Alternative coupling agents

Since silane agents are less effective with coupling lower-energy carbon black and CaCOs, other agents may be tried. For coupling these fillers, organometal-lic complexes based on neoalkoxy titanates and zirconates have been used as 

Even more complex recipes for coupling fibers in WPCs have been studied. For example, in one study, MAH grafted onto a styrene-ethylene-butylene-styrene block copolymer (SEBS-g-MAH) was added at 1%, along with 2% PP-g-MAH, in a WPC system. This reportedly doubled the impact strength over PP-g-MAH alone, though it reduced the modulus. However, when researchers used a WPC that was also loaded with nanoclay (l%-5%), the SEBS-g-MAH likewise increased impact strength, but the nanoday hdped support the modulus value [14-6]. 

For most operations that handle POs, the maximum reprocessing of in-house scrap material is a no-brainer, when it is permitted by the application. Recycling regrind keeps costs as low as possible, as well as allowing a company to consider itself more environmentally sustainable. Purchasing and reusing postindustrial or postconsumer POs can be a more difficult matter. 

Whether using scrap produced internally or recycled material from outside the operation, integrating recycled material with virgin material and creating a quality output is not easy, for several reasons  

and other POs typically are somewhat immiscible with one another and do not always process efficiently as blends. 

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PyBOP, proceeding through a presumed benzotriazolyl ester intermediate, was more effective than alternative coupling agents such as DCC, DCC/DMAP, DCC/1 -hydroxybenztriazole, and bromotris(dimethylamino)phosphonium hexafluorophosphate. 

The problem of epimerization during carbodiimide-mediated coupling of amino acids can also be overcome by the use of an alternative coupling agent. Once such system that still employs HOBT as an additive involves the use of bis(2-oxo-3-oxazolidinyl)phosphinic chloride (BOP-Cl) and N-... 

In a variation of this process, polymerization can start in the center (B segment, and A segments can then be polymerized onto each end. Alternatively, can be joined together by a coupling agent ... 

The product of this reaction (S—B LC) may initiate a further reaction with styrene monomer to give S—B—S LC. This, in turn, can react with an alcohol, ROH, to give S—B—SH + LiOR. Alternatively, S—B LC may react with a coupling agent such as an organohalogen (45) ... 

Organoboron compounds cannot react without proper activation. The use of oxygen bases is inherent in the standard Suzuki-Miyaura cross-coupling method. Fluorides (usually CsF) can be used as alternative activating agents, which is particularly useful in cases when the reagents are incompatible with oxygen bases for the reactions run under anhydrous conditions,24 (66) 241 Fluoride activation can be effective, however, even under aqueous phase-transfer conditions (67) 242... 

Purification is often required for the beads obtained by the techniques described above since undesired substances such as surfactants, coupling agents, etc. need to be removed. This is also valid for dye molecules noncovalently adsorbed on the surface of the beads since they usually have different properties (sensitivity, cross-talk to other analytes, leaching, etc.) compared to the molecules located in the core. The dye-doped beads can be purified by repeated precipitation which is achieved by adding salts (typically sodium chloride). In certain cases (typically for large beads) the addition of salts is not necessary so that the beads can be isolated by centrifugation. Washing with ethanol often helps remove lipophilic dye molecules adsorbed on the surface provided that the polymer is not swellable. Alternatively, dialysis can be useful especially if a hydrophilic water-soluble indicator is covalently coupled to the bead surface. 

Polymer resins were first introduced in the early 1940s as an aesthetic alternative to repair defects in anterior teeth. Some of the first resins were unfilled polymers of methyl methacrylate. Presently, these unfilled resins have been replaced by filled composite materials that limit the problems associated with polymerization volume shrinkage, abrasion or wear resistance, mechanical properties, water sorption, solubility, and thermal expansion. Polymeric composite materials generally consist of a monomer resin, a ceramic filler, a polymerization initiator or initiating system, and a coupling agent which binds the polymer... 

However, the chemical bonding theory cannot account for the increase in adhesion experienced between non-reactive matrices such as polyolefins and inorganic reinforcements in which chemical bonds will not be formed [4], This observation, among others, leads to an alternative proposal that an interphase composed of various constituents forms surrounding the reinforcement. This third phase in the composite is possibly formed through interdiffusion of physisorbed silane and matrix molecules in the interphase and perhaps via preferential adsorption of both matrix components as well as silane coupling agents on the reinforcement surface [5],... 

Aluminum isopropoxide has been used for the preparation of block copolyesters [147, 148]. Tri-block poly(e-CL-b-DXO-e-CL) was prepared by the sequential addition of different monomers to a living polymerization system initiated with aluminum isopropoxide in THF or toluene solution [95]. An alternative route for the preparation of the tri-block copolymer was to react the diblock poly(e-CL-b-DXO) containing an -OH functionality at the chain end using a difunctional coupling agent such as isocyanate or acid chloride (Scheme 18). However, the molecular weights were low and full conversion of monomers was not achieved. 

There have been few alternative syntheses of bortezomib (1) published in the literature. A more convergent route was proposed by Ivanov et al. employing N-pyrazinyl-Z-phenylalanine (28) as a coupling partner to amino boronic ester 20.31 The use of TBTU as coupling agent was shown to suppress racemization in the reaction. Despite a convergent approach being considered by Millennium, the linear approach was ultimately adopted for synthesis on scale. 

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