On the Use of Starch in Emulsion Polymerizations

Overcoming Challenges of Incorporation of Biobased Dibutyl Itaconate in (Meth)acrylic Waterborne Polymers

Polymeric derivatives of itaconic acid are gaining interest as biobased alternatives to petroleum-based monomers due to their versatility, renewable nature, commercial availability, and cost-effectiveness. Itaconate ester monomer's challenges incorporating in (meth)acrylic waterborne polymers are the low propagation rate, unfavorable reactivity ratios, and the depropagation process. To overcome these challenges, the seeded semibatch emulsion polymerization of 100% biobased dibutyl itaconate, methyl methacrylate, and butyl acrylate was investigated at different temperatures. Consequently, 30 wt % DBI was successfully incorporated within waterborne (meth)acrylates in short reaction times (4 h), obtaining high DBI incorporation (>90%). The results demonstrate that DBI incorporation influences the instantaneous monomer conversion, polymer's microstructure, and mechanical properties. By incorporating a biobased itaconate cross-linker, kinetics and mechanical characteristics of the polymers were improved. This combined approach can be implemented without altering industrial processes, resolving the commercialization dilemma for itaconate monomers to synthesize high-performance biobased polymers for adhesive and coating industries.

Quantum Chemical Investigation into the Structural Analysis and Calculated Raman Spectra of Amylose Modeled with Linked Glucose Molecules

This study presents a quantum chemical investigation into the structural analysis and calculated Raman spectra of modeled amylose with varying units of linked glucose molecules. We systematically examined the rotation of hydroxymethyl groups and intramolecular hydrogen bonds within these amylose models. Our study found that as the number of linked glucose units increases, the linear structure becomes more complex, resulting in curled, cyclic, or helical structures facilitated by establishing various intramolecular interactions. The hydroxymethyl groups were confirmed to form interactions with oxygen atoms and with hydroxymethyl and hydroxyl groups from adjacent rings in the molecular structures. We identified distinct peaks and selected specific bands applicable in various analytical contexts by comparing their calculated Raman spectra. Representative vibrational modes within selected regions were identified across the different lengths of amylose models, serving as characteristic signatures for linear and more coiled structural conformations. Our findings contribute to a deeper understanding of amylose structures and spectroscopic signatures, with implications for theoretical studies and potential applications. This work provides valuable reference points for the detailed assignment of Raman peaks of amylose structure, facilitating their application in broader research on carbohydrate structures and their associated spectroscopic properties.

Optimisation and characterization of double emulsion derived from rice starch, rice protein isolates and rice bran oil

This study focused on the development and evaluation of a stable emulsion system using rice starch, protein isolates, and bran oil as food ingredients. This was performed using a one-factor-at-a-time (OFAT) experimental strategy, which was subsequently refined using response surface modeling (RSM), and the emulsion was then characterized. The resulting quadratic polynomial model effectively captured all the responses, with regression coefficients exceeding 0.90. The emulsion activity index, emulsion stability index, and droplet size were 86.29 %, 93.44 %, and 100.59 nm, respectively. Turbidity was significantly influenced by particle size, with the double emulsion (sample B) exhibiting higher turbidity index (43,250.34 ± 0.046) than the reference sample (29,433.303 ± 0.018). The viscosity of the emulsion increased with the addition of the protein isolates. This inferred that a stable emulsion system derived from rice could serve a multifunctional purpose as carriers, fillers, and binders to enhance the physical, functional and sensory properties of foods.

Temperature responsive crosslinked starch-kraft lignin macromolecule

Starch is a natural polymer with a relatively simple structure and limited solubility in water. Kraft lignin (KL) is a complex biopolymer obtained as a by-product from the delignification of wood and grasses. The present work reports developing a temperature-responsive high molecular weight macromolecule from crosslinking KL and starch (KLS). The NMR and XPS analyses quantified the changes in the aromatic and anhydroglucose units of KL and starch, observing a higher content of C-O-C bonds, which confirms the presence of glycerol ether cross-linkages between starch and KL in KLS. The rheological analysis of KLS dispersions revealed the formation of a thermo-responsive structured network. The temperature-dependent water solubility and rheological characteristics of KLS were related to the presence of hydrophilic starch chains, crosslinking degree, and physicochemical characteristics of KL. The incorporation of KL and ether crosslinks increased the thermal stability of KLS. Because of its multiple functional groups and large molecular weight (3.6-4.2 × 10⁵ g/mol) that was arranged in an extended globular shape, KLS-5 formed a gel-like structure after a heating-cooling treatment. Overall, the results confirmed that incorporating lignin in starch would fabricate sustainable materials with potentially altered applications, such as temperature-responsive hydrogels and films.

Effect of ultrasound on the physical properties and processing of major biopolymers-a review

Designing and developing modern techniques to facilitate the extraction and modification of functional properties of biopolymers are key motivations among researchers. As a low-cost, sustainable, non-toxic, and fast process, ultrasound has been considered a method to improve the processing of carbohydrate and protein-based biopolymers such as cellulose, chitin, starch, alginate, carrageenan, gelatine, and guar gum. A better understanding of the complex physicochemical behavior of biopolymers under ultrasonication may fortify the eminence of this technology in advanced-level applications. This review summarizes the recent advances in biopolymer processing and the effect of ultrasound on the physical properties of the selected biopolymers. A major focus will be given to the mechanisms of action and their impact on the properties and extraction. At the end, some possible suggestions are highlighted which need future investigation for amending the physical properties of biopolymers using ultrasonication.

Copolymers of starch, a sustainable template for biomedical applications: A review

The outstanding versatility of starch offers a source of inspiration for the development of high-performance-value-added biomaterials for the biomedical field, including drug delivery, tissue engineering and diagnostic imaging. This is because starch-based materials can be tailored to specific applications via facile grafting or other chemistries, introducing specific substituents, with starch being effectively the "template" used in all the chemical transformations discussed in this review. A considerable effort has been carried out to obtain specific tailored starch-based grafted polymers, taking advantage of its biocompatibility and biodegradability with appealing sustainability considerations. The aim of this review is to critically explore the latest research that use grafting chemistries on starch for the synthesis of products for biomedical applications. An effort is made in reviewing the literature that proposes synthetic "greener" approaches, the use of enzymes and their immobilized analogues and alternative solvent systems, including water emulsions, ionic liquids and supercritical CO₂.

Preparation of glycidyl methacrylate grafted starch adhesive to apply in high-performance and environment-friendly plywood

In this paper, cassava starch was used as the main raw material to prepare high performance and environment-friendly starch-based adhesive. Starch was grafted with glycidyl methacrylate (GMA), and then cross-linked with sodium trimetaphosphate (STMP). Before preparation of plywood, polyaryl polymethylene isocyanate (PAPI) was mixed as chain extension agent. Prepared starch adhesives are used in wood-based panel applications. From the Fourier transform infrared (FTIR) analysis, it was found that GMA was successfully grafted to the starch adhesives which improved the hydrophobicity and shear strength of the adhesive. The plywood using modified starch adhesive at pH 4.50-5.50 showed the highest wet shear strength, 1.00 MPa, which was 163% higher than that using unmodified starch adhesive. The Scanning electron microscopy (SEM) results showed that the original morphology of starch particles were destroyed and became smaller during GMA grafting, which made the modified starch-based adhesive easier to penetrate into the bonding interface of plywood. The characterization results of the adhesive film also showed that the mechanical properties of the adhesive were better when the grafting reaction pH was 4.50-5.50. Graft copolymerization modification of starch improves the hydrophobic properties of starch binders.

Preparations of Poly(lactic acid) Dispersions in Water for Coating Applications

A green, effective methodology for the preparation of water-based dispersions of poly(lactic acid) (PLA) for coating purposes is herein presented. The procedure consists of two steps: in the first one, an oil-in-water emulsion is obtained by mixing a solution of PLA in ethyl acetate with a water phase containing surfactant and stabilizer. Different homogenization methods as well as oil/water phase ratio, surfactant and stabilizer combinations were screened. In the second step, the quantitative evaporation of the organic provides water dispersions of PLA that are stable, at least, over several weeks at room temperature or at 4 °C. Particle size was in the 200-500 nm range, depending on the preparation conditions, as confirmed by scanning electron microscope (SEM) analysis. PLA was found not to suffer significant molecular weight degradation by gel permeation chromatography (GPC) analysis. Furthermore, two selected formulations with glass transition temperature (Tg) of 51 °C and 34 °C were tested for the preparation of PLA films by drying in PTFE capsules. In both cases, continuous films that are homogeneous by Fourier-transform infrared spectroscopy (FT-IR) and SEM observation were obtained only when drying was performed above 60 °C. The formulation with lower Tg results in films which are more flexible and transparent.

Study of the Physical and Mechanical Properties of Thermoplastic Starch/Poly(Lactic Acid) Blends Modified with Acid Agents

In this work, we present a functionalization strategy of starch-poly(lactic acid) (PLA) blends with organic acids. Lactic and acetic acid were used as acid agents, and oleic acid was also included in the previous acids, with the aim of finding a synergy that thermodynamically benefits the products and provides hydrophobicity. The ratio of starch and sorbitol was 70:30, and the added acid agent replaced 6% of the plasticizer; meanwhile, the thermoplastic starch (TPS)–PLA blend proportion was 70:30 considering the modified TPS. The mixtures were obtained in a torque rheometer at 50 rpm for 10 min at 150 °C. The organic acids facilitated interactions between TPS and PLA. Although TPS and PLA are not miscible, PLA uniformly dispersed into the starch matrix. Furthermore, a reduction in the surface polarity was achieved, which enabled the wettability to reach values close to those of neat PLA (TPS–L-PLA increased by 55% compared to TPS–PLA). The rheological results showed a modulus similar to that of TPS. In general, there were transitions from elastic to viscous, in which the viscous phase predominated. The first and second-order thermal transitions did not show significant changes. The structural affinity of lactic acid with biopolymers (TPS–L-PLA) allowed a greater interaction and was corroborated with the mechanical properties, resulting in a greater resistance with respect to pure TPS and blended TPS–PLA (28.9%). These results are particularly relevant for the packaging industry.

Cross-linked-substituted (esterified/etherified) starch derivatives as aqueous heavy metal ion adsorbent: a review

Starch is a biopolymer with outstanding economic and environmentally friendly attributes which has driven technological innovations to enhance its applications in food and non-food industries. Starch is constituted by O-H groups with valency and electronic characteristics that can initiate adsorption of aqueous heavy metal ions (AHMIs). However, this can be enhanced using various modification sequences. A common procedure is the cross-linking and substitution of the O-H groups via esterification and/or etherification reactions to produce starch derivative adsorbents (SDAs) with improved structural and functional properties for adsorption of AHMIs. The efficiency of SDAs developed using these procedures depends on the botanical source of the native starch base, porosity and structural stability of the derivative (i.e. degree of cross-linking), substituted functional group(s), degree of substitution and the steric/conformation effects of the substituted groups. Many works have been done to optimize these factors, and this review highlighted some of the tailored procedures and the results obtained.

Starch nanoparticles modified with styrene oxide and their use as Pickering stabilizers

Starch nanoparticles (SNP) were modified with styrene oxide (STO) and successfully used as Pickering stabilizers in miniemulsion and emulsion polymerization.

Special Issue “Renewable Polymers: Processing and Chemical Modifications”

The use of renewable resources for polymer production is receiving substantial and ever-growing interest [...]

Comparative Study of the Performances of Al(OH)3 and BaSO4 in Ultrafine Powder Coatings

Ultrafine powder coatings are one of the development directions in the powder coating industry, as they can achieve thin coatings with good leveling and high surface smoothness comparable to liquid coatings. Compared to regular coatings, they experience a higher sensitivity to any incompatibilities, e.g., filler from coating components. The properties of fillers play a great role in the performance of coating films. Aluminum trihydrate (Al(OH)3) is a well-known filler in solvent-based coatings and other polymer industries. To study and evaluate the performances of Al(OH)3 in ultrafine powder coatings, a popular filler, barium sulfate (BaSO4) is used for comparison. Both fillers are added in ultrafine powder coatings based on two of the most commonly used resin systems (polyester-epoxy and polyester). The differences of physical and chemical properties between both fillers have significant influences on several properties of powder paints and coating films. The polar groups (hydrogen bond) in Al(OH)3 result in the strong interaction between inorganic filler and organic polymer matrix, thus decreasing the molecular network mobility and influencing the chain formation, which is verified by differential scanning calorimetric (DSC). The bed expansion ratio (BERs) of powder paints incorporated with Al(OH)3 are much higher than those with BaSO4, which indicate more uniform gas-solid contact during the spraying process. Samples with Al(OH)3 exhibit much lower specular gloss at 60°, which are expected to achieve remarkable matting effects. Superior corrosion resistances can be observed for almost all the coated panels incorporated with Al(OH)3 in contrast to those with BaSO4. Other aspects are slightly influenced by the difference between the two fillers, such as the angle of repose values (AORs) of powder paints, the impact resistance and flexibility of coating films.

Hydroxymethylation-Modified Lignin and Its Effectiveness as a Filler in Rubber Composites

Kraft lignin was modified by using hydroxymethylation to enhance the compatibility between rubber based on a blend of natural rubber/polybutadiene rubber (NR/BR) and lignin. To confirm this modification, the resultant hydroxymethylated kraft lignin (HMKL) was characterized using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. It was then incorporated into rubber composites and compared with unmodified rubber. All rubber composites were investigated in terms of rheology, mechanical properties, aging, thermal properties, and morphology. The results show that the HMKL influenced the mechanical properties (tensile properties, hardness, and compression set) of NR/BR composites compared to unmodified lignin. Further evidence also revealed better dispersion and good interaction between the HMKL and the rubber matrix. Based on its performance in NR/BR composites, hydroxymethylated lignin can be used as a filler in the rubber industry.