Effect of homopolymer poly(vinyl acetate) on compatibility and mechanical properties of poly(propylene carbonate)/poly(lactic acid) blends

Ternary Blends from Biological Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), Poly(propylene carbonate) and Poly(vinyl acetate) with Balanced Properties

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) has gained significant attention because of its biodegradability and sustainability. However, its expanded application in some fields is limited by the brittleness and low melt viscoelasticity. In this work, poly(vinyl acetate) (PVAc) was introduced into PHBH/poly(propylene carbonate) (PPC) blends via melt compounding with the aim of obtaining a good balance of properties. Dynamic mechanical analysis results suggested that PPC and PHBH were immiscible. PVAc was miscible with both a PHBH matrix and PPC phase, while it showed better miscibility with PHBH than with PPC. Therefore, PVAc was selectively localized in a PHBH matrix, reducing interfacial tension and refining dispersed phase morphology. The crystallization rate of PHBH slowed down, and the degree of crystallinity decreased with the introduction of PPC and PVAc. Moreover, the PVAc phase significantly improved the melt viscoelasticity of ternary blends. The most interesting result was that the remarkable enhancement of toughness for PHBH/PPC blends was obtained by adding PVAc without sacrificing the strength markedly. Compared with the PHBH/PPC blend, the elongation at the break and yield strength of the PHBH/PPC/10PVAc blend increased by 1145% and 7.9%, respectively. The combination of high melt viscoelasticity, toughness and strength is important for the promotion of the practical application of biological PHBH.

Smart photochromic materials based on polylactic acid

The smart photochromic materials based on polylactic acid (PLA) were prepared by melt-blending and hot-pressing, in which photochromic microcapsules (PM) were used as a functional additive, and poly(vinyl acetate) (PVAc) was introduced into the photochromic PLA blends for the first time to improve their properties. The crystallization and melting behavior, morphology, and photochromic performance of PLA/PVAc/PM blends were characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and spectrophotometer, respectively. The results showed that PVAc significantly improved the photochromic properties of PLA/PM blends. Under 30s UV irradiation, the blends reached a value of ΔE that could be recognized in 3 s by human eyes. This discriminative ΔE value could be maintained for at least 3 min after removal from UV irradiation. Meanwhile, the blend had outstanding photochromic durability and recyclability. Compared to ΔE for 0.5 h of continuous light irradiation, ΔE for 8 h of continuous light irradiation decreased by only about 1, to 14.1. In 25 cycles of 3 s UV irradiation, the values of ΔE for the first and 25th irradiation were 11.4 and 11.6, respectively. The blend showed different photochromic responses to different light intensities. The ΔE values of 8.6, 14.6, 14.6, and 18.4 for irradiation at 600, 800, 1000, and 1200 W/m² of solar intensity, respectively.

Research and Application of Polypropylene Carbonate Composite Materials: A Review

The greenhouse effect and plastic pollution caused by the accumulation of plastics have led to a global concern for environmental protection, as well as the development and application of biodegradable materials. Polypropylene carbonate (PPC) is a biodegradable polymer with the function of “carbon sequestration”, which has the potential to mitigate the greenhouse effect and the plastic crisis. It has the advantages of good ductility, oxygen barrier and biocompatibility. However, the mechanical and thermal properties of PPC are poor, especially the low thermal degradation temperature, which limits its industrial use. In order to overcome this problem, PPC can be modified using environmentally friendly materials, which can also reduce the cost of PPC-based products to a certain extent and enhance their competitiveness in terms of improving their mechanical and thermal properties. In this paper, we present different perspectives on the synthesis, properties, degradation, modification and post-modification applications of PPC. The modification part mainly introduces the influence of inorganic materials, natural polymer materials and degradable polymers on the performance of PPC. It is hoped that this work will serve as a reference for the early promotion of PPC.

Compatibilization and Characterization of Polylactide and Biopolyethylene Binary Blends by Non-Reactive and Reactive Compatibilization Approaches

In this study, different compatibilizing agents were used to analyze their influence on immiscible blends of polylactide (PLA) and biobased high-density polyethylene (bioPE) 80/20 (wt/wt). The compatibilizing agents used were polyethylene vinyl acetate (EVA) with a content of 33% of vinyl acetate, polyvinyl alcohol (PVA), and dicumyl peroxide (DPC). The influence of each compatibilizing agent on the mechanical, thermal, and microstructural properties of the PLA-bioPE blend was studied using different microscopic techniques (i.e., field emission electron microscopy (FESEM), transmission electron microscopy (TEM), and atomic force microscopy with PeakForce quantitative nanomechanical mapping (AFM-QNM)). Compatibilized PLA-bioPE blends showed an improvement in the ductile properties, with EVA being the compatibilizer that provided the highest elongation at break and the highest impact-absorbed energy (Charpy test). In addition, it was observed by means of the different microscopic techniques that the typical droplet-like structure is maintained, but the use of compatibilizers decreases the dimensions of the dispersed droplets, leading to improved interfacial adhesion, being more pronounced in the case of the EVA compatibilizer. Furthermore, the incorporation of the compatibilizers caused a very marked decrease in the crystallinity of the immiscible PLA-bioPE blend.

Investigation on compatibility of PLA/PBAT blends modified by epoxy-terminated branched polymers through chemical micro-crosslinking

In this study, a type of epoxy-terminated branched polymer (ETBP) was used as an interface compati- bilizer to modify the poly lactic acid (PLA)/poly(butylene adipate-co-butylene terephthalate) (PBAT) (70/30) blends. Upon addition of ETBP, the difference in glass transition temperature between PLA and PBAT became smaller. By adding 3.0 phr of ETBP, the elongation at break of the PLA/PBAT blends was found increased from 45.8% to 272.0%; the impact strength increased from 26.2 kJ·m−2 to 45.3 kJ·m−2. In SEM analysis, it was observed that the size of the dispersed PBAT particle decreased with the increasing of ETBP content. These results indicated that the compatibility between PLA and PBAT can be effectively enhanced by using ETBP as the modifier. The modification mechanism was discussed in detail. It proposes that both physical and chemical micro-crosslinking were formed, the latter of which was confirmed by gel content analysis.

Poly (lactic acid) blends: Processing, properties and applications

Poly (lactic acid) or polylactide (PLA) is a commercial biobased, biodegradable, biocompatible, compostable and non-toxic polymer that has competitive material and processing costs and desirable mechanical properties. Thereby, it can be considered favorably for biomedical applications and as the most promising substitute for petroleum-based polymers in a wide range of commodity and engineering applications. However, PLA has some significant shortcomings such as low melt strength, slow crystallization rate, poor processability, high brittleness, low toughness, and low service temperature, which limit its applications. To overcome these limitations, blending PLA with other polymers is an inexpensive approach that could also tailor the final properties of PLA-based products. During the last two decades, researchers investigated the synthesis, processing, properties, and development of various PLA-based blend systems including miscible blends of poly l-lactide (PLLA) and poly d-lactide (PDLA), which generate stereocomplex crystals, binary immiscible/miscible blends of PLA with other thermoplastics, multifunctional ternary blends using a third polymer or fillers such as nanoparticles, as well as PLA-based blend foam systems. This article reviews all these investigations and compares the syntheses/processing-morphology-properties interrelationships in PLA-based blends developed so far for various applications.