Synthesis And Application Of Waterborne Polysiloxaneurethane Copolymer As Textile Finishing Agent

Technical textile is physically and chemically modified textile with specialfunctions. Compared with the general textiles, technical textile is profitable. Textileswith high water resistance and fire retardancy are under great demand and applied inmany fields. Industrial pollution is getting more serious and it is imminent to prepareenvironment-friendly finishing agent with non-organic solvent and non-halogen.Siloxane is an important novel material with peculiar properties, such as excellentheat resistance, cold resistance, weather resistance, aging resistance, water-proof,fire resistance and physiologically inert. Textiles finished with siloxane-basedfinishing agent show excellent water resistance and soft handle. However, theapplication of siloxane-based finishing agent is limited because of the poormechanical properties, low surface adhesive strength and high cost. Polyurethanes(PUs) have been widely used as waterproof and breathable textile coatings due totheir properties of high mechanical strength and toughness, good resistance tochemical attacks and mechanical wear, excellent adhesion and extensibility.However, general PUs exhibit poor thermal stability and surface properties, limitingtheir applications in some fields. Recently, PU modification through siloxane attractsworldwide concern. It is expected to improve thermal stability, water resistance andsurface property of PU without substantially losing PU's excellent mechanicalproperties. The great difference in solubility parameters leads to poor compatibilitybetween PU and siloxane. Besides, the bonding force is weak because of the narrowinterfacial minor region of hard segments. The previous studies mainly focused onthe modification of thermoplastic, thermoset or moisture-curing PU using siloxane.There have been few studies about the synthesis of waterborne polysiloxaneurethanecopolymer as the textile finishing agent.In this dissertation, a novel waterborne polysiloxaneurethane copolymer (WPSUR)endued with the advantages of PU and siloxane was synthesized, which was main used as water resistance finishing agent for truerancotton textile. Series of stableWPSUR were prepared using amino-terminated polydimethylsiloxane (NS),dimethylolpropionic acid (DMPA), castor oil, polypropylene glycol and toluenediisocyanate (TDI). Meanwhile, NS with different molecular weights weresynthesized by hydroxyl-terminated polydimethylsiloxane (PDMS) reacting withaminopropylmethyldimethoxyl silane (DB-912) with a ratio of 1:2. Effect ofcarboxyl diols type, carboxyl contents, dihydroxy polyether type, castor oil contents,chain extender type, NS molecular weight, siloxane contents and the polymercontents on the particle size, storage stability and rheological properties of WPSURdispersion, meanwhile, effect of these factors on the water resistance, water contactangle, mechanical properties, heat degradation and stability of WPSUR films andadhesion between WPSUR and textile, were studied. Moreover, the water resistance,hydrostatic pressure resistance and water resistance durance of the truerancottontextile treated by water resistant WPSUR were also examined.Two types of carboxyl diols were used. One is glycol semi-ester (GSE)synthesized by glycerol and maleic anhydride, and the other is dimethylolpropionicacid (DMPA). Experiment results reveal that carboxyl contents of WPSUR exceed2.5 wt% and 1.6 wt% when using GSE and DMPA, respectively, and the resultedWPSUR possesses excellent storage stability.It is noted that castor oil with unsaturation and hydroxyl function groups has beenwidely used in polyurethane preparation. The multi-functional nature of castor oilmay contribute to the toughness of PU structure, and the long fatty acid chainprovides the properties of high flexibility and water resistance. WPSUR filmsexhibite more excellent water resistance and mechanical properties as compared withPU films. Their water contact angles reach 100°. Moreover, WPSUR films using NSas soft co-segment show high thermal degradation temperature about 413℃,approximately 30℃higher than that of typical PUs using hexamethylene diamine(HDA) and 3-(2-aminoethylamino) propyl dimethoxymethyl silane (APDMS) as thechain extenders. In order to further increase polysiloxane segment contents, longsiloxane side-chain amino-terminated polysiloxane S₃N₂ was synthesized using PDMS and DB-912 (PDMS:DB-912 = 3:2). Because of the higher molecular weightof S₃N₂, the WPSUR dispersions show poor storage stability when S₃N₂ was onlyused as the soft co-segment. WPSUR shows good general performance with thecondition of organic siloxane content being 30 wt%, castor oil content being 15 wt%,carboxyl content being 1.8 wt%, solid content being 30 wt% and the ratio of NS toS₃N₂ being 75:25. Tests of truerancotton textile treated with this kind of WPSUR areas follows: the hydrostatic pressure is 41 KPa, the degree of water resistance is classthree, the bonding strength is 7.0 N/cm, tensile strength is 5.2 MPa, and brittletransition temperature is -30℃. This textile finishing agent presents good stabilityand performance with promising application.The main innovation of this dissertation is using NS and S₃N₂ as the softco-segment instead of conventional low molecular weight fatty diamine andammonium alkyl silane coupling agent. The siloxane contents of WPSUR increasesignificantly, resulting in excellent water resistance and mechanical properties forWPSUR. Castor oil is used to get some crosslinking and long fatty hydrophobicchain, improving the water resistance.Waterborne polysiloxaneurethane/montmorillonite (WPSUR/MMT) was synthesizedusing castor oil, polypropylene glycol, TDI, DMPA and MMT. Morphology andphysical properties of WPSUR/MMT were tested and analysised by using WXRDand TEM. Results reveal that the clay platelets are fully dispersed and exfoliated.WPSUR/MMT films possess high water resistance and mechanical properties, due tothe ionic interactions between the clay and hard segments of WPSUR. Besides, thetensile strength and elongation at break of WPSUR/MMT composites containing 1wt % MMT are about 23% and 9.6% respectively, higher than those of the pristineWPSUR sample. Moreover, both organic clay and NS soft co-segment can improvethe thermal stability of WPSUR/MMT films.Flame retardant WPSUR (P-WPSUR), a novel phosphorous-nitrogen-siloxanecontaining intumescent flame retardant, was synthesized using polyols containingphosphorus, castor oil, polypropylene glycol, TDI, DMPA and NS. The phosphorus,nitrogen and siloxane present synergistic flame-retardant effect. Both phosphorus and siloxane can be used as flame retardant of cotton textile, but the increase ofphosphorus contents is more effective than increase of siloxane contents. P-WPSURpossesses good performance with 7.1 wt% phosphorus content and 20 wt% siloxanecontent. The char length of cotton textile treated with P-WPSUR is less than 100 nmwithout further smolding and continued burning, and the treated cotton textiles showgood flame retardancy property after eight home laundering wash/dry processes. TheLOI is 34 before home laundering wash, and 30 after 10 home laundering wash/dryprocesses. The tensile strength and brittle transition temperature of cotton textiletreated with P-WPSUR are 4.2 MPa and -30℃, respectively. The bonding strengthbetween P-WPSUR and cotton textile is 11.1 N/cm. The flame retardant WPSURalso presents good water resistance.