低不饱和度PPO-PLA基可降解聚氨酯材料的研究

【作者】 杨冬梅；

【导师】 范仲勇；

【作者基本信息】 复旦大学 ， 材料物理与化学， 2009， 博士

【摘要】 环境保护是人类在21世纪的最重大课题之一。塑料材料和合成纤维的大量使用,在自然环境中造成严重的“白色污染”。自上世纪80年代,人们开始研究和开发生物可降解聚合物及其制品来取代传统塑料,以减少环境污染。聚乳酸（PLA）是目前最为研究者关注的可降解聚合物材料之一。聚乳酸也称为聚丙交酯,是一种真正的新型绿色材料,其原料乳酸来源充分而且可以再生。聚乳酸不仅可以生物降解,而且生产过程无污染,可用多种方式进行加工,如挤压、纺丝、双轴拉伸,注射吹塑。产品具有良好的生物相容性、光泽度、透明性、手感,还具有一定的耐菌性、阻燃性和抗紫外性,因此用途十分广泛,可用作包装材料、纤维和非织造物等。在应用性能方面,PLA存在着脆性大,抗冲击性也较差的缺点。实验证明,借助共聚合技术对PLA进行改性,不仅可显著改善了PLA的缺陷,且易对材料降解性能实现调控,对降低产品成本也有显著的效果。本论文分别采用国产新型低不饱和度聚环氧丙烷（PPO）和ε-己内酯（ε-CL）,与PLA共聚制备了系列三枝化嵌段或无规共聚物。实现以柔性的PPO链段和CL链段对PLA链段的凝聚态调控的分子设计,并开发了系列新型环境友好可降解聚氨酯材料,包括PPO-左旋聚乳酸（PLLA）基和PPO-外消旋聚乳酸（PDLLA）基部分可降解聚醚-聚酯型聚氨酯泡沫材料、PPO-PLLA基全降解聚醚-聚酯型聚氨酯泡沫材料和全降解型的PLLA-PCL基聚酯聚氨酯泡沫材料等,对聚氨酯泡沫材料的开发进行了创新性的研究。论文的主要研究内容如下:（1）采用红外（FTIR）、凝胶渗透色谱（GPC）、基质辅助激光解吸电离飞行时间质谱（MALDI-TOF-MS）、氢核磁谱（¹H-NMR）、碳核磁谱(¹³C-NMR)对双金属氰化物混合物催化剂、连续法合成的国产新型低不饱和度聚醚多元醇的化学结构及组成等进行了详细的分析。在与通用聚醚多醇对比实验的基础上,揭示了低不饱和度聚醚多元醇的分子结构特点。通过差示扫描量热仪（DSC）和热失重分析（TGA）对聚醚多元醇的热性能进行了测试。为新材料的制备奠定了基础。（2）探索了以低不饱和度聚醚多元醇为原料,采用“一步法”以水为发泡剂合成软质聚氨酯泡沫的技术,解决了低不饱和度聚醚多元醇在发泡过程中易产生塌泡的问题。通过衰减全反射傅立叶变换红外光谱（ATR-FTIR）和DSC揭示了软质聚氨酯泡沫内部的微相形貌,结果表明聚氨酯内部既存在硬相氨酯或脲与软相聚醚之间的微相混合也存在微相分离,并以微相混合为主,微相分离程度较低。力学测试结果表明,低不饱和度聚醚软质聚氨酯泡沫在撕裂、压缩等性能上均好于通用聚醚软质聚氨酯泡沫。（3）以低不饱和度PPO三元醇为大分子引发剂,在辛酸亚锡的催化作用下,通过L-丙交酯或DL-丙交酯进行配位-插入开环聚合合成了PO与LA不同单体摩尔比和凝聚态的三枝化低不饱和度PPO-b-PLA嵌段共聚物。通过FTIR、GPC、¹H-NMR对PPO-b-PLA嵌段共聚物的化学结构和链组成等进行了详实的表征。研究结果表明PPO-b-PLA嵌段共聚物的分子量分布极窄,多分散系数（PDI）在1.0～1.1之间,其化学结构和链组成与分子实验设计基本一致。DSC和广角X射线衍射（WAXD）对PPO-b-PLA嵌段共聚物的凝聚态进行了研究。由于PLLA链段为等规立构构型,PPO-b-PLLA中的PLLA链段具有结晶能力,其结晶度随PLLA链段长度的降低而降低。由于PDLLA为无规立构构型,因此,PPO-b-PDLLA嵌段共聚物为无定形聚合物。TGA对PPO-b-PLA嵌段共聚物的热稳定性测试结果表明PLLA和PDLLA链段使嵌段共聚物的热稳定性得到了提高,其中立够规整度好的PLLA链段对共聚物热稳定性的提高贡献更大。（4）分别制备了基于三枝化低不饱和度PPO-b-PLA嵌段共聚物的从部分降解到全降解的新型聚氨酯泡沫材料。采用ATR-FTIR和DSC对PPO-b-PLA基聚氨酯泡沫的微相形貌进行了表征,研究证明了PLA链段的引入促进了聚氨酯内部的微相混合,并且PDLLA链段比PLLA链段对微相混合的贡献更大。另外,全降解PPO-b-PLA基聚氨酯泡沫内部的微相混合程度高于部分降解PPO-b-PLA基聚氨酯泡沫。通过AFM对聚氨酯的微相形貌观察结果显示纯的聚醚聚氨酯内部发生了微相分离;PPO-b-PLLA基部分降解聚氨酯泡沫中,等规立构的PLLA链段发生了微相分离,但没有观察到硬段氨酯或脲的微相分离;PPO-b-PDLLA基部分降解聚氨酯泡沫中,没有发生微相分离现象。PPO-b-PLA基部分降解聚氨酯泡沫在力学性能方面表现出了较高的撕裂和拉伸性能,并且PPO-b-PDLLA基部分降解聚氨酯泡沫无论在撕裂、拉伸、回弹性能上均好于PPO-b-PLLA基部分降解聚氨酯泡沫。碱催化水解实验证明PPO-b-PLA基聚氨酯泡沫的降解能力随PLA的含量增加而增加,且基于无规立构的PDLLA链段的聚氨酯泡沫的水解性好于基于等规立构的PLLA链段的聚氨酯泡沫。PPO-b-PLA基全降解聚氨酯泡沫的碱催化水解的速率和程度远高于PPO-b-PLA基部分降解聚氨酯泡沫。酶解实验证明,PPO-b-PLA基全降解聚氨酯泡沫具有酶降解能力;而PPO-b-PLA基部分降解聚氨酯泡沫的酶降解行为不明显。（5）以丙三醇为引发剂,辛酸亚锡为催化剂,通过丙交酯和ε-己内酯开环聚合反应合成了一系列分子量为3000左右,不同单体摩尔比的三枝化PLLA-r-PCL无规共聚物。通过FTIR、GPC和¹H-NMR对共聚物的化学结构和链组成进行了表征,结果表明PLLA-r-PCL为无规共聚结构,其化学结构和分子组成与实验设计基本一致。并以三枝化PLLA-r-PCL无规共聚物为原料合成了聚酯型全降解聚氨酯泡沫。ATR-FTIR和DSC证明了PLLA-r-PCL基聚氨酯泡沫中既存在微相分离又存在微相混合,且微相混合的程度远高于微相分离的程度。PLLA-r-PCL基聚氨酯泡沫在力学性能上表现为硬度较高的材料。碱催化水解和酶降解实验表明,PLLA-r-PCL基聚氨酯泡沫表现出了良好的降解能力。更多还原

【Abstract】 Environmental protection is one of the tasks of vital importance in the 21st century.The huge consumption of plastics and synthetic fibres has caused serious "white pollution" problems in the natural environment.Since 1980s,with the aim of reducing environmental pollution,people have started to develop biodegradable polymers and products as a substitute for general plastics.Poly（lactic acid）（PLA） has been one of the degradable polymers that attract the most attention of researchers.Poly（lactic acid）,also called polylactide,is an essentially novel green material because of the sufficient and renewable resources of lactic acid.In addition,PLA is biodegradable and its producing procedure is pollution free.PLA can be processed by many methods,such as extrusion,spinning,biaxially oriented,injection and blow molding.PLA products have good biocompatibility, brightness,clarity,touch feeling,and also reasonable fungus resistance,flame resistance,and anti-UV properties.Therefore,PLA products are widely used as packaging materials,fibres,and bonded yarn fabrics.However,PLA is brittle and of low impact resistance.Experiments show that the defects can be modified by copolymerizing PLA with other materials,and variable degradability and lower production costs can also be realized.In this work,triarm block or random copolymers were synthesized from domestic novel low unsaturated poly（propylene oxide）（PPO） orε-caprolactone（CL） together with PLA.The condensed matter of PLA segments is adjusted by the soft PPO or PCL segments.Furthermore,novel environmental friendly degradable polyurethane（PU） materials were investigated, including PPO-b-PLLA or PPO-b-PDLLA based partially degradable PU foams, PPO-b-PLLA based fully degradable PU foams,and PLLA-r-PCL based fully degradable PU foams.The main contents of this work are as follows.（1） Fourier transform infrared（FTIR）,gel permeation chromatography（GPC）, matrix-assisted laser desorption/ionisation-time of flight mass spectrometry （MALDI-TOF MS）,proton nuclear magnetic resonance（¹H-NMR）,and ¹³C nuclear magnetic resonance(¹³C-NMR) were carried out to investigate the chemical structure and composition of the domestic novel low unsaturated polyether polyols,which were synthesized by continuous process using double metal cyanide complex catalysts.The molecular structure of low unsaturated polyether polyols were characterized and compared with the general polyether polyols.Differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA） were measured to evaluate the thermal properties of the polyether polyols.Basic data were provided for further developing of new materials.（2） The synthesis of flexible PU foams from low unsaturated polyether polyols by one-stage process using water as blowing agent were investigated.The processing technic was found to be a good solution to the problem of collapse during the foam forming process from low unsaturated polyether polyols.The microphase morphology of flexible PU foams were investigated by attenuated total reflectance（ATR）-FTIR and DSC.The results show that both microphase mixing and microphase separation between the hard segments of urethane or urea and the soft segments of polyether present in flexible PU foams,while the microphase mixing is dominating.The mechanical tests show that both the tear propagation resistance and compression hardness of flexible PU foams made from low unsaturated polyether polyols are better than those of general flexible PU foams.（3） Triarm low unsaturated PPO-b-PLA copolymers of different PO/LA molar ratios and condensed matter were synthesized by ring-opening polymerization of L-lactide or DL-lactide using low unsaturated PPO triols as macromolecular initiator and stannous octoate as catalyst.FTIR,GPC,and ¹H-NMR were used to investigate the chemical structure and chain composition.It is proved that the copolymers all present narrow molecular weight distribution（PDI～1.0-1.1）.It was shown by DSC and wide angle X-ray diffraction（WAXD） that PPO-b-PLLA copolymers with isotactic PLLA segments are crystalline materials,and the crystallinity decreases with decreasing the PLLA segments length,whereas,PPO-b-PDLLA copolymers having atactic PDLLA segments are amorphous.The thermal stability of PPO-b-PLA copolymers was improved by introducing PLLA or PDLLA segments according to the results of TGA experiments,and PLLA segments were found to have a stronger effect than PDLLA segments.（4） PPO-b-PLA based partially degradable and fully degradable PU foams were synthesized.It was found by ATR-FTIR and DSC that the PLA segments improve the microphase mixing in PPO-b-PLA based PU foams.In addition,the contribution of PDLLA segments to the microphase mixing is greater than that of PLLA segments. The extent of microphase mixing in PPO-b-PLLA based fully degradable PU foams is greater than that in PPO-b-PLA based partially degradable PU foams.Atomic force microscope（AFM） was also used to examine the microphase morphology of PU foams.The results show that microphase separation of urethane or urea takes place in pure PPO foams.As for PPO-b-PLLA based partially degradable PU foams, microphase separation of PLLA segments is observed besides that of urethane or urea. No microphase separation is observed in PPO-b-PDLLA based partially degradable PU foams.The mechanical property tests show that PPO-b-PLA based partially degradable PU foams exhibit high performance in both tear propagation resistance and tensile properties.The tear propagation resistance,tensile,and rebound resilience properties of PPO-b-PDLLA based partially degradable PU foams are better than those of PPO-b-PLLA based partially degradable PU foams.Alkaline hydrolysis experiments prove that the degradability of PPO-b-PLA based PU foams increases with increasing PLA content,and the degradability of PPO-b-PDLLA based partially degradable PU foams is greater than that of PPO-b-PLLA based partially degradable PU foams.And the degradation rate and extent of PPO-b-PLA based fully degradable PU foams are far greater than those of PPO-b-PLA based partially degradable PU foams under alkaline hydrolysis condition.In contrast,pure PPO foams are non-degradable under the alkaline hydrolysis condition.Enzymatic degradations prove that PPO-b-PLA based fully degradable PU foams are degradable under enzymatic degradation condition,whereas the degradation behaviors of PPO-b-PLA based partially degradable PU foams are not obvious.（5） Triarm PLLA-r-PCL random copolymers with various monomer molar ratios were synthesized by ring-opening polymerization of L-lactide andε-CL using glycerol as initiator and stannous octoate as catalyst.FTIR,GPC,and ¹H-NMR were used to investigate the chemical structure and chain composition.It is confirmed that the copolymers are random copolymers,and the chemical structure and the chain composition of the copolymers are as expected as the initial molecular design.In addition,PLLA-r-PCL based fully degradable PU foams were synthesized from PLLA-r-PCL copolymers.It is found by ATR-FTIR and DSC that a slight microphase separation exists in this material.The mechanical property tests show that PLLA-r-PCL based PU foams exhibit high hardness.Moreover,PLLA-r-PCL based PU foams exhibit great degradability under both alkaline hydrolysis and enzymatic degradation condition.更多还原