Lec-5 Engineering Resins and Their Blends The term engineering polymer is applied to a processable resin, capable of being formed to precise and stable dimensions, having high ≥ performance at CUT≥ 100°C, and the tensile strength of σ 40 MPa . Five polymer families belong to this category: PA, PEST, PC, POM, and PPE. Engineering resins and their blends have been foamed: 1- Using mainly chemical foaming agents, e.g.,hydrazodicarboxylates, benzazimides or 5-phenyltetrazole. However, products of decomposition of these agents (e.g., alcohol, ammonia, water, etc.) were found to hydrolyze PC, PA, PC/ABS, or PEST, reducing the performance of foamed products. 2- For this reason, dihydrooxadiazinones were proposed as the preferred chemical foaming agents for the engineering resins, their compositions and blends. Dihydrooxadiazinones 3-Another method for foaming high temperature polymers profits from thermal instability of polypropylene carbonate (PPCO, MW = 1 to 1000 kg/mol). The process involves blending PPCO with a resin or its blend that is to be foamed. The blend is then heated to T > 300°C, sufficient to melt the principal resin and to decompose PPCO. Talc, wollastonite, clay, CaCO3 or citric acid can be used as a nucleating agent. The densities of the molded articles were reduced by at least 50%. 4- Most recently, foaming of the engineering resins by supercritical CO2 was introduced. Polyamides (PA): Polyamides are abbreviated as PA-, followed by the number of carbons in a di-amine and dicarboxylic acid, viz. PA-66 has six carbons in each component, etc. - Poly-ε-caprolactam or polyamide-6 (PA-6) was first studied by Von Brown in 1905-10, and 30 years later commercialized as Perlon™.
Lec-5 Engineering Resins and Their Blends The term engineering polymer is applied to a processable resin, capable of being formed to precise and stable dimensions, having high performance at CUT≥ 100°C, and the tensile strength of σ ≥ 40 MPa . Five polymer families belong to this category: PA, PEST, PC, POM, and PPE. Engineering resins and their blends have been foamed: 1- Using mainly chemical foaming agents, e.g.,hydrazodicarboxylates, benzazimides or 5-phenyltetrazole. However, products of decomposition of these agents (e.g., alcohol, ammonia, water, etc.) were found to hydrolyze PC, PA, PC/ABS, or PEST, reducing the performance of foamed products. 2- For this reason, dihydrooxadiazinones were proposed as the preferred chemical foaming agents for the engineering resins, their compositions and blends. Dihydrooxadiazinones 3-Another method for foaming high temperature polymers profits from thermal instability of polypropylene carbonate (PPCO, MW = 1 to 1000 kg/mol). The process involves blending PPCO with a resin or its blend that is to be foamed. The blend is then heated to T > 300°C, sufficient to melt the principal resin and to decompose PPCO. Talc, wollastonite, clay, CaCO3 or citric acid can be used as a nucleating agent. The densities of the molded articles were reduced by at least 50%. 4- Most recently, foaming of the engineering resins by supercritical CO2 was introduced. Polyamides (PA): Polyamides are abbreviated as PA-, followed by the number of carbons in a di-amine and dicarboxylic acid, viz. PA-66 has six carbons in each component, etc. - Poly-ε-caprolactam or polyamide-6 (PA-6) was first studied by Von Brown in 1905-10, and 30 years later commercialized as Perlon™.
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