热塑性淀粉/聚乙烯醇/蒙脱土三元纳米复合材料

用熔融挤出的方法制备了甘油塑化热塑性淀粉（TPS）/聚乙烯醇（PVA）/蒙脱土（MMT）纳米复合材料,添加蒙脱土和聚乙烯醇用以提高热塑性淀粉材料的力学性能。 在相对湿度50%的条件下,复合材料的XRD衍射谱图和透射电子显微镜测试表明,MMT以剥离状态均匀分布在TPS/PVA基体中;力学测试表明,当MMT的质量分数从0％增至5％时,复合材料的力学性能明显提高。 当蒙脱土的质量分数为3%时,复合材料最大抗张强度达到13.24 MPa,杨氏模量达到61.46 MPa。 这说明蒙脱土在复合材料中可以起到物理交联点的作用,提高了复合材料的力学性能。     

淀粉添加量和增塑剂对聚乙烯醇/淀粉复合材料结构与性能影响

近些年来，由于不可再生资源的消耗问题以及塑料垃圾等造成的白色污染等环境问题，人们对绿色环保产品的需求日益增长，高性能生物降解材料的开发受到越来越多的关注。采用醇解度适中的1788型聚乙烯醇(PVA1788)和玉米淀粉为原料，添加少量甘油与氯化钙，通过溶液流延法制得了聚乙烯醇/淀粉(PVA/ST)复合材料。研究了淀粉添加量以及增塑剂配比对PVA/ST复合材料结构与性能的影响。结果表明：淀粉的加入会导致PVA的结晶度明显下降，黏度提高，同时因为淀粉的高脆性，导致复合材料模量明显提高，力学性能明显下降；而加入的甘油和氯化钙作为增塑剂，能够减弱PVA和ST的分子间作用力，降低结晶度，提高材料的柔韧性。当加入甘油与氯化钙的比例均为PVA和ST总含量的10%时，复合材料的力学性能最优，拉伸强度约为16 MPa,断裂伸长率约为410%。     

N,N-双(2-羟乙基)-2-氨基乙磺酸钠为扩链剂的磺酸型聚氨酯水凝胶制备及性能

以异佛尔酮二异氰酸酯(IPDI)、聚乙二醇-2000(PEG)为主要原料,二羟甲基丙酸(DMPA)和N,N-双(2-羟乙基)-2-氨基乙磺酸钠(BES-Na)为亲水性扩链剂,制备了一系列磺酸型聚氨酯水凝胶(WPUHs)。 通过X射线衍射仪、热重分析仪和电子万能测试机对凝胶的结构和性能进行了表征。 结果表明,随着BES-Na质量分数的增加,WPUHs的热稳定性逐渐增加,WPUH7(BES-Na质量分数为3.46%)的压缩强度和压缩模量比WPUH1(BES-Na质量分数为0%)分别提高了2.9倍和3.6倍。 BES-Na的质量分数对WPUHs的溶胀初期过程影响显著,WPUHs的平衡溶胀比从20.6增加至29.3。 WPUHs具有良好的温度和pH敏感性,在10~45 ℃范围内,WPUH7平衡溶胀比从17.6增大至33.8,在pH值为2~10范围内,WPUH7平衡溶胀比从21.7增大至70.6。     

高分子量聚乙烯醇增强冰的研究

以本体光聚合法制备的高分子量聚乙烯醇(HMWPVA)为增强剂,考察了增强冰的力学性能.当HMWPVA的浓度为3%(质量分数)时,增强冰的拉伸强度、断裂伸长率、压缩强度和压缩模量分别为普通冰的11.7,3.5,2.3和2.1倍.对比试验发现PVA分子量对冰的拉伸性能影响较大,对冰的压缩性能影响较小.此外,在室温29℃时纯冰的融化时间为5 min,而4%HMWPVA增强冰的融化时间长达240 min.     

醋酸淀粉/聚乳酸的制备及性能的影响研究

采用自设计的双螺杆结构挤出制备聚乳酸(PLA)/醋酸淀粉(AS)的全生物降解材料,考察材料的AS的含量和取代度对复合材料动态流变性能、机械性能的影响。研究结果表明,AS含量明显影响复合材料的力学性能、复合黏度和储能模量:当AS含量从45%增加到70%,材料的拉伸强度下降,复数黏度和储能模量则提高。随着AS取代度由1.0上升为3.0,复合材料的复数黏度和储能模量下降,拉伸强度由12.0MPa上升为15.5MPa。对复合材料进行电镜扫描分析发现,AS以海岛结构形式分散在PLA的连续相中,取代度2.0的AS与PLA相容性最好,当其质量含量达到70%,材料的拉伸强度仍然不低于10.0MPa,具有较好的机械强度。     

微波发泡制备三聚氰胺甲醛泡沫塑料及其性能

用三聚氰胺、甲醛和DJ-1型增韧剂在碱性条件下制备了改性三聚氰胺甲醛树脂,将其与表面活性剂、发泡剂、固化剂充分混合搅拌,采用微波发泡炉在一定的功率下进行发泡制备三聚氰胺泡沫塑料.研究了增韧剂的用量、微波功率和发泡时间对泡沫结构和性能的影响.并用光学显微镜、TGA、驻波管对三聚氰胺泡沫塑料的泡孔结构、热学性能和声学性能进行了测试和分析.研究表明:当发泡液质量为50 g时,最佳发泡功率为2 kW,最佳发泡时间为60 s;DJ-1型增韧剂的加入使泡沫的韧性提高,当其质量分数为10％时,泡沫的拉伸强度达到0.112 MPa;泡沫的分解温度约400℃,此时的质量残留率接近60％;泡沫在中高频(≥1 000 Hz)区域的吸声系数高达0.9以上.     

碳纳米管的加入对聚偏氟乙烯/丙烯酸酯共混物形状记忆性能的影响

利用聚偏氟乙烯(PVDF)微小结晶的物理交联点作用,制备了形状记忆性能优异的聚偏氟乙烯/丙烯酸酯聚合物(PVDF/ACM)共混材料。为提高其形状回复应力,又将碳纳米管(CNT)引入该共混体系中,系统研究了PVDF/ACM/CNT三元体系纳米复合材料的制备、结构及性能。结果表明,碳纳米管在PVDF/ACM体系中分散均匀;在基本保持其形状记忆性能的前提下,加入质量分数为4%的CNT,材料在25℃时的储能模量由2000 MPa提高至3130 MPa。     

热塑性淀粉/聚丁二酸丁二醇酯合金的制备和结构性能表征

制备了高填充的甘油塑化淀粉（GTPS）/聚丁二酸丁二醇酯（PBS）合金,并对其结构性能进行了表征。结果表明：GTPS/PBS在合金加工过程中其扭矩以及力学性能随PBS质量分数的增加及甘油质量分数的减小而增大;扫描电镜（SEM）显示甘油可提高合金的相容性;动态力学分析（DMA）表明合金在玻璃态时的储存模量高于纯PBS,黏流态时则相反;合金的热稳定性随PBS和甘油质量分数的增加而有所提高;PBS的加入将合金的吸水率由100%以上降低到10%以下;淀粉和甘油的存在则均可提高PBS的降解率。     

聚乙烯/氧化铝复合材料形态、流变和力学性能

将聚乙烯（PE）和氧化铝（AO）熔融共混制得综合性能更好的PE/AO复合材料。通过对其进行流变分析、热力学性能分析、力学性能分析、导热性能分析和断面微观结构分析,探究AO质量分数对复合材料结构及性能的影响。结果表明,随着AO质量分数的增加,复合材料逐步转为脆性材料,其弹性模量、屈服强度、导热系数、储能模量同步增加;当AO质量分数为10%时,复合材料的断裂强度为18.2 MPa,综合性能最好。     

羟基磺基甜菜碱氟碳表面活性剂在油水界面的扩张粘弹性

氟碳表面活性剂是目前表面活性最高的特种表面活性剂,在三次采油等领域具有良好的应用前景。 用小幅周期振荡法研究了羟基磺基甜菜碱型氟碳表面活性剂(FS)在油-水界面的扩张粘弹性能,考察了振荡频率、FS质量分数、无机盐(NaCl、CaCl₂、MgCl₂)对FS在油-水界面的扩张粘弹性能的影响。 结果表明,FS溶液在油水界面的扩张模量、扩张弹性和扩张粘度随着FS质量分数的增加而出现最大值,随着频率的增大而略有增加。 加入无机盐时,扩张模量、扩张弹性随NaCl质量分数增大而出现最大值,而随着CaCl₂或者MgCl₂质量分数的增加,FS溶液的扩张模量、扩张弹性和扩张粘度减小,而当CaCl₂或者MgCl₂质量分数分别为0.05%、0.1%时,tanθ达到最大值。     

Foaming behavior,cellular structure and physical properties of polybenzoxazine foams

In this paper, polymer foams based on a benzoxazine resin have been successfully prepared using azodicarbonamide (ADC) as a chemical blowing agent and have been characterized regarding their foaming behavior, cellular structure, and physical properties. The effect of the ADC on the curing process of the resin was analyzed using differential scanning calorimetry and blowing agent decomposition was followed by thermogravitmetric analysis (TGA). The characterization of the cellular structure of the foamed samples was done using scanning electron microscopy. The mechanical properties of the foams were determined using compression tests and the thermal conductivity was assessed using the transient plane source method. The results indicated that the curing process and gas release took place in a similar time interval. The foams showed an isotropic cellular structure with relative densities in the range 0.35–0.60, and showed compressive strengths and compressive moduli in the range of 10–70 MPa and 400–1100 MPa, respectively. Thermal conductivities were in the range of 0.06–0.12 W m^?1K^?1. The findings in this paper demonstrate the possibility of producing polybenzoxazine foams using a simple process in which curing and foaming take place simultaneously. In addition, the mechanical characterization of these materials indicates that they are suitable for structural applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Foaming of trans‐polyisoprene using N2 as the blowing agent

Foaming of trans‐1,4‐polyisoprene (TPI) polymer was carried out through a batch process using nitrogen (N₂) as the blowing agent. TPI vulcanizates having varying crosslink densities were prepared by varying crosslinking agent content and curing time. The vulcanizates were then saturated with N₂ inside a pressure vessel at a pressure of 14 MPa and varying temperatures for 5 hours before effecting the foaming by rapidly quenching the pressure. The effects of varying the crosslinking agent content, silica filler content, and precuring time of the vulcanizates and the effects of varying the gas saturation temperature of foaming on the cell characteristics and physical properties of the foam prepared were investigated. The cells of the TPI foams had a spherical, closed structure. The density, expansion ratio, cell size, cell density, and tensile properties of the foams varied with varying crosslink density of the TPI vulcanizates as well as the saturation temperature of foaming. The important effects of crosslink density and saturation temperature on the N₂ solubility in the TPI matrix and thus on the foam expansion were discussed. The silica filler was found to be acting as a cell nucleating agent and reinforcing filler for the TPI foams.     

Towards novel super‐elastic foams based on isoperene rubber: Preparation and characterization

A novel and conventional closed cell polyisoprene rubber (IR) foams were produced by a single step limited‐expansion and two step unlimited‐expansion foaming process, respectively. The effect of 3 to 12 part per hundred rubber (phr) of azodicarbonamide (ADC) foaming agent on their structure and properties of developed novel foams were studied. In developed novel foams, the density was strangely independent of ADC content; however, the cell sizes conversely related to ADC content and it decreased by 60% (555‐330 μm) and the internal cell pressure build up from 1 to 3.7 atm, which was related to pressure‐free foaming method. The both reasons of compressed gas trapped inside cells and constant density not only caused unique enhancement in novel foams mechanical properties as hardness and modulus but also improved their dynamic properties as hysteresis and elasticity. Results of conventional IR foams showed that, their foam density as well as dynamic and mechanical properties sharply decreased with increasing ADC content from 3 to 12 phr. For clear expression, in samples with 12 phr of ADC, novel developed foams have more foam density (180%), more hardness (240%), more modulus (290%), and smaller cell size (75%) than conventional foams. Finally, novel developed foams were super‐elastic material with no hysteresis and no plastic deformation while conventional foams had 40% hysteresis and 10% plastic deformation under the same compression conditions.     

热塑性聚氨酯微孔发泡材料的表观密度与其力学性能的关系

用高压CO2流体通过升温发泡法制备了一系列不同表观密度的热塑性聚氨酯(TPU)微孔发泡材料,探究了TPU发泡材料的表观密度与其力学性能的关系.微孔发泡材料的泡孔结构和表皮结构由扫描电子显微镜表征;不同表观密度材料的力学性能利用万能材料试验机和旋转流变仪表征.研究发现:TPU微孔发泡材料的表观密度主要是由材料皮层厚度占比和泡孔层密度决定的,皮层厚度占比越小和泡孔面积占有率越高,泡沫的表观密度越小;微孔发泡材料在线性应变区的压缩模量E与材料表观密度ρ的关系为:E∝ρ1.7,符合泡沫材料压缩模量与表观密度呈指数关系的基本结论;循环压缩实验中,随微孔发泡材料表观密度减小,损耗百分比增大,残余应变减小;流变实验中,微孔发泡材料的模量随表观密度变化没有明显的变化,阻尼因子tanδ随泡沫表观密度变化不呈单一的规律性.同时,阐明了微孔发泡材料的压缩模量E和损耗百分比随表观密度变化的机理.     

接枝聚乳酸/塑化淀粉共混物的制备与性能研究

为提高聚乳酸(PLA)/淀粉共混物界面作用和降低成本,引入甲基丙烯酸缩水甘油酯(GMA)接枝聚乳酸和塑化淀粉(TPS),通过挤出和注射成型制备接枝聚乳酸/塑化淀粉共混物(PLA-g-GMA/TPS)。红外光谱分析证实,GMA成功接枝到PLA分子链上。对共混物的力学性能、热机械性能、微观形貌、热性能及亲水性等进行了系统研究,结果表明,选择GMA用量为6%(接枝率为1.51%)和TPS用量为10%时的拉伸强度、断裂伸长率及弹性模量最佳,分别为42.6MPa、8.9%及260MPa。FE-SEM观察结果表明,低含量TPS中颗粒被基体包覆或嵌入,界面平整,界面结合力强。DMA和DSC结果显示,不同质量配比的PLA-g-6%GMA/TPS共混物的Tg、储存模量、结晶度、结晶温度及熔融温度仅在小范围内发生变化。吸水率和接触角结果表明,低含量TPS的共混物吸水率和接触角变化幅度均小于高含量TPS体系。     

Extrusion foaming of semi-crystalline PLA and PLA/thermoplastic starch blends

Low density open-cell foams were obtained from polylactic acid (PLA) and from blends of PLA with thermoplastic starch (TPS) using CO(2) as a blowing agent. Two unexpected features were found. First, a 2D cavitation process in the fractured cell walls was unveiled. Elliptical cavities with dimensions in the 100-300 nm range were aligned perpendicular to large cell cracks clearly exhibiting 2D crazing prior to macroscopic cell rupture. Secondly, a significant crystallization rate increase associated with the CO(2) foaming of PLA was discovered. While the PLA used in this study crystallized very slowly in isothermal crystallization, the PLA foams exhibited up to 15% crystallinity, providing evidence that CO(2) plasticization and the biaxial stretching upon foam expansion provided conditions that could increase the crystallization rate by several orders of magnitude.     

基于天然聚多糖的环境友好材料（II）-麻纤维和芦苇纤维多元醇的生物降解聚氨酯

以麻纤维和芦苇纤维制备的植物多元醇为原料,合成具有良好性能的生物降解 性硬质聚氨酯泡沫体,其密度40 kg/m~3左右,压缩强度150 kPa,弹性模量4 MPa 。而且多元醇中植物原料含量越大,其性能越好,这使植物原料的充分利用和材料 生产成本的降低成为可能。土壤掩埋实验表明,泡沫体有很好的土壤微生物降解性 。     

Processing window for extrusion foaming of hydroxypropyl methylcellulose

Foamed materials are gaining an increased interest due to their good mechanical properties in relation to their low densities and an increased industrial demand can be expected. A few less attractive issues can however be associated with commodity foamed products. For instance the raw-material often originates from non-renewable, fossil-based, sources. Furthermore, degradation in nature is slow, therefor the disposed product is burned or end up in landfills. One possibility to reduce the impact on nature could be to produce foams from natural polymers such as starch or cellulose. In this study the possibility to produce foams from hydroxypropyl methylcellulose (HPMC) with water as blowing agent, by continuous extrusion, was investigated. A pre-study using a capillary viscometer, batch-extruder, was conducted to evaluate the foamability of HPMC. Due to promising results further experiments were conducted with a single-screw extruder. The goal was to find an adequate processing window for foaming. It was concluded that HPMC could successfully be foamed by continuous extrusion, although a careful tailoring of the processing parameters was required. Crucial parameters were here the temperature, pressure and residence time distribution in the extruder. Regions of the extruded foams were examined using optical and scanning electron microscopy and HPMC foams with a density in the range of that of fossil-based polymeric foams could be produced.     

Relaxation processes and structure of ultradrawn polyethylene

Solid-state extruded polyethylene fibers have been prepared, with a wide range of draw ratios and constant processing temperature. The draw ratios vary from 4 up to 30, and the processing temperature was always 398 K. The extruded material behaves anisotropically, owing to the high degree of chain orientation in the drawing direction. The modulus and linear expansion coefficients in the fiber axis direction have been measured, over a wide temperature range, from 140 K up to 320 K. These two properties are closely related to the degree of structural continuity of the fibers. A fibrous structure model is proposed to explain the temperature effects and the values obtained for the modulus and expansion coefficients, in terms of crystallinity and volumetric fraction of extended-chains structure. At least three relaxation processes can be identified which cause the structural continuity of the fibers to change with temperature.     

Increased expansion ratio,cell density,and compression strength of microcellular poly(lactic acid) foams via lignin graft poly(lactic acid) as a biobased nucleating agent

Green and renewable foaming poly(lactic acid) (PLA) represents one of the promising developments in PLA materials. This study is the first to use the lignin graft PLA copolymer (LG‐g‐PLA) to improve the foamability of PLA as a biobased nucleating agent. This agent was synthesized via ring‐opening polymerization of lignin and lactide. The effects of LG‐g‐PLA on cell nucleation induced by the crystallization, rheological behavior, and foamability of PLA were evaluated. Results indicated that LG‐g‐PLA can improve the crystallization rate and crystallinity of PLA, and play a significant nucleation role in the microcellular foam processing of PLA. LG‐g‐PLA improved the foam morphology of PLA, obtaining a reduced and uniform cell size as well as increased expansion ratio and cell density. With the addition of 3 wt% LG‐g‐PLA content, the PLA/LG‐g‐PLA foams increased the compressive strength 1.6 times than that of neat PLA foams. The improved foaming properties of PLA via a biobased nucleating agent show potential for the production and application of green biodegradable foams.