Study On Surface Modifying Of UHMWPE Fibers And Their Composites

Ultra high-molecular weight polyethylene (UHMWPE) fibers were treated by chromic acid oxidation, pyrrole and thiophene chemical deposition, and the method combined chromic acid oxidation with pyrrole chemical deposition, respectively. And different factors of these methods were discussed. Structures and properties of treated fibers were analyzed, and the effects of different treatment methods to them were illuminated. Morphology structures of polypyrrole (PPy) and polythiophene (PTh) coated on the surface of UHMWPE fibers were studied, and their shapes were confirmed, found the effect of their shapes to adhesion. Treated fibers were weaved to plain fabric and three-dimensional braiding fabric. And effects of different treatment methods to mechanic properties of these two kinds of fabrics composites were discussed. Finite element method was used to simulate the loading process of single fiber debonding, interfacial shear strength of fiber to epoxy resin was calculated, which compared with experimental value.When chromic acid was used to treat UHMWPE fiber, effects of acid ratio of chromic acid, processing time and temperature to adhesion of the fiber were studied. With the acid ratio increasing, surface of treated fiber became rough and etching degree increased, and interfacial shear strength of treated fiber to epoxy resin increased. With the treatment temperature rising, polarity of the fiber increased, interfacial shear strength increased too, at the same time, breaking tenacity of the fiber dropped off. So, the optimal chromic acid ratio was 7: 12: 150, the optimal processing temperature was 40℃and processing time was 5min.Effects of vacuum degree, oxidant concentration (ferric chloride solution), deposition temperature and time to interfacial shear strength were studied when pyrrole vapor depositing UHMWPE fiber. The results show that there were the maximal interfacial shear strength of PPy/UHMWPE fiber to epoxy resin when vacuum degree, oxidant concentration, temperature and processing time were 680mmHg, 1mol/l, 85℃and 1h, respectively. When pyrrole chemical liquid processing UHMWPE fiber, interfacial shear strength of treated fiber was enhanced with the oxidant concentration increased, and it had no effect by vector speed of coating machine. Structure of PPy/UHMWPE fiber was analyzed, the results show that there was no any chemical bond interaction between PPy and UHMWPE fiber, only intermolecular force. Morphology structures of PPy on the surface of UHMWPE fiber was made up of two layers, compact layer and loose layer. There was only PPy compact layer when PPy deposition time was short. Prolonging deposition time, PPy became compact layer and loose layer gradually.After chromic acid and pyrrole chemical vapor deposition treating UHMWPE fiber, mterfacial shear strength of treated fiber to epoxy resin increased. Compared this fiber and other fibers by chromic acid etching and pyrrole chemical vapor deposition respective, interfacial shear strength surpassed those of fibers. And there was no any intermolecular between PPy and UHMWPE treated by chromic acid.Effects of vacuum degree, oxidant concentration and processing time to interfacial shear strength were studied when thiophene chemical vapor deposition treated UHMWPE fiber. The optimal vacuum degree, oxidant concentration and processing time were 680mmHg, 2mol/l and 1h, respectively. The structure of PTh/UHMWPE fiber was analyzed, the results show that there was no any chemical bond interaction between PTh and UHMWPE fiber, only intermolecular, and PTh changed the thermal property of UHMWPE fiber, degree of crystal of fiber increased. Morphology structures of PTh depositing on the surface of UHMWPE fiber were made up of two layers, compact layer and loose layer, too. The key layer to interfacial shear strength was compact layer.After pyrrole chemical vapor treatment, mechanics property of PPy/UHMWPE plain weave fabric reinforced composites changed. Interlaminar shear strength and compressive strength increased with oxidant concentration and processing time increased. The optimal oxidant concentration and processing time were lmol/1 and 4h. And their bending strength first increased and then decreased when prolonging processing time, the optimal processing time was 4h. Increasing oxidant concentration, bending strength of treated fabric reinforced composites first increased and then decreased.After pyrrole chemical processing UHMWPE three-dimensional braided fabric, mechanics property of PPy/UHMWPE three-dimensional braided fabric reinforced composites changed, too. Different deposition methods had no effect to interlaminar shear strength of fabric reinforced composites. When pyrrole liquid deposition polymerization treating fabric, the optimal oxidant concentration was lmol/1, in which there is the maximal interlaminar shear strength. When pyrrole chemical vapor deposition polymerization treating fabric, the optimal oxidant concentration and processing time were 0.5mol/l and 4h, respectively. Bending strength of PPy/UHMWPE fiber three-dimensional braided fabric composites increased when prolonging processing time. And there was the maximal value after processing 4h. Compressive strength of composites increased with oxidant concentration enhanced. After pyrrole liquid processing UHMWPE three-dimensional braided fabric, compressive strength of its composites increased with oxidant concentration enhanced, and the optimal oxidant concentration was 2mol/l. However, optimal oxidant concentration and processing time were 0.5mol/l and 4h after pyrrole vapor treatment.Mechanics property of UHMWPE fiber three-dimensional braided fabric reinforced composites increased after chromic acid etching.Finite element method was used to simulate the loading process of single fiber debonding.Compared theorical value and experimental value of interfacial shear strength, theoretical value can reflect the adhesion of fiber and epoxy resin though it is higher than that of experimental value.