High-Tg porous polyimide films with low dielectric constant derived from spiro-(adamantane-2,9′(2′,7′-diamino)-fluorene)

Porous polyimide (PI) films with low dielectric constants and excellent thermal properties have been a pressing demand for the next generation of high-performance, miniature, and ultrathin microelectronic devices. A series of novel porous PI films containing fluorenyl-adamantane groups were prepared successfully via thermolysis of poly(ethylene glycol) (PEG) added in the PI matrix. The cross-sectional morphologies of porous PI films showed closed pores with diameters ranging from 135 to 158 nm, which were uniform and regular in shape without interconnectivity. These porous PI films exhibited excellent thermal properties with a glass-transition temperature at 376 °C whereas the 5% weight loss temperature in air excess of 405 °C due to enhanced rigidity afforded by fluorenyl-adamantane groups. Accompanied by thermolysis content of PEG increasing from 0 to 20 wt %, the density of porous PI films decreased, and the corresponding porosity grew significantly from 0 to 11.48%. Depending on porosity, the dielectric constant and dielectric loss of porous PI films significantly declined from 2.89 to 2.37 and from 0.050 to 0.021, respectively. These excellent properties benefit the as-prepared porous PI films for application as interlayer dielectrics, integrated circuit chips, or multichip modules in microelectronic fields. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47313.     

Effects of moisture on properties of epoxy molding compounds

In this article the effects of moisture on a novel epoxy molding compound, including the mechanical properties, temperature transition, and thermal degradation behavior, are studied. The experimental results reveal that the absorbed water acts predominantly as a crazing agent, continuously decreasing the mechanical strength with the time in water. The glass-transition temperature decreases at the early stage and is finally equilibrated. The thermal degradation behavior of the materials is not greatly influenced by the hydrothermal age. The decomposition of samples in oxygen is composed of two independent steps: the thermal degradation and oxidation at high temperature. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2253–2259, 2001     

温度敏感性PVP/CHI共混水凝胶的制备与溶胀性能

制备了戊二醛交联的PVP/CHI共混水凝胶,讨论了CHI∶PVP(质量比)、引发剂用量、交联剂用量、反应温度等主要条件对凝胶溶胀性能的影响.温度敏感性实验表明,凝胶分别在33℃、37℃出现最大平衡溶胀率,即具有多重温度敏感性.随着PVP含量的升高,凝胶在33℃时对温度的敏感程度升高、37℃时对温度的敏感程度降低,交联度增加使凝胶的温度敏感程度降低.另外,PVP含量升高使CHI结晶度降低,进而使PVP/CHI凝胶的玻璃化转变温度Tg降低.     

PECH和GAP的玻璃化转变温度研究（英）

Glycidyl azide polymer (GAP) is one of the most recognized and prominent azide polymer. Because of its superior properties,GAP is used extensively as a high energetic binder or plasticizer in propellants to increase burning and specific impulse. It is very important to research on the glass-transition temperature (Tg) of GAP and its precursor PECH (poly-epichlorohydrin) due to the Tg of binders is the key factor which can influence low temperature properties of solid propellants.     

Curing kinetics of anisotropic conductive adhesive film

Polymer-based conductive-adhesive materials have become widely used in many electronic packaging interconnect applications, such as chip-on-glass, chip-on-flex, etc. Among all the conductive-adhesive materials, anisotropic conductive adhesive film (ACF) is an attractive interconnect material because of its fine pitch capability. Anisotropic conductive-adhesive film is a thermosetting, epoxy matrix impregnated with a small amount of electrically conductive particles. During component assembly, the epoxy resin is cured to provide mechanical connection, and the conducting medium provides electrical connection in the z direction. The thermal cure process is critical to develop the ultimate electrical and mechanical properties of the ACF. In this paper, the curing reaction of ACF was studied with a differential scanning calorimeter (DSC) under isothermal conditions in the range of 120–180°C. An autocatalyzed kinetic model was used to describe the curing reaction. The rate constant and the reaction orders were determined and used to predict the progress of the curing reaction. A good agreement is found between the proposed kinetic model and the experimental reaction-rate data. The reaction-rate constants were correlated with the isothermal temperature by the Arrhenius equation. The glass-transition temperature also has been studied as a function of cure degree and moisture absorption.     

Electrical conductivity of modified poly(vinyl chloride)

Chemical modification of poly(vinyl chloride) (PVC) by dehydrochlorination with ethanolic KOH is found to yield modified PVC with conjugated polyene sequence. The semiconducting nature of ethoxide-modified PVC is illustrated with temperature dependence of conductivity (σ). The relative ratios (r) of conductivity,σ _modifiedpvc /σ _{unmodifiedpvc} , are greater than unity in the temperature range 50° to 180°C,r being maximum in the vicinity of glass-transition temperature (T _g).T _g inferred from conductivity-temperature profiles is found to be greater for modified PVC relative to unmodified PVC, which is explicable in terms of restricted free rotation limiting segmental motion. For comparison with the conductivity andT _g of ethoxide-modified PVC, LiCl-modified PVC and (aniline + S₂O ₈ ²⁻ )-modified PVC have also been studied.     

用于光纤光栅封装的环氧胶粘剂纳米改性研究

分析了环氧胶粘剂纳米改性机理,用AJ-Ⅲa型原子力显微镜(AFM)研究经纳米SiO2、TiO2和SiC粒子改性后环氧胶粘剂截面图形及组团结构,测试及分析了环氧胶粘剂的耐温性能和抗拉、剪切强度.结果表明,SiO2、TiO2和SiC混合掺入质量分数为4%时,玻璃化温度提高了43℃,抗拉强度提高了17.7%,剪切强度提高了28.6%.用改性后的胶粘剂封装的光纤光栅(FBG)传感器,经实验室和现场测试,可以用于40 Mpa、300℃的工况环境.     

挤压吹塑法制备淀粉基可食膜及其性能表征

以甘油为增塑剂,普兰多糖为黏合增强剂,采用熔融共混挤出技术制备热塑性淀粉,再挤出吹塑制备淀粉基可食膜。研究甘油对热塑性淀粉流变性、玻璃化转变温度、相变焓和微观形貌的影响;并研究了湿度环境对可食膜力学性能的影响及甘油对淀粉可食膜力学性能及热稳定性的影响。结果表明:甘油能有效的改善了热塑性淀粉的流变性和微观结构,降低热塑性淀粉的玻璃化转变温度,使淀粉结晶熔融焓变减小。实验制备的热塑性淀粉膜适宜在湿度40%的环境下使用;且在该湿度条件下,甘油添加量28%时,淀粉可食膜的纵向拉伸强度为5.26 MPa,断裂伸长率达到137.9%,横向拉伸强度为4.92 MPa,断裂伸长率为118.0%。     

共聚型聚酰亚胺纤维的结构与性能

通过湿法纺丝工艺制备了3,3′,4,4′-聚苯四甲酸酐(BPDA)-均苯四甲酸酐(PMDA)-对苯二胺(PPDA)三元共聚型聚酰亚胺纤维和用4,4′-二氨基二苯醚(ODA)部分代替PPDA的四元共聚型聚酰亚胺纤维,柔性单体ODA的引入有效提高了共聚纤维的断裂伸长率,但引起断裂强度、初始模量和玻璃化转变温度及热分解温度的降低。采用Kissinger和Flynn-Wall-Ozawa两种方法对两种纤维在空气中的热分解表观活化能进行了计算,均是加入ODA单体的共聚纤维的热分解表观活化能较低,由此造成其耐热性下降。     

宽温域高阻尼橡胶材料研究进展

文中介绍了宽温域高阻尼橡胶材料的作用机理、性能指标及其发展概况。阻尼橡胶的主要性能指标为损耗因子tanδ、玻璃化转变温度Tg、阻尼峰半高宽温度△0．7；影响阻尼橡胶性能的最主要因素是橡胶的分子结构，其次为填充体系、硫化体系。该文最后介绍了阻尼橡胶的改性方法：共混法、互穿网络法、填充法等。