Crosslinking network structure

Amino resins are those polymers prepared by reaction of either urea or melamine with formaldehyde. In both cases the product that results from the reaction has a well crosslinked network structure, and hence is a thermoset polymer. The structures of the two parent amino compounds are shown in Figure 1.1. 

Kinetic Gelation Modeling of Crosslinked Network Structure.197... 

Very recently, attempts have been made to develop PP/EOC TP Vs. In order to make TPVs based on PP/EOC blend systems, phenolic resin is ineffective because the latter needs the presence of a double bond to form a crosslinked network structure. Peroxides can crosslink both saturated and unsaturated polymers without any reversion characteristics. The formation of strong C-C bonds provides substantial heat resistance and good compression set properties without any discoloration. However, the activity of peroxide depends on the type of polymer and the presence of other ingredients in the system. It has been well established that PP exhibits a (3-chain scission reaction (degradation) with the addition of peroxide. Hence, the use of peroxide only is limited to the preparation of PP-based TPVs. Lai et al. [45] and Li et al. [46] studied the fracture and failure mechanism of a PP-metallocene based EOC based TPV prepared by a peroxide crosslinking system. Rajesh et al. 

The principal physical structural parameters that control the modes of deformation and failure and mechanical response of epoxies are (1) macroscopic inhomogenieties such as microvoids or concentrations of unreacted monomer, (2) the glassy-state free volume and (3) the crosslinked network structure characteristics. 

Two component spectra of plasma polymerized styrene (PPS) observed above 50 QC were interpreted in terms of a mesh-like crosslinked network structure. Broad and narrow components are attributed to the protons in crosslinked regions and oligomeric structures (which act as plasticizers), respectively 3i). 

The measurements of the branching parameter of various lignin fractions, led to conclusion that the chains of the lignin molecules in solution are densely packed or crosslinked [110, 111]. Rezanowich and co-workers [112] observed by electron microscopy that the lignosulphonates (LS) form spherical particles of a wide range of sizes. Recently, the results obtained using AFM (atomic force microscopy) had confirmed the fact that LS molecules in aqueous solutions form a crosslinked network structure, the shape of LS molecules changing with its concentration in aqueous solution [96]. 

This was utilized by Tian et al. to prepare a new elass of liquid erystal homopolymers of poly ll-[4- (3-ethoxycarbonyl- eoumarin- 7-oxy)-earbonyl-phenyloxy]-undecyl methacrylate containing a eoumarin moiety as a photo-crosslinkable unit. The preparations included polymers of various chain lengths. Also, liquid crystalline-coil diblock and liquid crystalline-coil-liquid crystalline triblock copolymers with polystyrene as the coil segment were formed. The polymers were reported to have been synthesized with the aid of atom transfer radical polymerization. The dimerization of the eoumarin moieties takes place upon irradiation with light of > 300 nm to yield crosslinked network structures. 

Figure 8 shows low shear rate rheological results for an ethylene homopolymer and an ethylene/1-hexene copolymer with catalyst 15/MAO [81]. Ethylene homopolymers by this catalyst exhibit the rheological behavior of linear chain polymers. In contrast, the copolymer displays a higher molecular weight and broader MWD than the corresponding ethylene homopolymers and, as shown in Fig. 8, in the copolymer melt the elastic behavior dominates even at the lowest frequencies. Behavior like this suggests the presence of widely different relaxation times, as in a crosslinked network structure (but the polymer was completely... 

CH2 bonds can be made per phenol group, allowing formation of a crosslinked network structure. 

The lower extremity of the failure envelope of Figure 9 correlate with the presence of a thermoset crosslink network structure. 

Harris and co-workers [276] have described high temperature (well above transition temperature (T )) C-NMR techniques for determining the crosslinked network structure formed when the diglycidyl ether of bisphenol A is cured with diphenylsulfone. 

Another scenario about the impact of crosslinked seed particles is briefly described as follows. When a crosslinked seed latex is swollen by second-stage monomers, the crosslinked network structure expands due to the solvency power of the newly incorporated monomers. When those monomers are con-... 

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