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1.
接枝淀粉的性质、应用及市场前景   总被引:1,自引:0,他引:1  
淀粉与合成高分子接枝共聚,可改善其亲水性、生物相容性、生物降解性,并赋予其良好的加工性能和力学性能。因此,接枝淀粉广泛运用于环境、医用等领域。文章综述了近年来接枝淀粉的性质及应用的研究,并对其前景进行了展望。  相似文献   

2.
采用种子乳液聚合技术合成了PB-g-SAN接枝共聚物,通过调整接枝聚合配方中的苯乙烯(ST)和丙烯腈(AN)的比例、氧化-还原引发剂和链转移剂(TDDM)的用量,分析了在PB-g-SAN合成过程中,接枝配方对ABS树脂物性结果的影响.分析表明调整接枝配方中的ST/AN配比为7228时,PB-g-SAN共聚物与SAN树脂相容性最好.  相似文献   

3.
采用紫外光引发自由基聚合液相接枝的方法,将甲基丙烯酸十二氟庚酯(G04)接枝聚合到使用室温等离子体预处理的聚丙烯(PP)片材表面,成功构建水接触角大于150°的超疏水表面。通过FTIR表征显示含氟聚合物以化学键的方式接枝在PP片材表面上。考察实验条件发现增大引发剂浓度、增加单体浓度以及提高反应温度均有利于提高表面接枝率,同时发现使用等离子体刻蚀的方法可以进一步提高表面接枝率。对接枝PP表面进行金相显微镜观察和水接触角(WCA)测量等表征,发现接枝PP表面形成了包括含氟聚合物的粗糙表面结构,水接触角随接枝率的增加而逐渐增大至150°以上。  相似文献   

4.
以小麦淀粉、苯乙烯为原料,过硫酸铵为引发剂,采用水溶液聚合法对淀粉进行接枝改性,分别讨论反应温度、引发剂用量及淀粉与单体配比对产物接枝率的影响.实验结果表明,最佳反应条件为:淀粉58℃左右预糊化30min,引发剂用量0.3g,淀粉与苯乙烯质量比1/2(20g/40g),反应温度70℃,反应时间3小时,可达最大接枝率56.2%.  相似文献   

5.
通过对聚酯织物进行碱处理,采用紫外光(UV)辐照接枝方法,在光引发剂二苯甲酮(BP)的存在下对PET聚酯织物进行紫外光照射,在其表面产生自由基从而接枝对苯乙烯磺酸钠(SSS)。采用相同的紫外光照强度,改变光照时间和接枝单体溶液浓度来研究对苯乙烯磺酸钠在聚酯织物上的接枝规律。采用了Nicolet670型傅立叶红外变换光谱仪,电子显微镜,分光光度计,MMT液态水分管理测试仪等手段对其结构及染色性、吸水性进行了表征。实验结果表明聚酯接枝对苯乙烯磺酸钠后,红外光谱出现特征吸收峰,扫描电镜(SEM)观测出接枝前后纤维表面形貌变化,其染色性、吸水性也有较大提高。  相似文献   

6.
本文系统研究了甲基丙烯酸(MAA)接枝聚丙烯的固相反应工艺,探讨了各因素对枝率的影响。在氮气保护下,于105-120摄氏度范围内,MAA和PP进行固相接枝反应,最佳反应条件为PP20g,MAA2.5mL,BPO占单体量1.5%,反应时间2.5hr,反应温度115摄氏度.所制备的PPg-MAA能改善PP与高岭土两相相容性及其复合材料的性能。  相似文献   

7.
《中国科学院院刊》2011,(4):464-464
中科院上海有机所高分子材料实验室的黄晓宁等人在分子设计的基础上.结合单体合成以及聚合物的化学修饰,利用活性自由基聚合的方法,设计合成了一系列具有特殊组成和结构的接枝共聚物,包括主链亲水的高密度接枝共聚物、具有小同侧链的蜈蚣状接枝共聚物以及接枝密度可调的接枝共聚物等,并进行了聚合物的白组装及应用研究。  相似文献   

8.
在聚丙烯基础上接枝丙烯酸得到PP-g-AA,对PP-g-AA在弱酸性溶液中对稀土离子的吸附规律进行考察,得出PP-g-AA对11种稀土离子的吸附量Q的规律及PP-g-AA对11种稀土离子的吸附速率常数。  相似文献   

9.
首先通过偶联剂3-丙烯酰基氧基丙基三氯硅烷对SBA15表面进行预处理,随后通过所得SBA15表面的丙烯酰基与α-二亚胺钯催化剂1进行成环反应,将催化剂1共价负载于SBA15孔道表面;进一步在乙烯压力1 atm和35°℃下催化乙烯在SBA15孔道表面接枝聚合,获得表面超支化聚乙烯(HBPE)接枝的SBA15(SBA15-g-HBPE);分别通过热重分析(TGA)、红外光谱(FT-IR)、小角X射线衍射(SAXRD)和透射电子显微镜(TEM)技术对改性前后SBA15的结构进行了表征,结果表明:通过所述工艺可实现HBPE在SBA15孔道表面共价接枝,接枝后SBA15仍保留完整孔道结构。在此基础上考察了所得SBA15-g-HBPE对聚氧乙烯(PEO)基聚合物电解质膜的改性作用,与改性前SBA15相比,SBA15-g-HBPE填充体系具有更优的离子导电性能,当填充15 phr的SBA15-g-HBPE8h,所得PEO基聚合物电解质膜的室温离子导电率较未填充体系提高近43倍。  相似文献   

10.
通过表面引发原子转移自由基聚合技术(SI-ATRP)使聚甲基丙烯酸甲酯(PMMA)接枝于有序介孔氧化硅(MCM41)粒子的孔道内外表面,制得表面PMMA接枝的MCM41复合粒子(MCM41-g-PM-MA)。进一步利用增塑剂碳酸丙烯酯(PC)与所得的MCM41-g-PMMA共同对PMMA基聚合物电解质膜进行改性,通过溶液浇铸工艺制得PMMA基复合型聚电解质膜。着重考察了MCM41-g-PMMA填充比例、MCM41表面PMMA接枝以及温度等因素对上述体系离子电导率的影响。红外光谱(FTIR)、热重(TGA)、高倍透射电镜(HRTEM)、小角X射线衍射(SAXRD)分析结果表明:PMMA已成功接枝于MCM41粒子的孔道内外表面。交流阻抗测试、差示扫描量热分析(DSC)表明:较改性前的MCM41填充体系,MCM41-g-PMMA填充的PMMA膜具有更优的离子电导率,同时具有更佳的热稳定性能。  相似文献   

11.
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors.  相似文献   

12.
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007.  相似文献   

13.
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction.  相似文献   

14.
Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies.  相似文献   

15.
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means.  相似文献   

16.
Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP.  相似文献   

17.
Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.  相似文献   

18.
<正>In Xishuangbanna,one of China’s most biodiverse regions,landscape has changed dramatically during the past three decades due to the conversion of tropical rainforest to rubber plantations.In steep areas,terraces are often constructed before planting rubber trees,which causes two important changes in the soil:the destabilization of soil in the bench terraces and the increased vulnerability of unvegetated riser faces to erosion.Few studies have documented the nature and intensity of erosion on bench terraces.Prof.LIU Wenjie and his colleagues from the Xishuangbanna Tropical Botanical Garden(XTBG)conducted a study in Menglun County(21°5′39″N,101°15′55″E),Xishuangbanna to evaluate the influence  相似文献   

19.
<正>Chinese scientists plan to apply Earth Observation technologies to protect the critically endangered wild camels(Camelus ferus).With the help of remote sensing,satellite positioning,geographical information system and wireless sensors networks,they will be able to access the distribution and population of the wild camels and protect their habitats.The project will be carried out by the International Research Center for Wild Camel Conservation,which was jointly established earlier this year by the Institute of Remote Sensing and Digital Earth(RADI)of the Chinese  相似文献   

20.
<正>The Paul Gerson Unna Research Group on Dermatogenomics was founded in October 2012 at the Partner Institute for Computational Biology.The ultimate goal of the group is to understand the biology of skin and skin appendages.  相似文献   

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