Novel temperature measurement method & thermodynamic investigations of amorphous polymers during high rate deformation

Polymers are frequently used in applications in which they may be exposed to high rate or impact loading, and there is growing industrial importance in understanding their mechanical behavior at different strain rates. An important aspect of this is the temperature rise due to adiabatic conditions in high rate loading. This paper describes research that has been performed to measure the temperature rise that occurs in specimens undergoing rapid deformation. A novel thermocouple design is presented and applied to PMMA and 20 wt% DINP-plasticized PVC, deformed at moderate and high strain rates. The measurements are accompanied by investigations of strain energy.     

Synthesis,characterization, and in vitro biocompatibility study of novel disulfide cross‐linked hydrogels based on poly(amic acid)

In this study, novel disulfide cross‐linked hydrogels were designed and synthesized. First, ethylenediaminetetraacetic dianhydride reacted with butanediamine and amino‐terminated polyethylene glycol via N‐acylation reaction to give biocompatible poly(amic acid) (PAA) with pendant carboxyl groups; then, the amino groups of cystamine reacted with carboxyl groups of PAA to generate disulfide cross‐linked network polymer (PAA‐SS). Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance imaging, gel permeation chromatography with multiangle laser light scattering, potentiometric titration, rheology, hydrolytic degradation, morphology, porosity, and in vitro biocompatibility studies were used to qualitatively and quantitatively characterize the obtained polymers. The results indicated that the equilibrium swelling ratio of the PAA‐SS decreased with the increase in Rm. The PAA‐SS provided good mechanical strength to maintain their integrity, and the storage modules (G′) of the hydrogels can be adjusted by Rm. The PAA‐SS presented co‐continuum pores, and the pore size correlated with the cross‐linking degree. The degradation of PAA‐SS could be controlled by regulating the concentration of dithiothreitol. Particularly, the PAA‐SS possessed an excellent biocompatibility, as the average proliferating rate of osteoblasts on PAA‐SS was appreciably higher than that on PAA and glass coverslips. In conclusion, the above obtained results demonstrate that the performance of the PAA‐SS outbalance and facilitate the application in biomedical region, particularly in bone tissue regeneration. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40930.     

Characterization of the surface energies of functionalized multi-walled carbon nanotubes and their interfacial adhesion energies with various polymers

The surface energies of pristine multi-walled carbon nanotubes (MWCNTs) and MWCNTs functionalized with carboxylic acid (MWCNT-COOH), acyl chloride and ethyl amine were characterized, and the effects of the changes in MWCNT surface energies on the interfacial adhesion and reinforcement of the composites were explored. When the surface energy of pristine MWCNTs was compared to that of functionalized MWCNTs, a decrease in the dispersive surface energy and an increase in the polar surface energy were observed. Interfacial adhesion energies between MWCNTs and various polymers were estimated from surface energy values of MWCNTs and various polymers. Among the MWCNTs, polyethylene, polystyrene and bisphenol-A polycarbonate (PC) had the highest interfacial energy with pristine MWCNTs, while nylon 6,6 and polyacrylamine exhibited the highest interfacial energy with MWCNT-COOH. When tensile properties and adhesion at the interface of PC and nylon 6,6 composites containing MWCNTs were examined, composites having high interfacial adhesion energy exhibited greater adhesion at the interface and reinforcement.     

High performance films of cellulose butyral derivative having a necklace-like annular structure in the side chains

We fabricated high performance films using cellulose butyral (CB) synthesized from native cellulose. Two-step reactions were adopted to produce the derivative CB, including etherification of cellulose with glycidol in NaOH/urea aqueous solution to yield O-(2,3-dihydroxypropyl) cellulose (DHPC), and butyralization of DHPC. Both DHPC and CB products were easily processed into a thin film by hot-press molding. The butyral modifier significantly improved the tenacity of highly ductile DHPC, by virtue of the possible chain-entangling action of the ring structures in the stretching process. Thereby the film toughness was markedly enhanced. The CB films exhibited excellent optical transparency and a good adhesive property to glass plates. Thus the films may be comparable to commercial poly(vinyl butyral) (PVB) films in optical and mechanical performances and therefore possess a potential applicability as interlayer for laminated glasses.     

The correlation between the ionic degree of covalent bond comprising polymer main chain and the ionic yield due to mechanical fracture

The mechanical force to polymeric materials in vacuum at 77 K produces mechano radicals, mechano anions and mechano cations due to homogeneous and heterogeneous scissions of the covalent bonds comprising polymer main chain. The ionic degree of the covalent bond was estimated by calculating the “absolute ΔMulliken atomic charge,” which was defined as the difference between the Mulliken atomic charges of the two adjacent atoms comprising the covalent bond of the polymer main chain. The ionic yield of the covalent bond increased with increasing the absolute ΔMulliken atomic charge. The empirical formula for the ionic yield was obtained with the absolute ΔMulliken atomic charge, and indicates that the ionic yield could be estimated from its chemical structure.     

Dendrimer as nanocarrier for drug delivery

Dendrimers are novel three dimensional, hyperbranched globular nanopolymeric architectures. Attractive features like nanoscopic size, narrow polydispersity index, excellent control over molecular structure, availability of multiple functional groups at the periphery and cavities in the interior distinguish them amongst the available polymers. Applications of dendrimers in a large variety of fields have been explored. Drug delivery scientists are especially enthusiastic about possible utility of dendrimers as drug delivery tool. Terminal functionalities provide a platform for conjugation of the drug and targeting moieties. In addition, these peripheral functional groups can be employed to tailor-make the properties of dendrimers, enhancing their versatility. The present review highlights the contribution of dendrimers in the field of nanotechnology with intent to aid the researchers in exploring dendrimers in the field of drug delivery.     

Atom transfer radical polymerization (ATRP): A versatile and forceful tool for functional membranes

The progress in atom transfer radical polymerization (ATRP) provides an effective means for the design and preparation of functional membranes. Polymeric membranes with different macromolecular architectures applied in fuel cells, including block and graft copolymers are conveniently prepared via ATRP. Moreover, ATRP has also been widely used to introduce functionality onto the membrane surface to enhance its use in specific applications, such as antifouling, stimuli-responsive, adsorption function and pervaporation. In this review, the recent design and synthesis of advanced functional membranes via the ATRP technique are discussed in detail and their especial advantages are highlighted by selected examples extract the principles for preparation or modification of membranes using the ATRP methodology.     

精氨酸精制重结晶过程控制与优化

研究了L-精氨酸在无外加影响因素的条件下,结晶温度、结晶时间、搅拌速度及降温速度对L-精氨酸重结晶的影响。研究结果表明,在相同的条件下,L-精氨酸的结晶温度控制在60℃,结晶率可达88%以上;慢速搅拌有助于晶体的生成;采用在高温时快速冷却,待降至一定温度后,再慢速冷却降温,可以保证L-精氨酸结晶体的颗粒度较为均匀;L-精氨酸的结晶时间在5 h附近为宜。通过重结晶过程的控制和优化可以有效改善精氨酸的产品品质,进一步缩小与国际先进水平的产品品质差距。     

变压吸附制氮性能主要影响参数的研究

介绍了变压吸附制氮技术的优点、原理方法及工艺流程,实验研究了吸附压力、吸附解吸时间、产品流量等主要工艺参数对变压吸附制氮装置性能的影响,最后得出实验装置的最佳工艺条件为:吸附压力0.8 MPa,吸附解吸时间54 s,均压时间4 s,产品气出气流量7 m3/h。此时,实验装置制得的产品氮气体积分数最稳定,平均体积分数98%以上,回收率在40%左右。