Mechanical Properties of Solution-Blended Graphene Nanoplatelets/Polyether-Ether-Ketone Nanocomposites

Molecular Origins of Shock Dissipation in Polymer-Based Nanocomposites

To explain the molecular origin of shock dissipation in polymer-based composites, a new method is proposed by absolutely quantifying the relative position between molecular chains, which directly reflects the shock dissipation energy between molecular chains and at the interfaces with nanofillers during mechanical deformation. The effects of nanofiller content and system temperature on energy dissipation were examined based on this newly proposed method, and the differences in energy dissipation between the thermosetting polymer (polydimethylsiloxane) and thermoplastic polymer (polyether-ether-ketone) under identical physical conditions were both studied to validate the reliability of the quantification method proposed in this paper. The present study offers a tool that provides theoretical insights to understand the molecular origins of shock dissipation in polymer composites as well as to facilitate the optimal design of composites with outstanding damping characteristics.

Ion Bombardment-Induced Nanoarchitectonics on Polyetheretherketone Surfaces for Enhanced Nanoporous Bioactive Implants

In spite of the biocompatible, nontoxic, and radiolucent properties of polyetheretherketone (PEEK), its biologically inert surface compromises its use in dental, orthopedic, and spine fusion industries. Many efforts have been made to improve the biological performance of PEEK implants, from bioactive coatings to composites using titanium alloys or hydroxyapatite and changing the surface properties by chemical and physical methods. Directed plasma nanosynthesis (DPNS) is an atomic-scale nanomanufacturing technique that changes the surface topography and chemistry of solids via low-energy ion bombardment. In this study, PEEK samples were nanopatterned by using argon ion irradiation by DPNS to yield active nanoporous biomaterial surface. PEEK surfaces modified with two doses of low and high fluence, corresponding to 1.0 × 1017 and 1.0 × 1018 ions/cm2, presented pore sizes of 15-25 and 60-90 nm, respectively, leaving exposed PEEK fibers and an increment of roughness of nearly 8 nm. The pores per unit area were closely related for high fluence PEEK and low fluence PEEK surfaces, with 129.11 and 151.72 pore/μm2, respectively. The contact angle significantly decreases in hydrophobicity-hydrophilicity tests for the irradiated PEEK surface to ∼46° from a control PEEK value of ∼74°. These super hydrophilic substrates had 1.6 times lower contact angle compared to the control sample revealing a rough surface of 20.5 nm only at higher fluences when compared to control and low fluences of 12.16 and 14.03 nm, respectively. These super hydrophilic surfaces in both cases reached higher cell viability with ∼13 and 34% increase, respectively, compared to unmodified PEEK, with an increased expression of alkaline phosphatase at 7 days on higher fluences establishing a higher affinity for preosteblasts with increased cellular activity, thus revealing successful and improved integration with the implant material, which can potentially be used in bone tissue engineering.

Lightweight and Flexible Graphene Foam Composite with Improved Damping Properties

As an elastomer, PDMS can effectively suppress vibration in various fields in a certain temperature range by its viscoelastic behavior in the vitrification transition region, but the vibration isolation effect is poor at high temperature. In this paper, a three-dimensional graphene oxide (GO) foam is fabricated by solution processing method and freeze-drying techniques. After sequential infiltration synthesis, a GO-foam-reinforced PDMS nanocomposite (GO/PDMS) is fabricated with improved damping ability. By adjusting the content of GO, the micros-tructure of GO foam can be sensitively changed, which is crucial to the damping properties of composites. In this paper, by the dynamic mechanical analysis (DMA) of pure PDMS and five kinds of GO/PDMS composites, it is proved that the GO/PDMS composites developed in this work have reliable elasticity and viscoelasticity at 25 °C, which is 100 °C higher than the applicable temperature of pure PDMS. The storage modulus can reach 3.58 MPa, and the loss modulus can reach 0.45 MPa, which are 1.87 times and 2.0 times of pure PDMS, respectively. This GO-based nanocomposite is an ideal candidate for damping materials in passive vibration isolation devices.