The Structure And Properties Of Polymer/Molecular Sieve Composites

Polymer composites have better mechanical properties and can be imparted more functions than neat polymer. The studies and designs for novel polymer composites attract interest of a large group of sicentists and engineers.Polyurethane elastomers (PU) are a family of macromolecular materials with rigid segment and soft segment. They have high strength and good elasticity at the same time and best wearable property. The hardness and elasticity of PU can be changed based on the application field. However, PU have bad polar solvent resistance and dynamic mechanical properties.Polypropylene (PP) has been used extensively as a raw material in the filed of automachine, chemical engineering and electrical appliances because of its excellent comprehensive property. PP is a kind of polycrystalline polymer. Different crystalline form with corresponding physical performance can be obtained based on different condition. Nucleating agent has effects on the crystalline morphology, performance and processing of PP. Therefore, modifying PP with nucleating agent is a significant means.β-phase PP with micropore structure has better impact strength, lower modulus and crystallization temperature. Methods of modifying PP to make up above deficiency are being looked for.Zeolite is a particular inorganic particle with micropore structure and much surface charges. It is a good idea to design functional composites with its uniform pore structure and strong adsorption property. It has a bright prospect in application, for example, damp-proof optical cable, osmotic membrane, nonlinear optical material and other functional material. The increasing of molecular sieve species provides good condition and chance for studying new polymer/ molecular sieve composites.What character does the composites have?What is the effect of the micropore structure and surface properties of molecular sieve on properties of composites? Whether the addition of zeolite can change the crystalline morphology of PP? The objectives of this paper are to make the questions above clear.PU/zeolite composites based on polyurethane, and PP/zeolite composites based on polypropylene were studied in this thesis.The onset of this paper were to prepare the PU/SBA-15 composites by assembling polyol into uniform micro pore of SBA-15. At the same time, the PU/13X composites and the PU/4A composites were designed and prepared. The mechanical properties and solvent resistance property of these composites were investigated and characterized. The grafting in the surface of zeolite, the dispersing of particles in PU bulk, dynamic mechanic properties of the composites, microphase separation between rigid segment and soft segment of PU and other properties were investigated by FT-IR, DSC, TG, DMA and SEM.On foundation of research above, a novel PU with microdomain structure and corresponding PU/zeolite composites were prepared and characterized.On the other hand, the effects of the surface of different kinds of molecular sieves on the morphology of PP/nucleating agent system were investigated.The crystallinity, crystalline morphology, heat distortion temperature and mechanical properties of PP/modified zeolite composites were investigated, and the action mechanism was discussed simultaneously.The main conclusions of this paper were as follows:Ⅰ. PU / SBA-15 composites1. The mechanical properties of the PU/SBA-15 composites prepared by following steps: 1)assembling with polyol into micro hole of SBA-15, 2) reacting with isocyanate, 3) using chain extender to extend the chain, do not have obvious improvement compared with neat PU.2. Using the SBA-15, the template (polyether P123) of which was not removed, to prepare composites, the hydroxyl groups of P123 in the micro hole of SBA-15 can react with -NCO group of isocyanate, so chains of PU can be connected with SBA-15 firmly. Tear resistance and tensile strength of this kind of PU/SBA-15 composites have obvious improvement at the same time. The results prove that it is feasible to prepare a composite by fixing polymer into the micro hole of inorganic particle and linking with polymer bulk. 3. The DMA results suggest that the PU with micro-domain structure possesses more storage modulus and less damping property.Ⅱ. Polyester PU/zeolite composites1. There are Si-OH or Al-OH on the surface of zeolite particles, and Si-OH or Al-OH can react with–NCO group of TDI. It is unnecessary to modify the surface of zeolite particles if excessive -NCO group is added in the preparation process of PU/zeolite composites.2. The SEM photographs reveal that the particles of zeolites 13X and 4A are dispersed homogeneously in PU bulk.3. The mechanical properties of PU/zeolite composites (PEU2/13X, PEU2/4A)were improved obviously with 3~7wt% zeolite. Heat resistance and solvent resistance of PEU2/13X and PEU2/4A composites improve greatly compared with neat PU (PEU2).4. The glass transition temperature (Tg) of soft segments was lowered with addition of zeolite particle in PEU2, so the micro-phase separation of hard segments and soft segments of PU was improved. The storage modulus of composites increased, and the damping property decreased.Ⅲ.Polyethyl PU/zeolite composites1. PGU/13X composites have better mechanical properties than neat PGU. The tensile strength and tear resistance strength are improved at the same time.2. Zeolite 13X can induce the crystallization of rigid segment of PGU, and change the crystalline morphology of rigid segment. Ⅳ. PU/zeolite composites with micro-domain structure1. The analysis of DMA results suggest that the PU composites which based on PEA/PTMG mixture made from as the following steps has micro-domain structure. Two kinds of prepolymers prepared by TDI and PEA, PTMG respectively,react with MOCA for some minutes respectively,and then, are mixed together to prepare micro-domain structure PU. The PU with micro-domain structure has higher storage modulus and loss modulus and lower damping property.2. The PU and PU/zeolite composites with different cross-linking density micro-domain structure can be prepared in the following steps.Dividing a prepolymer into two parts, each part react with different amount of MOCA calculated by different chain extension coefficient for some minutes respectively, then are mixed together to form PU with different cross-linking density micro-domain structure (marked PEU4m). Compared with the PU material with uniform structure, the PEU4m has slightly lower tensile strength and higher tear resistance, better solvent resistance and micro domain separation, higher storage modulus and lower damping property.3. The PEU4m/13X and PEU4m/4A composites with micro-domain structure have lower tensile strength, higher tear resistance strength and better solvent resistance compared with the PEU4/13X and PEU4/4A.Ⅴ. The influence of inorganic particles on the PP/β-form nucleating agents system 1. The final crystal form of PP in the system of PP/β-form nucleating agent/inorganic particles is determined by nucleating capability ofβ-form nucleating agent and inorganic particles. The nucleation-inducing capability of SiO2 and MCM-41on PP is strong. That of nano CaCO3 and zeolite 4A is weak. The nucleation-inducing capability of calcium ions on the surface of zeolite on PP is weaker than that of sodium ions on the surface of zeolite.2. The nucleation-inducing capability of inorganic particles on PP is relevant to the unit of SiO2 on the surface of inorganic particles. The more silicon atoms on the surface of inorganic particles are, the stronger nucleation-inducing capability is.3. Nucleation-inducing capability of zeolite 5A is weak, so zeolite 5A has excellent compatibility and synergism withβ-form nucleating agent. It refines spherulites of PP and promotes the crystallization temperature and crystallinity of PP.Ⅵ. The effect of modified zeolite on the properties of PP1. Modified zeolite 13X reduces the spherulites size and improves the crystallization temperature and increases crystallinity of PP. Bundle-like crystals of PP spherulites become thin, and the bundles of lamellae interlap and the interface between PP spherulites is blurry.2. The impact strength and flexural strength of PP/SiY2-13X composites and PP/SiY2-5A composites increase greatly. Especially when the content is 1.0wt%, the imapct strength of composites increase from 11.33 kJ/m2 of neat PP to 43.28 kJ/m2.3. Using zeolites as nucleating agents of PP is a useful exploration to design efficient nucleating agents.