Injectable, in situ-gelling magnetic composite materials have been fabricated by using aldehyde-functionalized dextran to cross-link superparamagnetic nanoparticles surface-functionalized with hydrazide-functionalized poly(N-isopropylacrylamide) (pNIPAM). The resulting composites exhibit high water contents (82-88 wt.%) while also displaying significantly higher elasticities (G' >60 kPa) than other injectable hydrogels previously reported. The composites hydrolytically degrade via slow hydrolysis of the hydrazone cross-link at physiological temperature and pH into degradation products that show no significant cytotoxicity. Subcutaneous injections indicate only minor chronic inflammation associated with material degradation, with no fibrous capsule formation evident. Drug release experiments indicate the potential of these materials to facilitate pulsatile, “on-demand” changes in drug release upon the application of an external oscillating magnetic field. The injectable but high-strength and externally-triggerable nature of these materials, coupled with their biological degradability and inertness, suggest potential biological applications in tissue engineering and drug delivery.
We have elucidated a cost effective fabrication technique to produce superhydrophobic polyvinylidene fluoride (PVDF/DMF/candle soot particle and PVDF/DMF/camphor soot particle composite) porous materials. The water repellent dry composite was formed by the interaction of non-solvent (methanol) into PVDF/carbon soot particles suspension in N,N-dimethylformamide (DMF). It is seen that longer quenching time effectively changes the surface morphology of dry composites. The nano broccoli like hierarchical microstructure with micro or nano scaled roughen surface was obtained for PVDF/DMF/camphor soot particle, which reveals water contact angle of 172° with roll off angle of 2°. However, composite coating of PVDF/DMF/candle soot particle shows nano cauliflower like hierarchical, which illustrates water contact angle of 169° with roll off angle of 3°. To elucidate the enhancement of water repellent property of PVDF composites, we further divulge the evolution mechanism of nano cauliflower and nano broccoli structure. In order to evaluate the water contact angle of PVDF composites, surface diffusion of water inside the pores is investigated. Furthermore, the addition of small amount of carbon soot particles in composite not only provides the crystallization of PVDF, but also leads to dramatical amendment of surface morphology which increases the surface texture and roughness for superhydrophobicity.
Polymer composites consisted of small hydrophilic pockets homogeneously dispersed in a hydrophobic polymer matrix are important in many applications where controlled release of the functional agent from the hydrophilic phase is needed. As an example, a release of biomolecules or drugs from therapeutic formulations or release of salt in anti-icing application can be mentioned. Here, we report a method for preparation of such a composite material consisted of small KCOOH salt pockets distributed in the styrene-butadiene-styrene (SBS) polymer matrix and demonstrate its effectiveness in anti-icing coatings. The mixtures of the aqueous KCOOH and SBS-cyclohexane solutions were firstly stabilized by adding silica nanoparticles to the emulsions and, even more, by gelation of the aqueous phase by agarose. The emulsions were observed in optical microscope to check its stability in time and characterized by rheological measurements. The dry composite materials were obtained via casting the emulsions onto the glass substrates and evaporations of the organic solvent. Composite polymer films were characterized by water contact angle (WCA) measurements. The release of KCOOH salt into water and the freezing delay experiments of water droplets on dry composite films demonstrated their anti-icing properties. It has been concluded that hydrophobic and thermoplastic SBS polymer allows incorporation of the hydrophilic pockets/phases through our technique that opens the possibility for controlled delivering of anti-icing agents from the composite.
Most of aquatic products are highly susceptible to deterioration and microbial spoilage during storage. A frequently used method to preserve them is achieved by cold storage. However, products preserved by traditional frozen method are prone to suffer undesired frozen damage. It will significantly impair postmortem quality of the products. To solve the problem, this work established a novel superchilling storage-ice glazing (SS-IG) approach using chitosan-catechin composite material. It can maximize the postmortem quality of preserved products during storage with avoiding the frozen damage.
The aim of this review was to compile recent evidence related to nanofilled resin composite materials regarding the properties and clinical performance. Special attention was given to mechanical properties, such as strength, hardness, abrasive wear, water sorption, and solubility. The clinical performance of nanocomposite materials compared with hybrid resin composites was also addressed in terms of retention and success rates, marginal adaptation, color match, and surface roughness. A search of English peer-reviewed dental literature (2003-2017) from PubMed and MEDLINE databases was conducted using the terms “nanocomposites” or “nanofilled resin composite” and “clinical evaluation.” The list was screened, and 82 papers that were relevant to the objectives of this work were included in the review. Mechanical properties of nanocomposites are generally comparable to those of hybrid composites but higher than microfilled composites. Nanocomposites presented lower abrasive wear than hybrids but higher sorption values. Their clinical performance was comparable to that of hybrid composites.
In this study, ground rice husks (GRH) in combination with polyvinyl-alcohol (PVA) fiber were used to produce low-cost and high-quality hybrid cementitious composites. Different amounts of GRH (2.5, 5.0, 7.5 and 12.5% in weight of cement) were added to the concrete. The work presented in this paper provides an insight into the use of an agricultural waste as effective additive in cement based materials. The properties of resultant cementitious composites including density, water absorption, flexural behavior and compressive strength were investigated. The results have shown that incorporation of ground rice husk in combination with PVA fiber can be effective in improvement of the flexural properties of cementitious composite. The study explored the effectiveness of this type of agricultural waste as a beneficial material in fine aggregate concrete materials.
The design of organic-inorganic hybrid composites has revolutionized application-driven materials design. Here, we show how hierarchically structured, 3D-printed ABS polymers can be surface-functionalized with lacunary polyoxometalate anions ([α-PW9O34]9-) featuring heavy-metal binding sites. The resulting composite is highly porous and can be used for the removal of transition-metal pollutants from water. Thus, a facile blueprint for decentralized production of water filtration devices is reported.
TiO₂/g-C₃N₄/PVDF composite membranes were prepared by a phase inversion method. A comparison of the performance and morphology was carried out among pure PVDF, g-C₃N₄/PVDF, TiO₂/PVDF and TiO₂/g-C₃N₄/PVDF composite membranes. The results of permeability and instrumental analysis indicated that TiO₂ and g-C₃N₄ organic-inorganic composites obviously changed the performance and structure of the PVDF membranes. The porosity and water content of 0.75TiO₂/0.25g-C₃N₄/PVDF composite membranes were 97.3 and 188.3 L/(m²·h), respectively. The porosity and water content of the 0.75TiO₂/0.25g-C₃N₄ membranes were increased by 20.8% and 27.4%, respectively, compared with that of pure PVDF membranes. This suggested that the combination of organic-inorganic composite with PVDF could remarkably improve UTS, membrane porosity and water content.
This study assessed the effect of water storage on the flexural strength (FS) of low shrinkage composites.
The contraction stress generated during the photopolymerization of resin dental composites is the major disadvantage. The water sorption in the oral environment should counteract the contraction stress. The purpose was to evaluate the influence of the water sorption of composite materials on polymerization shrinkage stress generated at the restoration-tooth interface. The following materials were tested: Filtek Ultimate, Gradia Direct LoFlo, Heliomolar Flow, Tetric EvoCeram, Tetric EvoCeram Bulk Fill, Tetric EvoFlow, Tetric EvoFlow Bulk Fill, X-tra Base, Venus BulkFil, and Ceram.X One. The shrinkage stress was measured immediately after curing and after: 0.5 h, 24 h, 72 h, 96 h, 168 h, 240 h, 336 h, 504 h, 672 h, and 1344 h by means of photoelastic study. Moreover, water sorption and solubility were evaluated. Material samples were weighted on scale in time intervals to measure the water absorbency and the dynamic of this process. The tested materials during polymerization generated shrinkage stresses ranging from 6.3 MPa to 12.5 MPa. Upon water conditioning (56 days), the decrease in shrinkage strain (not less than 48%) was observed. The decrease in value stress in time is material-dependent.