The flame‐retardant polyester fiber: Improvement of hydrolysis resistance

Abstract

As far as the flame-retardant polyester fibers are concerned, the copolymerization of phosphorus retardants is the most common method. But a serious problem is that the phosphorus-containing polymer is easily hydrolyzed. We investigated the flame retardancy and the hydrolysis properties of two poly(ethylene terephthalate) (PET) fibers, one with a phosphorus compound as a side chain (side-chain type: HEIM Toyobo Co., Ltd.), and one with a phosphorus compound inserted in the polymer backbone (main-chain type). Both types had almost the same properties of fibers and flame retardancy, but the main-chain type was hydrolyzed about two times faster than the side-chain type, and led to a decrease of toughness immediately. This difference of hydrolysis properties between main-chain type and side-chain type depends on whether a phosphonate ester bond is placed in the polymer backbone or the pendant site. In the case of the main-chain type, the scission of the polymer backbone chain occurs by hydrolysis of phosphonate ester bonds; however, in the case of the side-chain type, this does not occur. These results demonstrate that the flame-retardant polyester fiber with the side-chain type modifier gives sufficient flame retardancy and excellent hydrolysis resistance.

Flame‐retardant polyesters. II. Polyester polymers

“…Thermal degradation in a nitrogen flow showed similar trends for the two types of FRs: the FR polyesters degraded at lower temperatures than the normal polyesters. Sato et al9 proposed that a phosphorous‐containing polymer changes into a metaphosphoric acid and then into a polyphosphoric acid, and they assumed that the degradation of a pendant‐type polyester would be slower than that of a main‐chain type, but both polymers have the same flame retardancy. However, in this research, we observed a difference in the thermal degradation under heating and at a constant high temperature.…”

“…They did not examine the diethylene glycol (DEG) content in the polyesters and did not consider the thermal degradation caused by DEG. Sato et al9 compared the acidic hydrolytic resistance of the fibers according to the monomer types. They concluded that the flame retardancy was controlled by the phosphorous content and acidic hydrolytic resistance of the polymers and that a pendant type was better than a main‐chain type.…”

Halogenation of Graphene with Chlorine, Bromine, or Iodine by Exfoliation in a Halogen Atmosphere

“…Incorporating a chemically reactive phosphorus‐containing monomer into the polymer chain is one of the most efficient methods of improving the flame retardancy of polyesters. There have been many reports on the copolymerization of flame‐retardant monomers into polyester chains 10–24. Chang et al 11, 12 studied the thermal degradation of phosphorus‐containing copolyesters and investigated the synthesis of side‐chain‐type copolyesters containing the phosphorus linking pendent groups by charging 9,10‐dihydro‐10‐[2,3‐di(hydroxycarbonyl)propyl]‐10‐phosphaphenanthrene‐10‐oxide, terephthalic acid and ethylene glycol in one reactor.…”

“…Asrar et al 13 studied the synthesis of main‐chain‐type copolyesters of ethylene terephthalate and 2‐carboxyethyl(phenylphosphinic) acid and found that 2‐carboxyethyl(phenylphosphinic) acid can be copolymerized with terephthalic acid and ethylene glycol in the conventional melt polymerization process used for PET. The flame retardancy and the hydrolytic stability of two polyester fibers fabricated from the aforementioned copolyesters have been investigated by Sato et al 14 Both types of fibers had almost the same flame retardancy, but the main‐chain type was hydrolyzed about twice as fast as the side‐chain type, which led to a decrease of toughness immediately. Wang et al have synthesized some novel phosphorus‐containing copolyesters 15–18.…”

Copolymerization of 1‐oxo‐2,6,7‐trioxa‐1‐phorsphabicyclo[2,2,2]oct‐4‐yl methyl acrylate and (10‐oxo‐10‐hydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐yl) methyl acrylate with styrene and their thermal degradation characteristics

“…4,5 Such an approach is readily adaptable to step-polymerization polymers such as polyesters and thermoset plastics such as epoxy resins. [6][7][8][9][10][11][12][13] Remarkably, the flammability of polystyrenes with flame-retardant units covalently bonded to the polymer chain has been recently reported. 3,5,[14][15][16] The char residue of phosphoruscontaining copolymers after combustion was substantial because of the condensed-phase flameretardant action of phosphorus.…”