Strengthening of polyacrylonitrile (PAN) fiber networks with polyamide epichlorohydrin (PAE) resin

Highly Strong and Damage-Resistant Natural Rubber Membrane via Self-Assembly and Construction of Double Network

Natural rubber latex (NRL) is commonly employed to manufacture medical protective appliances. However, the characteristics of weakness and fragility of NRL membranes limit their further application. To achieve excellent strength and damage-resistance of the rubber membrane, this work reported a facile core-shell structure construction strategy via self-assembly with modified sodium lignosulfonate (MSLS) and NRL to create a tough membrane. The double network can be formed after introducing polyamide epichlorohydrin resin (PAE) into the NRL membrane. Specifically, the first robust MSLS-PAE network can break in advance to dissipate applied energy, thereby achieving high fracture energy and tensile strength of ~111.51 kJ m^-2 and ~37 MPa, respectively, which overtakes numerous soft materials. This work facilitates more studies on latex/lignin-based products with high performance and good stability for the functional application of biopolymer.

Improving Mechanical Strength and Water Barrier Properties of Pulp Molded Product by Wet-End Added Polyamide Epichlorohydrin/Cationic Starch

As desirable food packaging materials, pulp molded products have attracted great attention from both academia and industry. To endow the products with high mechanical strength and water barrier properties by low-cost wet-end additives to broaden their application fields, polyamide epichlorohydrin (PAE) or/and cationic starch (CS) were added to the pulp slurry after the addition of oil- and water-proof agents. Results showed that the optimal pulp molded product was obtained at a PAE and CS content of 1.0 and 0.6%, respectively. The resulting product had a dry strength of 24.4 kN/m, a wet strength of 4.22 kN/m, and a water absorption of 51.5%. The addition of CS was beneficial to the properties of the PAE wet-end added product due to the formation of hydrogen bonding with cellulose fibers and PAE, which also led to a decreased PAE dosage for health concern as food packaging materials. Finally, the PAE/CS wet-end added pulp molded product was applied for orange fresh-keeping in the fridge. The product displayed much more shape stability and lower weight increase in comparison with that of the product without the addition of PAE and CS. This indicated the great application prospects of our designed pulp molded product as a fruit freprospectssh-keeping packaging material.

Sustainable Barrier System via Self-Assembly of Colloidal Montmorillonite and Cross-linking Resins on Nanocellulose Interfaces

Cellulose nanofibrils (CNFs) are able to form strong oxygen-barrier films suitable for food packaging but lack the needed water resistance in comparison to plastics. Desired water barrier quality can be achieved by applying mineral additives within the nanofibrils network. In current contribution, a sustainable hybrid system with an improved water barrier function is proposed by incorporating colloidal montmorillonite nanoclay (MMT) and two cross-linking agents, namely, polyamidoamine epichlorohydrin (PAE) and Acrodur thermoset acrylic resin (ACR) into CNF interfaces. Continuous matrices were produced via evaporation-induced self-assembly of colloidal building blocks followed by appropriate heat-curing regime to impart internal cross-linking. The development of chromophore functionalities and formation of ester motifs on the hybrid matrix (with no evidence of degradation) were detected by Fourier-transform infrared (FT-IR) spectroscopy. Intercalation of clay, solely, reduced the water vapor transmission rate (WVTR) to some extent; however, a more remarkable decline (by 60%) was observed upon the curing and cross-linking process. In fact, combination of clay platelets and cross-linkers contributed to a denser film structure and restricted water passage. Also, an excellent resistance to oil and grease was observed in all the studied films (Kit number of 11). A reduction in tensile strengths and resistance to cracking at fold was noted and ascribed to MMT interference in cellulose interchain hydrogen bonds. This however was counteracted by the introduction of cross-linkers, apparently by aiding stress transfer within the matrix. MMT imparted a limited elevation in the surface free energy, pointing out to an induced hydrophilicity; however, surface energy values declined markedly upon using cross-linkers. Finally, thermal stability of hybrids was adversely affected, compared to neat CNFs. Our study suggests the potential utilization of low-cost, sustainable biobarrier films for application in food/drug packaging, where low permeation of moisture is highly desirable.