Polyamides heat stabilizers

Set B Based on the results of set A discussed below, a third set. Set B, was prepared (Table IV). Cyasorb 531 (a benzophenone UV light absorber) was found to be the most effective stabilizer in Set A. It was therefore rerun at an even lower add-on in Set B, and since it was the only UV light absorber included in Set A, a second type of UV absorber, Tinuvin 327 (a benzotriazole) was included in Set B. Two new non-polymeric hindered amine light stabilizers (HALS) Tinuvin 770 and Tinuvin 765 were also evaluated in Set B with the hope that they might be more effective than the polymeric HALS (Chimassorb 944LD) included in Set A which was quite detrimental to the heat stability. Combinations of these four additives were also applied in Set B. The three new compounds evaluated have been reported to be effective light stabilizers for polyester and polyamide fibers (Capocci, G., Ciba Geigy Corporation, Ardsley, NY, personal communication, 1986). 

Cerium sulfide pigments are produced from hydrated cerium oxide or oxalate and calcined in an oxygen-free, sulfide environment. They are silica-encapsulated to minimize water-reactivity and to improve heat stability and chemical resistance properties. Because of their low relative value-in-use, they are used primarily in engineering plastics and in particular the polyamides where high-performance organic colorant alternatives and other inorganic pigment alternatives are few. 

To obtain an integral protection of polymers, HAS is also combined with other stabilizers, aromatic phosphites in particular [129], Blends HAS/phosphite impart excellent light and heat stability to PO, polyamides, PC or PVC [13,129], Multicomponent blends HAS/phenol/phosphite, combined moreover with UVA or FR were proposed for protection of PUR, PO or PC [268,269]. A complementary mechanism should be accepted for the combinations. 

Sulfur-containing antistatic agents are recommended mainly for PVC and PS because they do not interfere with heat stabilizers. They are not suitable for PMMA, polyolefins, and polyamides. As examples, there are alkylpolyglycolether sulfates, R0(CH2CH20) S0JMe, which are marketed under the trade name Statexan HA (Bayer). 

Because of the increased heat stability, perylenes can be used in a wider variety of blends and alloys than the QA pigments. However, like the QAs, they are not recommended for materials containing polyamide resins. 

The anthraquinone dyes are based on the structure shown in Figure 4. Key properties are summarized in Table 3. Most commercial anthraquinone dyes have sufficient heat stability to be used in polycarbonate and thermoplastic polyesters. However, as indicated in Table 3, only a handful of these dyes are suitable for polyamide Figure 4. The anthraquinone resins and their blends and alloys. Even in these cases caution must ring system. applied. Polyamide materials colored with red anthraquinone... 

Antioxidants can be referred to as heat stabilizers and were previously discussed. Other heat stabilizers are metal complexes used in PVC and polyamide. The largest impact on colorability is with the metal complexes used to inerease the continuous use temperature rat-... 

The polymer has good heat stability and the strength is unaffected by heating up to 185 °C for five hours. The polyamide melts at 370 °C. When hexamethylenediamine is replaced with tetramethy-lenediamine, the melting point rises to 430 °C. The condensation product from isophthalic acid and tetramethylenediamine melts at 250 C. 

An example of a specialty aromatic polyamide is a fluorinated polyanude. It was prepared in an attempt to form a polymer with superior heat stability and resistance to hydrolytic attacks ... 

The aliphatic polyamide-imides prepared to date do not possess desirable properties. When aromatic diacids are employed, however, the products exhibit good heat stability and toughness. This led to the development of a number of useful materials. 

Diels-Alder reaction can also be used to modify the chemical structures of some aromatic polyamides. This improves their heat stability, raises their 7g values, and makes them rigid at higher temperatures. ... 

Uses Feed additive nutrient dietary supplement in table salt as source of dietary iodine catalyst in Sandmeyer reactions cloud seeding heat stabilizer for glass fiber-reinforced polyamides antioxidant/stabilizer... 

Heat stabilizers are chemical additives used to protect polymers, especially those that contain regular repeating units, against degradation resulting from heat or exposure to UV radiation. Complexes of Cul and CuCl with dioctyl H-phosphonate or bis(2-chloroethyl) H-phosphonate are efficient thermal stabilizers for polyamide [122]. Polyamide, containing 0.012% of Cu and 0.011% of P, shows a weak reduction in its viscosity measured in 1000 h. 

Polyamide thermoplastic elastomers are characterized by their high service temperature under load, good heat aging, and solvent resistance. They retain serviceable properties >120 h 302°F (150°C) without adding heat stabilizers. Addition of a heat stabilizer increases... 

Aromatic amorphous or semicrystalline polyamides, PARA, such as copolyamide from caprolactam, hexamethylenediamine and iso- and tere-phthalic acids, PA-6IT6, or copolyphthalamide, PPA, are frequent components of polymer blends. Their advantage is low permeability to liquids and gases, stiffness and high HDT. Several blends of PP with PARA have been described, e.g. with either PP-MA, PE-MA, or PP grafted either with acrylic acid or GMA. Usually, these blends must be heat stabilized with phosphite ester or hydrazine. The alloys are often reinforced by addition of glass fibers and talc. 

Nylostab S-EED is an aromatic HALS used as a multi-functional additive in polyamides. Due to a novel chemical structure, it combines the effect of a light and heat stabilizer, resulting in flow improvement particularly in fibres, and its action in the improvement of colour strength with pigments and dyes. 

In practical terms this means that the typical engine bay requirement of survival at around I30°C for 5000 hours is too severe for an unstabilized, unreinforced version of an engineering plastic like nylon, but acceptable for glass fibre reinforced nylon (e.g., in hot air intakes), and for heat stabilized unfilled nylon (e.g., in oil filler caps, cable ties and electrical connectors). Most reinforced nylon types will withstand much higher temperatures for a limited period, but for temperatures above about I30°C to be sustained for the whole life of the engine, it is necessary to go to more expensive materials, e.g., special polyamides like nylon 46, or aromatic thermoplastics like PPS or PES, or to high performance thermosets. 

Poly(amide-imide)s are more easily prepared than polyimides and have better heat stability than polyamides they have found use as magnet wire coatings. 

Solvent Yellow 163 and 167 are beginning to find applications in the coloration of polyamide 6,6. This non-reactive nature appears as a result of the replacement of the amine bridge with a sulfur atom. Solvent Red 168 is a bit bluer in shade than the Solvent Red 111 in acrylic, but has slightly increased heat stability and less sublimination problems. It also can be used in taillight applications. 

Newly developed perinones are being offered for mass coloration of nylon. As these dyes are non-reactive to the polyamide carrier, they give good performance in these resin systems. Structures have not been disclosed. Perinones show excellent light and heat stability in most resins. 

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