Novel cellulose derivatives. IV. Preparation and thermal analysis of waxy esters of cellulose

Cellulose esters with linear aliphatic acyl substituents ranging in size from C₁₂ (lauric acid) to C₂₀ (eicosanoic acid) were prepared in homogeneous solution (DMAc/LiCl) using a novel synthetic method based on the use of a mixed p-toluenesulfonic/carboxylic acid anhydride. The resulting waxy cellulose esters had a high degree of substitution (DS), between 2.8 and 2.9, and showed little degradation. Thermal analysis of these cellulose derivatives by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) revealed a series of transitions that represented motion by both ester substituents and cellulosic main chain. Broad crystallization and melting transitions attributed to side-chain crystallinity were observed in the range between −19 and +55°C; these side-chain T_m and T_c transition temperatures increased by 10°C per carbon atom of the ester substituent. The T_g of these derivatives increased linearly with increasing substituent size from 94°C for C₁₂ (cellulose laurate) to 134°C for C₂₀ (cellulose eicosanoate). Evidence of “main-chain” crystallization was not observed for these samples, except in the case of peracetylated C₁₂ and C₁₄ esters, which had T_m values of 96°C and 107°C, respectively. © 1996 John Wiley & Sons, Inc.     

Continuous cellulose fiber-reinforced cellulose ester composites. I. Manufacturing options

Thermoplastic fiber composites were prepared using high modulus lyocell (regenerated cellulose) fibers for reinforcement and cellulose acetate butyrate (CAB) as matrix. Choices were made with regard to fiber options (fabric versus continuous tow) and method of matrix deposition (prepregging by powder coating, film stacking, or solution impregnating). The results suggest that solution-prepregged fiber tow consolidated at circa 200°C produced unidirectional consolidated panels with tensile strength, modulus, and strain at failure values of approximately 250MPa,>20GPa and 3–4%, respectively, at fiber volume contents of approximately 60%. Modulus and ultimate tensile strength increased with fiber content, and modulus followed rule-of-mixture behavior. Adequate surface wetting and matrix-fiber adhesion were found with solution-prepregged composites. The unexpectedly low strain at failure (2 to <4%) was attributed to brittle matrix failure, and failure surfaces revealed that the fibers, for the most part, remained intact after the matrix had failed.     

Editorial

Editorial Introduction

Editorial     

Hard disc bose gas

It is pointed out that the integral whose asymptotic properties were investigated in a recent note by Hines et al., has a simple exact expression which should be useful for extending their results.     

Van der Waals attraction between two conducting chains

The inclusion of retardation in calculating the Van der Waals attraction from zero point energies for a conducting chain molecule is shown to lead to a small correction with the same separation dependence as when retardation is ignored.     

Study of the energy and charged multiplicity dependence of inclusiveπ− production in π−p interactions up to fermilab energies

Using new data from 100 $\text{GeV}\text{c π}{}^{\mathrm{?}}$ interactions, we find the energy dependence of the invariant cross-section in the target fragmentation (central) region to be consistent with an $\text{A + Bs}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{(C + Ds}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>4</mtext>}}\text{)}$ behavior. The leading particle peak near x = + 1 exhibits a width in x which becomes smaller with increasing energy and an integrated cross section which is approximately energy independent.     

Thermal smearing and screening in a strong magnetic field for Dirac materials in comparison with the two dimensional electron liquid

We compute and compare the effects due to a uniform perpendicular magnetic field as well as temperature on the static polarization functions for monolayer graphene (MLG), associated with the Dirac point, with that for the two-dimensional electron liquid (2DEL) with the use of comprehensive numerical calculations. The relevance of our study to the Friedel oscillations for the screening of the potential for a dilute distribution of impurities is reported too. Our results show substantial differences due to screening for the 2DEL and MLG which have not been given adequate attention previously.