanwhile, a part of the surface hydroxyl groups of SiC formed hydrogen bonds with PPS, thus weakening the oxidation activity. OMMT and SiC effectively postponed the thermal oxidative degradation of PPS due to synergistic effects.