Puxin Zhu

Structure and properties of urea-plasticized starch films with different urea contents

Films of thermoplastic starch (TPS) plasticized with different contents of urea were prepared by using a solution casting method. Scanning electron microscopy, X-ray diffraction and IR spectroscopy were used to characterize structures of the TPS films, respectively. Water vapor sorption isotherms and tensile properties of the films were determined. TPS films showed more smooth and transparent in appearance and less B-type crystallinity than the starch film without urea. The effect of urea content on the structure and behavior of the TPS film could be divided in three stages: (1) below urea 10% where urea interacted with starch via H-bonding and the films showed an antiplasticization effect, (2) from urea 10% to 30% where an apparent plasticization effect appeared on the starch because of free urea molecules as the effective plasticizer, and (3) a macroscopic phase separation occurred due to supersaturation of urea when urea content was more than 30%.

Adsorption thermodynamics and kinetics of disperse dye on poly(p-phenylene benzobisoxazole) fiber pretreated with polyphosphoric acid

Adsorption thermodynamic and kinetic studies of C. I. disperse dye 60 on PBO fiber pretreated with polyphosphoric acid (PPA) were carried out under the conditions of pH 6.0±0.2, initial dye concentration 0.05–1.0 g/L and liquor ratio 2,000: 1. The results showed that the equilibrium adsorption isotherm of the disperse dye on the pretreated PBO fiber was a Langmuir-Nernst mixed Model and the saturated adsorption capacity of the turning point was 1.046 mg/g. The thermodynamic parameters were calculated by the equilibrium adsorption isotherm, such as standard affinity, enthalpy change and entropy change, which indicated that the adsorption of disperse dye on the pretreated PBO fiber was an exothermic process. Based on the thermodynamic and kinetic data, the adsorption of the dye on the pretreated PBO fiber was a kinetics controlled process, and the disperse dye could only diffuse into the surface layer of pretreated PBO fiber. Meanwhile, the adsorption kinetics of disperse dye on pretreated PBO fiber well agreed with a pseudo-first-order kinetic model.

Synthesis and monolayer film of a series of new twin-tailed gemini cationic surfactants at the air/water interface

A series of new dimeric surfactants, twin-tailed gemini surfactants, 2(12)-s-2(12), were successfully prepared and characterized, and their monolayer films investigated by the measurement of surface pressure-area (π-A) and surface pressure-time (π-t) isotherms at the air/water interface by a Langmuir film balance. Compared to their monomeric counterparts, their collapse pressure (γcollapse) is smaller, whilst all the molecular area parameters are larger. The limited area (Alimited) and the initial area (Ainitial) of these twin-tailed gemini surfactants change with increasing spacer length s, and the surface pressure decreases with increasing time. It was also found that the higher the initial surface pressure, the larger the attenuation.

New disperse dyeing method of poly(p-phenylene benzobisoxazole) fiber pretreated with polyphosphoric acid

Poly(p-phenylene benzobisoxazole) fiber is considered as a high-performance fiber because of its high strength and excellent thermal and chemical stability. It has been used in industrial reinforcement, body armor and military camouflage. But the application of poly(p-phenylene benzobisoxazole) fiber used for protective clothing is limited because it is difficult to dye with conventional dyeing processes. In this work, a carrier dyeing method with disperse dyes was first used to dye the fiber after a pretreatment with polyphosphoric acid. The effects of the carrier structure and dyeing conditions on the color strength of dyed samples were investigated. In addition, the crystallinity and orientation degree of the poly(p-phenylene benzobisoxazole) fibers before and after pretreatment with phthalimide and benzyl benzoate were measured by X-ray diffraction and velocity-oriented test, respectively. The results suggested phthalimide and benzyl benzoate, as carrier, could effectively promote disperse dyeing of the PBO fiber pretreated with polyphosphoric acid. Meanwhile, the optimal conditions for the carrier dyeing were obtained, that is, concentration of carrier 4%, dyeing temperature 150 °C and time 120 min. By way of the carrier dyeing, the K/S value of dyed sample and the percentage of dye exhaustion were greatly improved, while the crystalline structure and orientation degree of the pretreated samples hardly changed. Furthermore, the decreases of the tensile strength and the limiting oxygen index of dyed poly(p-phenylene benzobisoxazole) sample were very little, and the color fastness was also satisfactory.

Effect of Hyperbranched Poly(trimellitic glyceride) with Different Molecular Weight on Starch Plasticization and Compatibility with Polyester

Hyperbranched poly(trimellitic glyceride) (PTG) plasticizers for starch were prepared by using trimellitic anhydride and glycerol as raw materials in a simple one-step synthesis. The structure and branching degree of PTGs were confirmed by Fourier transformed infrared, gel permeation chromatography and 1H nuclear magnetic resonance. The PTGs as plasticizers were composited with maize starch (S) via cooking and film formation. The structure and mechanical, thermal properties of the plasticized starch composites, and its adhesion to cotton and polyester yarns were studied in details. Results indicated that the PTG/S composites had better mechanical property and thermal stability, and lower moisture absorption than glycerol/starch (GLY/S) with the same content (w/w). With the increase in PTG molecular weight, elongation at break of PTG/S film decreased and tensile strength increased, and moisture absorption of PTGs/S reduced. In addition, PTGs/S had a better effect on adhesion to cotton and polyester yarns than GLY/S.

Preparation of triethylene glycol maleate and its effect on plasticization of oxidized starch

A plasticizer triethylene glycol maleate (TEG-MA) was synthesized. The dominated monoester of moderate hydrophobicity with apparent oil-water partition coefficient of 0.042 in the product was confirmed by acid value determination, HPLC and FTIR. Its plasticizing effect on oxidized starch was manifested by crystallization, aging behaviour, moisture absorption, and mechanical performance. X-ray diffraction data showed that the relative crystallinity of the plasticized starch decreased. Both the crystal and the crystallinity of starch films were rarely changed in aging. Moisture absorption relied on the ester content and relative humidity. The elongation at break increased significantly with plasticizer content more than 10% in the matrix.