RAFT乳液聚合制备聚（苯乙烯—丙烯腈）嵌段共聚物及其共混物性能

发布时间：2018-04-19 19:43

本文选题：RAFT乳液聚合 + 大分子RAFT结构　；参考：《浙江大学》2015年博士论文

【摘要】：苯乙烯-丁二烯-丙烯腈(ABS)树脂作为五大通用塑料之一,兼有聚丁二烯的韧性和抗冲击性,聚丙烯腈的耐热性和化学稳定性以及聚苯乙烯的刚性、光泽性和加工性,得到广泛应用。在此基础上发展起来的丙烯腈-苯乙烯-丙烯酸酯(ASA)树脂,进一步改善了ABS树脂的热氧化稳定性、光氧化稳定性和耐化学性,也逐渐成为一种重要的塑料材料。ABS和ASA的制备过程相似,但由于采用的是传统自由基聚合方法,橡胶相为接枝共聚或轻度交联结构,无法精确调控聚合物的分子链结构。本文采用新近发展的RAFT乳液聚合的方法,以双亲性聚丙烯酸-b-聚苯乙烯大分子RAFT试剂(AA-b-S-RAFT)作为乳化剂和调控剂,制备基于嵌段共聚物的ABS和ASA韧性塑料(嵌段型ABS和ASA韧性塑料)。系统研究苯乙烯(S)及苯乙烯／丙烯腈(AN)的RAFT乳液(共)聚合过程、嵌段型ABS和ASA韧性塑料的制备技术,探讨了聚合物分子链结构对材料相形态和机械性能的影响。具体的研究内容和结果如下：1)研究AA-b-S-RAFT的结构对苯乙烯乳液聚合的影响,结果发现乳胶粒径和乳胶粒数受丙烯酸链段长度的影响较大而阻聚期则受苯乙烯链段的长度影响较大。调节AA-b-S-RAFT的结构使其亲水亲油平衡值(HLB)为13-20时,聚合过程的可控性较好,聚合物分子量符合理论设计值,分子量分布较窄,且乳液稳定性好。AA-b-S-RAFT的HLB值过低,则乳液稳定性变差且最终产物的PDI较高；AA-b-S-RAFT的HLB值过高,则大分子RAFT试剂受引发剂过硫酸钾(KPS)的氧化作用影响较大,聚合物分子量明显高于理论设计值且产物的PDI较高。将引发剂KPS替换为偶氮二异氰基戊酸(V501),聚合物分子量与理论设计值相符很好但PDI较高(1.4)。在理论设计分子量一致的情况下,通过改变AA-b-S-RAFT的结构,乳胶粒径可在80 nm-172 nm间调控。当大分子RAFT的结构为AA20-b-S5-RAFT,体系阻聚期较短,聚合速率快,最终转化率高,聚合物分子量与理论设计值相符性较好,分子量分布窄(PDI=1.27),乳液稳定性好。2)以AA20-b-S5-RAFT为乳化剂和调控剂进行S和AN的RAFT乳液共聚合研究,结果发现共聚反应无阻聚期,且体系乳胶粒数受RAFT试剂浓度的改变影响很小。共聚过程可控性好,共聚物分子量随转化率线性增长且PDI低,但在高转化率下因凝胶效应的影响PDI急剧上升。凝胶效应的程度与SAN共聚物的理论分子量和组成密切相关。对于恒比点共聚(质量比m(S):m(AN)=3：1)的体系,通过在成核期结束后将聚合温度从70℃升至90℃可有效消除凝胶效应的影响,聚合终产物PDI仅为1.20左右。但随着AN含量的增加,凝胶效应越来越显著,即使升温也无法完全消除,同时AN含量的增加也使乳液的稳定性降低。3)利用RAF T乳液聚合技术,可控制备了SAN基体材料、系列SAN/PB嵌段共聚物、系列SAN/PBA嵌段共聚物,通过共混、注塑,制备嵌段型ABS和ASA韧性树脂,并研究聚合物分子结构与相形态和机械性能之间的关系,发现：a)采用乳液共混技术可制备出橡胶相粒子分散很好的嵌段型ABS和ASA韧性树脂,橡胶相粒子均匀分散是获得较好增韧效果的前提。相比于两嵌段共聚物,以三嵌段共聚物作为橡胶相的材料,在不损失模量和强度的条件下,断裂伸长率和拉伸断裂韧性显著提高,但缺口冲击强度降低。b)对比机械共混和乳液共混制备的嵌段型ASA材料,后者的拉伸性能(模量、强度、断裂伸长率和断裂韧性)远好于前者,但缺口冲击强度较差。将嵌段共聚物中的PBA段交联可大幅提高机械共混体系的拉伸性能。c)三嵌段共聚物的嵌段型ASA材料,弯曲模量与共混制备的嵌段型ASA材料相比基本不变,但弯曲强度显著提高。d)以理论分子量为60 kg/mol的SAN共聚物为基体相,橡胶含量为20%,可制备机械性能较为优良的嵌段型ABS和ASA韧性树脂。具体为：以SAN358-b-B4437两嵌段共聚物为橡胶相,乳液共混制备的嵌段型ABS材料,其弹性模量、屈服强度、拉伸强度、断裂伸长率、拉伸断裂韧性、弯曲模量、弯曲强度、缺口冲击强度和维卡软化点温度分别可达2100 MPa.48 MPa.33 MPa 30%、12.77 MJ·m-3、2270 MPa、77.7 MPa、28.38 KJ·m-2和99.5℃；以SAN358-b-CrBA936-b-SAN358三嵌段共聚物为橡胶相,机械共混制得嵌段型ASA材料,其弹性模量、屈服强度、拉伸强度、断裂伸长率、拉伸断裂韧性、弯曲模量、弯曲强度、缺口冲击强度和维卡软化点温度分别可达2140 MPa、48 MPa、43 MPa、61%、27.34 MJ·m-3、2160 MPa、74.0 MPa、7.84 KJ·m-2、和96.9℃。
[Abstract]:Styrene butadiene acrylonitrile (ABS) resin is one of the five major general plastics. It also has the toughness and impact resistance of polybutadiene, the heat resistance and chemical stability of polyacrylonitrile, the rigidity, luster and processability of polystyrene. Based on this, the acrylonitrile styrene acrylate (ASA) resin has been developed. The thermal oxidation stability, photooxidation stability and chemical resistance of ABS resin are further improved, and the preparation of an important plastic material is similar to that of.ABS and ASA. However, because of the traditional free radical polymerization, the rubber phase is graft copolymerization or slightly crosslinked structure, which can not accurately regulate the molecular chain structure of the polymer. In this paper, a newly developed RAFT emulsion polymerization method was used to prepare ABS and ASA ductile plastics (ABS and ASA ductile plastics) based on block copolymers, using -b- polystyrene macromolecule RAFT reagent (AA-b-S-RAFT) as a emulsifier and regulator. The RAFT emulsion of styrene (S) and styrene / acrylonitrile (AN) was systematically studied. The process of liquid (common) polymerization, the preparation of block type ABS and ASA ductile plastics, the influence of polymer molecular chain structure on the phase morphology and mechanical properties of the materials is discussed. The specific contents and results are as follows: 1) the effect of the structure of AA-b-S-RAFT on the emulsion polymerization of styrene is studied. The results show that the size of latex particles and the number of latex particles are chain acrylic. When the structure of AA-b-S-RAFT is 13-20, the polymerization process has a better controllability, the molecular weight of the polymer is in accordance with the theoretical design value, the molecular weight distribution is narrow, and the HLB value of the emulsion has a good stability and the HLB value of.AA-b-S-RAFT is too low. The stability of the liquid is worse and the PDI of the final product is higher; the HLB value of the AA-b-S-RAFT is too high, then the large molecular RAFT reagent is influenced by the oxidation of potassium persulfate (KPS), the molecular weight of the polymer is obviously higher than the theoretical design value and the PDI of the product is higher. The initiator KPS is replaced by the azo two ISO cyanyl valerate (V501), the molecular weight of the polymer and the molecular weight of the polymer The theoretical design values are good, but the PDI is higher (1.4). In the case of the uniform molecular weight of the theoretical design, by changing the structure of AA-b-S-RAFT, the size of latex particles can be controlled between 80 nm-172 and nm. When the structure of the macromolecule RAFT is AA20-b-S5-RAFT, the polymerization period is shorter, the rate of polymerization is faster, the final conversion rate is high, the molecular weight of the polymer and the theoretical design value are high. The consistency is good, the distribution of molecular weight is narrow (PDI=1.27) and the stability of emulsion is good.2). The copolymerization of RAFT emulsion with AA20-b-S5-RAFT as emulsifier and regulator is carried out by RAFT emulsion copolymerization. The results show that the copolymerization reaction has no hindrance period, and the number of latex particles in the system is little influenced by the change of RAFT reagent concentration. The copolymerization process has good controllability and the molecular weight of the copolymer is changed with the transformation. A linear increase in rate and low PDI, but a sharp rise in the effect of the gel effect on the PDI. The degree of the gel effect is closely related to the theoretical molecular weight and composition of the SAN copolymer. For the system of constant specific point copolymerization (mass ratio m (S), m (AN) =3:1), the polymerization temperature can be effectively eliminated by raising the polymerization temperature from 70 to 90 degrees centigrade after the completion of the nucleation period. With the effect of glue effect, the final product PDI of the polymerization is only about 1.20. But with the increase of AN content, the gel effect is becoming more and more obvious, and the stability of the emulsion can not be completely eliminated, while the increase of AN content also reduces the stability of the emulsion.3). Using RAF T emulsion polymerization technology, the SAN matrix material, a series of SAN/PB block copolymers and a series of SAN/P can be controlled. BA block copolymer, through blending, injection molding, preparation of block type ABS and ASA ductile resin, and studying the relationship between the molecular structure of the polymer and the phase morphology and mechanical properties. It is found that the emulsion blending technology can be used to prepare the block type ABS and ASA ductile resin with good dispersion of the rubber particles, and the uniform dispersion of the rubber particles is better. The precondition of toughening effect is compared with the two block copolymer, with three block copolymer as the rubber phase material, the elongation at break and tensile fracture toughness are significantly increased without loss modulus and strength, but the notch impact strength decreases by.B). The tensile properties of the ASA materials are compared with the Mechanical Co mixing and emulsion co mixing. The modulus, strength, breaking elongation and fracture toughness are better than the former, but the notch impact strength is poor. The PBA segment crosslinking in the block copolymer can greatly improve the tensile properties of the mechanical blending system.C) the block type ASA material of the three block copolymer, and the flexural modulus is basically the same as the block type ASA material prepared by the blend, but the bending strength is not constant. The SAN copolymer with a theoretical molecular weight of 60 kg/mol was used as the matrix phase and the rubber content was 20%. The block type ABS and the ASA ductile resin with better mechanical properties were prepared, and the block type ABS materials were prepared with SAN358-b-B4437 two block copolymer as rubber phase and emulsion blend, and their modulus of elasticity, yield strength and tensile strength were strong. Degree, elongation at break, tensile fracture toughness, flexural modulus, bending strength, notch impact strength and VEKA softening point temperature can reach 2100 MPa.48 MPa.33 MPa 30%, 12.77 MJ. M-32270 MPa, 77.7 MPa, 28.38 KJ. M-2 and 99.5 centigrade, and SAN358-b-CrBA936-b-SAN358 three block copolymer as rubber phase, and mechanical blending to make block type ASA material The modulus of elasticity, yield strength, tensile strength, elongation at break, tensile fracture toughness, flexural modulus, bending strength, notch impact strength and VEKA softening point temperature can reach 2140 MPa, 48 MPa, 43 MPa, 61%, 27.34 MJ. M-32160 MPa, 74 MPa, 7.84 KJ. M-2, and 96.9 degrees C, respectively.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ317

【参考文献】