In this work, the uniaxial stretching poly (vinyl alcohol) (PVA) films with glycerol as plasticizer were prepared to explore the influence of drawing temperature and drawing ratio. The structure and property were investigated with scanning electron microscope, wide-angle X-ray diffraction, X-ray diffraction, differential scanning calorimetry, mechanical tests, etc. With the increase of stretching temperature, the melting and crystallization temperatures increased. The tensile strength and Young modulus of glycerol/PVA films increased first and then decreased; when the temperature was 80°C, the tensile strength and Young modulus reached to maximum values of 197.2 and 470 MPa, respectively. In addition, with the increase of draw ratio, the orientation degree of the PVA molecular chains increased, indicating the improved regularity of molecular chains. When the PVA films were stretched to 4 times, the tensile strength and Young modulus of the films reached 162 and 143 MPa, respectively, which were 4 and 1.3 times compared with those of unoriented films. These environmentally friendly PVA films with excellent mechanical properties would find wide applications in the industry such as packaging, coating, etc. KEYWORDS glycerol, orientation, poly (vinyl alcohol), uniaxial stretching 1 | INTRODUCTION As a kind of biodegradable and eco-friendly materials, water-soluble poly (vinyl alcohol) (PVA) has been widely used in various industrial applications, such as biodegradable materials, chemical engineering, and so on. 1-4 The most important parameters influencing the physical properties of PVA are the molecular weight and alcoholysis degree. 5-7Due to the alcoholysis degree, PVA could be divided into 3 kinds with high (98%-100%), medium (87%-89%), and low alcoholysis degree (78%). 8 Poly (vinyl alcohol) with medium alcoholysis degree could dissolve in both hot and cold water, while PVA with alcoholysis degree more than 99% could only dissolve in hot water with temperature higher than 95°C. Compared with PVA with low alcoholysis degree, high alcoholysis PVA possesses higher water resistance, mechanical properties, as well as oxygen barrier properties, therefore exhibiting wider applications. 3,9 Stretching is mainly divided into uniaxial stretching and biaxial stretching, and it is well known that after stretching of films above its glass transition temperature (T g ), the molecular chain or molecular chain segments will rearrange toward the direction of external force. 10-12 For semicrystalline polymers, 13 stretching is an effective method to obtain oriented films with excellent mechanical, optical, and thermal properties, 14,15 which has been carried out at large-scale production for nearly 80 years. 16 These end-use properties are essentially controlled by stretching-induced crystallization of the polymer, which is affected by the stretching mode and processing conditions, such as temperature, stretching rate, and draw ratio (DR). 17,18 The processing conditions have strong impact on the morphology, crystalline structure...

It is known that grain refinement improves balance of strength and ductility of materials. As a technique to obtain fine-grained microstructure, dynamic recrystallization can be used in industrial processes. The authors reported that fine grains appear beneath the surface of Al-Mg alloy sheet by high-speed rolling. In this study, rolling conditions to form fine recrystallized microstructure were investigated. AA5052 alloy sheets were rolled at 500 m/min, 1000 m/min or 2000 m/min with thickness reduction of 30%, 50% or 70% at 473 K, 523 K, 573 K or 623 K. After the rolling, the sheets were water-quenched immediately. It is found that the critical strain for dynamic recrystallization is very large. For example, when the sheets are rolled at 1000 m/min and 623 K, thickness reduction greater than 76% is required for dynamic recrystallization.