基于相形态的微孔发泡PP/POE共混物泡孔结构调控

采用挤出共混制备3种不同相形态的厚壁聚丙烯/乙烯-辛烯共聚物(PP/POE)共混物样品,并对样品在110℃发泡温度下进行高压釜发泡.利用共混物相形态以及两相黏弹性和超临界二氧化碳溶解度的差异,有效地调控厚壁样品内泡孔的形状、分布和尺寸等,获得了3种典型的泡孔结构.分散相呈椭球状液滴的80/20 PP/POE共混物发泡后泡孔呈椭球状,且两者具有相同数量级的平均直径和密度;分散相呈长纤维状的80/20共混物发泡后泡孔呈长孔状,两者的平均直径较为接近.呈部分共连续相结构的60/40共混物发泡后形成了具有较高连通度的开孔结构.进一步地,通过改变发泡温度,获得了更接近共混物中液滴状分散相平均直径和密度的近似球状的泡孔以及具有更高连通度的开孔结构.     

PP/HDPE 共混物及其纳米复合材料超临界流体微孔发泡

通过间歇法制备了聚丙烯(PP)/高密度聚乙烯(HDPE)共混物及其纳米复合材料的微孔塑料.用扫描电镜对发泡样品的泡孔结构进行表征,研究了纳米粒子的类型和含量对泡孔结构的影响.结果表明:在PP中加入25%的HDPE可改善泡孔结构;在 PP/HDPE 共混物中加入纳米粒子可使泡孔的直径减小、密度增加、泡孔分布更均匀;泡孔直径随着纳米粒子含量的增加会出现先减小后增加的趋势.     

发泡聚乳酸/热塑性聚氨酯/二氧化硅纳米复合材料的泡孔结构

以超临界二氧化碳作为物理发泡剂,通过快速降压法制备聚乳酸(PLA)/热塑性聚氨酯(TPU)/二氧化硅(SiO2)纳米复合材料发泡样品。发泡样品的泡孔结构使用扫面电子显微镜进行观察。在低频区,SiO2增加PLA/TPU共混物的储能模量和复数黏度。SiO2的加入使PLA/TPU共混物发泡样品的泡孔直径减小、泡孔密度增大。SiO2对PLA/TPU共混物发泡样品泡孔结构的改善归因于SiO2的异相成核作用和对共混物流变性能的改善作用。     

PLA/PBS/DCP反应共混体系的结晶行为研究

通过熔融共混法制备了一系列聚乳酸(PLA)/聚丁二酸丁二醇酯(PBS)物理共混试样及PLA/PBS/过氧化二异丙苯(DCP)反应共混试样,采用示差扫描量热分析(DSC)法研究了物理共混试样结晶行为及反应共混试样的特殊结晶行为.结果发现,PLA与PBS的物理共混并未改善PLA的结晶性,而PLA/PBS/DCP反应共混时生成的交联/支化结构可起到异相成核作用,从而明显改善了反应共混体系的结晶性能,且随着DCP含量的增加,共混体系中两相结晶行为出现交替变化.     

尼龙6微孔发泡材料的制备及泡孔形貌调控

本文利用共混改性方法得到高熔体强度尼龙6基体,通过探索不同的工艺条件,获得不同倍率的尼龙6发泡材料,系统研究不同离聚体改性剂比例下对其熔体强度的影响.通过热性能测试和流变测试推测了其中微交联结构的存在.通过调节发泡工艺制备不同发泡倍率的尼龙6发泡材料,用扫描电镜(SEM)观测泡孔形貌.结果 表明,离聚体的加入大大提升尼龙6基体的熔体强度,实现了尼龙6超临界二氧化碳发泡的可能性,并获得了较大倍率的尼龙发泡材料.     

利用水的相变热调控聚丙烯发泡材料的泡孔结构

为了控制发泡体内部泡孔结构,以制备聚丙烯(PP)泡沫为例,提出在CO2作为发泡剂进行物理发泡过程中,以水为助发泡剂,利用其发泡过程中汽化吸热,原位冷却发泡体内部.将PP与聚乙二醇(PEG)熔融共混制备共混物(PP/PEG),PEG的存在赋予了共混物吸水的能力.采用红外线成像仪测试发泡体表层和芯部温度,利用扫描电子显微镜表征了泡孔结构.结果表明,与纯PP发泡体相比,在同样发泡条件下,PP/PEG共混物发泡体内部温度明显降低,内部与表层泡孔结构相近,且发泡倍率提高.进一步分析讨论了PP/PEG共混物发泡体内部温度明显降低的机理.这种方法适用于不同聚合物体系和不同发泡工艺,如:模压、挤出、釜式发泡工艺.     

高熔体强度聚丙烯及发泡珠粒的制备与研究

使用直接聚合法制备了具有宽分子量分布的高熔体强度聚丙烯。利用反应釜浸渍法,以上述高熔体强度聚丙烯为基础树脂可以制备聚丙烯发泡珠粒。利用扫描电子显微镜和熔体强度测试仪考察了聚丙烯发泡珠粒的制备工艺及基础树脂的熔体强度对泡孔结构的影响。结果表明,与普通商业化聚丙烯如T30S相比,较高的熔体强度有利于泡孔结构的控制。     

具有较高回弹性的乙烯-辛烯共聚物基微孔复合材料的传感性能

通过熔体混炼制备乙烯-辛烯共聚物/多壁碳纳米管/碳纤(POE/MWCNTs/CF,90/5/5,W/W/W)复合材料,采用超临界二氧化碳发泡法对其进行釜压发泡,分析3种发泡温度(55、60和65℃)下制备的微孔样品的泡孔结构,着重研究其对微孔样品压缩性能和传感器压阻响应(灵敏度和线性响应范围等)的影响.结果表明,55℃下制备的微孔样品呈现较均匀的泡孔结构、较窄的泡孔直径分布(主要在10～30μm范围内)和厚度适中、连续性高的泡孔壁,这使其具有较高的回弹性、压缩强度、压缩模量和电导率.采用这种微孔圆片封装成的传感器具有较宽的线性响应范围(0～30%压缩应变)和较高的灵敏度(应变因子为1.67),根据泡孔结构对此进行了分析.该传感器具有较快速的压阻响应和恢复性能以及良好的重复性,在1000次循环压缩/释放测试中表现出较高的稳定性和耐久性,且能检测手指按压、肘部弯曲、深蹲和脚踩等人体运动(对应较宽的压缩应变范围).研究表明,采用超临界流体发泡法制备泡孔结构较均匀、泡孔壁厚度适中且连续的微孔导电复合材料具有良好的传感性能.     

双峰泡孔结构聚苯乙烯材料的制备

以超临界二氧化碳(Sc-CO2)为物理发泡剂,在高压釜中采用两种温度设定方式和降压对聚苯乙烯(PS)进行发泡,测试、分析发泡样品的泡孔结构、泡体密度和断面润湿性能.结果表明,仅通过降压只获得单峰的泡孔结构,而升温与降压协同作用可获得双峰的泡孔结构,大、小泡孔分别在升温和降压阶段成核形成;在发泡温度100℃、饱和温度30~70℃下制备的发泡样品中,大、小泡孔的平均直径分别为50~216和10~15μm.大泡孔的直径较大和密度较高都有利于降低样品的泡体密度,最低达0.15 g/cm3.单峰泡孔结构能在一定程度上提高样品断面的疏水性,使静态接触角(CA)从PS的本征值(87.1°)增大至138.8°;双峰泡孔结构可赋予样品断面更高的CA(155.1°),呈现超疏水特性.     

聚乙烯-g-聚苯乙烯对线性低密度聚乙烯/聚苯乙烯共混物机械性能和发泡行为的影响

以通过开环易位聚合、加氢反应和原子转移自由基聚合技术结合制备的聚乙烯-g-聚苯乙烯(PE-g-PS)作为增容剂,研究了加入不同PS支链长度的PE-g-PS对于线性低密度聚乙烯/聚苯乙烯(LLDPE/PS)共混物的机械性能和发泡行为的影响。 以典型组成m(LLDPE):m(PS)=70:30共混物为例,考察了PE-g-PS对共混物拉伸性能的影响。 相对于二元共混物,增容剂的加入使得断裂伸长率、拉伸强度和屈服强度皆提高,且含长PS支链的增容体系提高更明显。 采用超临界CO₂釜式发泡工艺,考察了PE-g-PS中PS支链长度对共混物发泡行为的影响。 结果表明,相对于短PS支链体系,加入PE-g-PS_1.59k(PS相对分子质量为1590)后的泡孔结构更加均一,完全没有“缝隙”形貌的出现。 当发泡温度降至80 ℃时,即使存在LLDPE发泡空间限制作用(LLDPE无法发泡),加入支链长度更长的PE-g-PS_1.59k后泡孔分布也更加均一。     

聚丁二酸丁二醇酯与氯醚弹性体协同增韧改性聚乳酸多元共混体系

以来源于可再生资源聚丁二酸丁二醇酯(PBS)和氯醚橡胶(ECO)作为聚乳酸(PLA)的增韧改性剂,通过熔融共混的方法制备了PLA/PBS/ECO三元共混体系。动态力学分析和扫描电子显微镜结果表明,ECO促进了PBS和PLA之间的相容性。力学性能测试表明,ECO与PBS可实现对聚乳酸基体的协同增韧: PLA/PBS/ECO(70/20/10)显示出最优的拉伸性能,断裂伸长率高达270%;PLA/PBS/ECO(70/10/20)的冲击强度提高至23.7 kJ/m²,是纯聚乳酸的12倍。结合形态结构和冲击断面形貌分析表明ECO的存在可起到增容/增韧双重作用, 与柔性PBS产生良好的协同效应,有效改善聚乳酸材料的韧性。我们的研究表明,构造PLA-柔性生物聚酯和生物基弹性体多元共混体系是一种获得高性能生物基材料简单高效的手段。     

The Influence of Peroxide on Bubble Stability and Rheological Properties of Biobased Poly(lactic acid)/Natural Rubber Blown Films

This study investigated the effects of natural rubber(NR)and an organic peroxide on the rheological properties,mechanical properties,morphology,and bubble stability during film blowing of poly(lactic acid)(PLA).The NR and peroxide contents were varied from 0 wt%to 25 wt%and 0 wt%to 0.5 wt%,respectively.The results confirmed that the presence of well-dispersed NR could significantly improve the toughness,elongation at break,and processability of PLA films,where the optimal amount of NR was 15 wt%.For the reactive blending with peroxide,a suitable peroxide content for good film toughness and clarity was 0.03 wt%,while the higher content of 0.1 wt%could provide slightly higher processability.These contents are considered much lower than that in the PLA system(without NR),which required up to 0.5 wt%peroxide.The rheological studies indicated that the melt strength,the storage modulus(G’)and complex viscosity(η*)at low frequency could be correlated with good film blowing processability of the PLA/NR films at low gel contents.These parameters failed to correlate in the films having high gel contents as the deformation rate experienced by each test was different leading to the different levels of response to the type and amount of gels.     

Biodegradable Foaming Material of Poly(butylene adipate-co-terephthalate) (PBAT)/Poly(propylene carbonate) (PPC)

A biodegradable blend foaming material of poly(butylene adipate-co-terephthalate)(PBAT)/poly(propylene carbonate)(PPC)was successfully prepared by chemical foaming agent and screw extrusion method.First,PBAT was modified by bis(tert-butyl dioxy isopropyl)benzene(BIBP)for chain extension,and then the extended PBAT(E-PBAT)was foamed with PPC using a twin(single)screw extruder.By analyzing the properties of the blends,we found that Young’s modulus increased from 58.8 MPa of E-PBAT to 244.7 MPa of E-PBAT/PPC 50/50.The viscosity of the polymer has a critical influence on the formation of cells.Compared with neat PBAT(N-PBAT),the viscosity of E-PBAT increased by 3396 Pa·s and E-PBAT/PPC 50/50 increased by 8836 Pa·s.Meanwhile,the dynamic mechanical analysis(DMA)results showed that the storage modulus(E’)at room temperature increased from 538 MPa to 1650 MPa.The various phase morphologies(“sea-island”,“quasi-co-continuous”and“cocontinuous”)and crystallinity of the blends affected the spread velocity of gas and further affected the foaming morphology in E-PBAT/PPC foam.Therefore,through the analysis of phase morphology and foaming mechanism,we concluded that the E-PBAT/PPC 70/30 component has both excellent strength and the best foaming performance.     

Mixing of Racemic Poly(L-lactide)/Poly(D-lactide) Blend with Miscible Poly(D,L-lactide):Toward All Stereocomplex-type Polylactide with Strikingly Enhanced SC Crystallizability

Stereocomplex-type polylactide (SC-PLA) consisting of alternatively arranged poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) chains has gained a good reputation as a sustainable engineering plastic with outstanding heat resistance and durability,however its practical applications have been considerably hindered by the weak SC crystallizability.Current methods used to enhance the SC crystallizability are generally achieved at the expense of the precious bio-renewability and/or bio-degradability of PLAs.Herein,we demonstrate a feasible method to address these challenges by incorporating small amounts of poly(D,L-lactide) (PDLLA) into linear high-molecular-weight PLLA/PDLA blends.The results show that the incorporation of the atactic PDLLA leads to a significant enhancement in the SC crystallizability because its good miscibility with the isotactic PLAs makes it possible to greatly improve the chain mixing between PLLA and PDLA as an effective compatibilizer.Meanwhile,the melt stability (i.e.,the stability of PLLA/PDLA chain assemblies upon melting) could also be improved substantially.Very intriguingly,SC crystallites are predominantly formed with increasing content and molecular weight of PDLLA.More notably,exclusive SC crystallization can be obtained in the racemic blends with 20 wt％ PDLLA having weight-average molecular weight of above 1 ×10s g/mol,where the chain mixing level and intermolecular interactions between the PLA enantiomers could be strikingly enhanced.Overall,our work could not only open a promising horizon for the development of all SC-PLA-based engineering plastic with exceptional SC crystallizability but also give a fundamental insight into the crucial role of PDLLA in improving the SC crystallizability of PLLA/PDLA blends.     

Some effects of foaming of the poly(butylene adipate‐co‐terephthalate) modified by electron radiation

Investigation of the effect of electron radiation and foaming agent on some properties of poly(butylene adipate‐co‐terephthalate) (PBAT) was the aim of the present paper. The mass flow rate, weight‐average molecular weight of irradiated PBAT as well as the morphological structure of foamed samples, their density, tensile strength, and specific strength were determined. It was found that irradiation of PBAT induces growth in weight‐average molecular weight and decrease in mass flow rate, and as a consequence of this increase in viscosity of this polymer. It was also found that foaming of irradiated PBAT causes formation of homogeneous cellular structure or structure with a clear separation of large and small cells. Simultaneously, the irradiated and foamed PBAT shows smaller density than that of non‐irradiated and foamed PBAT. Moreover, electron radiation does not influence tensile strength of the foamed PBAT; however, it increases its specific strength, although only if the content of foaming agent is 1 wt%.     

环氧基团功能化弹性体增韧聚乳酸的性能

以2种不同结构的弹性体乙烯-辛烯共聚物接枝甲基丙烯酸缩水甘油酯(POE-g-GMA)和乙烯-丙烯酯甲酯-甲基丙烯酯缩水甘油酯三元共聚物(E-MA-GMA)增韧聚乳酸(PLA), 研究了接枝型与嵌段型弹性体的结构对聚乳酸增韧效果的影响. 结果表明, 接枝型聚合物POE-g-GMA与基体PLA之间具有良好的界面相互作用, 当POE-g-GMA的质量分数为15%时, 共混体系的缺口冲击强度为72.4 kJ/m², 而E-MA-GMA的质量分数为15%时, 共混体系的缺口冲击强度为32.4 kJ/m², 结果表明, 接枝型聚合物POE-g-GMA增韧效果明显优于嵌段型E-MA-GMA.     

Poly(lactic acid)/poly(butylene succinate)/calcium sulfate whiskers biodegradable blends prepared by vane extruder: Analysis of mechanical properties,morphology, and crystallization behavior

Ternary blends of PLA/PBS/CSW with different weight fractions were prepared using a vane extruder. The mechanical properties, morphology, crystallization behavior and thermal stability of the blends were investigated. For the PLA/CSW blend, the tensile strength decreased, the flexural strength and modulus increased compared with pure PLA. For PBS, the addition of CSW had little influence on the mechanical properties. For the ternary blends PLA/PBS/CSW, the tensile strength, flexural strength and modulus decreased compared with pure PLA, while the elongation at break and the impact strength increased significantly. The brittle-ductile transition of the blends took place when the PBS weight fraction reaching 30 wt%. As a soft component in the blends, PBS was beneficial to improve the tensile ductility and the toughness of PLA. SEM measurements reveal that PLA/PBS/CSW blends were immiscible. When the weight fraction of PBS was 50 wt%, significant phase separation was observed, and CSW had preferential location in the PBS phase of the blend. DSC measurement and POM observation reveal that CSW had a heterogeneous nucleation effect on PLA and PBS matrix. The addition of PBS improved the crystallization of PLA and the thermal resistance of the PLA/PBS/CSW blends significantly.     

聚2,5-呋喃二甲酸乙二醇酯/聚丁二酸丁二醇酯共混物的制备与表征

通过熔融共混制备了聚2,5-呋喃二甲酸乙二醇酯(PEF)/聚丁二酸丁二醇酯(PBS)共混物,探究了制备PEF/PBS共混物的影响因素,考察了共混温度、共混时间、螺杆转速、共混比例对PEF/PBS共混物力学性能的影响因素,并用示差扫描量热仪、热失重、扫描电子显微镜等技术手段对其热性能和相容性进行了表征。 结果表明,当PBS的含量为15%、共混温度为230 ℃,共混时间为90 s、螺杆转速为150 r/min时,为最佳共混制备条件,此时相容性最好,热性能良好,冲击强度和拉伸强度最大,冲击强度相对纯PEF提高了6倍,拉伸强度提高了近20%,从而大幅提高了PEF的冲击强度,有效地增强了PEF的抗冲击韧性。 这些工作为这一生物基聚酯材料的应用提供了可能。     

Improved Mechanical Properties of Poly(butylene succinate) Membrane by Co-electrospinning with Gelatin

Gelatin, a natural proteinous polymer, was used to co-electrospin with poly(butylene succinate) (PBS) in order to improve the mechanical properties of PBS membrane and facilitate its applications in biomedical field. The PBS/gelatin blend membranes have narrower distribution of fiber diameter and smoother surface than neat PBS membrane. The contact angles, water absorption rates and water uptakes of the PBS/gelatin blend membranes were measured, showing increased hydrophilicity. The interaction between PBS and gelatin was investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and differential scanning calorimetry (DSC). The mechanical properties of PBS/gelatin blend membranes in both dry and wet states were evaluated by uniaxial tensile tests. In the dry state, the PBS/gelatin blend membrane containing 10% gelatin has a 3-times increase in tensile strength without any adverse effect on ductility because of the existence of interaction between the two blend components, little change in crystallinity of PBS, and possible interaction between any adjacent fibers; the tensile strength and elongation at break are even better in the wet state attributed to some gelatin on fiber surfaces, which act as a binder in the presence of water. The potential applications of PBS/gelatin blend membranes were demonstrated by successful immobilization of thrombin, a clinically-used hemostatic drug. The thrombin-loaded membrane could be used for rapid hemostasis.