Graft polymers, clarity

Clarity of Graft Polymers with Varying Methyl Methacrylate/ Styrene Ratios. Refractive index considerations 7,8) and general state of the art considerations (8) favor methyl methacrylate (MMA) over styrene (St) as the major monomer portion of the matrix. With this in mind, we selected MMA/St ratios from 62/38 to 80/20 (wt %). Using a commercial Firestone butadiene latex (2004) to supply the 15% rubber graft, polymerization runs were made as outlined in Table I. 

Table I. Clarity of Graft Polymers with Varying MMA/St Ratios...

Notable among the alternative materials are the MBS polymers, in which methyl methacrylate and styrene are grafted on to the polybutadiene backbone. This has resulted in two clear-cut advantages over ABS. The polymers could be made with high clarity and they had better resistance to discolouration in the presence of ultraviolet light. Disadvantages of MBS systems are that they have lower tensile strength and heat deflection temperature under load. 

A high-impact polystyrene that has much better optical clarity than that obtained by usual blending or grafting techniques can be prepared by our technique. Polymers containing 90-95% styrene grafted to polybutadiene rubber by use of 12 mmole RLi-TMEDA/100 gram polymer showed quite good optical clarity. 

In a quite different but very important industrial area, free-radical polymerizations have made great inroads In the optimization of the desired commercial properties of impact-modified poly(vinyl chloride) (PVC). In a most sophisticated variation, grafted impact modifiers based on the quaterpolymerization of acrylic esters, butadiene, styrene, and acrylonitrile have been produced and almost precisely match the refractive index of PVC. The blending of the Impact modifier with PVC yields a completely clear polymer suitable for shampoo bottles and food containers. In addition to excellent clarity these polymers have extremely good impact strength combined with improved fabricability by flow molding equipment. 

For clarity, the following system of abbreviations will be used when referring to the various polymers discussed in this paper PLL(x)-g[) ]-PEG(z) signifies that the graft copolymer has a PLL backbone of molecular weight x kD a graft ratio, y, of lysine-mer/PEG side chain and PEG side chains of mol vrt z kDa. 

FIGURE 17.15 Direct electrochemical contact between an incoming AFM-SECM probe and the redox Fc heads of nanometer-sized, flexible chains (such as PEG or DNA), end-grafted onto an electrode substrate. The Fc heads are alternatively oxidized at the tip and reduced back at the substrate. For clarity, the tip is not drawn to scale. The chains are pictured in the mushroom conformation. (Adapted with permission from Abbou, J., Anne, A., and Demaille, C., Probing the structure and dynamics of end-grafted flexible polymer chain layers by combined atomic force—Electrochemical microscopy. Cyclic voltammetry within nanometer-thick macromolecular poly(ethylene glycol) layers, J. Am. Chem. Soc., 126,10095-10108, 2004. Copyright 2004 American Chemical Society.)... 

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