聚乙二醇增塑聚乳酸的非等温结晶动力学研究

采用DSC方法对聚乙二醇(PEG)增塑聚乳酸的非等温结晶动力学进行了研究。结果表明,PEG的加入明显提高了聚乳酸的结晶速度。对所得数据分别用Ozawa方程和莫志深方法进行了处理,发现在给定温度范围里非等温结晶时,PLA/PEG主要是以均相成核的三维生长方式结晶;PLA的结晶速度随着PEG分子质量的增加而升高。     

碳纳米管/聚乳酸复合材料非等温结晶动力学

研究了聚乳酸(PLA)与多壁碳纳米管(MWNTs)/PLA复合材料的非等温结晶动力学。利用硅烷偶联剂KH-550改性碳纳米管,并用溶液共混法制备MWNTs/PLA复合材料。利用DSC研究了材料的结晶过程,所得的降温曲线表明基体中的碳纳米管可以提高材料的结晶温度范围和结晶放热焓。采用Jeziorny法和Mo法研究了PLA与MWNTs/PLA复合材料的非等温结晶动力学,结果表明,适量的碳纳米管有效地起到了成核剂的作用,提高了材料的结晶速率。     

聚乳酸的非等温结晶动力学研究

采用差示扫描量热仪研究了聚乳酸(PLA)样品在5种不同升温速率下的非等温结晶行为,采用Jeziorny法、Ozawa法、Mo法等分析了PLA的非等温结晶动力学。结果表明：随着升温速率的增加,PLA的熔融结晶峰向高温端移动,结晶峰变宽,结晶时间变短,同时结晶也变差。利用Jeziorny法和Mo法求得Avrami指数n和Ozawa指数m,在不同升温速率下,结晶初期的Avrami指数n和Ozawa指数m接近,均处于2～3,说明PLA的均相成核以一维方式为主、二维方式为辅;在升温速率为5～20 K/min时,结晶中期的PLA Avrami指数n>5、Ozawa指数m>3.5,均高于结晶初期的Avrami指数n与Ozawa指数m,表明PLA除了呈现均相成核的三维生长方式之外,还出现了结晶堆积的现象;当升温速率为30～40 K/min时,结晶中期的Avrami指数n和Ozawa指数m均与初期表现一致,Avrami指数n在3.5左右,Ozawa指数m为2.5～3.5,表明该条件下PLA以均相一维和二维2种方式共存结晶。应用Mo法得到的升温速率F(T)随着相对结晶度的增加而增加,表明随着结...     

有机金属磷酸盐/聚乳酸复合材料的非等温结晶动力学研究

采用DSC对有机金属磷酸盐/左旋聚乳酸(NA/PLLA)复合材料的非等温结晶动力学进行了研究,并对所得数据用Jeziony方程进行了处理。结果表明有机金属磷酸盐(NA)能有效地提高PLLA的结晶度。NA对PLLA结晶过程的影响是成核效应和阻碍分子链的运动的协同作用,而且冷却速率的提升提高了添加剂对分子链的阻碍作用。Jeziony理论分析表明PLA及其复合材料的Avrami指数n均在2～3之间,前期PLA及PLA/NA复合材料可能以二维生长方式生长,而且NA的加入并未改变PLA的成核机理和生长方式。     

新型木塑3D打印材料聚乳酸/木粉复合材料的非等温结晶动力学

以聚乳酸(PLA)、杨木粉为原料,采用改进过磨头的双螺杆挤出机制备新型木塑3D打印材料PLA/木粉复合材料。利用SEM对新型木塑3D打印材料的断面形貌进行分析表征,利用DSC考察了新型木塑3D打印材料的非等温结晶行为,并利用莫志深方程对新型木塑3D打印材料的结晶动力学进行研究分析。结果表明:PLA/木粉复合材料内部存在大量空洞,而增韧剂POE的加入则会很好的改善这一缺陷,大幅度地减少空洞的数量;莫志深方程可以较好地分析新型木塑3D打印材料的非等温结晶动力学,木粉的加入能够起到一定的异相成核作用,提高了结晶温度,但降低了结晶速率;当木粉含量为20%时,PLA的结晶温度最高,结晶速率最快。     

表征高聚物非等温结晶动力学的参数——动力学结晶能力

根据 Jeziorny 对结晶的近似处理,导出了计算非等温动力学结晶能力(G_C)的简单表达式。用 DSC 对含有不同催化剂体系的聚对苯二甲酸乙二酯树脂进行了等速降温实验,并计算其 G_C。结果表明,由本文公式计算出的不同试样的 G_C 与 Jeziorny 公式的计算结果在变化趋势上是一致的,数值上约相差一倍。而与本文作者改进的 Jeziorny 方法的计算值十分接近。Jeziorny 方法需要求取达到结晶速度最大值时的时间 t_(max),结晶峰的半高宽 D,结晶速度极大值时的相对结晶度C_r(T_(max))等参数。改进的 Jeziorny 方法需求出结晶速度最快时的导数值 dC_r/dt|t=t_(māx)或dC_r/dT|T=T_(max)等参数。利用本文公式只要求得 C_r(T_(max))即可,使用十分方便。当结晶过程不存在二次结晶时,G_C 的大小与等温结晶速度的快慢是一致的,当结晶过程存在缓慢的二次结晶时,G_C 值变小。即结晶机理相差较大的试样之间所得 G_C 缺乏比较意义。     

聚乙二醇对聚丙烯复合材料非等温结晶动力学的影响

利用差示扫描量热仪(DSC)研究了聚乙二醇(PEG)对聚丙烯复合材料非等温结晶行为的影响,并采用Jeziorny法和Mo法分析了复合材料的非等温结晶曲线。结果表明:PEG的添加降低了聚丙烯复合材料的结晶温度,对聚丙烯结晶的成核及晶体生长均产生一定影响。当PEG用量由0增至5份时,复合材料的结晶峰温度和初始结晶温度降低,结晶速率增大。     

聚丙烯／滑石粉复合材料的等温结晶动力学

用差示扫描量热法(DSC)研究聚丙烯(PP)及PP／滑石粉复合材料的等温结晶过程。用Avrami方程全面分析PP／滑石粉的等温结晶动力学，并由此获得相关的动力学参数；用Kissinger方程研究滑石粉对PP／滑石粉复合材料结晶活化能的影响。研究表明：加入滑石粉后明显提高PP／滑石粉复合材料的结晶速率和结晶度；证明滑石粉能促进PP材料的结晶，并在PP结晶过程中起到异相成核作用。PP／滑石粉复合材料的等温结晶过程属于典型的异相成核机理。     

聚乙二醇增塑聚乳酸的等温结晶动力学研究

采用DSC方法对聚乙二醇(PEG)增塑聚乳酸的等温结晶动力学进行了研究。结果表明,PEG的加入提高了聚乳酸的结晶速度,在相同结晶温度下,随着PEG摩尔质量的增大,结晶速率增大,结晶活化能先减小后增大。不同摩尔质量PEG增塑PLA的结晶成核机理和生长方式一样。     

聚乳酸/四针状氧化锌晶须非等温冷结晶行为的研究

采用熔融共混法制备了聚乳酸(PLA)/四针状氧化锌晶须(T-ZnOw).用差示扫描量热仪研究了PLA及PLA/T-ZnOw的非等温冷结晶行为;用Jeziorny法和Mo法对其非等温冷结晶动力学进行了分析研究,并计算了相关的结晶动力学参数.结果表明,Jeziorny法和Mo法均能很好地描述PLA及PLA/T-ZnOw的非等温冷结晶过程,且结果一致.Jeziorny法分析表明,初次结晶阶段PLA及PLA/T-ZnOw的Avrami指数n1值范围分别为4.22～5.43和3.11～4.80,而二次结晶阶段的Avrami指数n2值范围分别为3.10～4.66和2.69～5.57,说明T-ZnOw的加入改变了PLA的成核和晶体生长规律.Mo法分析表明,在相同的X(t)下,PLA/T-ZnOw的F(T)值整体大于PLA,T-ZnOw的加入降低了PLA的结晶速率.偏光显微镜观察结果显示,随着T-ZnOw的加入,PLA球晶尺寸减小,数目增多,T-ZnOw促进了PLA的成核.     

聚丁二酸丁二醇酯/聚乙二醇硬脂酸酯共混物非等温结晶行为

以聚丁二酸丁二醇酯（PBS）和聚乙二醇硬脂酸酯（PEOST）为原料,采用溶液共混法制备了PEOST质量分数分别为10%（POS-10）和30%（POS-30）的两种合金材料。通过差示扫描量热法（DSC）研究了合金材料的非等温结晶行为,用莫志深（Mo）法分析了PBS的非等温结晶动力学,采用Kissinger法和Friedman法计算PBS的结晶活化能,并用红外（FTIR）和偏光显微镜（POM）进行表征。研究结果表明：PBS先结晶形成结晶微区不利于PEOST结晶,而较高含量的PEOST有利于PBS的结晶。受PBS先结晶的影响,POS-10降温DSC曲线没有出现PEOST的结晶峰,而POS-30在低的降温速率情况下出现了PEOST双结晶峰;升温DSC曲线中两试样均出现了PEOST的熔融峰。在相同的冷却速率下,POS-30的PEOST熔融温度（T_m）和熔融焓（△H_m）大于POS-10;POS-30的PBS结晶峰温度（T_p）、结晶焓（△H_c）大于POS-10,而结晶半峰宽（D）值更小;但两者的T_m和△H_m相当。随冷却速率的增加,PBS的D值增大,而PEOST的D值却降低;冷却速率的增加对PBS的T_m值影响不大,但使PEOST的T_m略有减小。Mo法适合用于共混物中PBS的非等温结晶动力学分析。POS-30的PBS绝对值结晶活化能要大于POS-10。POS-30在红外光谱谱图中出现了PEOST结晶的红外响应峰（1109cm^-1和841cm^-1）而POS-10没有。     

Relationship between the crystallization behavior of poly(ethylene glycol) and stereocomplex crystallization of poly(L‐lactic acid)/poly(D‐lactic acid)

Poly(l ‐lactic acid) (PLLA) is a good biomedical polymer material with wide applications. The addition of poly(ethylene glycol) (PEG) as a plasticizer and the formation of stereocomplex crystals (SCs) have been proved to be effective methods for improving the crystallization of PLLA, which will promote its heat resistance. In this work, the crystallization behavior of PEG and PLLA/poly(d ‐lactic acid) (PDLA) in PLLA/PDLA/PEG and PEG‐b‐PLLA/PEG‐b‐PDLA blends has been investigated using differential scanning calorimetry, polarized optical microscopy and X‐ray diffraction. Both SCs and homocrystals (HCs) were observed in blends with asymmetric mass ratio of PLLA/PDLA, while exclusively SCs were observed in blends with approximately equal mass ratio of PLLA/PDLA. The crystallization of PEG was only observed for the symmetric blends of PLLA_39k/PDLA_35k/PEG_2k, PLLA_39k/PDLA_35k/PEG_5k, PLLA_69k/PDLA_96k/PEG_5k and PEG‐b‐PLLA_31k/PEG‐b‐PDLA_27k, where the mass ratio of PLLA/PDLA was approximately 1/1. The results demonstrated that the formation of exclusively SCs would facilitate the crystallization of PEG, while the existence of both HCs and SCs could restrict the crystallization of PEG. The crystallization of PEG is related to the crystallinity of PLLA and PDLA, which will be promoted by the formation of SCs. © 2017 Society of Chemical Industry     

PBT非等温结晶动力学

用差示扫描量热法研究聚对苯二甲酸丁二酯（PBT）的非等温结晶动力学，并分别用Ozawa,Jeziorny和考虑综合因素法来处理PBT的非等温结晶数据。结果表明，PBT非等温结晶过程与Ozawa动力学方程相吻合，但不符合用Jeziorny方法处理的Avrami动力学方程；综合考虑温度和结晶程度对聚合物结晶速度的影响。PBT非等温结晶过程符合结晶动力学方程。     

Synthesis and nonisothermal crystallization kinetics of biodegradable poly(ethylene terephthalate-co-ethylene succinate)s

In the current work, a series of biodegradable poly(ethylene terephthalate-co-ethylene succinate)s (P[ET-co-ES]s) were prepared via a traditional melting polycondensation method. First of all, the structures of prepared copolymers were characterized by nuclear magnetic resonance and Fourier transform infrared measurements. Meanwhile, the thermal properties of prepared samples were analyzed by differential scanning calorimetry and thermogravimetric analysis measurements, respectively. Subsequently, the mechanical properties of the P(ET-co-ES)s were evaluated, the tensile strength of P(ET-co-ES)s decreased with increasing of PES content in copolymer, however, corresponding P(ET-co-ES)s exhibited better elongation at break. Next, the biodegradability of P(ET-co-ES)s was evaluated using lipase as degrading enzyme. The results presented that the biodegradability of P(ET-co-ES)s improved with PES content, the corresponding results were supported by scanning electron microscopy test. Finally, the Mo's modified Avrami equation was employed to analyze the nonisothermal crystallization kinetics of prepared copolymers. The results showed the addition of the PES component improved the crystallization properties of the prepared P(ET-co-ES)s. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48422.     

改性聚乙烯醇的非等温结晶动力学研究

通过差示扫描量热法(DSC)测定了己内酰胺水溶液改性的聚乙烯醇(PVA)降温结晶过程,并用Ozawa方法,Jeziorny方法和莫志深方法分析了改性PVA的非等温结晶动力学。结果表明:随着冷却速率增加,改性体系内起增塑作用的小分子由于其蒸发升华的减缓,改性PVA体系的运动能力增强,结晶度提高;莫志深方法能够较好地解释改性PVA的非等温结晶过程,即在单位时间内达到较大结晶度需较大的降温速率,且随着体系相对结晶度的增加,结晶速率降低。     

Non-isothermal crystallization and thermal transitions of a biodegradable, partially hydrolyzed poly(vinyl alcohol)

A study has been made of the non-isothermal crystallization behavior and thermal transitions of a biodegradable, partially hydrolyzed poly(vinyl alcohol) with 80% degree of saponification (PVA80). Possible sample degradation was first investigated, but no significant degradation or dehydration was detected using FTIR and DSC under the experimental condition. The non-isothermal crystallization of PVA80 was analyzed with Ozawa equation, and the Mo method of combining Ozawa and Avrami equations. Ozawa equation was only applicable in a narrow temperature range from 80 to 100 °C. The deviation from the Ozawa equation is not due to the secondary crystallization or the quasi-isothermal nature of the treatment. It is only a result of the large relative difference of the relative crystallinity values under different cooling rates. The Mo method demonstrated a success in the full temperature range investigated. The isoconversional method developed by Friedman failed to estimate the activation energy for this non-isothermal crystallization. Thermal transitions of PVA80 are associated with its complex hydrogen-bonding interactions. The melt-crystallized PVA80 sample, as that from film casting, followed by annealing at 60 and 80 °C, has a broad melting temperature range measured by DSC and FTIR. It was found that the melting behavior of a semicrystalline polymer can be probed via a non-crystalline hydrogen-bonded CO band using FTIR. The glass transition temperature T_g of PVA80 was raised about 20 °C, after the sample was melt-crystallized. The intensity of the hydrogen-bonded CO band increases when temperature was increased from 110 to 180 °C, due to the promoted hydrogen-bonding interactions between the CO groups in the amorphous phase and the hydroxyl groups from the crystalline phase, which is also the main reason for the increased T_g transition.     

支化PET的非等温结晶性能研究

采用直接酯化缩聚法,以3-羟甲基丙烷(TMP)或季戊四醇(PER)为支化剂,制备支化PET;探讨了支化剂对其结晶性能的影响;利用差示扫描量热(DSC)法研究了支化PET的非等温结晶性能。结果表明:支化剂TMP或PER的加入可以有效增强PET的结晶能力,但过量的支化剂会抑制PET的结晶;支化PET的非等温结晶Avrami指数为3.03~4.42,其结晶机理为均相成核和异相成核相结合;支化PET的结晶活化能比常规PET的低,支化PET结晶对温度的依赖性降低。     

Effect of crystallization temperature on crystal modifications and crystallization kinetics of poly(L‐lactide)

The crystalline structure of poly(L ‐lactide) (PLLA) have been found to quite depend on the crystallization temperatures (T_cs), especially in the range of 100?120°C, which is usually used as the crystallization temperature for the industrial process of PLLA. The analysis of wide‐angle X‐ray diffraction and Fourier transformed infrared spectroscopy revealed that 110°C is a critical temperature for PLLA crystallization. At T_c < 110°C and T_c ≥ 110°C, the α′ and α crystals were mainly produced, respectively. Besides, the structural feature of the α′‐form was illustrated, and it was found that the α′‐form has the larger unit cell dimension than that of the α‐form. Moreover, the crystallization kinetics of the α′ and α crystals are different, resulting in the discontinuousness of the curves of spherulite radius growth rate (G) versus T_c and the half time in the melt‐crystallization (t_1/2) versus T_c investigated by Polarized optical microscope and Differential scanning calorimetry, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

PBT蓄能发光复合材料非等温结晶动力学研究

采用差示扫描量热(DSC)法研究非等温条件下环形对苯二甲酸丁二醇酯(CBT)反应性挤出加工所制聚对苯二甲酸丁二醇酯(PBT)蓄能发光复合材料的结晶行为,分别采用Ozawa,Jeziorny及Mo方程拟合分析复合材料的非等温结晶动力学。结果表明:采用Ozawa及Jeziorny方程所获拟合曲线均不成线性;Mo方程可很好地描述PBT蓄能发光复合材料的非等温结晶过程,拟合所得PBT复合材料的单位时间里体系到达结晶度时的降温速率(F(T))值均较纯PBT的低,且粉体质量分数为15%时,其F(T)值最小,表明加入发光粉体可加速体系的结晶过程,然而在高降温速率下,较高浓度的发光粉体反而会降低体系的结晶速率。