Critical Thinking On Deformation Processing Of Pmma Into High-Strength Fibers

- A brief summary of the major findings of the paper.
This paper describes a study of processing of poly (methyl methacrylate) (PMMA) into fibers. Different draw ratios of the fiber products or degrees of fiber chain alignment were obtained under different deformation conditions and determined by a heat-induced relaxation method. The results of the strength tests on fiber products suggested that a higher degree of alignment leads to higher tensile strength, while decreasing alignment results in lower tensile strength but higher ductility.
2. Provide at least 4 MAJOR technical strengths to the paper and EXPLAIN why. In addition, please rank the strengths (1- most important, etc.)
1-Most importantly, the procedures of fiber tensile tests were described clearly, and the results were scientifically sound. This is the most important to this paper, which is focused on the mechanical properties of polymer fibers. The stress-strain curves of different fiber samples and the effects of true stress and true strain to length relaxation ratio were shown in Figure 7, 10, and 11, respectively.
2-The procedures of results of the heat relaxation were described clearly, and results were scientifically sound. The effects of the extrusion velocity, draw velocity, and fiber diameter on the length relaxation ratio of different fiber samples were presented in Figure 2-6.
3-The procedures of the extrusion and drawing of the polymer fibers were described very clearly with the drawing of the apparatus (Figure 1). Five variable parameters, including the temperature of the molten acrylic, the extrusion velocity, the diameter of the extrusion hole and the draw velocity, were described explicitly.
4-Least importantly, the texture of the fibers was determined by Scanning Electron Microscopy (SEM), and nice SEM pictures were shown in Figure 8 and 9.
3. Provide at least 4 MAJOR technical weaknesses to the paper and EXPLAIN why. In addition, please rank the weaknesses (1- biggest weakness, etc.)
1-Biggest weakness, the authors mentioned to determine the effects of thermal and mechanical processing conditions on the draw ratios of PMMA fibers. However, the discussion of the correlation between thermal and mechanical processing conditions and the fiber draw ratios was missing in the manuscript.
2-It is difficult for the audience to figure out how many fiber samples there were used in the study and what their processing conditions were. It is thus difficult to compare the material properties and processing conditions among different samples.
3-In the “Extrusion and Drawing” section in Results, the authors stated that a fast extrusion speed, a large extrusion hole diameter, and a slow draw rate result in larger fiber diameters. However, only the conclusion was shown, while the data of the diameter measurements was missing.
4-In the “Extrusion and Drawing” section in Results, the effects of the melting and cooling temperatures on fiber texture were described. However, the data showing the fiber texture of different samples was missing.
4. What is the 1 MAJOR technical aspect of the work that you would have done differently (and EXPLAIN why)?
I would present the differences in the surface appearance of different fiber samples using an optical microscope technique. SEM is commonly used for visualization of surface topographic/morphological features of materials. In addition, SEM gives better resolution and depth of focus compared to an ordinary optical microscope. Therefore, I would perform SEM on these samples using a Cambridge Instruments Model S120 scanning electron microscope as described in the Materials and Methods. In addition to describing the findings in the main text, I would include the high magnification (275X) SEM pictures and compare the picture of different fiber samples with different diameters side by side in the manuscript.