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We used a high-pressure differential scanning calorimeter (HP-DSC) to study polymer plasticization by compressed gases at pressures of up to 30 MPa for polylactide (PLA), polycarbonate (PC), isotactic polypropylene (iPP), and polystyrene (PS). The pressure reached values twice as high as the previously published data. We found that the polymer/carbon dioxide (CO 2 ) system's heating curves have an unidentified endothermic peak above 5 MPa, which turns out to be from CO 2 's phase transition. The HP-DSC could accurately determine the depression of the glass transition temperature (T g ), crystallization temperature (T c ), and melting temperature (T m ) of various polymers at low pressures by simply starting at a higher temperature to avoid CO 2 's phase transition; however, the increased plasticization effect of the dissolved CO 2 lowered the T g to the level of overlapping with CO 2 's phase transition phenomena at elevated pressures, and therefore, the depressed T g could not be measured above 6 MPa for PLA, PC, or PS. On the other hand, the T c of iPP decreased with an increase in pressure, whereas T m values of PLA and iPP decreased slightly with an increase in pressure and then remained almost unchanged above a certain pressure, which may indicate an increased hydrostatic pressure effect at elevated pressures.

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Crumb rubber concrete (CRC) is an environment-friendly material using crumb rubber as a composition of cement concrete. It provides an alternative method for recycling of waste tires scientifically. CRC exhibits numerous advantages compared to ordinary concrete. However, the application of CRC is limited due to its low compressive and tensile strengths. is paper puts forward a new modified method by adding steel fibers and nanosilica in CRC. Material properties' testing of eighteen concrete mixtures was investigated, considering different strength grades of CRC and crumb rubber contents. In addition, four different steel fiber contents (0%, 0.5%, 1.0%, and 1.5%) and three different nanosilica content (0%, 1%, and 2%) were taken into consideration. e brittle failure of the CRC can be improved and the mechanical properties can be enhanced according to the test results. More importantly, the modified CRC with 1.0% steel fiber content has relatively high compressive and splitting tensile strengths. Furthermore, the noncompactness of CRC can be effectively improved by nanosilica, enhancing the efficiency of steel fibers simultaneously. Finally, the failure mechanism of the modified CRC is discussed in this paper.

Poly(lactic acid)/polycarbonate blends were prepared by melt mixing. The transesterification reaction between poly(lactic acid) and polycarbonate was promoted by using tetrabutyl titanate as a catalyst. For poly(lactic acid)/polycarbonate (weight ratio of 75/25) blend with catalyst content up to 0.5 wt%, polycarbonate particles finely dispersed in the poly(lactic acid) matrix and the adhesion between the phases were improved, due to the enhanced compatibility by transesterification reaction. The blends were foamed by using batch-foaming process with CO2 as the blowing agent. Cell density of poly(lactic acid)/polycarbonate blend increased at low-catalyst content, while decreased at high-catalyst content, which was due to the changes of interfacial properties of blend phases through transesterification reaction and crystallinity of polycarbonate component. Cell types of poly(lactic acid)/polycarbonate blends were transferred from submicro-sized and even nanoscale cells to microscale cells by the deceased crystallinity of poly(lactic acid) component, which was caused by the increased degree of transesterification reaction and temperature. The declined viscosity of poly(lactic acid)/polycarbonate blend because of degradation during blend processing led to large cell size and low-cell density. However, the improvement of elasticity and viscosity of poly(lactic acid)/polycarbonate blend by transesterification reaction could decrease the cell size.