Thermal Behavior Of Composites Research Articles

Rheology and thermal behavior of polyamide reinforced with alumina whiskers

Alumina whiskers were melt-mixed with polyamide 12 to obtain new composites with high performance properties and similar processability of neat polyamide. Three kinds of alumina whiskers were used to prepare composites (purified fibers, ribbon-shaped fibers and silica-coated fibers). The rheology, morphology and thermal behavior of composites were evaluated as function of the type of whisker and its amount in the samples. In terms of rheological properties, modulus and viscosity were enhanced as function of the amount of filler added. Good dispersion of alumina whiskers in PA12 and an optimal filler-matrix interface were observed in morphological tests independently of the kind of fiber used. Studies on crystallization behavior indicated the nucleation action of whiskers, although the most important changes in crystalline state of PA12 were observed with ribbon-shaped and silica-coated fibers. Whiskers improved significantly the thermal stability of polyamide. But kinetics of degradation process studied using Coats-Redfern method indicates that the best behavior wasobtained principally with ribbon-shaped and silica-coated whiskers. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

Hydroxyapatite-Alginate Nanocomposite as Drug Delivery Matrix for Sustained Release of Ciprofloxacin

Hydroxyapatite is a bioceramic which has a wide range of medical application for bone diseases. To enhance its usage, we have prepared ciprofloxacin loaded nano hydroxyapatite (HA) composite with a natural polymer, alginate, using wet chemical method at low temperature. The prepared composites were analyzed by various physicochemical methods. The results show that the nano HA crystallites are well intact with the alginate macromolecules. For the composite system FT-IR and micro Raman results are reported in this paper. Studies on the drug loading and drug release have been done. The drug is pre-adsorbed onto the ceramic particle before the formation of composite. The thermal behavior of composite has been studied using thermo gravimetric analysis (TGA). This work, reports that the nanocomposite prepared under optimum condition could prolong the release of ciprofloxacin compared with the ciprofloxacin loaded hydroxyapatite.

Fabrication and Dielectric Properties of AlN Filled Epoxy Nano-composites

Epoxy resins were materials with excellent mechanical, electrical properties and good chemical stability. Thus, they had been used in various fields, especially in electrical and electronic application. However, because they were brittle material, the fields of application were limited. Adding nano-Aluminum Nitride (AlN) into Epoxy resins could improve the toughness of the composites, the thermal behaviors of composites could also be improved, but the influence on dielectric properties was not very clear. In this research, epoxy resin based composites were fabricated. The relationships between the dielectric properties and the nano-AlN particle content were investigated. The results showed that, both relative permittivity (ϵr) and dielectric loss tangent (tanδ) decreased to be less than that of monolithic epoxy when nano-AlN particle content was no more than certain amount, the DC volume resistivity (ρv) and low frequency resistivity decreased with increasing nano-AlN content (in certain range of content). AC breakdown strength (EB) did not have an obvious tendency with nano-AlN content.

Preparation and characterization of composites comprising modified hardwood and wood polymers/poly(vinyl chloride)

Chemical modification of hardwood sawdust from ash-tree species was carried out with a solution of maleic anhydride in acetone. Wood polymers, lignin, and cellulose were isolated from the wood sawdust and modified by the same method. Samples were characterized by Fourier transform infrared spectroscopy (FTIR), providing evidence that maleic anhydride esterifies the free hydroxyl groups of the wood polymer components. Composites comprising chemically modified wood sawdust and wood polymers (cellulose, lignin)-as variable weight percentages-, and poly (vinyl chloride) were obtained and further characterized by using FTIR spectroscopy and scanning electron microscopy (SEM). The thermal behavior of composites was investigated by using the thermogravimetric analysis (TGA). In all cases, thermal properties were affected by fillers addition.

Photochemical and thermal behaviours of poly(vinyl alcohol)/graphite oxide composites

The properties of poly(vinyl alcohol)/graphite oxide (PVAL/GO) composites were investigated during UV irradiation using a mercury lamp ( λ = 254 nm). The course of photochemical reactions was monitored by FTIR and UV–vis absorption spectroscopies as well as by estimation of insoluble gel amount formed during crosslinking. Changes in average molecular weights resulting from main chain scission in PVAL were measured by gel permeation chromatography. Composite microstructure was characterized by scanning electron microscopy and X-ray diffraction. The thermal behaviour of composites was determined by a thermogravimetric analysis. It was found that 0.1–5.0% GO addition to polymer bulk slightly hampers photooxidative degradation of PVAL. Thermal degradation in PVAL composites starts at somewhat lower temperatures in the presence of GO but this trend is changed in UV-irradiated samples.

Composites Based on ?-Ray Irradiated HDPE and HA

The evaluation of the mechanical and thermal behavior of composites(γ-HDPE-HA)based on gamma ray irradiated high density polyethylene(γ-HDPE)and hydroxyapatite(HA)showed an increase in the Young modulus values. This was attributed to the radiation effect and also to the HA addition. The tensile strength values were found in the range of those materials suitable for applications in the biomedicine field. The activation energy values allow estimating the optimum volume fraction of HA in theγ-HDPE to avoid detrimental properties in biomedicine applications of theγ-HDPE-HA composites.

A High K Nanocomposite for High Density Chip-to-Package Interconnections

ABSTRACTAC-coupled interconnects (ACCI) is a very exciting technology for achieving high-density chip-to-package interconnects while simultaneously providing a simple, mechanically robust interface. The technology combines the stress-relieving ‘underfill’ layer with the dielectric medium for capacitive coupling. For good AC coupling, it is desirable for the underfill material to have a permittivity around 20 at operating frequencies. However, there is a lack of microwave frequency data for high permittivity ceramic-polymer composite systems in the literature. This paper describes the development and microwave frequency characterization of high K nanocomposite underfill. For composite thick film preparation, 200 nm BaTiO3 nano-sized powder and photosensitive epoxy were used. The thermal behavior of composites was evaluated by DSC (differential scanning calorimetry). Dielectric properties were evaluated as a function of ceramic loading and curing temperature. The microwave dielectric properties were measured from 45 MHz up to 26.5 GHz to extract the capacitance and quality factor of the capacitor over the frequencies of interest using floating plate capacitors and T-resonator CPW structures. The permittivity was found to be ∼ 18 up to 14 GHz and the total Q factor of the capacitors was found to be 2 at 26.5 GHz for BaTiO3 (30 vol%)-epoxy composite. Dielectric loss was found to be 0.3 at 3 GHz, which would satisfactorily allow signaling well into the muti-gigabits range. The high K nanocomposite shows higher permittivity compared to materials currently used (air, K=1 or SiO2, K∼3.9) in capacitively coupled interconnects for chip-to-package communications.

A pyrolysis mass spectrometry study of polythiophene-polyamide composites

The thermal behavior of composites of polythiophene and polyamide prepared by mechanical blending and electrochemical synthesis of polythiophene onto an electrode coated with polyamide have been studied thoroughly by the pyrolysis approach under both direct and indirect pyrolysis mass spectrometric analysis conditions. It is determined that the electrolytic film has different properties from the mechanical mixture and the related homopolymers.