High molecular weight（Mw） poly（L-lactic acid）s（PLLAs） were synthesized using multifunctional epoxy compound（Joncryl-ADR4370） as chain extender. The products were characterized by gel permeation chromatography...High molecular weight（Mw） poly（L-lactic acid）s（PLLAs） were synthesized using multifunctional epoxy compound（Joncryl-ADR4370） as chain extender. The products were characterized by gel permeation chromatography（GPC） and spectroscopy（1HNMR and FTIR）. The results indicated that the Mw of PLLA increased with the increasing of the ratio of epoxy compound and the extending of reaction time. The highest Mw of PLLA reached 360 000 g/mol when the ratio of epoxy compound was 1.5 wt%. However, the reactants turned to cross-linking when the ratio of epoxy compound was over 1.5 wt%. Differential scanning calorimetry（DSC） measurements demonstrated that the glass transition（Tg） and melting temperatures（Tm） of products increased slightly as the increase of the molecular weight. Analysis of the hydrolytic degradation in vitro showed that the branched PLLA possessed the quicker degradability than that of the linear PLLA.展开更多
Reference materials for quantitative determination of regulated heavy metals, such as Pb and Cd in electronic components, were designed and investigated in terms of stability and homogeneity. Reference materials with ...Reference materials for quantitative determination of regulated heavy metals, such as Pb and Cd in electronic components, were designed and investigated in terms of stability and homogeneity. Reference materials with two concentration levels of heavy metals were prepared by spiking Pb and Cd compounds to epoxy molding compounds made by mixing silica powders and epoxy resin. The concentration changes of the reference materials during stability test for 1 a were not observed. In the homogeneity assessment, the as-prepared reference materials were studied by using three different analytical tools, inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray fluoroescence spectrometry (XRF) and laser ablation ICP mass. The results show different homogeneities by the characteristics of analytical tools and the materials.展开更多
The behavior of resistance high-g impact of EMC （epoxy molding compound） with two package models, small outline package （POS） and Globtop, was evaluated by experimental method used Hopkinson bar. At 120,000 g （ge...The behavior of resistance high-g impact of EMC （epoxy molding compound） with two package models, small outline package （POS） and Globtop, was evaluated by experimental method used Hopkinson bar. At 120,000 g （generated in the Hopkinson bar with widths about 70 μs） no damage in either the POS devices or the Globtop devices was observed. In order to enhance the EMC＇s ability of resistance high-g impact, buffering effect of epoxy resin was also studied. The experimental results above all show that EMC has a better performance of impact resistance at about 120,000 g, and epoxy resin can absorb the stress wave to have the protected ability. The study of this paper could serve as a basis for selection packaging materials and enhance its reliability in high-g impact environment.展开更多
基金Funded by the National Natural Science Foundation of China (No.30870609)the Natural Science Foundation of Chongqing (Nos.2009BA4025 and CSTC2009BB4382)the Foundation of Chongqing Municipal Education Commission(No.KJ091415)
文摘High molecular weight（Mw） poly（L-lactic acid）s（PLLAs） were synthesized using multifunctional epoxy compound（Joncryl-ADR4370） as chain extender. The products were characterized by gel permeation chromatography（GPC） and spectroscopy（1HNMR and FTIR）. The results indicated that the Mw of PLLA increased with the increasing of the ratio of epoxy compound and the extending of reaction time. The highest Mw of PLLA reached 360 000 g/mol when the ratio of epoxy compound was 1.5 wt%. However, the reactants turned to cross-linking when the ratio of epoxy compound was over 1.5 wt%. Differential scanning calorimetry（DSC） measurements demonstrated that the glass transition（Tg） and melting temperatures（Tm） of products increased slightly as the increase of the molecular weight. Analysis of the hydrolytic degradation in vitro showed that the branched PLLA possessed the quicker degradability than that of the linear PLLA.
基金Project(2010-0008-276) supported by NCRC (National Core Research Center) program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology
文摘Reference materials for quantitative determination of regulated heavy metals, such as Pb and Cd in electronic components, were designed and investigated in terms of stability and homogeneity. Reference materials with two concentration levels of heavy metals were prepared by spiking Pb and Cd compounds to epoxy molding compounds made by mixing silica powders and epoxy resin. The concentration changes of the reference materials during stability test for 1 a were not observed. In the homogeneity assessment, the as-prepared reference materials were studied by using three different analytical tools, inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray fluoroescence spectrometry (XRF) and laser ablation ICP mass. The results show different homogeneities by the characteristics of analytical tools and the materials.
基金Funded by the State Key Laboratory Foundation of China (No.9140C120704060C12)the Science and Technology Development Project of Universiti-esin of Shanxi Province
文摘The behavior of resistance high-g impact of EMC （epoxy molding compound） with two package models, small outline package （POS） and Globtop, was evaluated by experimental method used Hopkinson bar. At 120,000 g （generated in the Hopkinson bar with widths about 70 μs） no damage in either the POS devices or the Globtop devices was observed. In order to enhance the EMC＇s ability of resistance high-g impact, buffering effect of epoxy resin was also studied. The experimental results above all show that EMC has a better performance of impact resistance at about 120,000 g, and epoxy resin can absorb the stress wave to have the protected ability. The study of this paper could serve as a basis for selection packaging materials and enhance its reliability in high-g impact environment.
