Pp / Epdm / Expansion Of Preparation And Properties Of Flame Retardants / Layered Double Hydroxide Nanocomposites

With increasing the requirements of environment protection, fire safety, and properties of materials, inorganic flame retardant nanocomposites have been caused great attention to provide environment-friendly flame retardant materials. In the main part of the present thesis, the preparation, structure, and thermal stability of polypropylene (PP)/ ethylene-propylene-diene copolymer (EPDM)/ intumescent phosphorus-nitrogen flame retardanct (IFR)/ layered double hydroxide (LDH) (PP/EPDM/IFR/LDH) nanocomposites have been studied in detail. Besides, crystallization behavior of ethylene terephthalate–ε- caprolactone (TCL) copolyesters has also been studied. The main research contones and innovation points are as follows:1. PP/Mg3Al LDH nanocomposites were synthesized by solution intercalation method. Their structures, especially for the effect of LDH on crystallization behavior, flame retardant and thermal properties of nanocomposites have been studied indetail. X-ray diffraction XRD and transmission electron microscopy (TEM) results demonstrate that the exfoliated structure can be obtained and the nanoscaled LDH layeres are dispersed in the PP matrix. The differential scanning calorimetry DSC data and polarizing microscope PLM photos show that the LDH inorganic components can destroy theα-phase crystallization of PP which made the crystallinity decreased when the content of LDH layers is below 5 wt%. The nucleus growth mechanism of PP is changed from homogeneous nucleation to heterogeneous nucleation when the content of LDH layers is above 5 wt%, and the LDH layers become nucleating agent ofβ-phase crystallization in PP matrix which made the crystallinity increased. Thermogravimetric analysis (TGA) results show that the LDH layers can improve charring progress of PP and thus improve the thermal stability.2. The PP/EPDM/IFR/LDH nanocomposites were prepared by melt intercalation method. The results show that the addition of phosphorus-nitrogen compound (NP) does not change the intercalated structure of PP/EPDM/LDH nanocomposites. Synergistic effects of LDH with IFR of NP on the flame retardant and thermal properties of the PP/EPDM/IFR/LDH nanocomposites have been studied. Limiting oxygen index LOI and UL-94 test results show that only suitable ratio of LDH and NP can obtain the best flame retardant properties. TEM results demonstrate that LDH can help NP disperse more homogeneously in the polymer matrix. Scanning electron microscopy SEM photos show that more compact charred layers can be obtained from the PP/EPDM/NP/LDH sample than those from the PP/EPDM/LDH and PP/EPDM/NP samples when burning. The data from the CCT test and TGA tests indicate that the synergistic effects of LDH with NP can apparently decrease the HRR and MLR values and increase the degradation temperatures of the PP/EPDM/NP/LDH nanocomposites.3. The PP/EPDM/LDH ternary composites with different divalent metal cations were prepared by melt intercalation method. Their morphological structures and thermal degradation behaviors have been studied by comparasion. The results show that different LDH layers with different divalent cations exhibit the different dispersing state and the basal spacings increase with their increasing electronegativity which can form exfoliated structure, intercalated-exfoliated structures, and simple blending structure from the PP/EPDM/LDH samples. The TGA curves indicate the two-step decomposition processing occur in the exfoliated and intercalated-exfoliated samples. Interlayer water is desorbedat low temperature, while the loss of interlayer carbonate and dehydroxylation of the metal hydroxide occur at the higher temperature stage, and the formed charred layers enhance the thermal stability of PP/EPDM/LDH samples. The simple blending sample occurs only one-step decomposition process, which cannot form the charred layer to protect the polymer chain.4. The crystallization characteristic of ethylene terephthalate (ET) segment in ethylene terephthalate -ε- caprolactone (TCL) copolyester has been studied by wide angle X-ray diffraction (WAXD) and Fourier transformation infrared spectrum FTIR.Crystal lattice structure of ET segment in TCL copolyester is the same as that in pure PET, and the corresponding 2θposition does not change with the content of hard segment from WAXD patterns. But the crystal lattice size of ET segment decreases with decreasing the length of hard segment sequence. The gauche conformation content of glycol segment actually is the crystallinity of ET hard segment, increases with increasing the crystal temperature.