The characterisation of plastic used in a Gabo sculpture

The Nylon line used in a sculpture by the artist Naum Gabo has been investigated. The sculpture at the Tate Gallery in London shows signs of degradation and there is interest in determining the best replacement material in order to extend the life of the sculpture. Thermal analysis was employed to identify the original polyamide used in the artwork. The tensile properties of the degraded Nylon from the sculpture were compared with those of unaged Nylon and poly(vinylidene fluoride) (PVDF), identified as a potential replacement material. PVDF was proposed as the preferred replacement for the sculpture.     

大型仪器维护与维修(179~186)裂解器-气相色谱质谱联用仪的使用技巧及故障处理

在一定条件下, 高分子及非挥发性有机化合物遵循一定的裂解规律, 即特定的样品能够产生特征的裂解产物及产物分布.裂解器-气相色谱质谱联用仪(pyrolyzer-gas chromatograph-mass spectrometer, Py-GCMS)将快速热解技术同气相色谱质谱联用技术结合, 作为研究木质生物质快速热解产物的重要仪器, 可定性、定量分析难挥发复杂基质成分.以CDS5200-7890A-5975C Py-GCMS为例, 从仪器的原理出发, 介绍Py-GCMS的使用技巧, 详细说明Py测试样品要求及操作注意事项.着重总结分享了仪器维护保养及故障处理经验, 指出规范有序及安全高效地运行Py-GCMS, 不仅可以保障科研活动, 在一定程度上也可延长仪器的使用寿命.     

内蒙和吉林马勃的产地对比分析

采用扫描电子显微镜(SEM)、傅里叶变换红外光谱(FTIR)和裂解-气质联用(Py-GCMS)从微观形貌、元素组成、主要类别及小分子的化学组成等方面对产自内蒙和吉林的马勃中药材直接进行原位分析,并对产自两地的马勃进行区分。 SEM结果表明,内蒙马勃属于灰包科栓皮马勃属栓皮马勃;吉林马勃属于灰包科静灰球属长根静灰球菌。 FTIR光谱显示,内蒙马勃在酰胺Ⅰ带吸收峰1636 cm-1,而吉林马勃的在1654 cm-1。 吉林马勃二阶导数红外光谱在1625 cm-1有较强的吸收峰说明吉林马勃含芳香环骨架的化合物含量高于内蒙马勃,与Py-GCMS的结论中吉林马勃苯酚、对甲苯酚含量明显高于内蒙马勃相符。 另外,Py-GCMS结果可以分析出两地马勃的裂解成分及含量的差异。     

正渗透膜成分与结构分析

用裂解质谱的方法对美国HTI公司三种正渗透膜CTA-ES、CTA-NW和TFC-ES的成分进行了鉴定,并且利用扫描电子显微镜(SEM)对其结构进行了仔细的观察。结果显示,三种膜都是由醋酸纤维素、聚酯、聚砜、聚氨酯等高分子材料组成的层状结构。     

Cellulose ester-polyolefine binary blend: Morphological,rheological and mechanical properties

Binary blends of thermoplastic polymers, one being a polyolefin (high density polyethylene) and the other a bio-based polymer (cellulose acetate butyrate) were prepared with various components proportions. No compatibiliser was used. Depending on blend composition, different morphologies were obtained, from fine nodular to co-continuous. Blends viscoelastic and mechanical properties were studied in details in all range of compositions. The results obtained were interpreted using a careful analysis of the viscoelastic properties of the initial components and classical approaches developed for immiscible blends. Except the blends containing low amount of cellulose acetate butyrate finely dispersed in polyethylene, all other blends viscoelastic and mechanical properties follow the additive mixing rule.     

Studies on cellulose acetate-carboxylated polysulfone blend ultrafiltration membranes--Part I

Hydrophilic polysulfone ultrafiltration (UF) membranes were prepared from blends of cellulose acetate with carboxylated polysulfone of 0.14 degree of carboxylation. The effects of blend polymer composition on compaction, pure water flux, water content and membrane hydraulic resistance (R_m), have been investigated to evaluate the performance of the membranes. The performance of the blend membranes of various blend polymer compositions were compared with that of membranes prepared from pure cellulose acetate and blends of cellulose acetate and pure polysulfone. The hydrophilic cellulose acetate-carboxylated polysulfone blend UF membranes showed better performance compared to membranes prepared from pure cellulose acetate and blends of cellulose acetate and pure polysulfone.     

钾元素对生物质及其三组分热解的影响

采用机械混合法将KCl加入到纤维素、半纤维素、木质素以及稻壳和稻壳模拟物等生物质中,得到了一系列不同K含量的生物质样品,通过热重(TG)实验考察了K元素对生物质热解特性的影响.结果表明,K元素对生物质三组分热解特性的影响比较复杂,纤维素的最大热解失重速率随着KCl添加量的增加而降低,但KCl对半纤维素和木质素热解特性的影响不显著.无论是否添加KCl,模拟生物质的热解特性均可以认为是三组分热解的简单叠加.但酸预处理稻壳三组分间的稳定结构,导致其DTG曲线在300 ℃左右的热解峰由稻壳模拟物的尖峰变为肩峰,其热解焦炭收率也比稻壳模拟物的略低.此外,实验还采用浸渍法向酸预处理稻壳中添加了KCl.TG实验结果表明,K元素的存在对生物质热解具有一定的催化作用,但KCl的添加方式不同,生物质的热解特性有明显差别,生物质样品经机械混合添加KCl后,其热解焦炭收率呈下降趋势(纤维素除外),浸渍法添加的KCl导致酸预处理稻壳的最大热解失重速率和焦炭收率升高.     

Structure and mechanical properties of cellulose based scaffolds fabricated by selective laser sintering

This work presents the rapid fabrication of starch–cellulose and cellulose acetate scaffolds by selective laser sintering and the evaluation of the laser power, laser scan speed and the polymer particle size influence on the scaffold properties. The specimens were prepared using two different particle sizes and characterized by density measurements, scanning electronic microscopy (SEM) and a flexural test. The fine adjustment of process parameters was fundamental to warranty the processability of biodegradable cellulose based polymers by SLS. The specimens with lower particle size presented a higher degree of sintering, higher mechanical strength and a significant level of closed pores, as indicated by the density measurements and fractography analyses. The results obtained showed that is possible to fabricate scaffold structures using starch–cellulose and cellulose acetate materials by selective laser sintering.     

Transport of solutes through calix[4]pyrrole-containing cellulose acetate films

Films of cellulose acetate containing different concentrations of meso-octamethyl-porphyrinogen (calix[4]pyrrole) were prepared and characterized using UV-vis and FTIR spectroscopy, DSC and SEM. Incorporation of calix[4]pyrrole into cellulose acetate leads to a decrease in the degree of hydrophilicity of the polymeric matrix. However, a slight increase in the percentage of water uptake of the polymer is found with an increase of the initial amount of calix[4]pyrrole in the composite composition. This effect can be related to the plasticizing effect that the calix[4]pyrrole provokes in the cellulose acetate. A comparative study of transport parameters of oxygen and some non-associated electrolytes (sodium, copper(II) and nickel chlorides) was carried out. The diffusion coefficients of molecular oxygen through cellulose acetate films decrease with an increase of the concentration of calix[4]pyrrole in the composite films. The transport (diffusion and permeation) of the above mentioned electrolytes through a set of composite films shows a decrease of permeability and diffusion coefficients with an increase of calix[4]pyrrole concentration. Such behaviour is typical of systems where interactions between the polymer and diffusing species occur. However, from the analysis of the distribution coefficient, it was found that those interactions are only dependent on the calix[4]pyrrole content for 2:1 electrolytes.     

Permeation of water as a tool for characterizing the effect of solvent, film thickness and water solubility in cellulose acetate membranes

Cellulose acetate membranes have been used in many applications; of particular interest are reverse osmosis systems, and as a neutral matrix for incorporation of different polymers (e.g., conducting polymers), inorganic ions (e.g., lanthanides) and organic (e.g., pharmaceutical) compounds. The properties of the new polymers derived from cellulose acetate or blends depend on those of cellulose acetate. This work presents an attempt to find links between thermodynamic and kinetic properties of cellulose acetate membranes in equilibrium with water. Water diffusion coefficients in cellulose acetate membranes are reported, measured with a simple water permeation technique. The comparison of these values with the percentage of water uptake and polymer thickness leads to interesting conclusions related with different polymer properties.     

Phase behavior and structure of liquid crystalline solutions of cellulose derivatives

Summary Structural and thermodynamic characteristics of liquid-crystalline solutions of four cellulose derivatives in a range of solvents were studied. Basic observations were made on these systems using polarized light microscopy, small angle light scattering, dilute solution and concentrated solution viscosities. The polymers studied include hydroxypropyl cellulose (HPC), cellulose acetate butyrate (CAB), ethyl cellulose (EC), and cellulose triacetate (CT). The formation of the liquid crystalline phase was shown to strongly depend on polymer concentration, solvent type and temperature. The critical volume fraction of polymer required to form the liquid crystal phase varied significantly as the solvent changed. The critical volume fraction decreased with increasing solvent acidity and polymer intrinsic viscosity in a given solvent. The breadth of the two phase region seems to decrease with increasing acidity. The liquid crystalline phase was in most cases determined to be cholesteric. In all cases positively birefringent cellulose derivatives form negative spherulitic domains. In one case, the negativity birefringent system (cellulose triacetate) formed positively birefringent spherulitic liquid crystalline domains. This is interpreted to mean the structure organizes itself by a tangential alignment of polymer chains within the domain. SALS measurements appear to detect domains and in some cases cholesteristic pitch.With 5 figures and 4 tables     

Adsorption of carboxymethyl cellulose on polymer surfaces: evidence of a specific interaction with cellulose

The adsorption of carboxymethyl cellulose (CMC), one of the most important cellulose derivatives, is crucial for many scientific investigations and industrial applications. Especially for surface modifications and functionalization of materials, the polymer is of interest. The adsorption properties of CMC are dependent not only on the solutions state, which can be influenced by the pH, temperature, and electrolyte concentration, but also on the chemical composition of the adsorbents. We therefore performed basic investigation studies on the interaction of CMC with a variety of polymer films. Thin films of cellulose, cellulose acetate, deacetylated cellulose acetate, polyethylene terephthalate, and cyclo olefin polymer were therefore prepared on sensors of a QCM-D (quartz crystal microbalance) and on silicon substrates. The films were characterized with respect to the thickness, wettability, and chemical composition. Subsequently, the interaction and deposition of CMC in a range of pH values without additional electrolyte were measured with the QCM-D method. A comparison of the QCM-D results showed that CMC is favorably deposited on pure cellulose films and deacetylated cellulose acetate at low pH values. Other hydrophilic surfaces such as silicon dioxide or polyvinyl alcohol coated surfaces did not adsorb CMC to a significant extent. Atomic force microcopy confirmed that the morphology of the adsorbed CMC layers differed depending on the substrate. On hydrophobic polymer films, CMC was deposited in the form of larger particles in lower amounts whereas hydrophilic cellulose substrates were to a high extent uniformly covered by adsorbed CMC. The chemical similarity of the CMC backbone seems to favor the irreversible adsorption of CMC when the molecule is almost uncharged at low pH values. A selectivity of the cellulose CMC interaction can therefore be assumed. All CMC treated polymer films exhibited an increased hydrophilicity, which confirmed their modification with the functional molecule.     

Characteristics of thin cellulose ester films spin-coated from acetone and ethyl acetate solutions

Spin-coated films of cellulose acetate (CA), cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB) and carboxymethylcellulose acetate butyrate (CMCAB) have been characterized by ellipsometry, atomic force microscopy (AFM) and contact angle measurements. The films were spin-coated onto silicon wafers, a polar surface. Mean thickness values were determined by means of ellipsometry and AFM as a function of polymer concentration in solutions prepared either in acetone or in ethyl acetate (EA), both are good solvents for the cellulose esters. The results were discussed in the light of solvent evaporation rate and interaction energy between substrate and solvent. The effects of annealing and type of cellulose ester on film thickness, film morphology, surface roughness and surface wettability were also investigated. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Cellulose acetate as stationary phase in microcolumn LC

The retention characteristics of alkylbenzenes and polycyclic aromatic hydrocarbons (PAHs) have been examined in liquid chromatography on a microcapillary column packed with cellulose acetate. Particulate and fibrous cellulose acetate were used as the stationary phase. Fibrous cellulose diacetate was found to be of use as an alternative stationary phase for liquid chromatography, although the separation efficiency was low. The retention characteristics for planar PAHs were linearly correlated with the size of the molecules, but the retention behavior for alkylbenzenes and nonplanar PAHs was affected by exclusion. The retention order was strongly influenced by the addition of dimethylformamide or water to methanol in the mobile phase. The results suggested that the retention behavior is influenced by a slight change in the polymer matrix of cellulose acetate.     

Effect of humidity and solvent vapor phase on cellulose esters films

In the present study the effect of relative humidity (RH) during spin-coating process on the structural characteristics of cellulose acetate (CA), cellulose acetate phthalate (C-A-P), cellulose acetate butyrate (CAB) and carboxymethyl cellulose acetate butyrate (CMCAB) films was investigated by means of atomic force microscopy (AFM), ellipsometry and contact angle measurements. All polymer solutions were prepared in tetrahydrofuran (THF), which is a good solvent for all cellulose esters, and used for spin-coating at RH of (35 ± 5)%, (55 ± 5)% or (75 ± 5)%. The structural features were correlated with the molecular characteristics of each cellulose ester and with the balance between surface energies of water and THF and interface energy between water and THF. CA, CAB, CMCAB and C-A-P films spin-coated at RH of (55 ± 5)% were exposed to THF vapor during 3, 6, 9, 60 and 720 min. The structural changes on the cellulose esters films due to THF vapor exposition were monitored by means of AFM and ellipsometry. THF vapor enabled the mobility of cellulose esters chains, causing considerable changes in the film morphology. In the case of CA films, which are thermodynamically unstable, dewetting was observed after 6 min exposure to THF vapor. On the other hand, porous structures observed for C-A-P, CAB and CMCAB turned smooth and homogeneous after only 3 min exposure to THF vapor.     

Use of Enzymatic Digestion and Chemical Methylation Followed by Matrix-assisted Laser Desorption/Ionisation (MALDI) Mass Spectrometry to Sequence a 60kDa Commercial Fraction of Cellulose Acetate

Cellulose acetate was characterized by using enzyme in both digestion and chemical derivation and acetolysis. The fragments were normalised and compared on an anhydroglucose scale, using mass spectrometry to identify the different sized fragments. It was determined that at least two sub-populations for cellulose acetate existed within the parent. The macroscopic effect of this variation in the degree of acetylation will be a modification of the structural properties of the polymer chains. It was found that through comparison with enzyme-based degradation, an estimation of the acetylation topography of the cellulose acetate fraction could be made. Enzyme degradation produced a number of oligosaccharides of more than 10 glucose units, presumably resistant to enzyme degradation because they contained acetate groups. Chemical hydrolysis gave a random ladder of short sequences of mainly 3–4 glucose units some of which had a high methyl ether content, that were analysed by mass and converted to an anhydroglucose mass scale. This approach could be used to demonstrate differences between large biopolymers of cellulose acetate that previously gave an overall average rather than a specific ladder average.     

Thermoplastic Cellulose-Based Compound for Additive Manufacturing

The increasing environmental awareness is driving towards novel sustainable high-performance materials applicable for future manufacturing technologies like additive manufacturing (AM). Cellulose is abundantly available renewable and sustainable raw material. This work focused on studying the properties of thermoplastic cellulose-based composites and their properties using injection molding and 3D printing of granules. The aim was to maximize the cellulose content in composites. Different compounds were prepared using cellulose acetate propionate (CAP) and commercial cellulose acetate propionate with plasticizer (CP) as polymer matrices, microcellulose (mc) and novel cellulose-ester additives; cellulose octanoate (C8) and cellulose palmitate (C16). The performance of compounds was compared to a commercial poly(lactic acid)-based cellulose fiber containing composite. As a result, CP-based compounds had tensile and Charpy impact strength properties comparable to commercial reference, but lower modulus. CP-compounds showed glass transition temperature (Tg) over 58% and heat distortion temperature (HDT) 12% higher compared to reference. CAP with C16 had HDT 82.1 °C. All the compounds were 3D printable using granular printing, but CAP compounds had challenges with printed layer adhesion. This study shows the potential to tailor thermoplastic cellulose-based composite materials, although more research is needed before obtaining all-cellulose 3D printable composite material with high-performance.     

Introduction to pyrolysis-capillary gas chromatography.

By breaking large molecules into characteristic smaller fragments, analytical pyrolysis extends the use of gas chromatography to the analysis of polymeric materials, including natural polymers such as cellulose as well as synthetics. An understanding of the chemistry involved permits interpretation of the information present in these molecular fragments, with application to polymer and copolymer microstructure in addition to routine identification and quality control. Whether microfurnace, Curie-point or resistively heated filament, the pyrolysis device must be interfaced efficiently to the gas chromatography to make use of the resolving power afforded by capillary columns.     

Sorption and permeation behaviour of metal thiocyanate complexes on cellulose acetate polymers

Various metal thiocyanate complexes in aqueous solution were sorbed on solid cellulose acetate polymers. The sorption selectivity increased in the order Zn(2+) > Fe(3+) > Cu(2+) > Co(2+) > Ni(2+). The sorption behaviour followed a Langmuir-type adsorption isotherm, and the maximum adsorption capacity was 6.1 x 10(-5) mole of complex per g of polymer under optimum conditions. The zinc species sorbed appear to be NH(4)Zn(H(2)O)(SCN)(3) or (NH(4))(2)Zn(SCN)(4) according to analysis of the sorption equilibrium. The ion-association species formed by the complex zinc anion and the ammonium ion was supposed to be sorbed (or "extracted") onto the polymer matrix. As an application of sorption of metal complexes, a new hyperfiltration process was proposed for selective separation of metal ions. Thus, a mixture of metal thiocyanate complexes was hyperfiltered through cellulose acetate membranes. Permeation of certain metal complexes was preferred, and the selectivity was found to be similar to the sorption selectivity. These findings lead to a generalized idea that hyperfiltration separation of ionic species, particularly anionic metal complexes, can be attained by using polymer membranes which selectively adsorb or extract such ionic species as ion-association complexes onto the polymer matrix.     

Thermochemical conversion of cellulose in polar solvent (sulfolane) into levoglucosan and other low molecular-weight substances

Pyrolysis of cellulose in sulfolane, an aprotic polar solvent, was conducted at the temperature between 200 and 330 °C. Sulfolane was used as a good solvent for levoglucosan, the major anhydromonosaccharide formed from cellulose pyrolysis, for prevention of the polymerization reaction. Cellulose was observed completely decomposed into soluble products in sulfolane within 3, 10, 60 and 480 min at 330, 280, 240 and 200 °C, respectively. The soluble products had molecular weights less than 500 after acetylation (GPC analysis) and similar product composition to that from cellulose pyrolysis under nitrogen (levoglucosan, levoglucosenone, furfural and 5-hydroxymethylfurfural by HPLC analysis). Pyrolysis of cellulose in polar solvent, which can solubilize anhydromonosaccharides, is proposed as a method for selective formation of levoglucosan and other low molecular-weight (MW) substances. As well, the cellulose pyrolysis in sulfolane did not suffer from carbonization reactions (microscopic and IR spectroscopic analysis) as did cellulose pyrolysis under nitrogen or in dioctyl phthalate (a poor solvent for levoglucosan) which gave brown/black solids. The residues obtained from the pyrolysis in sulfolane were colorless and gave similar IR spectra to that of the original cellulose. Based on these results, a ‘surface-peeling mechanism’ is proposed, and the role of the solvent in the mechanism is discussed.