Fecha de publicación: -- Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE The image illustrates a graphical scheme of the synthesis pathways and characteristics of modified corn starch (Carbamoylethylated Starch), comparing its physical and chemical performance as an adhesive in agricultural fiber composites with conventional materials.

Synthesis Pathways: It depicts the chemical reaction between corn starch and acrylamide in the presence of sodium hydroxide or sulfate to produce the modified starch via different pathways (acidic and basic).
Mechanical Performance: The graphs compare key properties—such as modulus of rupture (MOR), water resistance/thickness swelling (TS), and formaldehyde emission (FF) among System (A), System (B), and native starch.
Environmental Enhancement: The scheme highlights the reduction of harmful emissions and the improvement of adhesion efficiency in bio-based materials as sustainable alternatives to petrochemical resins.


ABSTRACT
This study deals with integrating nitrogen- and chlorine-functionalized starch into urea-formaldehyde (UF) adhesives which offers a sustainable solution to formaldehyde emissions in rice straw composites. This research identifies the optimal synthesis parameters for acrylamide-modified starch (CES) and its chlorinated counterpart (CES-Cl, with the extent of functionalization evaluated based on the corresponding nitrogen and chlorine contents, reaching 3.68% N and 3.3% Cl, respectively. The resulting functionalized starches provided robust additives for developing low-formaldehyde-emission wood adhesives. When integrated into commercial UF systems at a 5% solid weight concentration, these derivatives significantly outperformed unmodified starch. Specifically, CES and CES-Cl reduced free formaldehyde emissions by up to 58.9 and 54%, respectively. Performance metrics showed a marked improvement; bond strength increased from 7.37 ± 0.14 MPa to 8.99 ± 0.22 MPa, while gel times were accelerated from 52 ± 2.2 to 41 ± 1.3 seconds. Thermal analysis (DSC/TGA) confirmed superior stability and curing behavior on rice straw fibers. Final wood composite testing revealed that moderate N/Cl levels (1.93% N/1.44% Cl) achieved optimal mechanical properties, including a Modulus of Rupture (MOR) of 12.7 ± 0.64 MPa. Conversely, higher functional content (3.68% N/3.3% Cl) yielded a 55% ± 2.7% reduction in free formaldehyde and enhanced water resistance. This modification offers a sustainable, high-performance approach for reducing formaldehyde emissions in wood composites while utilizing renewable starch and agricultural rice straw waste.