جستجوی مقالات مرتبط با کلیدواژه « میکروکپسول » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

 Epoxy resin is used in various industries such as adhesives, paints and coatings, aerospace and electronics due to its unique attributes. Epoxy curing agents can be generally classified in two groups of normal (room or high temperature) and latent curing agents. Latent curing agents are mixed with epoxy resins to obtain stable compounds at normal conditions. These compounds can cure epoxy resins rapidly when exposed to external stimulation, such as heat. Capsulation of curing agent as a cost-effective method has attracted an extensive attention to prepare non-reactive or latent curing agents. The concentration of microencapsulated latent curing agent significantly affects the final mechanical properties of cured epoxy resins.

The effect of concentration of microcapsules containing curing agent of 1-methyl imidazole by solid epoxy shell on the mechanical properties of epoxy resin was investigated using dynamic mechanical thermal analysis.

The effect of 20, 25, 30 and 35 phr (per hundred resin) microcapsules concentration in liquid epoxy on storage modulus (E′) and phase angle tangent (Tanδ) was investigated. The results showed that increasing the concentration of microcapsules in cured samples causes to advance storage modulus due to increasing the amount of curing agent and consequently increasing the density of crosslinks. On the other hand, it was found that liquid epoxy resin cured with 30 phr microcapsules has the highest glass transition temperature (48°C). The hardness test results also confirmed the results of thermal-mechanical dynamic test at the optimum microcapsule concentration. The results also indicated that at 30°C the storage module decreased by increasing microcapsule concentration from 20 to 25 phr.  The storage modulus of cured epoxy resins increased to higher values by increases in microcapsule concentration. Therefore, the epoxy resin cured by 35 phr microcapsule showed the highest storage module (723 MPa).

The purpose of this study is to invesigate the different finishing methods of the bedding non-woven textiles. The aroma materials used in this study were Jasmine flower powder, its alcoholic extract, and encapsulated extract containing antidepression active substances. A polyester non-woven fabric was finished with the above aroma materials using poly (acrylic acid) binder as an incorporating material on the surface of the non-woven fabric. Then, releasing behavior of the samples was investigated within a month.
The statistic results of the releasing behavior and measuring of the aroma materials odor intensity showed better results for the samples finished with the powdered flower and its encapsulated extract. However, the finished sample by the powdered Jasmine flower was not washable, so that the encapsulaed samples were selected for washing and abrashion fastness tests. Also, other properties containing releasing behavior, air permeability, and flexibility were measured.
The results showed, for disposable textiles, powdered Jasmine is more durable and affordable, economically. When long-term durable finishing is requied, using of the encapsulated extract is recommended.

Rapeseed oil-filled ethyl cellulose microcapsules were prepared using a two-step solvent evaporation method. The prepared oil-filled microcapsules were characterized by; optical microscopy, scanning electron microscopy and particle size analyzer. The mechanical properties of carboxylated styrene/butadiene copolymer latex films containing various levels of microcapsules were studied using DMTA and tensile strength measurements. The characterization test results showed that rapeseed oil-contained microcapsules with a regular spherical shape, diameter range of 10-45 μm, and a relatively rough porous shell were successfully prepared. The results also revealed that the overall mechanical properties of the latex films containing oil-filled microcapsules improved, due to reinforcing effect of capsules within the latex films; with the best results using 1-2 wt% of oil-filled microcapsules. The improved results were obtained in reinforcing the samples before tests such as tensile tension, capsule rupturing and the oil release within the polymeric network by maintaining the integrity of the films by plasticization of the surrounding polymeric network, increased elongation-at-break, and enhanced resistance against tear or break. With further increasing of microcapsules content up to 3 wt%, there was a drop in overall mechanical properties of latex films, due to possible aggregation of microcapsules, presence of free rapeseed oil within the latex film and weak polymer/microcapsules interface. A proper distribution and dispersion of oil-filled microcapsules within the latex film, and rupture of sufficiently large microcapsules under stress, oil release within the polymeric network and easy movement of the chains were the main requirements for achieving latex film with good mechanical properties.

Microcapsules containing n-hexadecane (HD) as the core and melamineformaldehyde (MF) prepolymer as the shell were prepared by in-situ dispersion polymerization. The effects of surfactants type and amount were studied in relation to the morphology and thermal properties of microcapsules. The morphology of the microcapsules was studied using scanning electron microscopy (SEM) and thermal properties were detected by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). SEM images showed that the increase in the amount of Triton X-100 (non-ionic) to SDS (ionic) ratio resulted in the agglomeration of the prepared microcapsules. This increase led also to lower encapsulated hexadecane and thermal stability of microcapsules. As a result, the optimum composition of the above surfactants for obtaining higher thermal stability and proper morphology wasfound to be 20 wt% of Triton X-100 and 80 wt% of SDS in the recipe. The optimum total amounts of surfactants was 4 wt%, which resulted in spherical and separate microcapsules. DSC and TGA analyses revealed that a sample prepared with 4 wt% of surfactants was not only successful in encapsulation of hexadecane but also showedhigher thermal stability compared with other formulations.