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Polymers in Special Uses
Published in Manas Chanda, Plastics Technology Handbook, 2017
As stated earlier, the developer used to dissolve or develop out the exposed regions of the DNS-based positive photoresist coatings is an aqueous base. There are two general types of these aqueous-base developers. The first type, the metal-ion containing developers, is based on metallic hydroxides. The need to eliminate metal ion contaminants in semiconductor processing has led to the development of a second category of metal-ion free developers. The most important members in this category are quaternary alkylammonium hydroxides, such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, etc., used in aqueous solutions.
Elastomer–Clay Nanocomposites
Published in Anil K. Bhowmick, Current Topics in ELASTOMERS RESEARCH, 2008
Susmita Dey Sadhu, Madhuchhanda Maiti, Anil K. Bhowmick
The way in which this is done has a major effect on the formation of a particular nanocomposite and this is discussed further below. A wide range of ω-amino acids have been intercalated between the layers of MMT [14]. Amino acids have been successfully used in the synthesis of polyamide 6-clay hybrids [15] because the acid function has the ability to polymerize the ε-caprolactum intercalated between the layers. The most widely used alkylammonium ions are based on primary alkyl amines put in an acidic medium to protonate the amine function. Their basic formula is CH3—(CH2)n–NH3+ where n is between 1 and 18. It is important to note that the length of the ammonium ions may have a strong impact on the resulting structure of nanocomposites. Lan et al. [16] showed, for instance, that those alkyl ammonium ions with chain length larger than eight carbon atoms were favoring the synthesis of delaminated nanocomposites, whereas alkylammonium ions with shorter chain lengths lead to the formation of intercalated nanocomposites. Alkyl ammonium ions based on secondary and tertiary amine have also been used [17]. Although the organic pretreatment adds to the cost of the clays, the clays are still relatively cheap feedstocks with minimal limitation on supply. The MMT is the most common type of clay used for nanocomposite formation; however, other types of clays can also be used depending on the precise properties required from the product. These clays include hectorites (magnesiosilicates), which contain very small platelets and synthetic clays (e.g., hydrotalcite), which can be produced in a very pure form and can carry a positive charge on the platelets.
Gemini surfactant based-organomontmorillonites: preparation, characterization and application in pickering emulsion
Published in Journal of Dispersion Science and Technology, 2022
Khadidja Taleb, Salima Saidi-Besbes, Isabelle Pillin, Yves Grohens
Emulsions stabilized by Montmorillionite (Mt), a highly hydrophilic 1:2 layered aluminosilicate clay mineral, are not stables. Partial wetting of Mt is usually required to enhance its adsorption at the oil-water interface and promote emulsification. Several methods have been reported for the modification of surface wettability of clays and clay minerals as adsorption or ion exchange reaction with organic cations,[26,27] organosilane grafting, binding of organic anions and, intraparticle and interparticle polymerization.[28] Ion exchange reaction of the exchangeable cations present in the clay interlayer space with alkylammonium surfactants is the most used and preferential method to prepare organoclays. It not only allows to change the clay surface properties from hydrophilic to hydrophobic but it also greatly enhance the interlayer spacing particularly for surfactant loading exceeding the CEC of clay. The resulting expanded organoclays (OMt) will attract more efficiently organic and inorganic species and enable to reach a high degree of exfoliation and dispersion in clay polymer nanocomposites.[29]
Identification of preferred combination of factors in manufacturing bioepoxy/clay nanocomposites
Published in Advanced Composite Materials, 2018
H. Salam, Y. Dong, I. J. Davies, A. Pramanik
On the other hand, the functionalisation of 20 wt% ESO on bioepoxy/clay nanocomposites with 3 wt% C15 (i.e., BC5 in Figure 3(e) and (f)) and 1wt% C10A (BC11, Figure 3(g) and (h)) demonstrated a mix of intercalated and exfoliated clay structures. The single black lines and small black dots represented typical layers of well dispersed clay platelets throughout sectioned nanocomposite samples. Moreover, BC5 samples (Figure 3(f)) clearly illustrated clay intercalated structures with size variations in clay layer areas, indicating the multidirectional orientation of clay layers. Similarly, BC11 samples, as shown in Figure 3(g) and (h) at higher magnifications, also presented similar orientations of clay layers in intercalated/exfoliated structures. Hence, it is clear that the functionalisation of bio-renewable ESO could enhance clay wettability in epoxy matrices, resulting in better interaction between matrices and fillers. However, as previously mentioned by Zhu and Wool [50], clay types (i.e., natural and organomodified clays) influenced the wettability of clay fillers in continuous matrices in nanocomposite systems. The incorporation of organomodified clay fillers was believed to improve clay wettability and interfacial bonding between clay fillers and epoxy matrices in contrast with those filled by natural clays. This was most likely associated with the presence of alkylammonium ion in clay interlayers for the effective improvement of clay wettability [48].
Some characterizations of a new metal–organic framework (n-C14H29NH3)2CdCl4 and the role of hydrogen bonding
Published in Phase Transitions, 2018
The properties of this series of compounds are related to the packing of the chains which is often metal dependence [14], i.e. compounds with the same alkylammonium ions, i.e. the same n and of different central metal ion (M) produce somewhat different packing. For example, in C10Cd two types of nonequivalent chains, A (one gauche bond between the first and the second carbon atoms) and B (one gauche bond between the second and the third carbon atoms), are closely packed (… ABAB …) and tilted by ±50° [21,25,43] with respect to the inorganic layers, Figure 12 but this is not the case of the present hybrid.