Hsien-Tang Chiu

A study of the combustion and fire-retardance behaviour of unsaturated polyester/phenolic resin blends

Abstract The thermal degradation and combustion behaviour of an interpenetrating network (IPN) structure of unsaturated polyester UP resin and a resole type of phenolic resin was studied. Thermal gravimetric analysis (TGA) was used to monitor the degree of thermal decomposition for the UP/phenol IPN structure and the change of the oxygen index (OI) was used to describe the variation of the combustion behaviour. The smoke density was measured via a non-flaming process to detect the amount of smoke generated during the combustion. A homemade cone calorimetric dynamic flammability evaluation system was assembled to analyse the gas evolved and to measure the heat release rate (HRR) during the combustion. Under simulated conditions of a burning field at the temperature of 757°C, the variation of the concentration of carbon monoxide (CO) and the HRR of the UP/phenol IPN structure were studied. The results show that modification of the essentially flammable UP resin by the phenol structure to form an IPN system cannot only remarkably improve the heat resistance but also help to suppress the smoke, toxic gas and heat release during the combustion.

The morphology and conductivity of polypyrrole/polyurethane alloy films

Polymeric composites with conductivities ranging from 10−4 to 1 S cm−1 were prepared by electrochemically polymerizing pyrrole in a matrix of polyurethane. The polypyrrole/polyurethane alloy films obtained were characterized by element analysis, electron microscopy and electrical conductivity measurements. The morphology of the films depended on the solvent, the electrolyte and the current density. The mechanism of the electrochemical polymerization showed that PPy grew in a treelike structure, with molecular chains extending from the electrode surface into the solution. The transition temperature of the PPy/PU increased with the PPy content.

The influence of dopant permeability on electrochromic performance of polypyrrole films

Detailed characteristics of the electrochromic performance of polypyrrole films under electrochemical doping and dedoping are studied. The response time for colour change in polypyrrole films depends on the dopant permeability. The change in film colour occurring in the redox reaction of the film is investigated in detail as a function of the dopant electrolyte solution and the thickness of the polypyrrole film. Three colour states for polypyrrole films are demonstrated: yellow green, dark brown, and blue.

Characterization of the rheological behavior of UHMWPE gels using parallel plate rheometry

The effects of shear flow, temperature, and gel concentration on the rheological behavior of the ultrahigh-molecular-weight polyethylene (UHMWPE) gel in gel spinning process were investigated. The gel point was determined using parallel plate rheometry in rotation mode with controlled stress. Likewise, the flow curves at various temperatures were determined with controlled shear rate from 10−2 to 10 s−1. Whereas the shear storage modulus (G′) was obtained in oscillation mode with controlled strain from 1 to 100%. The result shows that the gel point of the UHMWPE gel increases with increasing gel concentration. The result from the strain sweep indicates that G′ of the gel is 1.5 × 103 Pa, and it exhibits a plateau at low strain, but it is reduced with increasing strain. At low shear rates, for temperatures above gel point, all flow curves exhibit a plateau, then go down with increasing shear rate. Studying contributions from UHMWPE gel concentration, temperature, and shear rate for rheological view, we found that spinning at 6% UHMWPE (MW : 1.4 × 106 g/mol) gel and 140°C gives the best effect on formation of fiber structure.

Photochromic Behavior of Spiropyran and Fulgide in Thin Films of Blends of PMMA and SBS

Two types of photochromic colorants of either spiropyran or fulgide were dispersed in thin films of blends of polymethyl methacrylate (PMMA) and styrene-butadiene-styrene copolymer (SBS) with various ratios. The thin films were illuminated with ultraviolet light (365 nm) under various temperatures. The photochromic response was monitored with a multichannel photodetector. The results show that the color form of spiropyran is more stable in polar PMMA and caused a blue shift in the absorption spectrum of merocyanine.

Dynamic mechanical properties of the chemical oxidation on UHMWPE fibers for improved adhesion to epoxy resin matrix

The improved adhesion of an ultrahigh molecular weight polyethylene (UHMWPE) fiber to an epoxy from applying polypyrrole (PPy) was investigated using chemical oxidation polymerization. The interfacial shear strength of the PPy-treated fiber/epoxy was enhanced by 280%. Such an improvement was verified in the previous research using a pull-out test. Dynamic mechanical analysis (DMA) and a morphological examination were performed to evaluate the characteristics of the molecular motions of the UHMWPE fiber/PPy/epoxy composites. Two composite materials, a UHMWPE fiber/PPy and a UHMWPE fiber/PPy/epoxy, were tested by DMA. The results show that both the αc transitions of the PPy-treated fibers and its composites shift toward higher temperature. In the SEM photos of the UHMWPE fiber/PPy, a very clear roughening effect on the surface of PPy-treated UHMWPE fiber was also observed, which contributes much to the modification of the interface to the epoxy. The results show that an adhesion improvement mechanism for the PPy-treaded UHMWPE fiber is due to the surface roughening effect and the intermolecular interaction.

Study of rheological behavior and miscibility of epoxidized natural rubber modified neoprene

The Mooney viscosity, curing rates, vulcanization behavior, and the relationship between molecular motion of epoxidized natural rubber (ENR) and neoprene (CR) blends at different blending ratios have been studied. The experimental results of ENR/CR blends show that the Mooney viscosity decreased gradually. Plasticization was most pronounced at an ENR/CR ratio of 75/25 and is thus the easiest to process. Owing to the ring opening of the epoxy group of ENR, the rate of crosslink formation is much faster than that of CR at higher temperature. The vulcanized rate increased with increasing ENR content. The results indicated that 175 °C and 5 min were the optimum processing conditions for ENR/CR blends. The DMA spectra showed a single damping peak for the ENR/CR blends, which suggests that ENR and CR are miscible. As seen in the Arrhenius plot of frequency against Tg, the activation energy increased with increasing ENR contents. This suggests the existence of interpenetration of these two rubber molecular networks.

Heat Treatment Effects on the Mechanical Properties and Morphologies of Poly (Lactic Acid)/Poly (Butylene Adipate-co-terephthalate) Blends

In this study the relationships between mechanicals properties and morphology of the poly (lactic acid) (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) blends with or without heat treatment were investigated. The differential scanning calorimetry (DSC) analysis showed that blends have a two-phase structure indicating that they are immiscible. On the other hand, the PLA/PBAT (30/70) blend achieved the best tensile and impact strength because of its sea-island morphology, except for high PBAT content. The PLA/PBAT (70/30) and PLA/PBAT (50/50) blends showed irregular and directive-layer morphologies, in scanning electron microscopy (SEM) analysis, producing a break cross-section with various fiber shapes. Both blends showed lower tensile strength and impact strength than the PLA/PBAT (30/70). After heat treatment, the PLA/PBAT blends showed high modulus of tensile and HDT because of a high degree of crystallization. The high degree of crystallization in the blends, which originated in the heat treatment, reduced their impact strength and elongation. However, the effect of high degree of crystallization on the PLA/PBAT (30/70) blend was small because of its sea-island morphology.

Preparation and Properties of Conductive Polyimide Films

Carbon black and graphite granules were added to polyimide resin and the mixture was processed into films. The surface resistivity of the polyimide film can be as low as 0.1 Ω/cm2 upon the addition of these conductive granules. The effect of the content of conductive granules on the properties of polyimide, such as the conductivity, thermal stability, and the surface roughness, was studied. The results showed that smaller granule or higher content would enhance the conductivity but made the processing more difficult. The surface roughness was affected by the type of carbon black, the content, and the preparation conditions. For Pyre-ML type polyimide resin containing 9% of 975 carbon black, the thermal degradation temperature could reach as high as 610 °C.

The processing and mechanical properties of polypyrrole/polyurethane alloy films

Polymeric composites of polypyrrole/polyurethane (PPy/PU) were prepared by electrochemical polymerization. The resulting films had conductivities ranging from 10−4 to 1S cm−1, and showed significant improvement in their mechanical properties. By varying the conditions of polymerization, a range of mechanical, as well as electrical, properties could be obtained.