Corrosion Resistance Of Polyoxymethylene Fiber And Its Application Into Membrane Supporting Layer

Functional fibers and textiles have been widely used in various industries. In membrane separation, textiles were often used as the supporting layer for separation membrane to improve its mechanical properties. Non-woven fabrics and braided fabrics were the common supporting layers. Polyoxymethylene(POM) fiber as one of the new high-performance fibers in recently years, has excellent alkali resistance, good dispersion properties, resistance to chemicals and solvents, etc. It has been used as reinforcement in concrete. The research on the properties of the POM fiber was very rare. This paper systematically studied the corrosion resistance of polyoxymethylene fiber and its application in water filtration membrane as the supporting material.In this paper, the effects of acid and alkali treatments under different conditions of time,temperature and concentration on the structure and properties of POM fiber were studied by using a single variable method. The break strength, break elongation and Young’s modulus of the fiber were tested to explore its mechanical properties. The effects of different treatments on the crystallization structure of POM fiber were characterized by IR, XRD measurements. The scanning electron microscope was used to observe the changes of the surface morphology of the fiber. The interwoven fabrics of POM filament yarn and PTFE filament yarn were prepared as supporting fabric, the corrosion resistant vinyl ester resin as adhesive was adopted to prepare for fabric supported PTFE membranes, which can be used in strong alkaline waste-water filtration.The effects of fabrics, adhesive loading on the weight ratio, the strength of the composite membrane, the water flux and the average pore size of the composite membrane were studied.The study results of this paper showed that:(1) The alkali resistance of POM fiber was better than acid resistance. In low temperature and weak sulfuric acid for 24 h, the mechanical properties decreased significantly, and in high temperature and weak sulfuric acid for 24 h it was dissolved. But in mass concentration 20%,temperature 80 ℃, 120 h of sodium hydroxide, the residual mass ratio of POM fiber was 65%and the break strength was 5.86 cN/dtex. The IR spectrum showed that the fiber surface was not activated by acid and alkali treatment. After being treated by acid and alkali, fiber crystallinity increased. XRD experiments showed that different treatments had significant impact on the fiber crystallinity.(2) The corrosion of POM fiber was a process that was from the outside to the inner layer by layer. The mechanical properties of the fiber was related to the depth and size of the groove on the fiber surface.(3) The amount of vinyl ester attached on the substrate of the supported woven affected the composite film maximum. With increase of the amount of vinyl ester, the weight increase ratio of the composite film increased, the water flux and the average pore size decreased.(4) The best balanced properties of the supported composite membrane was obtained when22.2 tex × 15.6 tex, 160 picks /10 cm × 140 picks /10 cm, PTFE/POM interwoven fabric was used as the supporting layer, and then infiltrated 10 min, gelled 10 min with mass ratio 2.5:1diluted vinyl ester by ethanol, and compressed at 0.1 MPa, 20 ℃ for 20 min.