Fiber light stability

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). 

Fillers. Inert inorganic substances such as calcium carbonate, clay, silicates, and asbestos are often utilized in vinyl compositions where clarity is not a requirement. While the carbonates and clay are used ostensibly to reduce cost, beneficial results are forthcoming. The carbonates produce a dry, matte surface and are claimed, because of their alkaline nature, to benefit heat and light stability. Clay improves electrical insulation. Silicates enhance surface dryness. Asbestos fibers provide the reinforcement necessary for dimensional stability in floor tile. Antimony oxide, per se or as a surface coating on an inert carrier, provides flame retard-ance. Their only major adverse effects are to reduce tensile strength and elongation and require an increase in plasticizer level to compensate... 

Acrylics. Manufacturers of acrylic fibers have not generally published or confirmed the chemical composition of their fibers (116). Acrylic fiber will generally contain 85-94% acrylonitrile the balance is made up of comonomers having a specific function, such as to provide dye affinity for specific dye classes or to regulate diffusion of dye into the fiber. A list of typical comonomers has been published (116). Acrylic fibers may also contain heat (117) and light stabilizers (116). They may also contain a delustrant such as titanium dioxide. Some products contain optical brightening agents. These materials probably never exceed 4r-5% of the total composition. The cross-sectional shapes of the fibers vary (116). 

Significantly improved UV light stability is found with polymeric substrates stabilized with bis(2,2,6,6-tetramethyl-piperidinyl-4) sebacate, an example of hindered-amine class light stabilizers, compared with those stabilized with conventional light stabilizers. Application areas covered include polyolefin fibers, films and molded sections, polyurethane, and styrenics. Synergistic performance with o-hydroxyphenyl benzotriazoles in these polymers is apparent. 

Polypropylene. HALS (LS-1) provided outstanding light stabilizing effectiveness in polypropylene fibers (16 denier per filament) (Table I) ... 

An obvious strategy for avoiding the acid/base reactions between acidic FR decomposition products and basic HALS is to choose a nonhalogen, nonacidic FR. However, researchers at Ciba Specialty Chemicals followed the reverse path, developing an NOR HALS light stabilizer that is nonbasic and provides some flame retardance as weU to PP fiber. 

In recent years, the quality of polypropylene fiber has been improved to enhance such properties as light weight, moldability, light stability, coloration, recovery feasibility, flame resistance, and antistatic propensity. It is increasingly used for automotive interior furnishing and parts. 

Their chemical structures, as shown below, are rather bulky with molecular weights of 12,000-3,100 and 2,600—3,400, respectively. The melting point range is 100-135°C and 120-150°C for Chimassorb 2020. They impart excellent light stability and long-term thermal stability to polypropylene fibers. They are both thermally stable, and have low volatility and extractability and a low migration rate because of their polymeric nature. 

Steinlin and Saar reported the effect of various concentrations of pigments on the light stability of fine-denier polypropylene yarn (72 denier, 24 filament) containing varied levels of Tinuvin 770 [145]. Although Tinuvin 770 is not a preferred HALS stabilizer for fine-denier fibers, the data presented are of considerable interest. (The authors pointed out that Tinuvin 622 and Chimassorb 944 are preferred for polypropylene fibers.) The amount of energy required to reduce yarn strength by 50% was determined. Tinuvin 770 was added at 0.25,... 

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