Low-density polyethylene (LDPE) and ethylene vinyl acetate copolymer (EVA), which are non-polar and polar polymers, are immiscible and form a polyphase system. In this study, LDPE was mixed with 2.5%, 5%, 7.5%, 10%, 12.5% Ethylene-vinyl acetate (EVA-28) with a medium content of vinyl acetate (28% VA), respectively by injection molding machine and LDPE. Tensile strength and flexural strength were tested according to ASTM D638-02 standard and ISO 178 standard. The results showed that adding EVA-28 increased the elongation at break of the LDPE/2.5% EVA, LDPE/5% EVA and LDPE/10% EVA blend samples. In addition, the tensile and flexural strength of the LDPE/EVA blend decreases gradually as the EVA-28 content in the blend increases. The hardness decreases with the increasing EVA-28 content. EVA-28 spherical particles appeared scattered on the surface of the LDPE matrix, in the highest EVA-28 percent sample (12.5% EVA-28), the number of particles appeared to be quite a lot, and was dispersed quite evenly on the surface. The LDPE/EVA-28 blend achieved a higher elongation at the break than LDPE, in which 10% EVA-28 gives the highest elongation at break.

Poly (butylene terephthalate) (PBT) is a popular thermoplastic polyester resin but has low strength and low melting point. To improve its properties, PBT is often mixed with other resins, such as high-density polyethylene (HDPE). In this study, PBT/HDPE samples with 100% PBT, 5%, 10%, 15%, and 100% HDPE are generated and tested. The samples are analyzed by tensile strength, flexural strength, impact strength, and SEM tests. Adding HDPE will reduce tensile strength compared to pure PBT, in which 5%, 10%, and 15% PBT/HDPE samples obtain the values 40.23, 38.11, and 27.77 MPa, respectively. These values are lower than that of pure PBT but still higher than that of HDPE. Improving the HDPE portion mostly results in decreasing flexural strength. The flexural strengths of these samples are 87.79, 70.47, 55.3, 58.98, and 19.14 MPa corresponding to 100% PBT, 5%, 10%, 15%, and 100% HDPE samples, respectively. Moreover, the SEM microstructure of PBT and HDPE indicates a two-phase heterogeneous mixture with little or no adhesion between these phases.

Ductility and tensile strength are among the basic mechanical properties of polymers. Generally, it is difficult to enhance the ductility without significantly reducing the tensile strength. In this study, thermoplastic polyurethane (TPU) is mixed with 0%, 2.5%, 5%, 7.5%, 10%, and 12.5% polyamide 6 (PA6). The results show that the sample containing 100% TPU has the largest elongation of 690.5%. When PA6 is added, the elongation decreases gradually to 635.0%, 623.1%, 529.5%, 476.0%, 391.3%, and 242.8%, corresponding to 2.5%, 5%, 7.5%, 10%, 12.5%, and 100% PA6, respectively. The tensile strengths are 36.7, 33.8, 29.4, 26.5, 23.1, and 24.9 MPa, corresponding to 0%, 2.5%, 5%, 7.5%, 10%, and 12.5% PA6 samples, respectively. The tensile strength decreases gradually when the PA6 content is increased. Notably, the tensile strength of the 12.5% PA6 sample increases compared to the 10% PA6 sample. In addition, the hardness of the TPU/PA blend increases slightly as the PA6 ratio is increased. Finally, scanning electron microscope images demonstrate that PA6 particles act as particles dispersed or dissolved in TPU/PA blends.

No abstract

H13 steel surfaces are covered by coatings of Co-based alloy with 0, 10, 20, and 30 wt. % TiC using the laser cladding (LC) method. The morphological characteristics, growth mechanism, and the mechanical properties of TiC on the microstructure of the coatings were studied. The results show that TiC in the TiC/Co50 composite coating is composed of two parts: incompletely melted TiC and in situ TiC. TiC content has a great effect on the morphology of TiC, and it exists in different shapes: original TiC, fine-particle TiC, segregated TiC, petal-shaped TiC, and branch-shaped TiC. Additionally, the morphology of TiC in different areas of the coating is different, while TiC size gradually increases from bonding zone to surface. In the 10% TiC+Co50 coating, TiC mainly appears as undermelted, fine particles, precipitates, and having shapes of polygons and petals. From the bottom of this coating, the number of petal-shaped TiC has increased, and the particle size is also enlarged. In the 20% TiC+Co50 coating, the TiC in the coating mainly presents as undermelted, fine particles, and dendritic morphology. From the bottom of this coating to the surface, the particle size of the undermelted TiC shows a clear gradient change. Finally, the 30% TiC+Co50 coating does not have in situ TiC, and there is no obvious gradient change in the particle size of undermelted TiC. After coating by the LD method, the surface hardness is strongly enhanced. The average hardness of Co50 alloy, Co+10% TiC, and Co+20% TiC composite coatings is 499 HV0.2, 552 HV0.2, 590 HV0.2, and 824 HV0.2, respectively. These values are 2.4–4.0 times harder than that of the H13 substrate. The wear resistance of Co50 alloy, Co+10% TiC, and Co+20% TiC composite coatings is greatly higher than that of H13 steel, showing excellent wear characteristics. The friction coefficient of the coatings which have TiC is very stable. Therefore, the coatings can satisfy the requirement of tool steels applications. Additionally, the wear mechanism of the coating at room temperature is mainly brittle spalling, adhesive, and ploughing. At 700°C, the wear mechanism is mainly oxidation and fatigue.