Influence of the thermal history during injection molding of linear low density polyethylene (LLDPE) on the formation of unpleasant taste was investigated for assuring the taste of beverage in vending machines. LLDPE samples were molded using antioxidants; BHT, Irganox 1010, D, L-α-tocopherol and Irgafos 168. Tastes of soaked water of the samples were individually different, and such tastes were thereby responsible for the antioxidants. Furthermore, the tastes were changed when free chlorine (0.3 ppm) was added for sterilization. The antioxidants and their degraded products were identified in the soaked water as candidates of the unpleasant tastes by gas chromatography/mass spectrometry (GC/MS). Tastes of the identified compounds were evaluated by sensory test to determine their threshold concentrations for estimation of contribution to the unpleasant taste. From the thermal behavior of the antioxidants examined by thermogravimetry/differential thermal analysis (TG/DTA), decomposition of the antioxidant was observed in the temperature range of the molding. Moreover, formation of volatile compounds under the condition was evidenced by pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). The present study revealed that controlling the thermal history during molding is important to assure the quality of taste of beverage being contacted with the molded LLDPE, as well as general thermoplastics in vending machine.
A novel supramolecular crosslinked polymer system (polybutadiene topologycal gel, PBTG) was constructed by combining two components, cyclodextrin (γ-CD) oligomer and terminal end-capped macromonomer having polybutadiene (PB) unit. Photopolymerization of N,N-dimethylacrylamide (DMAA) was carried out in the presence of PBTG to obtain gel composed of movable cross-linking. The obtained PBTG exhibited the unique property different that of a conventional chemical gel (PB-DMAA gel). The PBTG showed relatively high thermal stability and good film-forming property. The temperature for 10% weight loss of the polymers was 400°C. The stress and the strain of the PBTG were 0.325MPa and 590.2%, respectively. Young’s modulus was 0.55KPa. The gelled product swelled well in N,N-dimethylformamide (DMF ; percentage swelling 1580%) and water (H2O ; percentage swelling 1460%).
In order to examine the effect of the wavelength on the photodegradation of poly(2,6-dimethyl-1,4-phenylene ether)(PPE), PPE films were exposed to monochromatic radiation in atomospheric condition at 23°C using Okazaki Large Spectrograph(OLS). The most effective wavelength for the photodegradation of PPE was found to be 300nm. The threshold wavelength of the main-chain scission, oxidation of the side group and the gel formation was around 310nm. Irradiating the monochromatic radiation shorter than 320nm on PPE, similar types of photodegradation prsoducts were obtained. It was found that ether bond breakage (the cleavage of the hydroxyl end group of the polymer) induced by the monochromatic irradiation was followed by the oxidation of methyl group(generation of aldehyde and carboxylic acid), formation of the crosslinking and production of the quinone-methide structure.
Poly(vinyl alcohol) (PVA) has been used as a consolidant to prevent flaking of paint pigments on traditional Japanese Shohekiga painted screens and panels. However, over time these PVA coatings can show degradation in the form of loss of transparency due to whitening.
It is believed that this whitening is caused by the scattering of visible light by cracks and wrinkles in the film. These surface defects are thought to be formed by intra- or inter-chain dehydration and chemical cross-linking on the PVA surface.
To validate this conclusion, test PVA films were subjected to quantified UV accelerated aging, because UV exposure is a likely cause of chemical degradation of the PVA layers on Shohekiga.
The test PVA films became white after being irradiated with UV light and then exposed to water vapor. The chemical mechanism was analyzed by spectroscopy and surface observations.
IR-coated iron wire, which was developed as wire rods for cage-type revetment around riverbanks, consists of 3 types of galvanized iron wire which is coated with primer and then laminated by extrusion with an ionomer resin. About durability of IR-coated iron wire, we compared the accelerated property of the WS-A(sunshine weather meter) test to the SUV(metal halide lamp) test with ionomer resin. As prior test revealed that the accelerating rate of the SUV test was 12 times faster than that of the WS-A test, on the basis of this supposition, we carried out durability evaluation tests by measuring tensile strength, elongation and C=O absorption in the IR spectrum(measuring the increase of carbonyl group) on IR-coated iron wire after the SUV test of 625h and the WS-A test for 7,500h. In conclusion, it was confirmed that the evaluation time of the SUV test is more than twenty times that of the WS-A test in ionomer resin.
To confirm that IR-coated iron wire meets the criterion of the Ministry of Land, Infrastructure and Transport, we carried out wear tests and accelerated corrosion tests after the SUV(metal halide lamp) tests of 625h which were cleared to be more than twentyfold the WS-A(sunshine weather meter) tests for 7,500h as shown in the previous paper. Furthermore, a cross sectional analysis of surface changes and changes of C=O absorption in the IR spectrum were carried out on 6.8 year old specimens cut from IR-coated iron wire in the field. In conclusion, the life of IR-coated iron wire was shown to be equal to 30 years or more, and from this and previous paper, we evaluated that SUV test could be used for an alternative test in twentieth of the time it took for WS-A test.