Quantification of the maleic anhydride grafted onto polypropylene by chemical and viscosimetric titrations, and FTIR spectroscopy

Enhancement and Compatibilization of Waste-Sourced Biocomposites Through Elastomer Blending and Matrix Grafting Modification

A novel elastomer-modified multicomponent, multiphase waste-sourced biocomposites, was prepared for converting waste biomass and plastic into value-added products. The effects of blending elastomer-olefin block copolymer (OBC) and maleic anhydride (MAH), and divinylbenzene (DVB) co-grafting of recycled polypropylene (rPP) matrix on the adhesion interface, structure, and properties of high wood flour-filled (60 wt.%) composites were thoroughly investigated. The results indicated that DVB introduced branched structures into the polymer matrix molecular chain and increased the MAH grafting rate. Co-grafting rPP/OBC blends enhanced the interfacial adhesion among rPP, OBC, and wood flour. Additionally, MAH-grafted OBC was prone to encapsulating rigid wood flour, thereby forming an embedded structure. Notably, the tensile modulus and impact strength of the final three-component composites increased by 60% and 125%, respectively, compared with the unmodified composites. Additionally, dynamic mechanical analysis revealed that DVB-induced branching promoted the formation of microvoids in the OBC shell layer surrounding the wood, which in turn induced significant plastic deformation in the polymer matrix. This work offers a facile and efficient method for preparing high-toughness, high-stiffness, and low-cost waste PP-based composites for automotive interiors, and indoor and outdoor decoration.

Investigating the Reactive Reinforcement Ability of Maleic Anhydride-Modified Cellulose Nanocrystals via In-Situ Emulsion Polymerization

CNC-based nanocomposites have gained substantial interest because of their enhanced thermomechanical properties for high-end engineering applications. The chemical modification of CNCs expands their applicability, making them suitable for use in hydrophobic polymer matrices. The current study investigates the reactive reinforcing ability of maleic anhydride-modified cellulose nanocrystals during the in situ polymerization of a vinyl monomer, i.e., styrene. Highly crystalline nanocellulose (CNCBG) was isolated from Lagenaria siceraria (Bottle gourd) peels via Hydrochloric acid, which was further modified to synthesize maleic anhydride-modified cellulose nanocrystals (MACNCBG) and characterized employing various techniques. MACNCBG exhibited higher suspension stability than CNCBG due to the introduction of carboxyl groups. Furthermore, polystyrene-based nanocomposites of 3 and 5 wt % filler loading were prepared, respectively. While PSMACNCBG (5 wt %) displayed a premature failure, PSMACNCBG (3 wt %) demonstrated enhanced mechanical properties compared to PSCNCBG (3 wt %) and PS. At the same filler loading, MACNCBG demonstrated a more remarkable reinforcing ability than CNCBG, owing to its reactive tendency. The appearance of a new peak between 3000-2800 cm-1 corresponds to the C-H stretching of the formed C-C bond (between C=C of MACNCBG and benzal carbon of PS) in the FTIR spectra, confirming the reactive nature of MACNCBG.

Characterizing graft distribution in maleic anhydride grafted polyethylene - GPC with IR and UV-detection

As commodity plastics, polyolefins are in high demand and used in innumerable applications. An important reason for their success-story is their high versatility in terms of applications. The application range of polyolefins was significantly extended through the development of functionalization. A common functionalization for improving the compatibility of polyolefins with more polar polymers and surfaces is grafting with maleic anhydride. While maleic anhydride-grafted polyolefins have found widespread application, methods for their characterization remain rudimentary compared to the developments seen in the structural characterization of polyolefins in general. Herein, we propose two new approaches for determining the degree of functionalization as a function of the molar mass of maleic anhydride grafted polyolefins. On the one hand, the latest generation bandpass filter-based IR detectors are shown to be sensitive to the carbonyl moiety of MAH. After optimization of analysis conditions, the relation between MAH content and molar mass could be unraveled in an easily applicable approach suitable for routine analysis. On the other hand, the high reactivity of MAH was leveraged in a tagging approach. By imidization with a UV chromophore, MAH distribution can be assessed by HT-GPC-UV with significantly higher sensitivity compared to HT-GPC-IR.

One-Step Bulk-Suspension Polymerization of Polyethylene Glycol-Based Copolymer Microspheres for Phase Change Textiles

The paper presents a feasible strategy through one-step bulk-suspension polymerization, grafting PEG onto an in situ synthesized copolymer. In more detail, PEG was grafted onto a homemade polystyrene/maleic anhydride copolymer (SMA) via bulk-suspension polymerization with poly(vinyl alcohol) as a suspending agent. According to the optimal reaction conditions, the grafting rate of PEG was 56.2% through chemical titration experiments. At the same time, the quantitative relationship between the grafting rate and enthalpy was demonstrated for the first time in a PEG-based solid-solid phase change material (S-SPCM). Morphology observation revealed that the obtained S-SPCM is made up of white microspheres of approximately 100-150 μm. The powdery product polystyrene/maleic anhydride grafted polyethylene glycol (SMA-g-PEG) obtained through bulk-suspension polymerization endowed that the whole product could be used directly as a phase change material without postprocessing. The melting enthalpy and crystallization enthalpy of SMA-g-PEG were 79.3 J/g and 76.9 J/g, respectively. Based on the effective fixed load of PEG, the macrostructure of SMA-g-PEG was almost unchanged at 70 °C compared with the macrostructures at 20 °C, and the latent heat of SMA-g-PEG was decreased slightly after 1000 thermal cycles. Overall, the obtained SMA-g-PEG can be used as a filler in insulation materials and composited with fibers to obtain phase change thermoregulated smart textiles.

Thermoreversible Cross-Linked Rubber Prepared via Melt Blending and Its Nanocomposites

A covalent adaptable network based on the thermoreversible cross-linking of an ethylene-propylene rubber through Diels-Alder (DA) reaction was prepared for the first time through melt blending as an environmental-friendly alternative to traditional synthesis in organic solvents. Functionalization of the rubber with furan groups was performed in a melt blender and subsequently mixed with different amounts of bismaleimide in a microextruder. Cross-linking was confirmed by FT-IR spectroscopy and insolubility at room temperature, while its thermoreversible character was confirmed by a solubility test at 110 °C and by remolding via hot-pressing. Mechanical and thermomechanical properties of the obtained rubbers showed potential to compete with conventionally cross-linked elastomers, with stiffness in the range 1-1.7 MPa and strain at break in the range 200-500%, while allowing recycling via a simple melt processing step. Nanocomposites based on the thermoreversible rubber were prepared with reduced graphene oxide (rGO), showing significantly increasing stiffness up to ca. 8 MPa, ∼2-fold increased strength, and thermal conductivity up to ∼0.5 W/(m K). Results in this paper may open for industrially viable and sustainable applications of thermoreversible elastomers.

Cross-Linking of Polypropylene with Thiophene and Imidazole

In this work, two novel routes to synthesis cross-linked polypropylene (PP) are introduced by using two different precursors (2-thiophenemethyl amine (TMA) and 1-(3 aminopropyl) imidazole (API)), both cross-linked with 1,1′-(methylenedi-4,1-phenylene) bismaleimide (BM) at two different annealing temperature values (T = 50 °C and T = 150 °C). Both Diels–Alder (DA) and Michael addition reactions were successfully performed with TMA and API, respectively, albeit with different reactivity. Imidazole clearly shows a higher reactivity compared to thiophene. In addition, an increase in annealing temperature leads to a higher degree of cross-linking. The highest degree of cross-linking was obtained by the imidazole product after annealing at 150 °C (IMG1A150) as evident from the highest complex viscosity (|η*|) value of IMG1A150. A difference in rheology and thermal properties between the imidazole and thiophene cross-linked products was also observed. However, both products have superior melt properties and thermal stability compared with the starting material. They show processability at high temperatures. The melt flow behavior and de-cross-linking at higher temperatures can be tuned depending on the choice of imidazole or thiophene. This study shows an advance on the cross-linked PP processing and its product performances for further application on the commercial scale.

Cassava and banana starch modified with maleic anhydride-poly (ethylene glycol) methyl ether (Ma-mPEG): A comparative study of their physicochemical properties as coatings

This study proposes a simple route to obtain starch grafted copolymers from cassava and banana starches chemically modified with amphiphilic maleic anhydride-poly (ethylene glycol) methyl ether (Ma-mPEG). The starches were extracted from cassava (StC) and banana (StB) pulp and characterized by FTIR spectroscopy, amylose content, scanning electron microscope (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and average molecular weight. Starches were chemically modified with amphiphilic Ma-mPEG in three mass ratios 1:1, 1:2 and 1:3. Thermal behavior and interactions of Ma-mPEG/starch in the St-g-(Ma-mPEG) copolymers were studied by DSC and TGA. The T_g values showed a higher plasticizer effect in the copolymers obtained from StC. Films were formed from StC-g-(Ma-mPEG) and StB-g-(Ma-mPEG) copolymers, thermal and morphological properties were studied. An increase in the mass ratios of Ma-mPEG and the absence of the glycerol in the formulations formed homogeneous films. StC-g-(Ma-mPEG) 1:3 with 2% concentration showed a potential use as coating in strawberries, presenting a lower weight loss (15.5 ± 5.7%) than the control sample (18.6 ± 3.3%).

Performance of concrete containing recycled masks used for personal protection during coronavirus pandemic

After the coronavirus outbreak, a tremendous amount of personal protective equipment has been produced and used by the health service and every human. Proper medical waste management becomes an important problem, which must be solved with a minimal environmental impact. The presented manuscript introduces the recycling process, during which personal protection masks are transformed into polypropylene fibers being an addition to a concrete mixture. The designed recycling procedure provides the entire disinfection of probably contaminated medical wastes, is straightforward, and potentially enables one to modify the properties of the final product. The applied dosage referred to 1 mask per 1 L of concrete. The final product of face masks processing was studied using Fourier-transform infrared spectroscopy, thermogravimetric analysis, surface free energy, contact angle measurements, and melt flow index. The analysis indicated that polypropylene is its main component. Two concrete mixtures were composed, i.e., with the addition of processed masks and the reference one. The following properties were determined to compare the modified concrete with the reference one: compressive and tensile strength, frost resistance, water transport properties, resistance to high temperature. The obtained results indicated that the addition of processed masks slightly increased the compressive strength (by about 5%) and decreased the tensile strength (by about 3%). Simultaneously, it was reported that the addition did not affect material properties related to concrete durability as frost resistance, water permeability, and fire performance. The results evinced, that the addition of processed facemasks into concrete did not deteriorate its properties. Therefore, it is a possible way of the protective masks processing and reusing with the high recycling capacity. Further study should be conducted to optimize the dosing and to modify the properties of PP strings to improve hardened concrete properties.

Cross-Linking of Polypropylene via the Diels-Alder Reaction

In this work, the possibility of preparing cross-linked polypropylene (PP) via Diels−Alder (DA) chemistry is explored. The overall strategy involves reaction of maleated polypropylene (the starting material), furfuryl amine (FFA), and bismaleimide (BM) as the cross-linking agent. The occurrence of reversible cross-linking was studied by checking the presence of relevant peaks in FTIR spectra, i.e., CH out-of-plane bending vibrations of the furan ring’s peak (γCH) at an absorption band of 730−734 cm−1, CH=CH of the BM aromatic ring’s stretching vibrations (υCH=CH) at an absorption band of 1510 cm−1, and the DA adduct (C-O-C, δDAring) at an absorption band of 1186 cm−1. In agreement with the spectroscopic characterization, the presence of a cross-linked network is also confirmed by rheology, namely the higher storage modulus (G′) compared with loss modulus (G″) value (G′ >> G″), as obtained via temperature sweep. Both the maleic anhydride (MA) content as well as the annealing temperature (50 °C and 120 °C) favor the DA reaction, while only partial de-cross-linking (retro DA) is observed at the higher temperature range of 150−200 °C. In addition, the products show higher mechanical robustness and thermal stability compared to the starting material.

Surface Defects of TPO Injected Foam Parts for Automotive Applications

Benefits of reduced vehicle weight can have an important environmental impact since there is a 6 to 8% improvement in fuel efficiency for every 10% in weight reduction. In this work, foaming technology is used to produce injection molded TPO parts (thermoplastic olefin compounds) for the automotive industry with a minimum of 20% weight reduction while retaining a glossy surface quality. It was found by Guo et al. (2006, 2007) that the best strategy to raise the surface quality was to decrease the shot size, the cycling time and the temperature of the injected melt. However, the targeted objective of a minimum of 20% weight reduction was not achieved in these preliminary experiments. Therefore, in this work a blend of TPO and maleic anhydride modified polypropylene (PP-g-MA) was used in order to promote TPO foamability and improve the surface quality of injected parts. Under these conditions, we managed to produce injected molded TPO samples with a 24% weight reduction and good surface quality. Moreover, we investigated the effect of PP-g-MA in the TPO system by performing rheological measurements and photoacoustic Fourier transform infrared (PA-FTIR) analysis to characterize the PP-g-MA physico-chemical interactions with TPO.

Experimental Investigation of Polypropylene Composite Drawn Fibers with Talc, Wollastonite, Attapulgite and Single-Wall Carbon Nanotubes

Isotactic polypropylene (PP) composite drawn fibers were prepared using melt extrusion and high-temperature solid-state drawing at a draw ratio of 7. Five different fillers were used as reinforcement agents (microtalc, ultrafine talc, wollastonite, attapulgite and single-wall carbon nanotubes). In all the prepared samples, antioxidant was added, while all samples were prepared with and without using PP grafted with maleic anhydride as compatibilizer. Material characterization was performed by tensile tests, differential scanning calorimetry, thermogravimetric analysis and Fourier transform infrared spectroscopy. Attapulgite composite fibers exhibited poor results in terms of tensile strength and thermal stability. The use of ultrafine talc particles yields better results, in terms of thermal stability and tensile strength, compared to microtalc. Better results were observed using needle-like fillers, such as wollastonite and single-wall carbon nanotubes, since, as was previously observed, high aspect ratio particles tend to align during the drawing process and, thus, contribute to a more symmetrical distribution of stresses. Competitive and synergistic effects were recognized to occur among the additives and fillers, such as the antioxidant effect being enhanced by the addition of the compatibilizer, while the antioxidant itself acts as a compatibilizing agent.

Self-Stable Precipitation Polymerization Molecular Entanglement Effect and Molecular Weight Simulations and Experiments

In this paper, we developed a reactive molecular dynamics (RMD) scheme to simulate the Self-Stable Precipitation (SP) polymerization of 1-pentene and cyclopentene (C5) with maleic anhydride (MAn) in an all-atom resolution. We studied the chain propagation mechanism by tracking the changes in molecular conformation and analyzing end-to-end distance and radius of gyration. The results show that the main reason of chain termination in the reaction process was due to intramolecular cyclic entanglement, which made the active center wrapped in the center of the globular chain. After conducting the experiment in the same condition with the simulation, we found that the distribution trend and peak value of the molecular-weight-distribution curve in the simulation were consistent with experimental results. The simulated number average molecular weight (Mn) and weight average molecular weight (Mw) were in good agreement with the experiment. Moreover, the simulated molecular polydispersity index (PDI) for cyclopentene reaction with maleic anhydride was accurate, differing by 0.04 from the experimental value. These show that this model is suitable for C5–maleic anhydride self-stable precipitation polymerization and is expected to be used as a molecular weight prediction tool for other maleic anhydride self-stable precipitation polymerization system.

Upgrading Recycled Polypropylene from Textile Wastes in Wood Plastic Composites with Short Hemp Fiber

This research reports the manufacturing and characterization of green composites made from recycled polypropylene obtained from the remnants of polypropylene non-woven fabrics used in the textile industry and further reinforced with short hemp fibers (SHFs). To improve the interaction of the reinforcing fibers with the recycled polymeric matrix, two types of compatibilizing agents (maleic anhydride grafted, PP-g-MA, and maleinized linseed oil, MLO) were added during melt-processing, the percentage of which had to remain constant concerning the amount of fiber loading to ensure complete reactivity. Standardized test specimens were obtained by injection molding. The composites were characterized by mechanical (tensile, impact, and hardness), thermal (DSC, TGA), thermomechanical, FTIR, and FESEM microscopy tests. In addition, color and water uptake properties were also analyzed. The results show that the addition of PP-g-MA to rPP was satisfactory, thus improving the fiber-matrix interaction, resulting in a marked reinforcing effect of the hemp fibers in the recycled PP matrix, which can be reflected in the increased stiffness of the samples. In parallel to the compatibilizing effect, a plasticizing effect was obtained by incorporating MLO, causing a decrease in the glass transition temperature of the composites by approximately 6 °C and an increase in ductility compared to the unfilled recycled polypropylene samples.

Protective Low-Density Polyethylene Residues from Prepreg for the Development of New Nanocomposites with Montmorillonite: Recycling and Characterization

A sustainable alternative to the destination of polyethylene (PE) residue from the prepreg package was established. This work intends to develop nanocomposites for packaging containing neat low-density polyethylene (LDPE), a compatibilizer agent (maleic anhydride grafted-LDPE, LDPE-g-MA), recycled LDPE obtained from the protective films of prepreg (rLDPE) and montmorillonite (MMT). The rLDPE, from the prepreg shield, has a primary role during the transport and storage of prepreg, which can be composed of epoxy resin and carbon fiber or glass fiber. However, this rLDPE is withdrawn and discarded, besides, it is estimated that tons of this material are discarded monthly by the company Alltec Materiais Compostos Ltd. (São José dos Campos-SP, Brazil). Due to several factors, including the lack of technology for recycling, the majority of this material is incinerated. In this context, this work presents a technical and ecologically viable alternative for the use of this discarded material. Nanocomposites of LDPE/rLDPE blends and montmorillonite (MMT) with different contents (0.0, 1.0, and 3.0 wt%) and with the addition of compatibilizer agent (LDPE-g-MA) were prepared by extrusion process. Test specimens were obtained by hot pressing in a hydropneumatic press followed by die-cutting. The nanocomposites produced using rLDPE presented good mechanical, thermal, and morphological properties, being the ideal concentration of 1 wt% MMT. Thus, the results obtained confirmed the viability of recycling LDPE from the prepreg package which contributes to the reduction of waste and the use of this material in technological applications.

Synthesis of Propylene-co-Styrenic Monomer Copolymers via Arylation of Chlorinated PP and Their Compatibilization for PP/PS Blend

A series of propylene-co-styrenic monomer copolymers were synthesized using the Friedel–Crafts alkylation reaction between chlorinated PP and substituted benzene, and the effects of these copolymers on a PP/PS (80/20) blend were investigated by using the impact test, morphology observation, thermo- and dynamic mechanical analysis, and rheology measurements. The results showed that the compatibilization efficiency varied as the variation of the substitute on the benzene ring of the styrenic monomer unit was incorporated in the PP chain in an order of methyl > ethyl > methoxyl. The copolymers bearing a crystalline isotactic polypropylene chain sequence and rubbery propylene-co-styrene-like unit chain segments may prepossess imaginable applications, giving an example for the synthesis and applications of PP-based copolymers, initiating a new way to broaden the polyolefin-based material family.

Synthesis and Characterization of Lignin Hydrogels for Potential Applications as Drug Eluting Antimicrobial Coatings for Medical Materials

Lignin is the second most abundant biopolymer on the planet. It is a biocompatible, cheap, environmentally friendly and readily accessible material. It has been reported that these biomacromolecules have antimicrobial activities. Consequently, lignin (LIG) has the potential to be used for biomedical applications. In the present work, a simple method to prepare lignin-based hydrogels is described. The hydrogels were prepared by combining LIG with poly(ethylene glycol) and poly(methyl vinyl ether-co-maleic acid) through an esterification reaction. The synthesis took place in the solid state and can be accelerated significantly (24 vs 1 h) by the use of microwave (MW) radiation. The prepared hydrogels were characterized by evaluation of their swelling capacities and with the use of infrared spectroscopy/solid-state nuclear magnetic resonance. The prepared hydrogels showed LIG contents ranging between 40% and 24% and water uptake capabilities up to 500%. Furthermore, the hydrophobic nature of LIG facilitated loading of a model hydrophobic drug (curcumin). The hydrogels were capable of sustaining the delivery of this compound for up to 4 days. Finally, the materials demonstrated logarithmic reductions in adherence of Staphylococcus aureus and Proteus mirabilis of up to 5.0 relative to the commonly employed medical material poly(vinyl chloride) (PVC).

Hydrogels based on poly(methyl vinyl ether-co-maleic acid) and Tween 85 for sustained delivery of hydrophobic drugs

Hydrogels based on poly(methyl vinyl ether-co-maleic acid) and Tween 85 were prepared for hydrophobic drug delivery. The hydrogels were synthesized following a simple procedure carried out in solid state. The process did not require the use of any solvent and, as it is based on an esterification reaction, no toxic by-products were obtained. The resulting hydrogels contained Tween 85 inside the structure and due to the amphiphilic nature of this compound, hydrophobic domains within the hydrogel structure were formed. The obtained hydrogels showed good swelling capacities ranging from 100% to 600%. The esterification reaction that took place between poly(methyl vinyl ether-co-maleic acid) and Tween 85 was confirmed by infrared spectroscopy. Hydrogels were loaded with a hydrophobic drug model, Curcumin (CUR), showing that the hydrogels were able to retain up to 36 mg of CUR per g of hydrogel. Additionally, the synthesized hydrogels provided in vitro sustained CUR release over periods of up to 30 days. Finally, and due to the mucoadhesive nature of the prepared materials, one of the hydrogels was tested in vitro as an oral drug delivery system. For this purpose, the selected material was milled into microparticles (45-90 µm diameter). The release of CUR from the microparticles was evaluated under simulated gastric and intestinal conditions. The microparticles were able to release their cargos in 7 h. However, further work is required to optimize this system for oral drug delivery applications.

Synthesis and characterization of hyaluronic acid hydrogels crosslinked using a solvent-free process for potential biomedical applications

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A single step solid state crosslinking reaction has been developed to obtain hyaluronic acid hydrogels.

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The use of microwave radiation reduces significantly the crosslinking time.

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The synthesized materials allowed sustained release of a model molecule (methylene blue) for a period of up to 2 days.

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The material can be used to prepare micro-engineered devices such as microneedles through a micromoulding process.

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The resulting hydrogels showed anti-infective and bacteriostatic properties.

Hyaluronic acid (HA) is a natural linear polysaccharide that has been used extensively in the biomedical field as it is a biocompatible, biodegradable, nontoxic and non-immunogenic polymer with high water affinity. Besides, the presence of multiple acid and hydroxyl groups in the HA molecule makes it an ideal candidate for chemical modification. The present paper describes the synthesis and characterization of HA-based hydrogels. For this purpose, aqueous mixtures containing 5% (w/w) of HA and different concentrations of Gantrez S97 (GAN) (1, 3 and 5% w/w) were used to prepare HA-based hydrogels. The mixtures were dried and the hydrogels were obtained after heating the solid material at 80 °C for 24 h. GAN is the acid form of an methylvinylether and maleic anhydride copolymer and contains multiple acid groups that can form ester bonds when reacting with the multiple hydroxyl groups present in HA chains. The method described here present potential to be applied for the preparation of HA-based biomaterials with a defined form as the crosslinking reaction between HA and the crosslinker takes place in solid phase. Besides, the method can be considered an environmental-friendly process as no organic solvents or potentially toxic substances were used. The esterification reaction was confirmed by infrared spectroscopy and dynamic scanning calorimetry measurements. The loading and release capabilities of the hydrogels were evaluating by using methylene blue (MB) as a model molecule. The hydrogels showed a high affinity for MB showing loadings up to 0.35 mg MB per mg of hydrogel. Moreover, the hydrogels were capable of sustaining the MB release over two days. The use of microwave radiation was evaluated to reduce the crosslinking time from 24 h to 1 h, but this procedure needs to be optimized in future studies. As the crosslinking procedure takes place in solid state, the HA/GAN hydrogels were used to prepare micro-engineered device, microneedle arrays. Finally, the antimicrobial properties of the hydrogels were evaluated. The results showed that the hydrogels presented anti-infective properties.

Development and Characterization of Polyurethane and Acrylonitrile Butadiene Styrene and their Compatibilized Blends

Novel blends of polyurethane and acrylonitrile butadiene styrene, in both forms, compatibilized and uncompatibilized, were developed by melt reactive extrusion technique in a twin-screw extruder. This technique involved acrylonitrile butadiene styrene grafted maleic anhydride (ABS-g-MAH) as the compatibilizer. The objective of this study was to enhance the rigidity characteristics of polyurethane by melt blending acrylonitrile butadiene styrene into polyurethane using a compatibilizer. The blends were analyzed using different techniques to confirm the occurrence of compatibilization reaction between the parent polymers and the compatibilizer. It is observed that addition of the compatibilizer has improved the mechanical properties of the resultant blends.

Quantification of anhydride groups in anhydride-based epoxy hardeners by reaction headspace gas chromatography

We demonstrate a reaction headspace gas chromatographic method for quantifying anhydride groups in anhydride-based epoxy hardeners. In this method, the conversion process of anhydride groups can be realized by two steps. In the first step, anhydride groups in anhydride-based epoxy hardeners completely reacted with water to form carboxyl groups. In the second step, the carboxyl groups reacted with sodium bicarbonate solution in a closed sample vial. After the complete reaction between the carboxyl groups and sodium bicarbonate, the CO₂ formed from this reaction was then measured by headspace gas chromatography. The data showed that the reaction in the closed headspace vial can be completed in 15 min at 55°C, the relative standard deviation of the reaction headspace gas chromatography method in the precision test was less than 3.94%, the relative differences between the new method and a reference method were no more than 9.38%. The present reaction method is automated, efficient and can be a reliable tool for quantifying the anhydride groups in anhydride-based epoxy hardeners and related research.

Photodegradation behavior and mechanism of poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) random copolymers: correlation with copolymer composition

Norrish type I and II mechanisms occurred in PETG copolymers. The inherent photostability of PETG decreased with increasing CHDM content. The higher CHDM content resulted in the higher crosslinking degree.

Anti-Aging Performance of Cardanol Grafted onto Polypropylene by Reactive Extrusion

The cardanol grafted onto polypropylene (CAPP) was prepared by reactive extrusion with polypropylene (PP) and natural renewable cardanol, which could improve the inherent defects of PP such as chemical inertness and hydrophobicity. Moreover, the cardanol grafted onto PP could resolve the degradation of PP during the process of reactive extrusion, storage and application. In this paper, the yield strength, tensile strength, elongation at break of modified and unmodified PPs were tested during the aging process. A possible aging mechanim of PP and anti-aging mechanism of cardanol grafted onto PP were proposed. Results showed that the initiator dicumyl peroxide caused the degradation of PP chains during the aging processing. After being aged for 24 h, the yield strength CAPP0 decreased from 28 MPa to 15 MPa and the elongation at break reduced by 795%. CAPPs possessed outstanding anti-aging performance owing to the cross-linking and entanglement of the side chains of cardanol grafted onto PP. The yield strength, tensile strength and the elongation at break of CAPP5 changed lightly even when it was in long-term irradiation for 480 h. The CAPPs had better anti-aging properties than the mixture of PP and 5% of cardanol. CAPP containing 3% of cardanol could effectively prevent the degradation of the main chain polypropylene.

Grafting of maleic anhydride on polypropylene by reactive extrusion: effect of maleic anhydride and peroxide concentrations on reaction yield and products characteristics

A series of polypropylenes (PPs) grafted with maleic anhydride (MA), prepared by reactive extrusion in a twin screw extruder with different contents of peroxide and MA, was characterized. For each sample, the amount of grafted MA, the molecular weight distribution, the viscoelastic properties in small amplitude oscillatory shear and the transition temperatures and enthalpies were measured. The respective influence of initial MA and peroxide concentrations on these parameters was characterized. In particular, it was shown that the rheological properties are only controlled by the molecular weight, whatever the way it has been obtained, by varying either MA content or peroxide concentration. Moreover, it is clearly shown that the presence of MA tends to enhance the PP degradation due to the peroxide.