Additives reactive modifiers

Properly functionalised additives can react with polymer substrates to produce polymer-bound functions which are capable of effecting the desired modification in polymer properties, hence the use of the term reactive modifiers. As an integral part of the polymer backbone, reactive modifiers are useful vehicles for incorporating the desired chemical functions to suit the specialised application. Being molecularly dispersed, the problem of solubility expressed under 2 above is avoided. Implicitly, the bound-nature of the function is not subjected to the normal problems of the loss of additives from the surface which are common with both high and low molecular mass additives. The bound nature of the function must be fully defined for the conditions of service. 

Current interest in reactive modifiers is in the areas of polymer property enhancement and improvement in additive performance. Reactive modifiers can be incorporated into commercial polymers by,... 

Approach ii is applicable to all thermoplastic polymers and offers considerable practical advantage since reactively modified polymers can be readily produced by normal commercial high-shear mixing procedures at no additional cost. 

REACTIVE MODIFIERS FOR IMPROVING ADDITIVE PERFORMANCE-REACTIONS DURING MELT PROCESSING... 

In the absence of oxygen or any other radical trap, however, mechanochemically formed macroalkyl radicals (scheme I, I) can be made to react with chemically reactive modifiers, RM, (see scheme Id) this forms the basis of an in-situ synthesis of polymer adducts i.e., the functionalised additive/modifier becomes chemically bound onto the polymer backbone. 

A good example of a reactive modifier which has been used (14) to enhance properties of polyolefins is maleic anhydride (MA). The formation of maleic adduct in polypropylene (PP), for example, can be used to effect several modifications e.g. to improving hydrophilicity, adhesion and dyeabflity. Moreover, the polymer-maleic adduct has an availabla additional functionality to effect other chemical modifications for achieving the desired material design objectives. Reactions of MA with polymers in solution are described in the patent literature (15). 

Radiation chemistry in polymer research, 168-169 Reactive macroalkyl radicals, formation, 409 Reactive modifiers addition of reactive antioxidants on rubbers, 417 adhesion, 420,422 demanding applications, 414,416 improving additive performance during melt processing, 412 polymer bound antioxidant, 418-419/ Reduced poly(vinyl chloride),... 

This intermediate, like 6-APA, incorporates a primary amine that can be coupled with a host of side chains. The presence of an additional reactive function, the allylic acetate at the 3 position, provides an additional center that can be modified. The observation that both types of modifications provided unproved antibiotics has resulted in the synthesis of hundreds of analogues. The very few examples discussed below barely scratch the surface in this field. One of the earliest examples of a doubly derivatized 7-ACA derivative, cephalothin (19-1), is stUl widely used as an antibiotic. Acylation of (18-4) with 2-thiophenylacetyl chloride gives the corresponding amide (19-2). Heating that product with pyridine leads to the displacement of the allyl acetate by the basic nitrogen. The resulting product, cephalothin (19-3), is isolated as the internal betaine [23]. 

The studies of Yamaki et al. on metallic additives which modify the reactivity of Li electrodes toward solution species and thus improve Li cycling efficiency. 

Increasing reactivity in the Pauson-Khand reaction. The PK reaction originally suffered from a lack of substrate scope and low reaction yields which prevented it from being widely employed. The discovery of new reaction conditions (additives and modified methods) led to an improvement in yields and reaction times, allowing the scope of the reaction to be expanded. 

Monosaccharides (e.g., glucose), disaccharides (e.g., sucrose), and oligosaccharides can be obtained readily from natural sources, either directly or by hydrolysis of natural carbohydrate polymers. These can be used to either modify synthetic adhesive resins or to replace them altogether. In addition, reactive derivatives could be synthesized from these compounds and used to formulate adhesive polymers. 

For example, the ellipsometric technique was used to determine the interfacial thickness in SAN/PA blends, compatibilized by addition of SMA [Yukioka and Inoue, 1991, 1993]. A thin bi-layer film of SMA/SAN was prepared then mounted on a thick PA substrate. The interfacial thickness varied with the compatibilization time from A1 = 2 to 30 nm. The method was also used to study the interphasial thickness variation in PCL blends with CTBN or CTBR. Without a reactive modifier (aminopropyltriethoxysilane, APS), the measured thickness was A1 = 3 nm, upon addition increasing to 6 nm [Okamoto and Inoue, 1993]. 

Uses Reaction rate accelerator copolymerizes readily with most other vinyl monomers modifies hydrophilic properties in systems incl. adhesives, coatings, cosmetics, textiles, syn. fibers, textile sizes, protective colloids, lube oil additives reactive diluent in UV- and electron beam-curable systems (coatings, inks, adhesives) aids pigment disp. (inks) intermediate for modified phenolic resins of interest as plasticizers, dye intermediates, textile assistants... 

The chemical modification is the widely used, easily manageable method of improving the fire resistance of polymers. It can be done synthetically, simultaneously with the copolymerization with reactive modifier via, for example, introduction of replaced bisphenols, various acids, other oxy-compounds. Or it can be done by addition of reactive agents during the process of mechanic-chemical treatment or at the stage of reprocessing of polymer melt [113]. 

Sine sol-gel synthesis is a bottom-up approach, the homogeneous incorporation of various dopants and additives in, for example, mixed composition materials is relatively facile and has been demcaistrated numerous times. This attribute is especially important to pyrotechnics as additives to modify the reactivity, spectral, or thermal output are a necessity [36,37]. 

To the vinylester resins, thixotropic agents are added, for example silica fume (silicon dioxide in microspheres, which is a by-product of the glass industry), to obtain a behaviour adequate to their use also in open moulds. In addition, to improve their toughness, CTBN polymers (carboxyl-terminated copolymers of butadiene and acrylonitrile) are widely employed as reactive modifiers. This occurs since the CTBN-modified vinylester oligomers act as compatibilizers for blending additional butadiene copolymer (Burchill and Pearce, 1996). 

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