【作者】 张琪；

【导师】 王朝；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2023， 硕士

【摘要】 高分子透明材料因其质轻、美观和独特的光学性能,广泛应用于水杯、食品封装、光学零件、家具装饰等领域,为人们生活带来了诸多便利。聚(对苯二甲酸/乙二醇)酯(PET)作为一种大宗的聚酯材料,因其价格低廉,性能优异受到了各界广泛关注。但PET为半晶型聚合物,因此在其成型过程中极易产生结晶现象,从而影响成品的透光率;更为重要的是PET的玻璃化转变温度(T_g)虽然已经高于大多数聚酯材料,但其T_g仍然难以满足日常生活中的中高温场景使用需求。因此,本论文在PET的结构基础上,引入生物基2,3-丁二醇(2,3-BDO)和1,4-环己二醇(1,4-CHD)两种单体,设计并合成了低成本的高T_g透明聚酯材料,以期用于光学器件等领域。论文的主要工作如下:本论文第一部分中,在PET分子结构设计基础上,引入生物基2,3-BDO进行改性。2,3-BDO是一种廉价的生物基单体,具有两个不对称侧甲基,能有效破坏PET的结晶结构;可以赋予链段强刚性,对提高聚酯T_g有显著作用。因此本论文利用其部分取代乙二醇(EG),通过一锅熔融法制备了三元透明共聚酯,即聚(对苯二甲酸/乙二醇/2,3-丁二醇)酯(P23BET)。为了解决因单体反应活性低造成的难聚合问题,探究了反应装置、催化剂以及聚合温度对聚合反应的影响,确定了最佳聚合工艺,制备得到的共聚酯分子量最高可以达到22500 g/mol。通过各测试手段探究了2,3-BDO单元占比对材料性能的影响。当2,3-BDO投料超过醇类单体的50 mol%时,P23BET表现为T_g在90℃以上的无定型透明材料,但其透光率和冲击强度等方面会随2,3-BDO的增加而下降;当2,3-BDO投料低于醇类单体的50 mol%时,共聚酯会出现结晶现象。因此接下来选择综合性能最优的P23BET-50%,对其性能进行进一步改善。本论文第二部分,在P23BET-50%的基础上,保持2,3-BDO摩尔占比不变,引入刚性1,4-CHD单体部分取代EG,制备四元聚(对苯二甲酸/乙二醇/2,3-丁二醇/1,4-环己二醇)酯(P23BECT)。在结构中引入1,4-CHD后进一步抑制了结晶,提高了P23BECT的T_g,并解决了因2,3-BDO引入过多导致的分子量下降,黄变等问题。通过~1H-NMR和FT-IR表征了1,4-CHD单体的成功引入,并通过热学、光学、力学等测试详细探究了不同1,4-CHD占比对共聚酯结构与性能的影响。P23BECT表现为无定型透明聚酯,在不牺牲分子量的情况下T_g得到大幅度提升,透光率由88%提升至91%左右。P23BECT性能优良,成本低廉,有望在光学器件等领域有所应用。更多还原

【Abstract】 Due to its lightweight,beautiful appearance and unique optical properties,polymer transparent materials are widely used in water cups,food packaging,optical parts,furniture decoration and other fields,bringing a lot of convenience to people’s life.Polyethylene terephthalate(PET),as a kind of bulk polyester material,has attracted wide attention because its low price and excellent properties.But unfortunately,PET is a semi-crystalline polymer,so it is very easy to produce crystallization in its forming process,which affects the transmittance of the finished product.More importantly,although the glass transition temperature(T_g)of PET is already higher than most polyester materials,it is still difficult to meet the needs of daily life in medium and high temperature scenarios.Therefore,in this thesis,based on the structure of PET,two monomers of Bio-base 2,3-butanediol(2,3-BDO)and 1,4-cyclohexadiol(1,4-CHD)were introduced to design and synthesize a high T_g transparent polyester material with low-cost.It was expected to be used in fields such as optical devices.The main work of the thesis is as follows:In the first part of this thesis,on the basis of the molecular structure of PET,Bio-based 2,3-BDO was introduced for modification.2,3-BDO is a cheap Bio-based monomer with two asymmetric lateral methyl groups,which can effectively destroy the crystalline structure of PET.It can bring strong rigidity to the chain segment and has a significant effect on improving polyester T_g.Therefore,ternary transparent copolyesters,which were named poly(terephthalic acid/ethylene glycol/2,3-butanediol)ester(P23BET),were prepared by one-pot melting process by using it to partially replace ethylene glycol(EG).In order to solve the difficult polymerization problem caused by low reactivity of monomer,the influence of reaction device,catalyst and temperature on polymerization reaction was explored.The optimal polymerization reaction process was finally determined,and its Molecular Weight could reach up to 22,500 g/mol.The effects of 2,3-BDO ratio on the properties of materials were investigated by various testing methods.When the2,3-BDO feed ratio exceeds 50%,P23BET is an amorphous transparent material with T_g above 90℃,but its transmittance and impact strength decrease with the increase of 2,3-BDO.When the 2,3-BDO feed ratio is lower than 50%,the copolyester will crystallize.Therefore,P23BET-50%with the best comprehensive performance was selected to further improve its properties.In the second part of this thesis,on the basis of P23BET-50%,rigid 1,4-CHD monomer was introduced to partially replace EG to prepare the quaternary copolyesters which were named poly(terephthalate/ethylene glycol/2,3-butanediol/1,4-cyclohexadiol)ester(P23BECT)under the condition of constant molar ratio of 2,3-BDO.The introduction of 1,4-CHD into the copolyesters structure further inhibited the crystallization capacity,improved its T_g,and solved the problem of molecular weight reduction and yellowing caused by excessive introduction of 2,3-BDO.The successful introduction of 1,4-CHD monomer was characterized by ~1H-NMR and FT-IR,and the effects of different1,4-CHD feed ratios on the structure and properties of copolyesters were investigated by thermal,optical and mechanical tests.P23BECT is an amorphous transparent polyester,whose T_g is greatly improved without sacrificing molecular weight,and its transmittance is also increased from 88%to 92%.P23BECT has excellent performance and low cost,which is expected to be applied in optical devices and other fields.更多还原