Prepolymer composition

Apicella, A., Nicolais, L., Carfagna, C., de Notaristefani, C., Voto, C. 27th National SAMPE Meet., San Diego, 1982, The Effect of the Prepolymer Composition on The Environmental Ageing of Epoxy Based Resins ... 

As might be expected, these differences in the pre-gel properties are also reflected in the post-gel regime. The sol fraction varies more smoothly with conversion for the branched prepolymer compositions, cf. Figures 3 and 6. But because the gel point is at (so... 

First and most importantly, real-time NIR monitoring enabled real-time control of the process. For a given product, the molecular weight and end-group balance in the prepolymer exiting the front end or melt part of the process must be controlled at specified levels in order for the back end or solid-phase part of the process to successfully produce the intended polymer composition. In addition, the variability in prepolymer composition must be controlled with very tight tolerances to keep the variation in final product composition within specification limits. Since the process dynamics in the front end were more rapid than those in conventional PET processes, the conventional analytical approach involving off-line analysis of samples obtained every 2-A hours was not sufficient to achieve the desired product quality. 

Title Prepolymers, Prepolymer Compositions, High-Molecular-Weight Polymers with Pore Structure, and Dielectric Films... 

Another development that has triggered the revival of liquid polysulphides as modifiers for epoxy resins has been the introduction of polysulphide-epoxy prepolymer compositions which have no mercaptan odour in the uncured state. The manufacture of such compositions involves the co-reaction of epoxy resin in molar excess with a suitable liquid polysulphide in the absence of a catalyst to give ... 

Such a procedure was followed with our data. Based on the prepolymer composition It was decided that Butanol, Butane,... 

Examination of cur data for peaks due to monomer which might be formed from unzipping reactions showed no detectable amount being produced. This is not unexpected because the prepolymer composition is approximately 50% acrylate type monomers and, therefore, degradation by unzipping is unlikely. 

Urethane polymer morphology can be quickly characterized by means of DSC and TMA analyses. These thermal analyses are valuable tools in determining the interrelationship of the many formulation variables of urethane polymer systems polyol type and molecular weight, hard segment type and concentration, and various prepolymer compositions. 

Ultra-low monol PPG diols are commercially available in molecular weights from 2000 to 12,000. A product summary is given in Table 9.4. To determine the formulating range of the various diols in MDI/BDO cured elastomers, we prepared MDI prepolymers based on the 2000, 4000 and 8000 MW diols at a wide range of isocyanate contents. These prepolymers were chain extended with BDO to produce elastomers with a broad range of properties. Tables 9.5 to 9.7 summarise the prepolymer compositions and viscosities, processing characteristics and physical properties of these elastomers. 

The blocked isocyanate function of aminimides also allows their use as polyurethane adhesives. Thus bis(aminimides) crosslink with polyester or polyether diols to yield a range of elastomers dependent upon the structure of the bis(aminimide) and the co-reactant chosen. For example, bis(aminimides) mixed with polyhydroxyl components can provide stable, single-package prepolymer compositions which yield polyurethanes on heating without the problem of isocyanate moisture sensitivity which can plague polyurethane applications. 

Kase and co-workers [174] investigated an isocyanate prepolymer composition using HPLC and field desorption MS. 

The copolymerization approach has successfully been applied for poly(ester-urethane)s by equipping the prepolymers with elastomeric properties by copolymerization. e-Ca-prolactone-lactic acid copolymers have been reported to result in a significant increase in the strain and the flexibility [62]. Table 3.2 shows the changes in the material properties that have been achieved by varying the prepolymer composition [50, 62]. 

Figure 11. Histograms representing the prepolymer composition (mole %) obtained with POTM-4 or POTM-12 (see Fig. 8) and MDI (molar ratio 1 3). The open cut-off areas of the columns represent the theoretically expected additional portion, the hatched areas the experimentally found additional portion of (macro)diisocyanates in the prepolymer by assuming or comparing to most probable statistics, rp snectivelv-...

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