软段分子链结构对PUF性能的影响

通过将聚乙二醇(PEG)、聚己内酯(PCL)、聚乳酸(PLA)和聚四氢呋喃醚(PTMG)等不同特性的聚合物链段引入聚氨酯(PU)基体,制备了具有不同软段结构的聚氨酯泡沫塑料(PUF)。考察了不同软段分子链结构对PUF力学性能、热性能及在土壤中降解性能的影响。结果表明,随着软段中PEG或PLA含量的增加,PUF的拉伸强度下降;不同软段结构PUF的玻璃化转变温度顺序为:PTMG1000相似文献   

1，3-丁二醇对PCL／MDI体系聚氨酯弹性体力学性能的影响

首先以聚己内酯多元醇（PCL）、4,4’-二苯基甲烷二异氰酸酯（MDI）、液化MDI和MDI-50为原料合成聚氨酯（PU）预聚体,再用混合扩链剂制备聚氨酯弹性体。讨论了预聚体异氰酸酯基（NCO）含量、异氰酸酯类型、1,3-丁二醇（1,3-BDO）含量、聚酯软段相对分子质量对聚氨酯弹性体力学性能的影响。结果表明：提高预聚体NC0基含量可使弹性体的硬度、300％定伸应力、拉伸强度和撕裂强度明显提高,拉断伸长率和冲击弹性则下降;纯MDI弹性体综合力学性能最好,液化MDI次之,MDI-50最差;提高1,3-BDO含量可使弹性体的硬度、撕裂强度和冲击弹性明显下降;软段相对分子质量为1000的聚氨酯弹性体的硬度、300％定伸应力、拉伸强度和撕裂强度较高,软段相对分子质量为2000的聚氨酯弹性体的拉断伸长率和冲击弹性较高。     

1,3-丁二醇对PTMG/MDI体系聚氨酯弹性体力学性能的影响

以纯4,4′-二苯基甲烷二异氰酸酯（MDI）MDI-100、液化MDI（C-MDI）、MDI-50和四氢呋喃均聚醚（PTMG）为原料合成聚氨酯（PU）预聚体,再分别与KD和KC扩链剂制备PU弹性体。研究了1,3-BDO含量、异氰酸酯类型、预聚体NCO基含量、聚醚软段相对分子质量对PU弹性体力学性能的影响。结果表明,提高1,3-BDO含量可使PU弹性体的硬度、撕裂强度和冲击弹性明显下降;纯MDI弹性体综合力学性能最好,液化MDI次之,MDI-50最差;提高预聚体NCO基含量可使弹性体的硬度、300%定伸应力和撕裂强度明显提高,拉断伸长率和冲击弹性则下降;软段相对分子质量为1000时,PU弹性体的300%定伸应力、拉伸强度和撕裂强度均增加;软段相对分子质量为1800以上,拉断伸长率和冲击弹性增加。     

复合软段耐热聚氨酯泡沫塑料的制备及表征

选用以丙三醇为起始剂制备的聚醚多元醇N303与聚醚多元醇H303进行复配,采用一步法制备了N303/H303复合软段聚氨酯泡沫塑料（PUF）,研究了N303/H303复合软段配比以及二氧化硅（SiO2）填料对PUF性能的影响。结果表明,N303/H303复合软段PUF压缩模量与冲击强度均高于单一软段PUF; 随软段中H303含量增大,PUF压缩模量与冲击强度呈先上升再下降的趋势,在N303/H303质量比为50/50时达到最大值; 添加5 %~15 %（质量分数,下同）的SiO2能作为成核剂,PUF泡孔均匀性提高且细化泡孔;PUF高温压缩性能保持较好。     

聚己内酯二醇/聚四氢呋喃聚醚二醇并用比对混炼型聚氨酯性能的影响

以聚己内酯二醇（PCL2000）和聚四氢呋喃醚二醇（PTMG1000）并用作为软段单体、二苯基甲烷二异氰酸酯为硬段单体,合成混炼型聚氨酯（MPU）。保持硬段含量不变,研究PCL/PTMG并用比（质量比）对MPU性能的影响。结果表明：随着PTMG用量的增大,MPU的玻璃化温度降低;MPU硫化胶的拉伸强度、拉断伸长率和撕裂强度均先增大后减小,DIN磨耗量增大,热氧老化后的拉伸强度和拉断伸长率降幅明显增大;当PCL/PTMG并用比为90/10时,MPU硫化胶的拉断伸长率和撕裂强度最大,分别为518%和66 kN·m-1;仅加入PCL的MPU硫化胶的DIN磨耗量最小, 为0.014 4 cm3。     

PTMG／TDI型聚氨酯弹性体的制备及力学性能研究

以聚四氢呋喃醚二醇（PTMG）、2,4-甲苯二异氰酸酯（TDI）、3,3’-二氯-4,4’-二胺基二苯甲烷（MOCA）或3,5-二甲硫基甲苯二胺（E-300）为主要原料,采用预聚体法合成浇注型聚氨酯弹性体（PUE）。分析了预聚体NCO基含量、PTMG软段相对分子质量、两种扩链剂以及扩链系数对PUE力学性能的影响。结果表明,随着预聚体NCO基含量增加,PUE的硬度、拉伸强度、300％定伸应力和撕裂强度提高,扯断伸长率下降,扯断永久形变发生微小变化;随着软段相对分子质量的不断提高,PUE的硬度、拉伸强度、300％定伸应力和撕裂强度缓慢下降,而扯断伸长率和扯断永久形变升高;在其它条件相同时,扩链剂E-300与MOCA相比,综合力学性能较好。     

PEG／N100／NG弹性体胶片交联结构及其低温力学性能研究

通过DSC（差示扫描量热法）对PEG／N100／NG弹性体胶片的结构进行了研究,并分析了其静态和动态力学性能。研究表明,结晶的聚乙二醇（PEG）微粒在弹性体中作为应力集中物吸收了大量的拉伸能量,从而大大提高了PEG／N100／NG弹性体胶片的韧性,且PEG相对分子质量越大,PEG／N100／NG的交联结构越稳定,从而弹性体胶片的静态力学性能越好;随着PEG相对分子质量增大,动态模量曲线都发生了很大变化,储能模量E下降,力学损耗已。和tanα的β松弛峰温下降,相对强度先大幅提高,后略有下降;随着N100含量增加即R值增大,β松弛峰温即玻璃化转变温度Tg逐步下降,峰强度也随之下降。     

水发泡抗静电半硬质聚氨酯泡沫塑料的制备和性能研究

采用内部添加导电炭黑（CB）方法,通过一步法模塑成型工艺制备了不同导电炭黑或硬段（HS）含量的水发泡抗静电半硬质聚氨酯泡沫塑料（SRPUF）。测试了SRPUF的红外光谱、导电性能、力学性能和黏弹性。结果表明,随着导电炭黑或硬段含量的增加,SRPUF的体积电阻率下降;随着导电炭黑含量的增加,SRPUF的拉伸模量提高,拉伸强度和断裂伸长率显著下降;随着硬段含量的增加,SRPUF的拉伸和压缩模量增大,抗压能力提高,拉伸强度基本不变,而断裂伸长率显著下降;随着导电炭黑或硬段含量的增加,SRPUF的玻璃化转变温度（Tg）分别向低温和高温方向移动,动态模量则均在温度低于Tg时逐渐下降,温度高于Tg时逐渐提高。     

纤维状海泡石/天然胶乳复合胶膜的力学及热稳定性能

采用乳液共混法制备了纤维状海泡石/天然胶乳复合胶膜,研究了海泡石的结构及复合胶乳的胶体性能,考察了纤维状海泡石用量对硫化复合胶膜力学性能、断裂形态及热稳定性的影响。结果表明,随着纤维状海泡石用量的增加,天然胶乳的黏度增大,机械稳定性下降。复合胶膜的拉伸强度和撕裂强度先增大后减小,500%定伸应力增大,扯断伸长率降低;当纤维状海泡石用量为3份时复合胶膜表现出良好的力学性能。与天然胶乳薄膜相比,纤维状海泡石/天然胶乳复合胶膜的热稳定性有所提高。     

多元醇对NDI型聚氨酯微孔弹性体性能的影响

讨论了多元醇摩尔质量及种类对1,5-萘二异氰酸酯(NDI)型聚氨酯微孔弹性体性能的影响。研究发现,摩尔质量对弹性体的拉伸强度无明显影响,但摩尔质量增大能够降低弹性体的玻璃化转变温度(Tg),促进软段结晶,并增加弹性体的拉断伸长率;通过对聚己内酯二醇(PCL)/NDI与聚己二酸乙二醇丙二醇酯(PEPA)/NDI弹性体的DSC分析,发现PEPA/NDI弹性体无软段结晶峰,其拉伸性能较之PCL/NDI弹性体有所下降;而从DMA的分析结果可知,PEPA/NDI弹性体具有更宽的使用温度范围及在常温下更好的动态力学性能。     

Effects of storage on thermomechanical properties of poly(ɛ-caprolactone) blends containing poly(vinyl pyrrolidone/iodine)

Abstract

This study reports the effects of: the molecular weight ratio of poly(?-caprolactone) (PCL) in blends containing polymer of high (50 000 g mol^-1 ) and low (4000 g mol^-1 ) molecular weight; the concentration (0, 1, and 5 wt-%) of poly(vinyl pyrrolidone/iodine) (PVP/I); and storage at 30°C and 75% relative humidity; on the thermomechanical properties of films prepared by solvent evaporation from solutions containing both PCL and PVP/I. The tensile properties were found to be statistically dependent on the molecular weight ratio of PCL but not on the concentration of PVP/I. The reductions in tensile strength and elongation at break associated with increasing amounts of low molecular weight PCL were attributed to a reduction in the concentration of chain entanglements. No changes were observed in viscoelastic properties or the glass transition temperature. Following storage there were no changes in the tensile strength, glass transition temperature, or viscoelastic properties of the films; however, significant reductions in elongation at break were observed. It is suggested that this is due to hydrolytic chain scission of amorphous PCL. Inclusion of 5 wt-% PVP/I increased this process in films containing 100 : 0 and 80 : 20 high/low molecular weight PCL (but not 60 : 40), but the extent of this was small. This study highlighted significant aging properties of PCL in a moist atmosphere. Consequently, it is recommended that suitable packaging materials should be employed to control the exposure of PCL films to water during storage.     

Plasticized poly(lactic acid) with low molecular weight poly(ethylene glycol): Mechanical,thermal, and morphology properties

Poly(lactic acid) PLA was plasticized with low molecular weight poly(ethylene glycol) PEG‐200 to improve the ductility of PLA, while maintaining the plasticizer content at maximum 10 wt%. Low molecular weight of PEG enables increased miscibility with PLA and more efficient reduction of glass transition temperature (T_g). This effect is enhanced not only by the low molecular weight but also by its higher content. The tensile properties demonstrated that the addition of PEG‐200 to PLA led to an increase of elongation at break (>7000%), but a decrease of both tensile strength and tensile modulus. The plasticization of the PLA with PEG‐200 effectively lowers T_g as well as cold‐crystallization temperature, increasing with plasticizer content. SEM micrographs reveal plastic deformation and few long threads of a deformed material are discernible on the fracture surface. The use of low molecular weight PEG‐200 reduces the intermolecular force and increases the mobility of the polymeric chains, thereby improving the flexibility and plastic deformation of PLA. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4576–4580, 2013     

不同分子量PCL增韧PLA的结构与性能

采用两种不同分子量的聚(ε-己内酯)(PCL)(粘均分子量60 000和3 000)与聚乳酸(PLA)在175℃下共混10 min制备PLA/PCL共混物。通过动态流变、扫描电子显微镜(SEM)和力学性能等研究了PLA/PCL共混物的结构和性能。动态流变显示,在PCL低含量(质量分数小于15%)时,PCL与PLA是相容的,质量分数为15%时PCL与PLA表现出明显的相分离行为。SEM显示,随着PCL含量的增加,PCL相的尺寸变大;低分子量PCL(L-PCL)的相尺寸明显大于高分子量PCL(H-PCL),而且相形态不是规则的球状。随着PCL含量的增加,共混物的拉伸强度下降,而断裂伸长率增加。当H-PCL质量分数为8.3%时,PLA/H-PCL共混物的断裂伸长率为137.32%。当H-PCL质量分数为15%时,其断裂伸长率高达232.76%。在添加相同含量PCL时,PLA/H-PCL共混物的拉伸强度高于PLA/L-PCL;而PCL质量分数8%时,共混物的断裂伸长率相差不多,当PCL质量分数大于8%时,PLA/H-PCL共混物的断裂伸长率明显比PLA/L-PCL共混物的高。     

PCL／CaSO4复合材料的力学性能研究

采用不同粒度的CaSO4与聚己内酯（PCL）熔融共混，并对复合后的材料进行了力学性能研究。研究表明，复合材料的拉伸强度及断裂伸长率随着CaSO4的含量的增多而降低。偶联剂的种类和用量对复合材料的力学性能都有影响，其中用硅烷类偶联剂JH-0187处理过的效果最好，最佳用量为2％，此时拉伸强度和断裂伸长率分别为25MPa和750％。此外，CaSO4的粒径对复合材料的力学性能也有影响，粒径越小复合材料的拉伸强度和断裂伸长率越好。     

PET-PEG共聚酯性能的研究

通过共缩聚反应合成了ＰＥＴ－ＰＥＧ共聚酯,采用ＤＳＣ法测定了共聚物的结晶性能、结晶速度,还测试了共聚物的力学性能,结果表明：ＰＥＧ的加入能有效地增加分子链柔性,改善结晶性能,其中ＰＥＴ－ＰＥＧ６０００在１００℃的半结晶时间为０．７ｍｉｎ,ＰＥＧ的含量在２０％以下,拉伸性能没有恶化,冲击强度、断裂伸长率大大提高     

Effect of PEG molecular weight on the tensile toughness of starch/PCL/PEG blends

The blend of a gelatinized starch and poly(ε‐caprolactone) (PCL) was prepared and the effect of starch gelatinization on the mechanical properties of the blend was studied. The gelatinization of starch resulted in good dispersion of the starch in the PCL matrix and a higher modulus and strength of the blend. The mechanical properties of the starch/PCL/poly(ethylene glycol) (PEG) blends were also investigated. From the change of the toughness of the blends with the PEG molecular weight, it was found that the blend containing PEG of molecular weight 3400 shows the highest tensile toughness. It was also found from the SEM images that the blend containing PEG of molecular weight 3400 had the smallest domain size of the starch dispersion phases, which implies that PEG of the proper molecular weight could effectively stabilize the interface of the starch/PCL blend. The PEG of the proper molecular weight seems to locate mainly at the interface between the starch and PCL phases and to interact with both the starch phase and the PCL phase. The interactions between starch and PEG and between PCL and PEG in the blend were studied using DSC and FTIR techniques. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2049–2056, 2000     

Effects of processing parameters and molecular weight distribution on the tensile properties of polypropylene fibers

The tensile properties of polypropylene fibers, produced in a short-spin line, are correlated with the parameters of the three processing stages (spinning, drawing, and annealing), and with the molecular weight distribution. In general, tensile stiffness and strength increase with increasing molecular orientation, while the elongation at break decreases. The degree of orientation is determined by the deformation ratios and temperatures of the first two stages. Tensil modulus and strength also increase with increasing annealing stage shrinkage ratio. All the tensile properties, including the elongation at break, increase with increasing average molecular weight. The mechanisms of crystallization and deformation are related to the molecular weight distribution in different ways. Hence, the tensile modulus is highest for broad distributions when the draw ratio is low, and for narrow distributions when the draw ratio is high. The tensile strength increases and the elongation at break decreases as the width of the molecular weight distribution decreases, for all combinations of processing parameters. The distribution of tensile strength, for fibers with high draw ratios, broadens as the molecular weight distribution narrows. The total draw ratio of fibers, as experienced during processing and testing, and the true stress at break, are discussed in terms of deformation rates and relaxation times. © 1994 John Wiley & Sons, Inc.     

Mechanical and thermal properties of UV-curable polyurethane and polyurea acrylates

Soft-segment molecular weight, soft-segment crystallization, hard-segment-type, and reactive diluent level were examined in urea and urethane acrylates. Increasing soft-segment molecular weight led to a decreased tensile modulus, increased strength, and increased elongation at break. Soft-segment crystallization increased the modulus below the melting temperature, but decreased the modulus above the melting temperature because crystallization interfered with cross-linking. Materials with hard segments that allowed for greater phase separation showed a higher modulus, higher ultimate stress, and higher ultimate elongation. Materials with reactive diluents 2-hydroxyethyl methacrylate (HEMA) and N-vinyl pyrrolidinone (NVP) showed qualitatively different behavior. HEMA caused the modulus and strength to increase with little effect on elongation up to concentrations of 50 wt %; at higher concentrations, the elongation decreased. NVP also increased the modulus and strength; however, at 40 wt % NVP, ultimate elongation increased in a well-phaseseparated system and decreased in a poorly phase-separated system. In tensile tests, samples with 40% NVP also showed substantial sample necking and drawing. © 1993 John Wiley & Sons, Inc.     

RFL coated aramid short fiber reinforced thermoplastic elastomer: Mechanical, rheological and morphological characteristics

Composite based on a new generation metallocene catalyzed thermoplastic elastomer ethylene-octene copolymer (EOC) and resorcinol formaldehyde latex (RFL) coated aramid short fiber was prepared by varying the short fiber loading from 1 to 10 phr. The mechanical, morphological and rheological characterizations were carried out. The impact of a low molecular weight maleic anhydride grafted 1, 2 polybutadiene (MA-g-PB) on various properties was also investigated. It has been observed that with increasing the short fiber content both the low strain modulus and modulus at 100% increase but the tensile strength and elongation at break decrease. The improvements in tensile strength coupled with elongation at break and good fiber dispersion particularly at high fiber loaded composite were achieved with the incorporation of MA-g-PB, which indicates that it acts as an interface modifier through compatibilization between the fiber and the EOC matrix as well as a good dispersing agent. The understanding of adhesion between the fiber and the polymer and the sticking of polymer traces on the tensile fractured fiber surface of the composite by scanning electron microscopic analyses further support the compatibilizing action of MA-g-PB. The melt rheological behavior such as storage modulus, loss modulus, complex viscosity and storage viscosity of the composites were investigated using a Rubber Process Analyser (RPA) under strain and frequency sweep mode.