A mathematical model to describe the molecular weight and polydispersity index (Q) in poly(l-lactide) (PLLA) thermal degradation has been developed. Based on the random chain scission mechanism, effects of temperature and time on the molecular weight and polydispersity index are included in this model. It incorporates the degradation and recombination reaction of PLLA thermal degradation, while taking into account the equal probability assumption. The developments of molecular weight and polydispersity index of PLLA polymer in the thermal degradation process were investigated at temperature ranging from 180 -220°C, the experimental data show PLLA reaches its thermal degradation equilibrium in 2 h. The simulated results of this model are compared with the measured molecular weight and polydispersity index of the PLLA polymer. The changes of the molecular weight and polydispersity index in the PLLA thermal degradation can be predicted by this model.

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Wool fabrics, ultrasonically treated in various chemical conditions and for different time durations, were analysed for thermal properties by thermo-gravimetric analysis and differential scanning calorimeter, in comparison with the untreated fabric. Fabric mechanical properties, such as bending and tensile performance, and changes in fibre morphology were also evaluated before and after ultrasonic treatment. It is found that wool treated with ultrasonics at the appropriate time, has less mass loss and a higher thermal degradation temperature than that without ultrasonic treatment or with prolonged ultrasonic treatment. Resistance to thermal degradation is reduced when wool is ultrasonically treated in the presence of alkali. Differential scanning calorimeter analysis shows that while ultrasonic treatment has little effect on fibre crystallinity, an appropriate treatment can provide wool with increased water absorption. Ultrasonic treatment stiffens wool fabric to some extent when the treatment time is prolonged. The addition of detergent alone to the ultrasonic bath has little effect on fabric tensile behaviour, whereas a treatment with both detergent and alkali produces severe fibre damage and significant loss of fabric tensile strength.

Scouring is the first stage of wool processing and is essential for determining the quality of fiber. Traditional aqueous scouring is a method that emulsifies and removes contaminants (such as wool grease, suint, and dirt) from the fiber surface; however, it promotes wool felting and is energy and water intensive. This study has shown that modification of the traditional wool scouring line by introducing an ultrasonic device could be a viable alternative for the wool scouring industry. A standard six-bath wool scouring line was retrofitted with two ultrasonic panels working at 80 kHz in bath 2. Scouring was carried out in three modes: conventional mode without the transport rake, ultrasonic mode without the transport rake, and conventional mode with the transport rake. Fiber samples after scouring were measured for color index, residual grease content, and residual ash content. Ultrasonic scouring was found to improve removal of grease and ash from the wool fiber. Modifications were proposed for the design of an industrial scouring line including the addition of fiber transport and dunking rollers and number of baths for the installation.

Experimental investigations on lap welding of magnesium alloy to steel using resistance spot welding with Cu-Zn alloy interlayer are carried out. The effect of welding time, welding current and interlayer thickness on the bonding mode of interface and joint strength has been investigated using mechanical testing and metallurgical examination. The results show that the strength of Mg-steel joints without an interlayer could reach 30 MPa by the optimization of welding current and time. The addition of alloy elements, realized by adjustment of interlayer thickness, has a noticeable effect on mechanical properties and microstructure of the joints. Particularly, with the addition of Cu-Zn interlayer (0.1 mm in thickness), the tensile strength could attain 62 MPa. Owning to the addition of the Cu-Zn alloy interlayer, a metallurgical bonding between Mg alloy and steel is achieved based on the formation of intermetallic compounds of CuMgZn and solid solutions of Cu in Fe. In addition, the formation of pores at the interface of Mg alloy and steel is adverse for the strength improvement of joints.