本文選題：聚對苯二甲酸乙二醇酯(PET)　切入點：雙酚A氰酸酯(BADCy)　出處：《北京化工大學》2011年博士論文

【摘要】：聚對苯二甲酸乙二醇酯(PET)具有優(yōu)異的透明性,耐化學性和阻隔性被廣泛的應用于包裝領域,但是在熔融的加工過程中,PET易發(fā)生熱降解、熱氧化和水降解等反應,使其分子量下降,影響了加工性,也使制品的機械性能和化學性能降低,限制了其應用。針對上述問題,本課題使用化學擴鏈法增加PET的粘度和降低端羧基含量,滿足PET的加工需求。 使用氰酸酯(BADCy)作為擴鏈劑,與常用的擴鏈劑環(huán)氧和二苯基甲烷二異氰酸酯(MDI)進行對比,對熔融狀態(tài)的PET進行擴鏈。比較了擴鏈后的PET的熔體扭矩,特性粘度和粘均分子量,結果表明BADCy對PET的擴鏈效果較MDI和環(huán)氧E-51好。采用紅外譜圖來驗證PET和BADCy的擴鏈反應,并對BADCy的擴鏈機理進行了詳細說明。通過對擴鏈后PET扭矩,特性粘度以及羧基含量的測試,研究了反應時間,BADCy的含量以及不同轉(zhuǎn)速對PET擴鏈效果的影響。結果表明,隨著反應時間的延長會增加PET的分子量,但是時間過長會引起熱降解。隨著氰酸酯含量的增加,擴鏈反應速度增加,PET的擴鏈效果增加。轉(zhuǎn)速的加快有利于剪切作用的加強,使得混合效果加強,但強烈的剪切會引發(fā)PET的降解。通過熔體流動速率(MFR)儀,擴展流變儀以及DSC測試,對擴鏈后的PET的流變性能以及結晶性能進行了表征。研究發(fā)現(xiàn),PET的擴鏈限制了PET分子鏈的運動,使熔體的流動性能降低,結晶不完善,結晶困難,熔點溫度低。 氰酸酯可在熱或在催化劑作用下可發(fā)生環(huán)化反應,形成帶有三嗪環(huán)結構的均聚物-氰酸酯的三聚體。本課題利用其三聚體的多官能度,高網(wǎng)絡結構來提高其作為PET擴鏈劑的擴鏈效果。利用紅外譜圖計算出氰酸酯單體的轉(zhuǎn)化率用來表征三聚體的含量。通過GPC來進一步測試三聚體的分子量及分子量分布。通過扭矩,特性粘度,羧基含量以及凝膠含量的測試對比了三聚體的含量對PET擴鏈的影響。結果表明,三聚體的存在可以使PET的擴鏈效果增加,但是當三聚體含量過高時,總的官能團活性降低,擴鏈效果減弱。通過熔體流動速率(MFR)儀,擴展流變儀以及DSC的測試,對擴鏈后的PET的流變性能以及結晶性能進行了表征。進一步的證明了擴鏈的發(fā)生,改善了PET的流變性能,阻礙了PET的結晶。 本課題嘗試使用熱致相分離(TIPS)法制備PET膜,選擇二甲基亞砜(DMSO),二苯甲酮,N-甲基吡咯烷酮(NMP)作為PET的稀釋劑。通過掃描電鏡(SEM)對稀釋劑種類,PET初始濃度和分子量以及冷卻溫度對膜結構的影響進行了研究。結果表明,稀釋劑與聚合物的相互作用不同,所制得的微孔膜結構不同。相容性好的PET/二苯甲酮體系,PET富集相呈現(xiàn)球狀結構,隨著聚合物濃度的增加,PET球尺寸減小。相容性差的PET/NMP和PET/DMSO體系分別呈現(xiàn)蜂窩狀和雙連續(xù)的結構。隨著濃度和分子量的增加,孔徑變小,體系由液-液相分離轉(zhuǎn)變?yōu)楣?液相分離。隨著冷卻溫度的增加,其孔徑增加,PET的富集相由球狀成長為片狀。
[Abstract]:Poly (ethylene terephthalate) (PET) has excellent transparency, chemical resistance and barrier properties. However, PET is easy to undergo thermal degradation, thermal oxidation and water degradation during melt processing.The molecular weight of the product is decreased, the processability is affected, and the mechanical and chemical properties of the product are decreased, which limits its application.In view of the above problems, the chemical chain extension method is used to increase the viscosity of PET and reduce the content of carboxyl terminal, so as to meet the processing requirements of PET.The chain extender of PET in molten state was studied by using cyanate ester Bad Cyclone as chain extender, compared with common chain extender epoxy and diphenyl methane diisocyanate.The melt torque, intrinsic viscosity and viscosity average molecular weight of PET after chain extension were compared. The results showed that the chain extension effect of BADCy on PET was better than that of MDI and epoxy E-51.The chain extension reaction between PET and BADCy was verified by infrared spectroscopy, and the mechanism of BADCy chain extension was explained in detail.By testing the torque, intrinsic viscosity and carboxyl content of PET after chain extension, the effects of reaction time and different rotational speeds on the chain extension effect of PET were studied.The results showed that the molecular weight of PET would be increased with the increase of reaction time, but the thermal degradation would be induced if the reaction time was too long.With the increase of cyanate content, the chain extension effect of PET increased with the increase of chain extension rate.The acceleration of rotational speed is beneficial to the strengthening of shear effect and the mixing effect is strengthened, but the strong shear will lead to the degradation of PET.The rheological properties and crystallization properties of PET after chain extension were characterized by melt flow rate tester, extended rheometer and DSC.It is found that the chain extension of PET limits the movement of PET molecular chain, reduces the fluidity of melt, makes the crystallization imperfect, the crystallization is difficult, and the melting point temperature is low.Cyclization reaction of cyanate ester can take place in heat or under the action of catalyst to form trimer of homopolymer-cyanate ester with triazine ring structure.In this paper, the multifunctional and high network structure of trimer is used to improve the chain extension effect as PET chain extender.The conversion of cyanate monomers was calculated by infrared spectroscopy to characterize the content of trimer.The molecular weight and molecular weight distribution of trimer were further measured by GPC.The effects of trimer content on PET chain extension were compared by measuring torque, intrinsic viscosity, carboxyl content and gel content.The results show that the existence of trimer can increase the chain extension effect of PET, but when the content of trimer is too high, the total functional group activity decreases and the chain extension effect weakens.The rheological properties and crystallization properties of PET after chain extension were characterized by melt flow rate tester, extended rheometer and DSC.It is further proved that chain extension can improve the rheological properties of PET and hinder the crystallization of PET.The effects of initial concentration and molecular weight of PET and cooling temperature on the structure of PET films were studied by scanning electron microscopy (SEM).The results show that the structure of microporous membranes is different due to the different interaction between diluent and polymer.The enriched phase of PET/ benzophenone system with good compatibility shows spherical structure and decreases with the increase of polymer concentration.The PET/NMP and PET/DMSO systems with poor compatibility have honeycomb and double continuous structures, respectively.With the increase of concentration and molecular weight, the pore size becomes smaller and the system changes from liquid-liquid separation to solid-liquid separation.With the increase of cooling temperature, the pore size of PET increases from spherical to flake.
【學位授予單位】：北京化工大學
【學位級別】：博士
【學位授予年份】：2011
【分類號】：O631.3

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