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.

As 3D-printed (3DP) patterns are solid and durable, they can be used to create thin wall castings, which is complicated with wax patterns because of the wax’s fragility and high shrinkage ratio. According to this study’s experiment results, polylactic acid (PLA), polyvinyl butyral (PVB), and castable wax (CW) are suitable materials for preparing investment casting (IC) cavities. The results indicate that the casting product with the highest-quality surface is obtained using a cavity prepared using a CW-printed pattern. PLA- and PVB-printed patterns provide a good surface finish for casted products. In addition, the roughness of both the printed and casted surfaces increases as the printing layer height increases. The roughness of the casted surface varies from 2.25 μm to 29.17 μm. This investigation also considers the correlation between the infill ratio and mechanical properties of PLA-printed patterns. An increase in the infill ratios from 0% to 100% leads to a significant increase in the tensile properties of the PLA-printed pattern. The obtained results can be practically used.

Polybutylene terephthalate (PBT) is a brittle polymer with the disadvantage of low impact toughness, so it is not easy to meet the requirements of both high tensile strength, flexural strength, and high impact strength. In this study, PBT/polycarbonate (PC) blends at different ratios of 95/5, 90/10, 85/15, and 80/20 are investigated. Tensile strength, flexural strength, and unnotched Izod impact strength are studied according to the ASTM D638, ASTM D790, and ASTM D256 standards. The results show that tensile strength, which increased with increasing PC content, is 53.00, 62.34, 60.59, 62.98, and 64.46MPa for 0, 5, 10, 15, and 20 PC samples. Flexural strength and elastic flexural testing of PBT/PC blends are higher than neat PBT. In addition, the unnotched Izod impact strength of PBT/PC is also higher than PBT. However, when PC content increases, impact strength tends to decrease. Impact strength is 44.82, 80.46, 68.82, 50.45, and 48.05kJ/m² corresponds to 0, 5, 10, 15, and 20 PC, in which 5 PC sample is twice as high as the impact strength of PBT. Microstructure of the blends has shown that PC has become dispersed phase in PBT matrix. The size and quantity of dispersed PC particles increase with increasing PC rate in the blend. Thus, when adding PC, PBT/PC all meet the requirements of high tensile strength, flexural strength, and high impact strength. The PBT/5 PC model gives the highest impact strength while still ensuring durability, which potential application for making car door handles.

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.

Poly(butylene terephthalate) has the disadvantage of being brittle, so recycled polymer is often used less in real life. In this study, recycled poly(butylene terephthalate) was mixed with low-density polyethylene utilizing the plastic mixer and injection molding machine to improve it elastic modulus. The analyses were carried out by using the mixture of poly(butylene terephthalate) and 10 wt % of low-density polyethylene. The results indicate that tensile strength of the mixture is higher than that of pure polyethylene but less than that of recycled poly(butylene terephthalate). However, the mixture has the higher elastic modulus than pure polymers and its hardness is improved also.