• 폴리머
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• 제39권3호
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• pp.499-505
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• 2015

Dimethyldimethoxysilane(DMDMS), methyltrimethoxysilane(MTMS)과 phenyltrimethoxysilane(PTMS)을 이용하여 폴리유기실록산 열 경화성 코팅액을 제조하고 가교도와 페닐기 함량이 코팅액과 도막 물성에 미치는 영향을 살펴보았다. Si-NMR 측정에서 얻어진 D $T^{Me}$ $T^{Ph}$ 구조 코팅액 조성비가 사용된 DMDMS, MTMS, PTMS의 몰 비로부터 얻어진 이론치와 일치함을 확인할 수 있었다. 가교밀도가 높을수록 그리고 페닐 함량이 낮을수록 실록산 결합의 증가에 의하여 코팅액 분자량이 증가됨을 알 수 있으며 페닐기 증가는 코팅액 굴절률 증가에 매우 큰 영향을 미침을 알 수 있었다. 가교밀도가 높을수록, 페닐기 함량이 감소할수록 코팅도막 경도는 증가되었으며 내열특성 또한 우수해짐을 확인할 수 있었다. 이상의 결과로부터 같은 실록산 결합을 갖는 폴리유기실록산 코팅제라도 치환도에 따른 가교도 조절과 페닐기 함량에 따라 코팅액 물성이 달라짐을 확인할 수 있었다.

• Journal of Pharmaceutical Investigation
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• 제36권2호
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• pp.83-87
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• 2006

Poly(acrylic acid) (PAA) was identified to possess good mucoadhesive properties ensuring its application to extend the retention times of the formulations at the oral cavity, intended route of administration using the polymer. In the noncross-linked state, PAA will swell and become eroded owing to the presence of salivary flow from the site of application. The formation of cross-links between the polymer chains will allow swelling but prevents the erosion of the dosage form. In the current study, cross-linking was achieved by esterification of the PAA chains with sucrose. The density of crosslinking was modified by changing sucrose concentration and the duration of cure time. The cross-linking density of the polymer hydrogel was assessed by equilibrium swelling studies. The mucoadhesion testing method allowed a comparative study of the hydrogels prepared. An inverse relationship between equilibrium swelling and peak detachment force showed that increased PAA chain density per unit area enhanced the mucoadhesive interaction.

• Biomaterials and Biomechanics in Bioengineering
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• 제1권3호
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• pp.163-174
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• 2014

The objective of this study is to prepare an artificial extracellular matrix (ECM) for cell culture by using polymer hydrogels. The polymer used is a cytocompatible water-soluble phospholipid polymer: poly[2-methacryloyloxyethyl phosphorylcholine (MPC)-n-butyl methacrylate-p-nitrophenyloxycarbonyl poly(ethylene oxide) methacrylate (MEONP)] (PMBN). The hydrogels are prepared using a cross-linking reaction between PMBN and diamine compounds, which can easily react to the MEONP moiety under mild conditions. The most favorable diamine is the bis(3-aminopropyl) poly(ethylene oxide) (APEO). The effects of cross-linking density and the chemical structure of cross-linking molecules on the mechanical properties of the hydrogel are evaluated. The storage modulus of the hydrogel is tailored by tuning the PMBN concentration and the MEONP/amino group ratio. The porous structure of the hydrogel networks depends not only on these parameters but also on the reaction temperature. We prepare a hydrogel with $40-50{\mu}m$ diameter pores and more than 90 wt% swelling. The permeation of proteins through the hydrogel increases dramatically with an increase in pore size. To induce cell adhesion, the cell-attaching oligopeptide, RGDS, is immobilized onto the hydrogel using MEONP residue. Bovine pulmonary artery endothelial cells (BPAECs) are cultured on the hydrogel matrix and are able to migrate into the artificial matrix. Hence, the RGDS-modified PMBN hydrogel matrix with cross-linked APEO functions as an artificial ECM for growing cells for applications in tissue engineering.

• Macromolecular Research
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• 제16권3호
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• pp.189-193
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• 2008

Thermal cross-linking method of poly(vinyl alcohol) (PVA) using poly(acrylic acid) (PAA) was carried out on PVA/PAA hydrogels. The level of gelation was measured in the PVA/PAA hydrogels with various PAA contents. The swelling behavior at various pHs showed that the swelling kinetics and water contents of the PVA/PAA hydrogels reached equilibrium after 30 h, and the time to reach the equilibrium state decreased with increasing PAA content in the hydrogel. The water content increased with increasing pH of the buffer solution. The permeation and release of the drug were tested using indomethacin as a model drug. The permeated and released amounts of the drug increased with decreasing the PAA content because of the low free volume in the hydrogel due to the higher cross-linking density. The kinetic profile of drug release at various pHs showed that all samples reached the equilibrium state within the 5 h.

• Elastomers and Composites
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• 제58권3호
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• pp.136-141
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• 2023

Polyacrylic rubber (ACM) is well known for its excellent heat resistance and chemical stability. Additionally, its performance can be readily manipulated by modifying its functional groups, rendering it highly attractive to various industries. However, extreme climate changes have necessitated an expansion of the operating temperature range and lifespan of ACM products. This requires the optimization of both the compounding process and functional-group design. Hence, we investigated the relationship between the cross-linking system and mechanical properties of an ACM with a carboxylic cure site. The crosslink density is determined by chemical kinetics according to the structure of additives, such as diamine crosslinkers and guanidine accelerators. This interaction enables the manipulation of the scotch time and mechanical properties of the compound. This fundamental study on the correlation analysis between cross-linking systems, physical properties, and storage stability can provide a foundation for material research aimed at satisfying the increasingly demanding service conditions of rubber products.

• Transactions on Electrical and Electronic Materials
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• 제11권2호
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• pp.69-72
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• 2010

This study investigates the thermal and mechanical properties of insulation elements through the mixing of epoxy based micro and nano particles. Regarding their thermal properties, differential scanning calorimeter and dynamic mechanical analyser were used to calculate the cross-linking densities for various types of insulation elements. The mechanical properties of the bending strength, the shape and scale parameters, were obtained using the Weibull plot. This study obtained the best results in the scale parameters, at 0.5 phr, for the bending strength of the epoxy nano-and-micro mixture composites.

• 한국염색가공학회지
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• 제35권1호
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• pp.8-19
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• 2023

Silicone rubber is widely used in most industries due to diverse advantages like heat stability, UV stability, durability, chemical resistance, environment friendliness, inertness and so on. But there is limitation to expand applications due to relatively weak rubber strengths such as tensile strength and tear strength, especially in fabric coating applications. The purpose of this study is to find influence of coating agent on performances of rubber and coated fabrics and their correlation according to different crosslinking densities of silicone rubbers. Addition cure type of silicones were formulated using crosslinked MQ-type silicone resin consisting of M (R₃SiO_1/2) and Q (SiO_4/2) and linear polymers. Raw materials used were; 1) linear vinyl endblocked polymers and vinyl functional MQ resin as main polymers, 2) linear silicone hydride polymers as crosslinkers, 3) platinum catalyst and 4) inhibitor to control curing speed. Rubber specimens were prepared to check mechanical strength using universal testing machine (UTM). Crosslinking density was calculated using Flory-Rhener equation using solvent swelling method. Differential scanning calorimetry (DSC) and scanning electron microscope (SEM-EDS) were used to characterize rubbers. Consequently, it was found that physical properties of silicone rubbers and coated fabrics can be expected by crosslinking density of rubbers. Silicone rubber formulations that contain 20 ~ 30 wt% of vinyl MQ resin showed strongest balanced performances.

• 접착 및 계면
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• 제19권2호
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• pp.74-82
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• 2018

아크릴레이트 기반의 점착제를 가교 시키는 기술은 다양하게 소개되어 왔다. 본 연구에서는 에폭시 변성 단량체와 메틸아지리딘 가교제를 활용하여 높은 가교 밀도를 가지는 아크릴 구조체를 만들었다. 베이스구조체를 제조하기 위해서 빠른 제조 공정이 가능하고 무용제 공정이 가능한 UV 중합 기술을 활용했다. FT-IR, 경화거동 및 접착특성 평가를 통해 UV경화도 및 2차경화 온도에 따른 특성 변화를 확인하고자 하였다. 겔분율은 선경화 $800mJ/cm^2$, 120도 후 경화온도 조건에서 50%이상 확보할 수 있었으며, 180도 경화조건에서 80%이상 확보 할 수 있었다. 경화 시간이 길어짐에 따라 경화도가 100%에 도달하였으며 이를 통해 열경화를 통한 2차 경화가 효과적임을 확인 할 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제34권5호
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• pp.1333-1338
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• 2013

Chitosan-based nanoparticles (CSNP) were prepared through ionic cross-linking and gelation of chitosan (CS) by tripolyphosphate (TPP). CS properties such as molecular weight, and preparation conditions were screened and the resulting nanoparticles were examined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The obtained particles were consistently spherical with an overall diameter of approximately $107{\pm}20$ nm. They were successfully used as a carrier for Zidovudine, an anti-human immunodeficiency virus (HIV) which, to our knowledge, is novel. The encapsulation ability, loading capacity, and controlled release behavior for these CSNP was evaluated. Results indicated that their intrinsic properties were strongly affected by properties inherent to CS such as molecular weight, and by the preparation condition, such as cross-linking density, which depends on the concentration of the cross-linker. In vitro release tests for the entrapped zidovudine showed that the CNNP provided a continuous release that can last upwards 20 h.

• Fibers and Polymers
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• 제5권3호
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• pp.225-229
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• 2004

The effect of UV and $^60{Co}$ gamma radiations on the physical and mechanical properties of nylon 6 mono-filaments with different draw ratios has been studied. Specimens were exposed to either up to 25 Mrad of gamma or up to 168 hrs of intense UV irradiation. The results show that nylon mono-filaments exposed to gamma rays, with much higher quantum energy than UV, undergo a larger extent of molecular chain scission. Higher irradiation dose also results in the production of insoluble, macroscopic three-dimensional cross-linked network structure. The amorphous regions with a lower density of cohesive energy (lower molecular orientation) show a higher extent of cross linking reaction whereas amorphous regions with a higher density of cohesive energy (higher orientation) show higher extent of chain scission reaction, irrespective of UV ray or gamma ray irradiation.