Injection Molding of Polymers and Polymer Composites.

Injection molding technology has been widely adopted to fabricate multifunctional polymeric components or structural parts for applications in fields such as automotives, electronics, packaging, aerospace, and many others [...

Fabrication of Lightweight Polyimide Foams with Exceptional Mechanical and Thermal Properties.

Lightweight polyimide foams (PIFs) with exceptional thermal resistance and compressive properties are fabricated by heating polyester ammonium salts (PEASs) which are prepared by copolymerizing 4, 4'-diaminobenzanilide (DABA), 4, 4'-diaminodiphenyl methane (MDA) and 3, 3', 4, 4'-benzophenone tetracarboxylic dianhydride (BTDA). Hydrogen bonds are formed between CONH and CO in the PI chains due to the addition of DABA and the melt viscosity of PEAS precursors increase with increasing content of DABA, which is advantageous to bind the foaming gases for cell expansion. The expansion ratio of PEAS precursors is increased from 633% to 1133% when the molar ratio of MDA/DABA is changed from 10:0 to 6:4.

Fabrication of Highly Thermally Resistant and Self-Healing Polysiloxane Elastomers by Constructing Covalent and Reversible Networks.

The fabrication of self-healing elastomers with high thermal stability for use in extreme thermal conditions such as aerospace remains a major challenge. A strategy for preparing self-healing elastomers with stable covalent bonds and dynamic metal-ligand coordination interactions as crosslinking sites in polydimethylsiloxane (PDMS) is proposed. The added Fe (III) not only serves as the dynamic crosslinking point at room temperature which is crucial for self-healing performance, but also plays a role as free radical scavenging agent at high temperatures.

Improving the Ablation Properties of Liquid Silicone Rubber Composites by Incorporating Hexaphenoxycyclotriphosphonitrile.

The ablative properties of epoxy-modified vinyl silicone rubber (EMVSR) composites containing hexaphenoxycyclotriphosphonitrile (HPCTP) have been systematically studied. The strength of the ablation char layer was greatly enhanced with the addition of HPCTP, which induced the formation of a more complete, denser, and thicker char during oxyacetylene ablation tests. Moreover, the HPCTP-containing EMVSR composites demonstrated lower thermal conductivity and pyrolysis rate when compared with those without HPTCP.

Anisotropic and Lightweight Carbon/Graphene Composite Aerogels for Efficient Thermal Insulation and Electromagnetic Interference Shielding.

High-performance and lightweight carbon aerogels (CAs) have attracted considerable attention in various fields such as electrochemistry, catalysis, adsorption, energy storage, and so on. However, finding an environmentally friendly and efficient preparation method and achieving a controllable performance of CAs are still a challenge. Herein, a series of anisotropic carbon/graphene composite aerogels were synthesized by unidirectional freezing of polyamic acid ammonium salt/graphene oxide (PAS/GO) suspension followed by lyophilization, thermal imidization, and carbonization.

Improving the Heat and Ablation Resistance of Silicone Rubber Composites by Incorporating Hollow Microspheres.

For thermal protection materials (TPMs) which are used to protect space vehicles from extreme thermomechanical environments, the thermal conductivity of the original material and the char layer that has formed during ablation plays a significant role in determining the ablation performance. In order to investigate this, in this study, we introduced glass hollow microspheres (GHMs), phenolic hollow microspheres (PHMs), and acrylonitrile-methyl methacrylate copolymer hollow microspheres (AMHMs) into silicone rubber (SR), and the ablation performance of these composites was systematically studied. The thermogravimetric results showed that the residue yield of the SR composites was increased with the incorporation of the hollow microspheres.

Improving Thermal Conductivity of Injection Molded Polycarbonate/Boron Nitride Composites by Incorporating Spherical Alumina Particles: The Influence of Alumina Particle Size.

In this work, the influences of alumina (AlO) particle size and loading concentration on the properties of injection molded polycarbonate (PC)/boron nitride (BN)/AlO composites were systematically studied. Results indicated that both in-plane and through-plane thermal conductivity of the ternary composites were significantly improved with the addition of spherical AlO particles. In addition, the thermal conductivity of polymer composites increased significantly with increasing AlO concentration and particle size, which were related to the following factors: (1) the presence of spherical AlO particles altered the orientation state of flaky BN fillers that were in close proximity to AlO particles (as confirmed by SEM observations and XRD analysis), which was believed crucial to improving the through-plane thermal conductivity of injection molded samples; (2) the presence of AlO particles increased the filler packing density by bridging the uniformly distributed BN fillers within PC substrate, thereby leading to a significant enhancement of thermal conductivity.

Carbonization of Graphene-Doped Isocyanate-Based Polyimide Foams to Achieve Carbon Foams with Excellent Electromagnetic Interference Shielding Performance.

Lightweight carbon foams with excellent electromagnetic interference (EMI) shielding performance were prepared by carbonization process, using isocyanate-based polyimide foams as carbon precursors. The influence of carbonization temperature and graphene-doping on the morphological, electrical and EMI shielding effectiveness (SE) of corresponding carbon foams was studied in detail. Results showed that the addition of graphene was beneficial to the improvement of electrical conductivity and EMI shielding performance of carbon foams.

Crystallization and Microstructure Evolution of Microinjection Molded Isotactic Polypropylene with the Assistance of Poly(Ethylene Terephthalate).

In this work, a series of isotactic polypropylene/poly(ethylene terephthalate) (iPP/PET) samples were prepared by microinjection molding (μIM) and mini-injection molding (IM). The properties of the samples were investigated in detail by differential scanning calorimetry (DSC), Wide-Angle X-ray Diffraction (WAXD), Polarized light microscope (PLM) and scanning electron microscopy (SEM). Results showed that the difference in thermomechanical history between both processing methods leads to the formation of different microstructures in corresponding iPP/PET moldings.

Effect of Hybrid Carbon Fillers on the Electrical and Morphological Properties of Polystyrene Nanocomposites in Microinjection Molding.

The effect of hybrid carbon fillers of multi-walled carbon nanotubes (CNT) and carbon black (CB) on the electrical and morphological properties of polystyrene (PS) nanocomposites were systematically investigated in microinjection molding (μIM). The polymer nanocomposites with three different filler concentrations (i.e.

Pain after discontinuation of morphine treatment is associated with synaptic increase of GluA4-containing AMPAR in the dorsal horn of the spinal cord.

Withdrawal from prescribed opioids results in increased pain sensitivity, which prolongs the treatment. This pain sensitivity is attributed to neuroplastic changes that converge at the spinal cord dorsal horn. We have recently reported that repeated morphine administration triggers an insertion of GluA2-lacking (Ca(2+)-permeable) α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPAR) in the hippocampus.

Group II/III metabotropic glutamate receptors exert endogenous activity-dependent modulation of TRPV1 receptors on peripheral nociceptors.

There is pharmacological evidence that group II and III metabotropic glutamate receptors (mGluRs) function as activity-dependent autoreceptors, inhibiting transmission in supraspinal sites. These receptors are expressed by peripheral nociceptors. We investigated whether mGluRs function as activity-dependent autoreceptors inhibiting pain transmission to the rat CNS, particularly transient receptor potential vanilloid 1 (TRPV1)-induced activity.

Group II metabotropic glutamate receptor activation on peripheral nociceptors modulates TRPV1 function.

Transient receptor potential vanilloid 1 (TRPV1) receptors are critical to nociceptive processing. Understanding how these receptors are modulated gives insight to potential therapies for pain. We demonstrate using double labeling immunohistochemistry that Group II metabotropic glutamate receptors (mGluRs) are co-expressed with TRPV1 on rat dorsal root ganglion (DRG) cells.

Mechanism by which peripheral galanin increases acute inflammatory pain.

Galanin (GAL) is a neuropeptide involved in pain transmission. Intraplantar GAL at low doses enhances capsaicin (CAP)-induced pain behaviors in rat, suggesting an excitatory role for GAL under acute inflammatory conditions. The mechanisms underlying this pro-nociceptive action have not yet been elucidated.

Somatostatin modulates the transient receptor potential vanilloid 1 (TRPV1) ion channel.

Activation of peripheral somatostatin receptors (SSTRs) inhibits sensitization of nociceptors, thus having a short term or phasic effect [Pain 90 (2001) 233] as well as maintaining a tonic inhibitory control over nociceptors [J Neurosci 21 (2001) 4042]. The present study provides several lines of evidence that an important mechanism underlying SSTR modulation of nociceptors is regulation of the transient receptor potential vanilloid 1 ion channel (TRPV1, formerly the VR1 receptor). Double labeling of L5 dorsal root ganglion cells demonstrates that approximately 60% of SSTR2a-labeled cells are positive for TRPV1.

Pro-nociceptive role of peripheral galanin in inflammatory pain.

We investigated the peripheral function of galanin (GAL) in capsaicin (CAP)-induced inflammatory pain. Intraplantar GAL (0.1 ng/microl) alone does not produce nociceptive behaviors.

Somatostatin receptors on peripheral primary afferent terminals: inhibition of sensitized nociceptors.

Somatostatin (SST) is in primary afferent neurons and reduces vascular and nociceptive components of inflammation. SST receptor (SSTR) agonists provide analgesia following intrathecal or epidural administration in humans, but neurotoxicity in the central nervous system (CNS) has been reported in experimental animals. With the rationale that targeting peripheral SSTRs would provide effective analgesia while avoiding CNS side effects, the goals of the present study are to investigate the presence of SSTRs on peripheral primary afferent fibers and determine the behavioral and physiological effects of the SST agonist octreotide (OCT) on formalin-induced nociception and bradykinin-induced primary afferent excitation and sensitization in the rat.