ABSTRACT
Poly(lactic acid) (PLA) is a relatively brittle polymer, and its low melt strength, ductility, and thermal stability limit its use in various industrial applications. This study aimed to investigate the effect of poly(methyl methacrylate) (PMMA) and PMMA/silica hybrid particles on the mechanical properties, interfacial adhesion, and crystallization behavior of PLA/block acrylic elastomer. PLA/block acrylic elastomer blends exhibit improved flexibility; however, phase separation occurs between PLA and block acrylic elastomer domains. Valid time-temperature superposition (TTS) measurements of viscoelastic behavior were obtained and exhibited interfacial adhesion with the addition of PMMA or PMMA/silica in PLA/block acrylic elastomer blends. In particular, the phase separation temperature was increased by the incorporation of PMMA/silica hybrid particles, which suggests a potential role for these particles in improving the phase stability. In addition, PMMA inhibits crystallization, while PMMA/silica acts as a nucleating agent, thus increasing the crystallization rate and crystallinity degree.
ABSTRACT
The extreme elasticity and reversible deformability of rubber, which is one of the most versatile polymers in modern society, is dependent on several factors, including the processing conditions, curing system, and types of additives used. Since the rubber's mechanical properties are influenced by the existing structural crosslinks, their correlation with the crosslink characteristics of rubber was investigated using the equilibrium swelling theory of the Flory-Rehner equation and the rubber-filler interaction theory of the Kraus equation. Herein, we examined whether the accelerator and reinforcement agent quantitatively contributed to chemical cross-linkages and rubber-filler interaction. In conclusion, the accelerator content supported the chemically crosslinked structures of the monosulfides and the disulfides in natural rubber (NR). Additionally, these results demonstrated that the mechanical properties and the thermal resistance of NR were dependent on the crosslink characteristics. The findings of this study provide an insight into the development and application of NR products for the mechanical optimization of rubber-based products.
ABSTRACT
The mechanical properties and tear resistance of an ecofriendly flexible packaging film, i.e., poly(lactic acid) (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) film, were investigated via a blown film extrusion process. The application of PLA and PBAT in product packaging is limited due to the high brittleness, low stiffness, and incompatibility of the materials. In this study, the effects of various plasticizers, such as adipate, adipic acid, glycerol ester, and adipic acid ester, on the plasticization of PLA and fabrication of the PLA/PBAT blown film were comprehensively evaluated. It was determined that the plasticizer containing ether and ester functionalities (i.e., adipic acid ester) improved the flexibility of PLA as well as its compatibility with PBAT. It was found that the addition of the plasticizer effectively promoted chain mobility of the PLA matrix. Moreover, the interfacial adhesion between the plasticized PLA domain and PBAT matrix was enhanced. The results of the present study demonstrated that the plasticized PLA/PBAT blown film prepared utilizing a blown film extrusion process exhibited improved tear resistance, which increased from 4.63 to 8.67 N/mm in machine direction and from 13.19 to 16.16 N/mm in the transverse direction.
ABSTRACT
Polypropylene (PP) foam offers superior thermal and mechanical properties and versatile applications. However, the linear structure of PP hinders the fabrication of a uniform and fine foam, owing to changes in the melt strength with variations in the temperature. The foamability of the material can be improved by fabricating modified PP by introducing long-chain branches by grafting and chain extension reactions, using glycidyl methacrylate (GMA) and adipic acid (AA). Adding 5 phr GMA to PP optimizes the graft ratio. AA as a chain extender forms a long-chain branched structure, as confirmed by the melt flow index, morphology, and thermal and dynamic viscoelastic properties. Variations in foaming characteristics according to the AA content, temperature, volume expansion ratio, and oven residence time have also been observed. An optimal volume expansion ratio of â¼14 is obtained at an AA content of 1.5 phr and foaming for 11 min at 240 °C.
