纤维素/聚乙二醇共混物相变行为及在DMSO/PF和DMAC/LiCl中相容性的研究

纤维素和聚乙二醇在二甲基亚砜／多聚甲醛（DMSO/PF）、二甲基乙酰胺／氯化锂（DMAC/LiCl）溶剂体系中表现出不同的相容性，同时再生共混物也表现出不同的相变行为。在DMSO体系下，聚乙二醇和纤维素在溶液状态下具有较好的相容性，再生共混物的相变焓较大，相变性质为固一固态相转变；而在DMAC／LiCl体系中，纤维素和聚乙二醇的相容性较差，再生后共混物的相变焓很小，相变性质为固一液相转变。纤维素在该两溶剂体系中的溶解机制及分子间的相互作用状态不同是导致它和聚乙二醇的共混相容性差异和再生共混物相变行为不同的原因。     

纤维素/聚乙二醇共混物的相容性及形态结构研究

通过DSC、SEM研究了纤维素和聚乙二醇共混物的热行为及两组分在共混物中的分布形态。聚乙二醇和纤维素并混后，结晶度、相变熵、相变温度降低，且降低程度随共混物中纤维素含量的增大而增大，共混物中纤维素和聚乙二醇具有很好的相容性；纤维素和聚乙二醇在共混物中的形态表现为均一、连续的相结构，没有出现相分离。     

聚乙二醇／聚丙烯酰胺共混物的制备及性能研究

通过微波加热法制备聚丙烯酰胺,将其与聚乙二醇共混制备聚乙二醇／聚丙烯酰胺（PEG,PAM）共混物,采用傅立叶变换红外线光谱（FTIR）,差示扫描量热仪（DSC）,X射线粉末衍射仪（XRD）,熔点偏光显微镜等测定共混物的性能。结果显示共混物中PEG与PAM形成氢键,共混物的升降温过程中具有吸热和放热峰,相变温度和相变焓随共混物中PAM含量的增加,逐渐降低。PAM的存在对PEG的结晶过程造成了破坏,共混使PEG难以形成均匀球晶,结晶粒子变大。     

纤维素／聚乙二醇共混物相变行为及在DMSO／PF和DMAC／LiCl中相容性 …

纤维素和聚乙二醇在二甲基亚砜／多聚甲醛（ＤＭＳＯ／ＰＦ）、二甲基乙酰胺／氯化锂（ＤＭＵＡＣ／ＬｉＣｌ）溶剂体系中表现出不同的相容性,同时再生共混物也表现出不同的相变行为。在ＤＭＳＯ体系下,聚乙二醇和纤维素在溶液状态下具有较好的相容性,再生共混物的相变焓较大,相变性质为固－固态相转变;而在ＤＭＡＣ／ＬｉＣｌ体系中,纤维素和聚乙二醇的相容性较差,再生后共混物的相变焓很小,相变性质为固－液相转变。纤维素     

PEG/活性炭复合物的热性能研究

以活性炭颗粒（ACG）为吸附增强材料,聚乙二醇（PEG6000）为相变材料,采用物理共混法制备了PEG/活性炭复合物。利用差示扫描量热仪、导热系数测定仪、高温综合热分析仪对所得复合材料的热性能进行了研究。结果表明,加入活性炭颗粒,可提高材料的导热系数和热稳定性。     

化学法和共混法制备的PEG/CDA相变材料的性能比较——储热性能与链结构的关系

通过IR、DSC和X -ray研究了用化学键联法和溶液共混法制备的聚乙二醇 /二醋酸纤维素 (PEG/CDA)型相变材料的相变热焓、相变温度和结晶度等物性 ,探索了两种材料的链结构与储热性能的关系。结果表明 ,对相同PEG含量的共混材料和化学改性材料而言 ,共混物的相变焓要大于化学改性材料的相变焓 ;但化学改性物是一种固固相变材料 ,而共混物不具有固固相变特性 ,只是一种形状稳定的固液相变材料     

化学法和共混法制备的PEG／CDA相变材料的性能比较：储热性能？…

通过IR、DSC和X-ray研究了用化学键联法和溶液共混法制备的聚乙二醇/二醋酸纤维素(PEG/CDA)型相变材料的相变热焓、相变温度和结晶度等物性,探索了两种材料的链结构与储热性能的关系.结果表明,对相同PEG含量的共混材料和化学改性材料而言,共混物的相变焓要大于化学改性材料的相变焓;但化学改性物是一种固固相变材料,而共混物不具有固固相变特性,只是一种形状稳定的固液相变材料.     

PET／聚乙二醇共混物结晶行为的研究

应用光学解偏振光法、温度-形变法和DSC法研究了PET/聚乙二醇(PGL)共混物的结晶行为。结果表明,聚乙二醇是PET优良的结晶促进剂,随着聚乙二醇含量的增加,共混物的结晶速率明显提高,DSC热谱图上的熔融结晶温度(T_(mc))和冷却结晶温度T_(cc)差比纯PET增大了31℃,扩大了结晶温度范围,同时T_g下降,使共混物的注射模塑温度可望有较大的降低。     

新型PP/IPN相变纤维的纺制

以聚乙二醇丙烯酸酯为相容剂,将聚N-羟甲基丙烯酰胺/聚乙二醇互穿网络聚合物(简称IPN)与聚丙烯(PP)共混并纺丝,制备新型PP/IPN相变纤维。测试了共混物的流变性能,共混纤维的力学性能、热性能及回潮率。结果表明:共混物为切力变稀流体,共混纤维断裂强度随IPN含量的增加先增大后下降,相变焓随IPN含量的增大而提高,共混纤维的吸湿能力较纯PP高。当w(IPN)为20%时,断裂强度保持在3 cN/dtex以上,熔融相变焓达17.10 J/g,回潮率达0.68%。     

聚乳酸/聚乙二醇共混物的热氧稳定性研究

热氧稳定性是材料加工、应用的重要参数。采用差热、热重分析研究聚乳酸/聚乙二醇共混物的热氧稳定性。混合比例相同,PEG相对分子质量对共混物热氧稳定性能的影响趋势不同;PLLA/PEG共混物的共混比例不同时,热氧稳定性降低幅度与共混物中PLLA百分数不成比例;PLLA/PEG共混物的热失重曲线中出现的转折表明共混物降解过程中PLLA链与PEG链可能发生了化学反应。     

Poly(ethylene glycol)/poly(methyl methacrylate) blends as novel form‐stable phase‐change materials for thermal energy storage

In this study, we focused on the preparation and characterization of poly(ethylene glycol) (PEG)/poly(methyl methacrylate) (PMMA) blends as novel form‐stable phase‐change materials (PCMs) for latent‐heat thermal energy storage (LHTES) applications. In the blends, PEG acted as a PCM when PMMA was operated as supporting material. We subjected the prepared blends at different mass fractions of PEG (50, 60, 70, 80, and 90% w/w) to leakage tests by heating the blends over the melting temperature of the PCM to determine the maximum encapsulation ratio without leakage. The prepared 70/30 w/w % PEG/PMMA blend as a form‐stable PCM was characterized with optical microscopy and Fourier transform infrared spectroscopy. The thermal properties of the form‐stable PCM were measured with differential scanning calorimetry (DSC). DSC analysis indicated that the form‐stable PEG/PMMA blend melted at 58.07°C and crystallized at 39.28°C and that it had latent heats of 121.24 and 108.36 J/g for melting and crystallization, respectively. These thermal properties give the PCMs potential LHTES purposes, such as for solar space heating and ventilating applications in buildings. Accelerated thermal cycling tests also showed that the form‐stable PEG/PMMA blend as PCMs had good thermal reliability and chemical stability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study on phase change characteristics of PEG/PAM coupling blend

A novel solid–solid phase change materials with polyethylene glycol (PEG) worked as phase change substance and polyacrylamide (PAM) as solid skeleton was synthesized by coupling blend. Their phase change behaviors and structure analysis was studied by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), they had reversible solid–solid phase change properties. The result indicates that the PEG/PAM PCMs has great transition enthalpy and suitable phase transition temperature in the phase transition process. It can be considered as promising PCMs. Otherwise, their crystallization behavior were analyzed by polarization optical microscopy (POM), the crystalline degrees of these phase change materials were affected due to the intermolecular interaction and chemical bond. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polyethylene glycol‐sugar composites as shape stabilized phase change materials for thermal energy storage

Polyethylene glycol (PEG)‐sugar composites have been investigated as cost effective shape‐stabilized phase change materials for thermal energy storage. PEGs form internal hydrogen bonds stabilizing their chains at solid state. However low molecular weight PEGs are liquid due to short chains as high molecular weight PEGs have too little concentration of hydroxyl groups. Therefore, glucose, fructose, and lactose are used as hydrogen bond source in this study. Consequently it is found that sugars stabilized PEGs up to 90% PEG constitution in solid state except for 90%PEG10,000/10% fructose blend. Fourier transform‐infrared (FT‐IR) analysis revealed considerable interactions between PEGs. The maximum changes in the spectra were observed in the OH stretching region as band broadening due to increasing hydrogen bonding interactions. Differential scanning calorimetry (DSC) analysis are used to determine phase change temperatures and enthalpy of the shape‐stabilized composites that are slightly lower than those of PEG precursors due to the interference effect of sugar in crystallization process. The enthalpies of the blends are 89%, 95%, and 94% of expected from 90%PEG/10% glucose blends, 93%, 94%, and 93% of expected from 90% PEG/10% fructose blends, and 99%, 96%, and 96% of expected from 90% PEG/10% lactose blends respectively when PEGs with 1,000; 6,000; and 10,000 g/mol average molecular weights are used respectively. The diameter of the spherulitic crystals of PEGs decreases with the addition of any of sugar derivatives and spherulites of the composites turns to semi‐amorphous solid structures at temperatures above melting point of PEG precursor. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Solution miscibility and phase‐change behavior of a polyethylene glycol–diacetate cellulose composite

Polyethylene glycol (PEG) and diacetate cellulose (CDA) exhibit good miscibility in acetone solution. The miscibility is related to the molecular weight of PEG, which increases as miscibility decreases. The phase‐change behavior of PEG in composite with CDA prepared from the miscible solution was found to be completely different from that of pure PEG. When the PEG fraction in the composites was less than 85%, PEG within the composite did not melt into liquid; even when the temperature was 40°C higher than the melting point of PEG, the PEG–CDA composite exhibited solid–solid phase‐change behavior. Thermal analysis indicated that the PEG–CDA composite had greater enthalpy and exhibited good thermal stability. The PEG–CDA composite that exhibited solid–solid phase‐change behavior can be used as a new kind of phase‐change material for thermal energy storage and temperature control. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 652–658, 2003     

Preparation and characterization of PEG/MDI/PVA copolymer as solid–solid phase change heat storage material

In this article, a novel solid–solid phase change heat storage material was synthesized via a two‐step condensation reaction of high molecular weight poly(ethylene glycol) (PEG4000) with poly(vinyl alcohol) (PVA) and 4,4′‐diphenylmethane diisocyanate (MDI). To characterize the resulting product in comparison with pristine PEG4000, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analyses, and polarization optical microscopy measurements were employed to investigate functionality, thermal properties, and crystalline behavior. The results indicated that the crosslinking phase change material showed typical solid–solid phase transition properties, and its phase change enthalpy reached 72.8 kJ/kg. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Kinetic parameters of thermal degradation of polyethylene glycol‐toughened novolac‐type phenolic resin

The miscibility and thermal degradation of poly(ethylene glycol) (PEG)‐toughened novolac‐type phenolic resin were investigated. Differential scanning calorimetry (DSC) results confirmed that the phenolic resin/PEG blend was blended completely. Infrared spectra show that hydrogen bonding existed in the blends. Thermal degradation of PEG blended with novolac‐type phenolic resin was studied utilizing a dynamic thermogravimetric technique in a flowing nitrogen atmosphere at several heating rates (i.e., 5, 10, 20, 40°C/min). Thermal degradation of phenolic resin/PEG blends takes place in multiple steps. The thermal behavior and the thermal stability affected the thermal degradation, which coincided with the data from the thermal degradation of novolac‐type phenolic resin/PEG blends by thermogravimetric analysis (TGA). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 188–196, 2001     

Effect of casting solvent on characteristics of hexanoyl chitosan/polylactide blend films

Blend films of hexanoyl chitosan (H‐chitosan) and polylactide (PLA) were cast from corresponding blend solutions in chloroform, dichloromethane, or tetrahydrofuran. Thermal degradation behavior of the as‐prepared blend films was intermediate to those of the pure components and no significant effect from the type of the casting solvent was observed. All of the blend films exhibited one composition‐dependent glass transition temperature, but the results only suggested partial miscibility of the components in the amorphous phase at “low” contents of H‐chitosan. As revealed by solvent etching technique, the as‐prepared blend films prepared from the blend solutions in chloroform and dichloromethane showed extensive phase separation of the two components, with the minor phase forming into discrete domains throughout the matrix. Both thermal and X‐ray analyses showed that the apparent degree of crystallinity of the PLA component in the blends decreased monotonically with increasing H‐chitosan content and the choice of the casting solvent did not have an effect on the structure of PLA crystals. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Interactions in blends containing chitosan with functionalized polymers

The phase behavior of blends containing chitosan with poly(vinyl‐alcohol) (PVA) and poly(2‐hidroxyethyl methacrylate) (P2HEM) was analyzed. Blends were obtained by casting from acetic acid solution (HAc) and 1,1,1,3,3,3 hexafluoro‐2‐propanol (HF2P) and studied by DSC, FT‐IR, and TGA. The phase behavior of the blends of chitosan with PVA and P2HEM, studied by DSC, shows that the systems behave as one‐phase systems in HAc as well as in HF2P according to the DSC results. According to the results of FT‐IR analyses of the different absorptions of the blends, relative to the pure components, they show an important shift that is considered evidence of an interaction between the components of the blends. The thermogravimetric analysis of the blends and the pure components shows that the temperature for thermal degradation of the blends is higher that that of the pure components, irrespective of the solvent casting from which the mixture was obtained. These results are interpreted as the formation of a new product that corresponds to a compatible polymer blend. The compatibilization of these systems is attributed to strong interactions, like hydrogen bonds formation between the functionalized polymers and chitosan, due to the presence of interacting functional groups in all the polymers studied. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1953–1960, 2005     

Dynamic mechanical and tensile properties of poly(N-vinyl pyrrolidone)-poly(ethylene glycol) blends

Mechanical properties of miscible blends of high molecular weight poly(N-vinyl pyrrolidone) (PVP) with a short-chain, liquid poly(ethylene glycol) (PEG) of molecular weight 400 g/mol have been examined as a function of PVP-PEG composition and degree of hydration. The small-strain behavior in the linear elastic region has been evaluated with the dynamic mechanical analysis and compared with the viscoelastic behavior of PVP-PEG blends under large strains in the course of uniaxial drawing to fracture and under cyclic extension. A strong decoupling between the small-strain and the large strain properties of the blends has been observed, indicative of a pronounced deviation from rubber elasticity in the behavior of the blends. This deviation, also seen on tensile tests under fast drawing, is attributed to the peculiar phase behavior of the blends and the molecular mechanism of PVP-PEG interaction. Nevertheless, for the PVP blend with 36% PEG, under comparatively low extension rates, the reversible contribution to the total work of deformation up to ε=300% has been found to be maximum at around 70%, while the blends containing 31 and 41% PEG behave rather as an elastic-plastic solid and a viscoelastic liquid, respectively.     

Aging of poly(lactide)/poly(ethylene glycol) blends. Part 2. Poly(lactide) with high stereoregularity

Blending poly(ethylene glycol) (PEG) with poly(lactide) (PLA) decreases the T_g and improves the mechanical properties. The blends have lower modulus and increased fracture strain compared to PLA. However, the blends become increasingly rigid over time at ambient conditions. Previously, it was demonstrated that a PLA of lower stereoregularity was miscible with up to 30 wt% PEG. Aging was due to slow crystallization of PEG from the homogeneous amorphous blend. Crystallization of PEG depleted the amorphous phase of PEG and gradually increased the T_g until aging essentially ceased when T_g of the amorphous phase reached the aging temperature. In the present study, this aging mechanism was tested with a crystallizable PLA of higher stereoregularity. Changes in thermal transitions, solid state structure, and mechanical properties were examined over time. Blends with up to 20 wt% PEG were miscible. Blends with 30 wt% PEG could be quenched from the melt to the homogenous amorphous glass. However, this composition phase separated at ambient temperature with little or no crystallization. Changes in mechanical properties during phase separation reflected increasing rigidity of the continuous PLA-rich phase as it became richer in PLA. Construction of a phase diagram for blends of higher stereoregular PLA with PEG was attempted.