Synthese, Characterizations of Phosphorus-Containing Copolyesters and Theie Bends with PET
|摘要:||本論文旨在研究以含磷化合物導入對苯二甲酸二甲酯 (PET) 達成其難燃化之目的，探討導入含磷單體之結構與磷含量對聚酯之物性、熱安定性及難燃性的影響；並針對其共聚酯中含磷單體之鏈排序加以探討，進而將高磷含量的PET-co-PEDDP共聚酯P30作為高分子量型難燃劑與PET摻配並探討其性質。
本研究發現使用H2PtCl6為微加成反應之觸媒可促使磷化合物DOP (9,10-dihydro-9-oxa-10-phosphaphenanthrene-1O-oxide) 與依康酸之微加成反應於較低溫反應 (110℃ vs. 160℃) 並獲得較高轉化率 (＞98% vs. 81%) 而使所有反應物 (DOP、對苯二甲酸、依康酸及乙二醇)可一次進料於反應槽並以一反應槽一批次之方式合成含磷共聚酯，而不需先行合成含磷共單體DDP(9,10-dihydro-10[2,3-di(hydroxycar-bonyl)propyl]-9-oxa-10-phosphaphenanth-rene-1O-xide)，所合成之磷含量不同的含磷共聚酯並以FTIR，1H-NMR及DSC完成鑑定分析。
於聚酯鏈中導入大的磷基團 (DDP) 側懸於主鏈導致分子鏈的規則性下降，並阻礙其結晶，而改變聚酯的熱性質。此系列含磷共聚酯之LOI值均大於33，難燃性優越。對含磷共聚酯而言，高的磷含量導致低結晶、低熔點、低熱裂解溫度及低的抗張強度，但有高的LOI值、碳焦殘留量及耐衝擊強度。含磷共聚酯與PET有相似的流變行為，其Tg大約在77℃附近 (76.8℃∼77.2℃)；此外，聚酯中導入磷基團側懸於主鏈並未改變其結晶格。
含磷共聚酯的熱安定性由TGA或酸價的分析結果，均顯示隨共聚酯中磷含量增加而變差。130℃氧氣狀態下熱處理含磷共聚酯PET-co-PEPP系其酸價隨磷含量之增加兩增加，顯示即使是在低於共聚酯的熔點溫度下，其熱安定性仍是隨磷約含量增多而熱安定性下降。而在相同的狀態下，共聚酯PET-co-PEDDP系，則不太受熱處理影響。聚酯的熱安定性順序是PET > PET-co-PEDDP系 > PET-co-PEPP系。PET-co-PEPP系共聚酯是於聚酯主鏈中導入磷原子致使原子熱安定性下降明顯且其熱裂解機構為主鏈切斷裂解，而PET-co-PEDDP系共聚酯是將磷原子側懸於主鏈旁不易快速引起主鏈切斷裂解，故維持良好熱安定性。由IR及1H-NMR光譜分析結果顯示共聚酯PET-co-PEPP系中苯憐酸酯單位的P-O鍵易受熱斷裂。
The objective of this study was initiated to impart phosphorus of polyester to provide flame retardancy. We incorporated phosphorus moieties into polyester chain and studied the effect of phosphorus moiety structure and its content on thermal, rheological, mechanical and flame retardant behavior of polyester. Furthermore, we used the phosphorus-containing copolyester PET-co-PEDDP P30 as a high molecular weight flame retardant to blend with PET. PET-co-PEDDPs were synthesized by charging DOP, itaconic acid, terephthalic acid and ethylene glycol in one reactor to carry out the microaddition reaction (using H2PtCl6 as catalyst), esterification reaction and polycondensation reaction. H2PtCl6 has demonstrated to be a highly efficient micro-addition catalyst. The use of the H2PtCl6, catalyst makes it possible to charge all the reactants in one reactor to produce high molecular weight phosphorus-containing copolyesters without requiring the pre-synthesis of the DDP. These resulting copolyesters were identified by FTIR, 1H-NMR and DSC analyses. Thermal characteristics, thermal stabilities, intrinsic viscosities, acid values, rheological and mechanical properties of these copolyesters were also characterized. The presence of the bulky pendent phosphorus side groups in the copolyester tends to decrease the structural regularity and retards its crystallization. However, the cystal lattice of all copolyesters does not vary with incorporating of the pendent phosphorus side groups in the backbone of the copolyester. The LOI values of all phosphorus containing copolyesters are all greater than 33. Higher phosphorus content results in decreasing crystallinity, lower melting temperature, lower decomposition temperature as well as lower tensile strength, but increases the residual char after thermal degradation and higher limiting oxygen index. The rheological behaviors of copolyesters remain similar to that of PET. The glass temperatures of copolyesters are all around 77℃ (76.8-77.2℃). Two series of phosphorus-containing copolyesters have been characterized using a 400MHZ 1H-NMR. The chemical shifts of methylene protons of the ethylene glycol unit vary with different sequence. Molar fractions of the phosphorus-containing comonomer, their sequential distributions and degrees of randomness were determined through analyses of the corresponding multiplet of the methylene protons in the ethylene glycol unit. For copolyester PET-co-PEDDP series, molar fractions of the DDP comonomer can also be obtained from the intensities of DDP aliphatic protons. For copolyester PET-co-PEPP series, molar fractions of PPA can also be obtained from the resonance intensities of PPA aromatic protons. These monomer fractions obtained from H-NMR analyses are close to the values determined by UV method. The degrees of randomness of copolyesters of PET-co-PEPP and copolyesters of PET-co-PEDDP were found to be 0.66-0.83 and ~l. The thermal stability of copolyesters decrease as the phosphorus content is increased as shown by thermogravimetric and acid vale analyses. At 130@C (a temperature lower than Tm) under oxygen atmosphere, the PET-co-PEPPs degraded significantly as indicated by the rapid increase of the acid value. On the contrary, PET-co-PEDDPs degraded insignifrcantly under the same condition. The observed thermal stability order is PET > PET-co-PEDDPs > PET-co-PEPPs. The incorporation of the phosphorus linkage into the main chain results in lower thermal stability of PET-co-PEPPs. On the contrary, the phosphorus linkage as pendant groups (PET-co-PEDDP) does not readily cause main chain scission and maintains better thermal stability. IR and NMR spectrum analyses revealed that the ethylene phosphonate unit (P-O bond) is more readily been attacked. The P30/PET blends possess higher crystallization rate than the copolyesters containing equal phosphorus content. Thermal and rheological behavior of P30/PET blends is similar to PET or the phosphorus-containing copolyesters. The P30/PET blends can be considered to be compatible because a single Tg was obtained from DSC or DMA for these P30/PET blends. The SEM/EDX phosphorus-mapping image of the P30/PET blend showed uniform distribution of the phosphorus moieties within the P30/PET matrix, another indication of a compatible blend between P30 and PET. Flame retardant efficiency of the P30/PET blend is identical to that of the copolyester with equal phosphorus contents. Blending of high phosphorus content copolyester with PET provides an easy and feasible way to obtain a flame retardant PET.
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