Thermoset blends

Figure 3.1 Phase diagram illustrating the phase separation mechanisms of thermoplastic/thermoset blends at constant cure temperature...

Table 3.1 Cure Schedule for the Curing of PEI/Thermoset Blend...

Figure 3.20 Model for the morphology formation during curing of thermoplastic/thermoset blend via (a) NG only (b) NG followed by SD dispersed thermoplastic rich phase (c) NG followed by SD bicontinuous, and (d) NG followed by SD dispersed thermoset rich phase (e) SD only...

Vlassopoulos et al. (1998) examined the gelation of three epoxy-rubber thermoset blends (based on TGDDM/DDS/(acrylonitrile/butadiene rubber/methacrylic acid copolymer) of the same chemistry but different pre-cure treatments. The pre-treatments used heat and catalysts to promote epoxy-carboxyl reactions, and there was some evidence of a decrease in gelation time and an effect on pre-gel rheology with these treatments. 

Although it is sometimes hard to distinguish some thermoset blends from co-reacting thermosets, thermoset blends can be ideally classified as follows ... 

In a majority of cases, the thermoset/thermoset blends are actually formulated by the fabricator or the end user during the fabrication and processing of such materials as composite prepregs, printed circuit boards, laminates and adhesives. The formulations and compositions are often kept proprietary and are designed to meet their own individual requirements. 

Although the dynamically vulcanized blends such as EPDM/PP (Santoprene ) and NBR/PP (Geolast ) have sometimes been referred in the literature as semi-IPNs, we considered them as blends of crosslinked elastomer dispersions in a thermoplastic matrix and as such treated them under the elastomer blends. There is yet another class of thermoplastic/thermoset blend system in which a minor amount of the crosslinkable monomer(s) is allowed to polymerize in the thermoplastic matrix forming a loose network. 

Blends of the commodity polymers with more specialty polymers are limited although many specific examples exist in the patent/open literature. In the design of polymer blends for specific application needs, countless opportunities can be envisioned. Examples may include PE/poly(s-caprolactone) (PCL) blends for biodegradable applications (proposed), polyolefin (PO)/poly(vinyl alcohol) (PVAL) blends for antistatic films, PO/silicone rubber blends for biomedical applications, PO/thermoplastic polyurethane TPU (or other thermoplastic elastomers) for applications similar to plasticized PVC, functionalized PO/thermoset blends. 

From a general point of view, the challenge in the case of reaction-induced phase separation is to create new morphologies (particle sizes at the nanometer scale, transparent two-phases materials, interconnected phases, etc.) and to control the properties of the interface (adhesion, and also the internal stress concentration). For size adjustment, it is possible to superimpose a thermal quench to the reaction-induced phase separation [144], In the case of thermoplastic blends the interfaces or interphases can be modified and modelled by the use of block copolymers, especially triblock terpolymers ABC [145]. A similar systematic approach can be developed in thermoset blends and the results are expected to be different to those obtained by the use of functionalized modifiers [71,138, 146-148]. 

Zheng S, Lu H (2003) Miscibility and phase behavior in thermosetting blends of polybenzoxazine and poly(ethylene oxide). Polymer 44 4689-4698... 

Cabanelas, J.C. Serrano, B. Baselga, J. (2005). Development of cocontinuous morphologies in initially heterogeneous thermosets blended with polyfmethyl methacrylate). Macromolecules, Vol.38, No.3, (February 2005), pp. %l-970, ISSN 0024-9297. 

Girard-Reydet, E. Sautereau, H. Pascault, J.P. (1999). Use of block copolymers to control the morphologies and properties of thermoplastic/ thermoset blends. Polymer, Vol.40, No.7, (March 1999), pp.1677-1687, ISSN 0032-3861. 

Molded plastic, smaller die sizes (PDIP, QFP) High strength, low-temperatiue processing (<250°C), moisture resistance Silver-filled epoxy, modified cyanate-ester and thermoplastic/ thermoset blends... 

Crystallization Phenomenon in Miscible Thermoplastic/ Thermosetting Blends... 

Thus, several properties of the common bisphenol A-diglycidyl ether-based epoxy thermosets can be improved by cocuring with a commercial bisphenol A-dicyanate ester, and the blend is more cost-effective than the cyanate ester alone. Such epoxy/cyanate ester thermoset blends exhibit improvements in processability, toughness, hot-wet performance, and low dielectric properties. 

Epoxy/cyanate ester thermoset blend-based composites have low dielectric constant desirable for advanced radomes, microwave anteimas, and stealth aircraft composite applications. Other applications include its use in copper clad laminates, semiconductor devices, and fire-resistant aircraft structural composites. 

Blendur PU-based thermoset blend Bayer AG/Miles... 

Daron 40 Unsaturated polyester/polyurethane thermosetting blends for fiber-filled systems DSM... 

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