共聚酯的结晶性能研究

通过添加二元酸或二元醇来制备共聚酯,采用DSC对共聚酯的结晶性能展开研究,分析了二元酸或二元醇对共聚酯结晶性能的影响。     

聚(丁二酸丁二酯-co-衣康酸丁二酯)的合成

用含不饱和双键基团的衣康酸作共聚单体,采用直接熔融酯化聚合法制备可生物降解的聚(丁二酸丁二酯-co-衣康酸丁二酯)。共聚物的相对分子质量及其分布、溶解性能、热性能及结晶性能均受分子链中衣康酸含量的影响,当衣康酸摩尔分数达50%时,共聚物成为不溶/熔的交联弹性体。     

聚丁二酸丁二醇酯基共聚物及其多嵌段共聚物的合成与性能

采用“一步法”,以丁二酸酐（SAA）和1,4–丁二醇（BDO）为单体、端羟基二元醇为共聚单体合成了聚丁二酸丁二醇酯（PBS）及一系列端羟基二元醇共聚物,同时使酚酞与SAA的缩聚产物参与SAA和BDO的共聚反应,并通过链段调节合成法制备兼具刚性链段和柔性链段的可生物降解三嵌段共聚聚酯热塑性弹性体聚(丁二酸丁二醇酯-共-酚酞丁二酸丁二醇酯)（SAA-PHE-PBS）,研究了PBS及其共聚物的分子量、化学结构组成、热性能和结晶性能,此外,使用南极假丝酵母脂肪酶B测试了PBS及其共聚物的生物降解性能。结果表明,端羟基二元醇共聚物的玻璃化转变温度变化幅度不大,熔融温度无明显改变,结晶度降低,亲水性有所改善,生物降解性能得到大幅度提升;三嵌段热塑性弹性体SAA-PHE-PBS的玻璃化转变温度升高,结晶度与PBS相差不大,疏水性更强,共聚合物的残重率有所增加,生物降解性能有不同程度的降低。     

可降解液体地膜的研究现状及应用展望

系统归纳了一种完全可生物降解农业覆盖材料——可降解液体地膜的种类、特点和性能,重点介绍和分析了基于高分子接枝共聚机理的天然高分子材料类液体地膜的代表性技术及其制备机理。同时,对国内外代表性液体地膜材料的应用现状及效果进行了评估,并针对目前液体地膜的发展难点提出见解,以期为新型液体地膜材料的开发及其性能的提升提供技术支撑。     

可生物降解PEG/PBS高分子相变储能材料的制备

以聚乙二醇(PEG)为相变物质,可生物降解脂肪族聚酯——聚丁二酸丁二酯(PBS)为骨架支撑材料,通过接枝共聚法和偶联共混法制备了PEG/PBS高分子固-固相变材料.采用红外光谱和差示扫描量热法研究了相变材料的结构和相变行为;利用偏光显微镜(PLM)观察了相变材料的结晶形态.结果表明:接枝共聚法和偶联共混法制备的相变储能材料均具有可逆的相转变特性.两种相变材料中,相变物质PEG的结晶相转变焓分别为83.9,103.2 kJ/g,结晶峰值温度分别为21.4,23.9℃;此外,在等温结晶过程中,可观察到采用两种方法制备的PEG/PBS相变材料中存在尺寸大小不均匀的混合球晶形态;同均聚物相比,球晶尺寸均变小,PBS的环带球晶形貌消失.     

产品开发

生物降解材料新秀——共聚酯前途光明 目前已开发成功的生物降解材料聚乳酸、聚羟基烷酸酯、聚已内酯、聚碳酸亚丙酯、聚碳酸亚乙酯、聚丁二醇丁二酸酯、聚乙烯醇等,由于产品性能和成本等因素,在大范围推广受限,而脂肪-芳香族共聚聚酯作为生物降解材料新秀,兼具脂肪族聚酯良好的生物降解性、生物相容性和芳香族聚酯优异的力学性能及热稳定性,而且生产成本低,开发和市场前景非常广阔。     

软段种类对超支化形状记忆聚氨酯形态结构的影响

以几种不同的聚酯多元醇为原料,合成了超支化形状记忆聚氨酯(HBSMPUR).通过差示扫描量热仪、广角X射线衍射仪、傅立叶变换红外光谱仪、原子力显微镜等测试手段对材料进行了结构表征和形态分析,系统研究了软段种类对HBSMPUR形态结构的影响.研究发现,软段聚酯二元醇的链节越长,分子量越大,HBSMPUR的结晶性能越好;以聚己二酸己二酯、聚已二酸丁二酯为软段制备的HBSMPUR的结晶性能较好.     

低熔点快固化聚酯热熔胶的合成与性能研究

在对苯二甲酸二甲酯(DMT)和1,4-丁二醇(BD)合成聚酯体系中引入其它共聚组分,制备了快速结晶的低熔点共聚酯热熔胶,其熔点约为70～120℃。由于熔点越低结晶性能越差,因此在合成聚酯热熔胶的基础上,进一步对其进行改性,且对组成与性能的关系进行了研究。结果表明,聚酯热熔胶的熔点和结晶性能随DMT含量的增加而升高;二元醇体系的配比和含量对熔点和结晶性能有很大影响,当混合二元醇物质的量比为1时具有最低的熔点,BD/HD(1,6-己二醇)体系比EG(乙二醇)/HD体系的结晶速率快,BD/HD体系中结晶速率随HD含量的增加而加快。     

磺酸盐型水性聚酯-丙烯酸树脂杂化体的合成研究

第一步先将间苯二甲酸-5-磺酸钠(5-SSIPA)和新戊二醇(NPG)投入到反应瓶中制得聚酯中间体;第二步将一定量的聚酯中间体与配方量的二元酸和二元醇投入到反应瓶中,并用椰子油酸对其进行改性,制备出酸值＜5 mgKOH/g的水性不饱和聚酯;第三步,过氧化苯甲酰(BPO)作为自由基聚合的引发剂,将甲基丙烯酸甲酯(MMA)...     

PET溶胀聚合反应研究进展

溶胀聚合是制备高分子质量聚酯的有效手段.文章综述了溶胀剂、溶胀温度、催化剂浓度、氮气流量、颗粒大小及结晶对溶胀聚合反应的影响,介绍了从低粘度聚酯预聚体通过溶胀聚合制备高分子质量聚酯的工艺新思路.溶胀聚合动力学机理研究表明,溶胀促进了端基扩散,促进了溶胀反应,但溶胀对内扩散的影响尚有待进一步研究.     

聚酯链结构定制及其构效关系

聚酯材料的物理性能与可生物降解性为其聚集态结构所决定,而聚合物链的化学组成、序列和拓扑结构又是决定聚合物聚集态结构的最关键因素。为此,本文从基于聚合过程调控的聚酯链结构定制出发,总结了嵌段、长支链、梳状、星型、超支化与树枝状结构聚酯的定制方法;评述了链结构与聚酯热与力学性能之间的构效关系,探讨了链结构对聚酯降解性能的影响规律,前人的研究表明共聚物嵌段长短影响着结晶聚集态结构,长支链的存在有助于聚酯结晶温度与结晶度的提高;链的结晶能力、链长及亲疏水性决定了聚酯的降解性能。文中还对高性能可生物降解聚酯材料的开发进行了展望。     

不同构型聚乳酸共混体系的立构复合结晶研究进展

左旋聚乳酸(PLLA)和右旋聚乳酸(PDLA)在共混体系中可形成立构复合(sc)结晶,与聚乳酸(PLA)同质结晶材料相比,sc 结晶材料具有良好的耐热性和耐化学稳定性。因此,sc 结晶是改善PLA 综合性能的一种有效手段。但在PLLA/PDLA 共混体系中,存在各自的同质结晶与两者之间sc 结晶的竞争,所以制备高耐热sc 型PLA 材料的关键之一是理解其sc 结晶的形成条件与机理,进而调控和促进其sc 结晶程度。在PLLA/PDLA 共混物中,sc 结晶受聚合物化学结构、结晶与加工条件等诸多因素影响,其影响规律和机理较复杂。根据PLLA/PDLA共混物sc 结晶行为影响因素的不同,从聚合物分子量、立构规整性、共混比例、分子链拓扑结构、结晶方式与条件、加工助剂和其他组分加入6 个方面出发,详细综述了PLLA/PDLA 共混物sc 结晶及其sc 材料制备的研究进展,以期为高耐热生物基PLA 材料的加工制备提供指导。     

Thermal properties and crystallization behaviour of blends of poly(ε‐caprolactone) with chitin and chitosan

Blend films of poly(ε‐caprolactone) (PCL) with chitin and chitosan were prepared as completely biodegradable polyester/polysaccharide composites. Differential scanning calorimetry and Fourier‐transform infrared (FTIR) spectroscopy revealed that the crystallization of PCL, which had been suppressed by blending with chitin and chitosan, progressed with the elapse of time after film preparation. The suppression of crystallization of PCL by blending with polysaccharides was also observed by solid‐state ¹³C NMR spectroscopy. Furthermore, FTIR spectra indicated that the extent of hydrogen bonding between PCL and polysaccharides, which suppressed the crystallization of PCL, decreased with elapse of time after film preparation. Wide‐angle X‐ray diffraction indicated that the polysaccharides affected the crystallization of PCL and slightly deformed its crystalline lattice. Copyright © 2003 Society of Chemical Industry     

PBAT/organoclay composite films: preparation and properties

Environmental problems caused by the increased waste associated with short-term use of plastic materials, particularly by the food packaging industry, prompted the search for biodegradable alternatives. This contribution studied one of these alternatives, poly(butylene adipate-co-terephthalate)—PBAT, a polymer that is fully biodegradable in common landfills, compounded with a small amount of Cloisite 20A organoclay. Materials were mixed in a laboratory internal mixer and films prepared in a chill roll extruder. Results show that the presence of organoclay does not increase degradation of the polymer matrix during processing, nor affects its crystallization characteristics. However, organoclay addition significantly diminished oxygen and carbon dioxide permeability of the films, making them a very interesting alternative for the food packaging industry.     

生物降解塑料中国专利分析研究

对1989年-2006年4月期间公开的生物降解塑料技术中国专利进行了检索，从历年专利申请量、专利类型、申请人构成、专利技术特征等方面进行了分析，结果表明：我国生物降解塑料企业对于生物降解塑料技术的研究还没有足够的自主知识产权，而日本、美国、德国和意大利等国家的生物降解塑料企业在此领域的技术实力较强，国内企业应该重点关注。目前生物降解塑料的发展方向是淀粉僳合物共混塑料、全淀粉热塑性塑料、生物聚酯型、聚乳酸、二氧化碳塑料等全生物降解塑料，如何提高产品性能、降低生产成本是发展生物降解塑料的关键。     

Filling of poly(lactic acid) with native starch

Poly(lactic-acid) (PLA), a biodegradable polyester with excellent properties for different polymer applications, will play a major role in future markets for biodegradable polymers. But only if the currently very high price level can be reduced significantly to at least 4 $US/kg. Therefore, studies to fill poly(lactic acid) (PLA) with relative inexpensive native corn starch were conducted. Because PLA is a very brittle material with a glass transition point at 54°C, filling of PLA with native starch might seem unrealistic, as the brittleness is increased by the dispersed starch granules. To avoid this, low molecular weight poly(ethylene glycol) (PEG) is introduced into the PLA to enhance crystallization and to lower the glass transition temperature significantly under possible usage temperatures. The polymer that is modified in this way is then filled with native starch. The thermal behavior of the achieved di- or triblends is determined by means of differential scanning calorimetry (DSC) and the degradation behavior at high temperature has been looked at with the help of thermogravimetric analysis (TGA).     

Plasma treatment‐induced fluorine‐functionalized multi‐walled carbon nanotubes to modify poly(ethylene terephthalate) obtained via in situ polymerization

The introduction of carbon nanotubes in a polymer matrix can markedly improve its mechanical properties and electrical conductivity, and much effort has been devoted to achieve homogeneous dispersions of carbon nanotubes in various polymers. Our group previously performed successfully fluorine‐grafted modification on the sidewalls of multi‐walled carbon nanotubes (MWCNTs), using homemade equipment for CF₄ plasma irradiation. As a continuation of our previous work, in the present study CF₄ plasma‐treated MWCNTs (F‐MWCNTs) were used as a nanofiller with poly(ethylene terephthalate) (PET), which is a practical example of the application of such F‐MWCNTs to prepare polyester/MWCNTs nanocomposites with ideal nanoscale structure and excellent properties. As confirmed from scanning electron microscopy observations, the F‐MWCNTs could easily be homogeneously dispersed in the PET matrix during the in situ polymerization preparation process. It was found that a very low content of F‐MWCNTs dramatically altered the crystallization behavior and mechanical properties of the nanocomposites. For example, a 15 °C increase in crystallization temperature was achieved by adding only 0.01 wt% F‐MWCNTs, implying that the well‐dispersed F‐MWCNTs act as highly effective nucleating agents to initiate PET crystallization at high temperature. Meanwhile, an abnormal phenomenon was found in that the melt point of the nanocomposites is lower than that of the pure PET. The mechanism of the tailoring of the properties of PET resin by incorporation of F‐MWCNTs is discussed, based on structure–property relationships. The good dispersion of the F‐MWCNTs and strong interfacial interaction between matrix and nanofiller are responsible for the improvement in mechanical properties and high nucleating efficiency. The abnormal melting behavior is attributed to the recrystallization transition of PET occurring at the early stage of crystal melting being retarded on incorporation of F‐MWCNTs. Copyright © 2009 Society of Chemical Industry     

Preparation of poly(β-hydroxybutyrate) and poly(lactide) hollow spheres with controlled wall thickness

In recent years, polymer microcapsules have attracted more and more attention because of their specific properties and applications in encapsulation and drug delivery. Great effort has been made to investigate the preparation methods, structure controls as well as the property designs for the polymer microcapsules. In this work, we reported an effective route for the preparation of poly(β-hydroxybutyrate) (PHB) and poly(lactic acid) (PLA) hollow spheres with controlled wall thickness, which involves the graft polymerization of the biodegradable polymers from the surface of silica spheres followed by removing the template cores. Nuclear magnetic resonance spectroscopy (NMR), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscope (TEM) have been used to prove the structure of the hollow sphere and the intermediates. The result reveals that with the increase of reaction time the wall thickness of the hollow sphere will increase gradually.     

Review: Crystallization of Biodegradable Polymers

Understanding the crystallization behavior of polymer is significant both theoretically and practically as it decides the microscopic structure of polymer and determines final physical properties of the product. This article provides deep insight into the process of crystallization by exploring various models proposed for crystallization, factors determining crystallization, thermodynamics and kinetics in detail. The correlation of crystallinity with various properties is also discussed. For kinetics evaluation, the basic hypotheses of various models, as well as their relative drawbacks are also underlined. This article also reviews the crystallization behavior of widely useful biodegradable polymers such as poly(?-caprolactone) and poly(lactic acid).     

Polymers with Esters of Phosphoric Acid Units: From Synthesis,Models of Biopolymers to Polymer?Inorganic Hybrids

Syntheses, some properties, and applications of the poly(alkylene phosphate)s prepared either by ring-opening polymerization (ROP) or by polycondensation are described mostly on the basis of the data from our laboratories. The ROP of some cyclic phosphates and H-phosphonates are living and/or controlled process. Transesterification of the products of the reaction of an excess of dimethylphosphonate with glycols leads to polymers with M_n close to 5×10⁴. Poly(alkylene phosphate)s with five or six atoms in repeating units bear resemblance to the main chains of nucleic and teichoic acids. These and similar poly(alkylene phosphate)s with different repeating units were used as liquid membranes for the efficient separation of cations as well as to modify the medium for CaCO₃ crystallization. In this latter process, a diblock copolymer with ionic and nonionic block was used. Poly(alkylene phosphate)s constituted the ionic block and the nonionic block was formed from poly(ethylene glycol); together with CaCO₃ polymer inorganic hybrids were formed.