The step curing method decided by curing kinetics equation and isothermal viscosity curve for electrical epoxy packaging materials

Author(s):  
Kun Wang ◽  
Wei Yang ◽  
Yun Chen ◽  
Chong Zhang ◽  
Li Yin ◽  
...  
Author(s):  
Anders Egede Daugaard ◽  
Kaustav Goswami ◽  
Anne Ladegaard Skov

In recent years, UV chemistry has gained importance in curing of elastomers as it allows for rapid reactions at ambient temperature and thereby saves energy in processing. Current techniques often apply platinum in the UV-cured systems, which is challenged by the increasing cost of platinum. A novel platinum free photochemical curing method for soft poly (dimethyl siloxane) (PDMS) networks based on commercially available starting materials was developed. Soft PDMS networks were obtained through photochemical thiol-ene crosslinking of α,ω-vinyl terminated PDMS with a hexa-functional thiol PDMS. Investigations showed that direct photochemical crosslinking led to slow curing kinetics and resulted in a soft PDMS with inferior materials properties. The efficiency of the crosslinking chemistry was substantially improved, through development of a two-step curing reaction. Initially, the crosslinker and excess linear α,ω-vinyl-PDMS were reacted below the gel-point under UV irraditation into hyperbranched structures. The hyperbranched structures were found to be fast and efficiently crosslinked into ideal networks with good mechanical properties. Finally the approach also allows for localization of fillers in the polymer matrix. The properties of the prepared networks were investigated by both rheology and dielectric spectroscopy.


INEOS OPEN ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 64-70
Author(s):  
O. N. Zabegaeva ◽  
◽  
D. A. Sapozhnikov ◽  
B. A. Bayminov ◽  
S. A. Zinov'eva ◽  
...  

2017 ◽  
Vol 62 (2) ◽  
pp. 19-28
Author(s):  
Onuc Cozar ◽  
◽  
Nicolae Cioica ◽  
Elena Mihaela Nagy ◽  
Constantin Coţa ◽  
...  

2007 ◽  
Vol 10 (-1) ◽  
pp. 33-34 ◽  
Author(s):  
Stanislav Zeman ◽  
L'ubomír Kubík
Keyword(s):  

2018 ◽  
Vol 3 (2) ◽  
pp. 44-53
Author(s):  
S.D. Akoto

This study sought to: (1) identify the types and sources of Non-Timber Forest Products (NTFPs) traded; (2) find the frequencyof the NTFPs trade and (3) identify the challenges in NTFPs trading in the Sunyani Municipality. The survey was carried outfrom February, 2014 to April, 2014 mainly at the Sunyani Central and Nana Bosoma Markets in the Sunyani Municipality. Thetarget population comprised NTFPs collectors (gatherers), sellers and consumers. Respondents were purposively sampled. Atotal of 100 respondents were engaged in this study. The NTFPs were grouped into six categories namely; food, medicine,building materials, packaging materials, artefacts and domestic utensils. Key informants’ interviews were also conducted atthe Sunyani Forest Services Division to triangulate the data already gathered. Statistical Package for Social Sciences was usedto analyze the data obtained. The study demonstrated that domestic utensils (37%), food (33%), medicinal products (12%),packaging materials (9%), artefacts (6%) and building materials (3%) were the types of NTFPs traded in the two market centers.The results also showed that majority of the respondents (77%) harvest their NTFPs from forest lands as against 23% whoharvest from communal lands. A significant proportion of the respondents (52%) traded in above 40 kg of NTFPs and only 4%were seen trading in 10 kg of NTFPs. The study further highlighted that food (28%) and domestic utensils (26%) were regularlybrought to the market centers on weekly basis whilst significant proportions of medicinal products (9%), building materials(3%) and artefacts (4%) were brought to the market venues on monthly basis. Cumbersome permit procedure (40%), increasedmarket demand (15%) and financial constraints (20%) were identified as some of the challenges encountered in NTFPs tradingin the Sunyani Municipality. To ensure strict monitoring and sustainability of the resource, there is the need for sensitizationprogramme on the importance of NTFPs in rural livelihood and why their conservation is vital in meeting the needs of thepresent generation whilst not undermining their potential in supplying the needs of future generations.


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