Polymeric modifiers

An early U.S. patent [154] claims that mixing polypropylene with various resins such as other polyolefins, epoxy resin [155], polyamides, polyalkenimines, polyesters, polyamino-triazoles, polycaprolactam and mixtures thereof will result in a dyeable product when spun 

An important factor to consider on the blending of polymeric materials is that most polymers are incompatible with polypropylene on the molecular scale. This might cause many problems, such as macro-phase separation during blending, low interface adhesion, low tensile transfer rate, and low physical properties, which may be even lower than the unmodified polymer. To sustain good fiber properties, controlling the phase structure and interface adhesion is a necessity. 

There are now polymer products in the market for the dyeability modification of polypropylene. Based on journal reports, Eif-Atochem and Centexbel, both EU firms, have developed polymeric additives that are compatible with polypropylene [157]. These compatible polymers imparted outstanding dyeability to spun fibers with selective dispersion dyestuff. 

---

PVF has low solubdity in all solvents below about 100°C (61). Polymers with greater solubdity have been prepared using 0.1% 2-propanol polymerization modifier and were characterized in /V, /V- dim ethyl form am i de solution containing 0.1 AlLiBr. ranged from 76,000 to 234,000... 

Modified Bitumen Membranes. These membranes were developed in Europe during the late 1950s and have been used in the United States since the late 1970s. There are two basic types of modified asphalts and two types of reinforcement used in the membranes. The two polymeric modifiers used are atactic polypropylene (APP) and styrene—butadiene—styrene (SBS). APP is a thermoplastic polymer, whereas SBS is an elastomer (see Elastomers, thermoplastic elastomers). These modified asphalts have very different physical properties that affect the reinforcements used. 

A series of tests [15] were conducted to compare three types of polymeric modifiers for PVC Du Ponf s Elva-loy 741, a copolymer of ethylene, vinylacetate, and carbon monoxide Goodyear s Chemigum P83, a copolymer of butadiene and acrylonitrile and 566TPU from our lab, a polyester-based TPU. Some of the results are provided in Tables 5 and 6. 

Table 12 Polymeric Modifiers Used for Various Matrices in Engineering ...

Apart from the mentioned advantages, the polymeric reagents covalently adsorbed by silica also diminish its inherent non-specific adsorptivity. One of the ways to synthesize a polymeric modifier of this type is a copolymerization of a vinylsilane with a compound of the desired functionality. The segments carrying silyl groups will condense with the surface silanols forming anchors or trains . 

It should be noted that for polymerization-modified perlite the strength parameters of the composition algo go up with the increasing initial particle size. [164]. In some studies it has been shown that the filler modification effect on the mechanical properties of composites is maximum when only a portion of the filler surface is given the polymerophilic properties (cf., e.g. [166-168]). The reason lies in the specifics of the boundary layer formation in the polymer-filler systems and formation of a secondary filler network . In principle, the patchy polymerophilic behavior of the filler in relation to the matrix should also have place in the failing polymerization-modified perlite. 

Properties of Polymerization-Filled Composites and Compositions with Polymerization-Modified Fillers... 

Materials of the second type can be classified as composites with polymerization-modified fillers (PMF) or filler concentrates. 

We have already noted in an earlier section that treatment of filler with a finishing agent also increases its abrasive attack on the parts of the processing equipment [271], At the same time it has been shown indirectly in [297,298] and directly by microscopic inspection in [294] that a synthesized polymer film remains on the polymerization-modified filler after the processing treatment, that is, there is always a medium which protects the molding equipment from the abrasive attack of the filler. In view of these observations, the polymeric composites with PMF are comparable, in terms of abrasive activity, with unfilled polymers [226, 227],... 

Physico-Mechanical Properties of Composites with Polymerization-Modified Fillers (PMF)... 

For composites with polymerization-modified filler it is typical that the physico-mechanical characteristics should increase symbatically with the quantity of polymer which becomes attached to the filler in the polymerization process. This effect has been observed for polyethylene [293, 321], poly(vinyl chloride) coats [316], and in [336, 337] for kaolin coated with poly(vinyl acetate) and introduced into the copolymer of ethylene and vinyl acetate. 

The effects that the most commonly used polymeric modifiers have on the properties of PET are shown in Table 14.13. 

TABLE 1. Polymerization Scoping Studies for Poly(4-methyl-l-pentene) Using a Hafnium Salt Catalyst with Selected Polymerization Modifiers... 

Experiment Catalyst Polymerization Modifier Polymerization Modifier (mmol) Reaction Temperature (°C) Yield (%) Efficiency (gPP/mgHf)... 

In another process, patented by Berens [67], the additive must again be solubilized in the supercritical solvent, as in Sand s process but, in this case, the patent is mainly concerned with reactive monomers that successively polymerize, modifying the host polymer. Nevertheless, in some examples (with a film of polyurethane), the problem of solid-drug impregnation is also considered. 

A termination frequently encountered in many polymerizations results from a chain transfer process. In a radical polymerization such a reaction involves usually a transfer of a hydrogen atom and yields a radical which may or may not initiate further polymerization. The first alternative may be referred to as a proper chain transfer reaction, and such a transferring agent is known as a polymerization modifier. The second alternative is known as an inhibition or retardation of polymerization, the inhibitor or retarder being a substance which forms a stable radical, not sufficiently reactive in respect to the monomer, and therefore unable to initiate further polymerization. 

Yield quantitative Current efficiency 30-607o Polymerization modifier... 

Su, S., Jiang, D. D., and Wilkie, C. A. Novel polymerically-modified clays permit the preparation of intercalated and exfoliated nanocomposites of styrene and its copolymers by melt blending, Polym. Degrad. Stab. (2004), 83, 333-346. 

Co(acac)3 is frequently used as a probe for enantioseparation efficiency of col-umns " . A monolytic capillary silica gel column was functionalized with methacrylate residues in two steps, as shown in equation and then it was impregnated with cellulose or amylose (51a, b) which was modified so that 30% of the R groups were the methacrylate group 52 and the rest was identical to R (53). For further stability of the column, the polymeric modifier was immobilized on the silica gel by in situ copolymerization with an olefinic monomer such as 2,3-dimethylbutadiene. Only the column containing cellulose modified as in 51a was able to separate the Co(acac)3 racemic mixture, whereas neither cellulose nor amylose modified as in 51b did, although they were successful in resolving other racemic mixtures ° °. ... 

As can be seen, with the acetic anhydride being split, the old chain is terminated while a new chain starts growing. Such a process is called chain transfer , and the agent causing it, in this case the acetic anhydride, is known as the polymerization modifier . 

I j Initiator for polymerization, modified Bessel functions, electric current Electric current density A/m2 ... 

Henry constant for absorption of gas in liquid Free energy change Heat of reaction Initiator for polymerization, modified Bessel functions, electric current Electric current density Adsorption constant Chemical equilibrium constant Specific rate constant of reaction, mass-transfer coefficient Length of path in reactor Lack of fit sum of squares Average molecular weight in polymers, dead polymer species, monomer Number of moles in electrochemical reaction Molar flow rate, molar flux Number chain length distribution Number molecular weight distribution... 

Use Polymerization modifier, intermediate, metalcleaning and polishing compounds. 

Use Polymerization modifier, insecticide intermediate, vulcanization accelerator intermediate, nonionic surface-active agent. 

Use Antioxidants, fungicides, oil additives, plasticizers, insecticides, stabilizers, polymerization modifiers, stabilizer in tin-sulfur compounds, stripping agent for polysulfide rubber. 

Mica, because of its platelet structure is a very useful filler. Its performance is improved by increasing the compatibility between filler and polymer. Silane modification is one simple and frequently used method. An alternative method involves a polymeric modifier which, in the case of polypropylene formulations, is polypropylene modified by maleic anhydride. Such modifiers act more as compatibilizers. They are added in small amounts to a system containing both mica... 

---