含有悬挂链结构的新型聚氨酯阻尼材料的研究

在以甲苯二异氰酸酯(TDI)、六亚甲基二异氰酸酯(HDI)、聚四氢呋喃醚二醇(PTMG)、蓖麻油为原料的聚氨酯(PU)弹性体体系中加入了一种新型含有悬挂链结构的二元醇扩链剂,制得新型阻尼材料;论述了硬段及交联剂的种类和配比对PU阻尼性能的影响。结果表明:悬挂链结构二元醇扩链剂的加入,可有效提高PU弹性体在Tg之后的阻尼因子,显著改善其阻尼性能。     

基于网络结构设计制备宽温域高阻尼聚氨酯弹性体

从网络结构角度出发,设计以聚乙二醇单甲醚(mPEG)与甲苯2,4-二异氰酸酯(TDI)反应所制得预聚体为悬挂链,聚酯二元醇和TDI反应制得预聚体为弹性链,超支化H201作为交联扩链剂制备无规网络结构的聚氨酯弹性体。采用动态力学分析仪、原子力显微镜以及正电子湮没寿命谱等表征其结构与性能,从自由体积、微相分离、氢键作用等结构与性能之间的关系深入探讨聚氨酯宽温域高阻尼机理。研究结果表明,随着悬挂链含量增加,R值(n(-NCO)/n(-OH))减小,聚氨酯的微相分离程度降低,相容性增加,氢键作用增强,自由体积增大,聚氨酯的有效阻尼(tanδ≥0.3)温域可达175℃(-60~115℃),为一种基于网络结构设计的新型聚氨酯阻尼材料。     

扩链剂对MDI型聚氨酯结构与性能的影响

扩链剂类型对聚氨酯（PU）的结构性能有较大影响。分别采用1,4-丁二醇（BDO）、对苯二酚二羟乙基醚（HQEE）、3,3’-二氯-4,4’-二氨基二苯基甲烷（MOCA）和封端二苯基甲烷二胺（S-MDA）为扩链剂,制备了聚四氢呋喃醚二醇（PTMG）/MDI型PU弹性体。通过红外光谱、差示扫描量热法、动态力学热分析及热重分析等方法,研究了扩链剂结构对PU微相分离及性能的影响。结果表明,胺类扩链剂生成的脲基有利于硬段间形成强氢键,软硬段间微相分离程度更大,提高了硬段结晶度、力学强度和耐热性,降低了软段玻璃化转变温度和损耗因子。     

聚氨酯弹性体结构与动态力学性能研究

讨论了扩链剂的结构对聚氨酯弹性体的形态结构和动态力学性能的影响。指出对于相分离严重的聚氨酯体系,在扩链剂中引入侧基会有效地降低微区尺寸,亦即改善软段和硬段之间的相容性,含脂肪环的扩链剂不但能增加体系的相容性,而且脂肪环的构象变化也会增加聚氨酯的力学损耗。     

一种硅氧烷杂化聚氨酯弹性体的制备及动态力学性能

用4,4′-二苯基甲烷二异氰酸酯(MDI)、聚四氢呋喃醚二醇和γ-氨丙基三乙氧基硅烷(KH550)为主要原料,制备出新型硅氧烷杂化聚氨酯弹性体。通过红外光谱,动态力学分析,原子力显微镜等研究了产物的结构及性能。结果表明,不同于传统二胺或二醇扩链的聚氨酯弹性体硬段晶区的片层结构,硅氧烷杂化聚氨酯弹性体硬段区为三维网络状结构,受力时不易破碎和滑移,其软段玻璃化转变温度较4,4′-二氨基二苯甲烷(MDA)扩链型弹性体向低温方向移动9℃,具有更完整的相分离程度和更低的力学损耗。     

扩链剂结构对聚碳酸酯型聚氨酯性能的影响

以聚碳酸酯二元醇为软段，二苯甲烷二异氰酸酯(MDI)为硬段，采用不同链长及同分异构的扩链剂合成了聚碳酸酯二醇型聚氨酯弹性体(PCDL-PUE),通过傅里叶变换红外光谱、差示量热扫描分析、动态机械性能分析等多种方法，对样品进行表征。结果表明：扩链剂链长越短，合成的聚氨酯综合性能越好，同时带有支链的扩链剂合成的聚氨酯具有软段结晶。     

环氧树脂E-51改性聚氨酯弹性体的制备与性能研究

采用预聚体法合成了以4,4′-二环己基甲烷二异氰酸酯(HMDI)、聚醚多元醇等为主要原料,1,4-丁二醇(BDO)为扩链剂,环氧树脂E-51为改性剂的聚氨酯弹性体(PUE),通过万能材料试验机、傅里叶变换红外光谱仪、动态力学分析仪等表征手段,对HMDI型PUE力学性能、阻尼性能、热稳定性等进行研究,重点讨论了环氧树脂E-51的添加量对弹性体拉伸强度、断裂伸长率、微相分离结构、热稳定性等性能的影响规律。结果表明,环氧树脂(EP)中的环氧基团发生开环反应,能有效地改善聚氨酯(PU)和EP分子间的相容性及相互贯穿;随EP添加量的增加,拉伸强度、微相分离程度先增加后减少、断裂伸长率逐渐减小的趋势;热失重分析表明,EP的加入,可以提高聚氨酯的热稳定性。     

耐热型聚氨酯的合成制备与性能

提高聚氨酯耐热性能是聚氨酯应用研究热点。文章以聚醚多元醇(PPG)、4,4′—二苯基甲烷二异氰酸酯(MDI)、3,3—二氯—4,4—二氨基二苯基甲烷(MOCA)为主要原料,采用预聚体法制备聚氨酯(PU),探讨了扩链系数对聚氨酯耐热性能的影响。结果表明,随着扩链系数的增加,聚氨酯的综合力学性能、耐热性能先升高后降低,动态机械分析(DMA)显示,增加扩链系数使得PU玻璃化转变温度(T_g)的内耗峰向高温方向移动。当扩链系数为0.04时,聚氨酯力学性能最佳,拉伸强度为64.16 MPa,弯曲强度为84.69 MPa,冲击韧性为8.88 kJ/m~2,阻尼因子最大值(Tanδmax)为1.108,热分解初始温度达到315℃。     

低分子量HTPB聚氨酯弹性体的制备及其性能

为改善高固含量高聚物黏结炸药(PBX)和丁羟推进剂的工艺性能,以低分子量的端羟基聚丁二烯(HTPB)、异佛尔酮二异氰酸酯(IPDI)为主要原料,选用一缩二乙二醇(DEG)为扩链剂,采用二步法制备了聚氨酯弹性体。研究了催化剂用量对浆料黏度的影响,固化参数R及扩链剂用量对HTPB聚氨酯弹性体力学性能的影响。试验结果表明,当催化剂质量分数为0.004%时,适用期可达5 h;R值为1.1,DEG羟基含量占反应总羟基量的60%时,聚氨酯弹性体力学性能较好,拉伸强度达7.60 MPa,断裂伸长率达540.21%。动态力学分析(DMA)测试结果显示,低分子量HTPB聚氨酯弹性体有两个明显的玻璃化转变温度,说明样品存在明显的微相分离结构。     

对苯二酚-双(β-羟乙基)醚扩链聚醚型聚氨酯的研究

分别用对苯二酚 -双 (β-羟乙基 )醚 ( HQEE)和 1 ,4-丁二醇 ( BDO)作扩链剂 ,采用本体一步法合成几种不同硬段含量 ( 0～ 50 % )的二苯基甲烷 - 4,4′-二异氰酸酯 /聚四亚甲基醚二醇的聚醚型聚氨酯 ,借助 DSC和 IR等手段分析该聚氨酯的结晶性以及氢键行为 ,最后认为 HQEE扩链聚醚型聚氨酯的微相分离程度较高 ,这是由其形成的硬链段刚性较强所致。     

正确理解供应链与价值链的关系

首先较系统地概述了供应链和价值链的涵义,发展和研究状况,在此基础上深入地探讨了两者的本质区别与联系。两者有不尽相同的地方,如价值链思想是面向效益,着眼点是企业的价值增值过程;供应链思想是面向效率,主要是围绕物流、降低成本和提高生产率方面。但两者也有许多交叉的地方,如价值链研究把成本优势作为重要方面之一,供应链的发展也逐渐强调联系的重要性等。正确理解供应链与价值链的关系可以为实现两者的有效管理提供一     

Leagile supply chain: design drivers and business performance implications

In the context of a dynamic and hypercompetitive business environment, effective supply chain design helps organisations to align resources for improved flow of products and services and satisfy customers’ diverse needs. Scholars have proposed several mutually exclusive supply chain designs such as efficient versus responsive, and lean versus agile. Quantitative testing has revealed that supply chain designs of many firms do not match with what was conceptually expected. To address this mismatch, in this study, a new approach to supply chain leagility is introduced and the impact of uncertainty as the key design driver of supply chains on leagility is investigated. The partial least squares (PLS) was employed to analyse data collected from 299 Australian firms by administering a structured questionnaire. Results indicate that higher performance is achievable on minimising the deviation from a balanced supply chain in which aspects of both leanness and agility are equally embedded. Further, the level of uncertainty directly and positively affects the Deviation from Leagility (DFL) index.     

Literature review on disruption recovery in the supply chain*

Recent research underlines the crucial role of disruption events and recovery policies in supply chains. Despite a wealth of literature on supply chain design with disruption considerations, to the best of our knowledge there is no survey on supply chain with disruptions and recovery considerations. We analyse state-of-the-art research streams on supply chain design and planning with both disruptions and recovery considerations with the aim of relating the existing quantitative methods to empirical research. The paper structures and classifies existing research streams and application areas of different quantitative methods subject to different disruption risks and recovery measures. We identify gaps in current research and delineate future research avenues. The results of this study are twofold: operations and supply chain managers can observe which quantitative tools are available for different application areas; on the other hand, limitations and future research needs for decision-support methods in supply chain risk management domains can be identified.     

Revealing interfaces of supply chain resilience and sustainability: a simulation study

Dynamics of structures and processes is one of the underlying challenges in supply chain management, where multiple dimensions of economic efficiency, risk management and sustainability are interconnected. One of the substantiated issues in supply chain dynamics is resilience. Resilience has a number of intersections with supply chain sustainability. This paper aims at analysing disruption propagation in the supply chain with consideration of sustainability factors in order to design resilient supply chain structure in regard to ripple effect mitigation and sustainability increase. Ripple effect in the supply chain occurs if a disruption at a supplier cannot be localised and cascades downstream impacting supply chain performance. This simulation-based study helps to identify what sustainability factors mitigate the ripple effect in the supply chain and what sustainability factors enhance this effect. The results indicate that (i) sustainable single sourcing enhances the ripple effect; (ii) facility fortification at major employers in regions mitigates the ripple effect and enhances sustainability; and (iii) a reduction in storage facilities in the supply chain downstream of a disruption-risky facility increases sustainability but causes the ripple effect.     

A graph-based model to measure structural redundancy for supply chain resilience

Globalisation and lean initiatives increase the vulnerabilities of the supply chains (SC), where disruptions in any plant in a supply chain network (SCN) can propagate throughout the whole SCN. Redundancy is part of the SC re-engineering to improve supply chain resilience (SCRES). This paper presents a conceptual model of an SCN using graph theory, considering the relationships between plants and materials. Based on the model, the structural redundancy of the SCN is measured, which is used to assess SCRES. This assessment approach focuses on the resilience of the SCN against disruptions. Case studies are discussed to illustrate the applicability of this model and show that increasing structural redundancy of the SCN improves SCRES against disruptions.     

制造企业转型电子商务的价值链研究

本文的研究将依据两条线索展开,一条是迈克尔．波特的企业价值链一电子商务下的企业价值链一虚拟价值链,即企业价值链线索;另一条是迈克尔,波特的行业价值链一电子商务下的行业价值链一价值网,即行业价值链线索。通过以上两条线索分析制造企业价值链的演化过程,指出在电子商务时代,制造企业应该注意到物理价值链和虚拟价值链的理论正在发展,分工的高度专业化和对合作的强调,又导致企业之间虚拟价值链寻求整合,演变为价值网,而价值网随着合作的动态变化而改变,企业必须高度关注这些变化并运用新的价值链理论指导企业实践,才能赢得竞争优势。     

Emerging trends in supply chain architecture

This paper traces significant developments in technology, quality, measurement, and relationships that have led to the study of supply chain networks. The paper introduces five principles of supply chain networks—velocity, variability, vocalize, visualize, and value—that have moved supply chain architecture from an art to a science. Finally, the paper uses each principle to point to an important, emerging trend in supply chain architecture.     

供应链设计、供应链整合、信息共享与供应链绩效的关系研究

构建了供应链设计、供应链整合、信息共享及供应链绩效之间关系的理论模型,并以广东省珠三角地区162家制造企业为调查对象,对供应链设计、供应链整合、信息共享及供应链绩效之间的关系进行实证研究。研究结果表明,供应链设计对供应链整合、供应链绩效均有显著的正向影响;供应链设计对信息共享的直接影响并不显著,却会以供应链整合为中介对信息共享产生间接影响;供应链整合对信息共享、供应链绩效有显著的正向影响;而低层次的信息共享对供应链绩效并无显著影响。根据上述实证研究结果,本研究结合中国情境给出了相关管理启示。     

过渡金属催化烯烃聚合

论述了烯烃聚合催化剂的发展更新过程,催化聚合的过程。涉及配位聚合的链增长机理、单体几种可能的插入模式及聚合的立构控制方式、链转移或链终止机理以及可能存在的催化活性中心的失活过程。对于过渡金属催化烯烃聚合的理解有助于催化剂设计的理性化。     

基于分形理论的供应链管理模型分析

为了克服日益复杂的供应链问题,在分形理论的基础上介绍了分形供应链的概念和特点,认为分形供应链所具有的自相似、自组织、自优化等特点可以很好地提高供应链的灵活性,增强适应环境的能力.在此基础上进一步研究了分形供应链的结构模型和运作模型,探讨了其现实意义.