Integration of Multivariate Statistical Control Chart and Machine Learning to Identify the Abnormal Process Parameters for Polylactide with Glass Fiber Composites in Injection Molding; Part I: The Processing Parameter Optimization for Multiple Qualities of Polylactide/Glass Fiber Composites in Injection Molding

This paper discusses the mixing of polylactide (PLA) and glass fiber which use injection molding to produce a functional composite material with glass fiber properties. The injection molding process explores the influence of glass fiber ratio, melt temperature, injection speed, packing pressure, packing time and cooling time on the mechanical properties of composite. Using the orthogonal table planning experiment of the Taguchi method, the optimal parameter level combination of a single quality process is obtained through main effect analysis (MEA) and Analysis of variance (ANOVA). Then, the optimal parameter level combination of multiple qualities is obtained through principal component analysis (PCA) and data envelopment analysis (DEA), respectively. It is observed that if all the quality characteristics of tensile strength, hardness, impact strength and bending strength are considered at the same time, the optimal process conditions are glass fiber addition 20 wt %, melt temperature 185 °C, injection speed 80 mm/s, holding pressure 60 MPa, holding time 1 s and cooling time 15 s, and the corresponding mechanical properties are tensile strength 95.04 MPa, hardness 86.52 Shore D, impact strength 4.4408 J/cm², bending strength 119.89 MPa. This study effectively enhances multiple qualities of PLA/GF composite.

Development of Biodegradable Rigid Foams from Pineapple Field Waste

Pineapple materials sourced from agricultural waste have been employed to process novel bio-degradable rigid composite foams. The matrix for the foam consisted of starch extracted from pineapple stem, known for its high amylose content, while the filler comprised non-fibrous cellulosic materials sourced from pineapple leaf. In contrast to traditional methods that involve preparing a batter, this study adopted a unique approach where the starch gel containing glycerol were first formed using a household microwave oven, followed by blending the filler into the gel using a two-roll mill. The resulting mixture was then foamed at 160 °C using a compression molding machine. The foams displayed densities ranging from 0.43-0.51 g/cm³ and exhibited a highly amorphous structure. Notably, the foams demonstrated an equilibrium moisture content of approximately 8-10% and the ability to absorb 150-200% of their own weight without disintegration. Flexural strengths ranged from 1.5-4.5 MPa, varying with the filler and glycerol contents. Biodegradability tests using a soil burial method revealed complete disintegration of the foam into particles measuring 1 mm or smaller within 15 days. Moreover, to showcase practical applications, an environmentally friendly single-use foam tray was fabricated. This novel method, involving gel formation followed by filler blending, sets it apart from previous works. The findings highlight the potential of pineapple waste materials for producing sustainable bio-degradable foams with desirable properties and contribute to the field of sustainable materials.

Recent advances in compatibility and toughness of poly(lactic acid)/poly(butylene succinate) blends

Poly(butylene succinate) (PBS) has good impact strength and high elongation at break. It is used to toughen biodegradable poly(lactic acid) (PLA) materials because it can considerably improve the toughness of PLA without changing the biodegradability of the materials. Therefore, this approach has become a hotspot in the field of biodegradable materials. A review of the physical and chemical modification methods that are applied to improve the performance of PLA/PBS blends based on recent studies is presented in this article. The improvement effect of PLA/PBS blends and the addition of some common fillers on the physical properties and crystallization properties of blends in the physical modification method are summarized briefly. The compatibilizing effects of nanofillers and compatibilizing agents necessary to improve the compatibility and toughness of PLA/PBS blends are described in detail. The chemical modification method involving the addition of reactive polymers and low-molecular-weight compounds to form cross-linked/branched structures at the phase interface during in situ reactions was introduced clearly. The addition of reactive compatibilizing components is an effective strategy to improve the compatibility between PLA and PBS components and further improve the mechanical properties and processing properties of the materials. It has high research value and wide application prospects in the modification of PLA. In addition, the degradation performance of PLA/PBS blends and the methods to improve the degradation performance were briefly summarized, and the development direction of PLA/PBS blends biodegradation performance research was prospected.

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.

Complex cellular structure evolution of polystyrene/poly (ethylene terephthalate glycol-modified) foam using a two-step depressurization batch foaming process

In order to decrease the cell size and maintain very high volume expansion ratio simultaneously, a methodology for the preparation of complex cellular structure (CCS) in polystyrene/poly(ethylene terephthalate glycol-modified) (PS/PETG) blend using two-step depressurization pressure batch foaming process was proposed. First, the optimum foaming temperature for PS and PS/PETG blend, respectively, were confirmed by one-step depressurization foaming process. Then, the CCS in PS and PS/PETG blending foam were fabricated by two-step depressurization foaming process at the optimum foaming temperature. The rheological properties of PS and PS/PETG blend were tested by dynamic rotational rheometer. The dispersion morphologies and foam morphologies were observed by scanning electron microscope. The lowest densities of PS and PS/PETG blending foams were obtained at the temperature of 136℃. The interfaces between PS and PETG could act as nucleation sites for the cell nucleation, which were helpful to fabricate the CCS. The CCS could be controlled by tuning the degree of the first-step depressurization and the holding time. The results showed that the large cells could be beneficial to decrease the foam density and the presence of small cells was beneficial to increase the cell number.

How much do nanoparticle fillers improve the modulus and strength of polymer foams?

Nanofiller reinforcing agents can significantly improve the strength and modulus of polymer foams. But these improvements are often accompanied by changes in foam density (or equivalently the expansion ratio or void volume). The efficacy of nanofillers as reinforcing agents can only be judged once the density differences are accounted for. We review the literature and show that representing the data on Ashby charts of modulus against foam density is an effective way of evaluating whether nanofillers have a significant reinforcing effect or not. The literature suggests that strength and improvements due to nanofiller – after accounting for foam density changes – are typically modest for thermoplastic foams. However, major improvements are possible for reactively generated foams, especially flexible polyurethane foams.

Effect of stearic acid/organic montmorillonite on EVA/SA/OMMT nanocomposite foams by melting blending

The effects of stearic acid (SA)/organic montmorillonite (OMMT) on the morphology and mechanical properties of nanocomposite foams based on ethylene vinyl acetate (EVA) copolymer were studied. The dispersion of montmorillonite layers was characterized by both X-ray diffraction and transmission electron microscopy. The cellular microstructure of the foamed samples was observed by scanning electron microscope. The effects of SA/OMMT on the mechanical properties of the EVA-based foams were also investigated. It was found that the combined effects of the existence of SA/OMMT led to bimodal foam structure in EVA/SA/OMMT nanocomposite foams. Compared with pure EVA foams, the density of EVA/SA/OMMT foams became lower with the addition of SA/OMMT, while the peel strength and elongation-at-break of the samples were increased.

Study on rheological and extrusion foaming behaviors of chain-extended poly (lactic acid)/clay nanocomposites

Chain-extended poly(lactic acid) /clay nanocomposites were prepared through extrusion process. The effects of the content and dispersion morphology of clay on the molecular weight distribution and rheological behavior of chain extended poly(lactic acid) were discussed. The chain extender/clay ratio would strongly affect the molecular weight and gelation degree of poly(lactic acid), thus affecting the melt strength and melt elasticity. The melt strength increased with increasing clay content, reaching a maximum value, after which it decreased. Then chain extended poly(lactic acid) /clay were foamed with supercritical CO2, and the cellular structure, cell size, cell density were investigated. The introduction of clay would increase the cell density. The results indicated that a homogeneous and finer cellular morphology could be achieved with a proper content of chain extender and clay in poly(lactic acid).