Polymer Dispersion Group

Furthermore, collaborative testing was carried out by participants in the Polymer Dispersion Group of the International Biodeterioration Research Group (IBRG) in which the viability in polymer dispersions of 175 microbial species was evaluated (Gillatt, 1995) (Table 9). Sixteen representative organisms were selected from... 

IBRG (2001). A method for the evaluation of biocidal compounds in aqueous-based polymer dispersions, draft 5.3, November 2001, IBRG Polymer Dispersion Group Document IBRG/PD/01 /Oil, IBRG Secretariat, Hook, Hants, UK. 

The introduction of monomers containing polar groups such as tertiary amines, imidazoles, pyrrolidones, pyridines, etc., gives the polymer dispersant properties that will be discussed in the article on dispersant additives for lubricants. 

These monomers provide a means for introducing carboxyl groups into copolymers. In copolymers these acids can improve adhesion properties, improve freeze-thaw and mechanical stability of polymer dispersions, provide stability in alkalies (including ammonia), increase resistance to attack by oils, and provide reactive centers for cross-linking by divalent metal ions, diamines, or epoxides. 

All of these intermolecular forces influence several properties of polymers. Dispersion forces contribute to the factors that result in increased viscosity as molecular weight increases. Crystalline domains arise in polyethylene because of dispersion forces. As you will learn later in the text, there are other things that influence both viscosity and crystallization, but intermolecular forces play an important role. In polar polymers, such as polymethylmethacrylate, polyethylene terephthalate and nylon 6, the presence of the polar groups influences crystallization. The polar groups increase the intensity of the interactions, thereby increasing the rate at which crystalline domains form and their thermal stability. Polar interactions increase the viscosity of such polymers compared to polymers of similar length and molecular weight that exhibit low levels of interaction. 

Methyl methacrylate (MMA) is one of the most important monomers [80-82]. It forms the basis of acrylic plastics and of polymer dispersion paints. The traditional production is by the formation of acetone cyanohydrin, elimination of water and hydrolysis of the nitrile group, followed by the ester formation. In the carbon-carbon bond forming reaction large amounts of excess HCN and ammonium bisulfate are left as waste. Although these problems have been addressed there is still much room for improvement. In particular the number of reaction steps should be reduced and, in order to achieve this, cyanide should be avoided. The building block to replace it is CO. 

A further improvement in the polymer dispersant area is possible with the appropriate design of a polymer-attached anchoring group, which has specific affinity for pigment surface. In several examples. 

Farrokhpay, S. et al.. Influence of polymer functional group architecture on titania pigment dispersion. Colloids Surf. A, 253, 183, 2005. 

Alkyl benzene sulphonates are one of the most important groups of surfactants and detergents. More particularly, lin. dodecylbenzenesulphonate is used as an anionic emulsifier for manufacturing of E-PVC as well as for polymer dispersions, whereas the usage of the branched tetrapropylenebenzene sulphonate, TPS, has been reduced to a very limited number of applications. 

MA can be used as comonomer together with the vinylic monomers (ternary copolymerisation ACN - styrene - MA) and the graft species is formed in situ by the reaction of the resulting copolymer ACN - styrene - MA with the polyether polyol, by its terminal hydroxyl groups. Another variant is to use a styrene - MA copolymer as NAD. This copolymer proved to be a very good NAD for high styrene content polymer dispersions in polyethers. Of course the real NAD is made by the reaction of a MA unit with the terminal hydroxyl group of the poly ether [57]. 

The resultant polymer dispersion of cured epoxy resin is stabilised by a NAD resulting in situ from the reaction of a small part of the hydroxyl groups in the polyether polyol, with the epoxy group of the epoxy resin (reaction 6.27) [89]. 

The majority of active substances used currently are not very water-soluble. A very important technological task is to enhance water solubility. Three possibilities concerning polymers are going to be presented i) formulation of polymer dispersions and polymer solutions, ii) incorporation of apolar active substances into the micelles formed from copolymers, and iii) encapsulation of the active substance in dendrimers or its binding to the functional groups of the dendrimer [7, 9]. 

The colloidal dispersions and thin films containing poly-iV-(epoxypropyl)-carbazole (PEPC) and Ag-Au nanoparticles were prepared and investigated by TEM and UV-vis spectroscopy. The interaction between poly-iV-(epoxypropyl)-carbazole and Ag-Au nanoparticles were studied by IR-spectroscopy. It was shown that interaction of nanoparticles and polymer functional groups is determined by the conditions of a polymer addition. 

Alternatively, chemical cross-linking reactions can also be used to harden polymer dispersions (oxidative drying or oven drying). An example is the cross-linking of hydroxyl groups of the polymer dispersions with hexamethoxymethylmelamine resins. 

An absolute method for molecular weight determination is matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) (Kona et al., 2005 Creel, 1993 Nielsen, 1999 Cho et al., 2001). The sample is dispersed in a UV-absorbing matrix (e.g., trans -cinnamic acid or 2,5-dihydroxybennzoic acid). Irradiation with a UV laser induces evaporation of ionized polymer chains, which are then detected using TOF. The technique requires relatively narrow MWD samples. Alternative ionization methods have been employed, such as electrospray ionization mass spectrometry (ESI-MS), which may have advantages for certain polymer end groups (Vana et al., 2002). IFFF and MALDI-TOF can be coupled to analyze polydisperse samples and polymer mixtures (Kassalainen and Williams, 2003). 

---