Globally increasing environmental awareness and the possibility of increasing price and dwindling supply of traditional petroleum-based plastics have led to a breadth of research currently addressing environmentally friendly bioplastics as an alternative solution. In this context, hemicellulose, as the second richest polysaccharide, has attracted extensive attention due to its combination of such advantages as abundance, biodegradability, and renewability. Herein, in this review, the latest research progress in development of hemicellulose film with regard to application in the field of food packaging is presented with particular emphasis on various physical and chemical modification approaches aimed at performance improvement, primarily for enhancement of mechanical, barrier properties, and hydrophobicity that are essential to food packing materials. The development highlights of hemicellulose film substrate are outlined and research prospects in the field are described.

Polylactic acid (PLA) is one of the most productive biodegradable materials. Its bio-based source makes it truly carbon neutral. However, PLA is hard to crystallize as indicated by a low crystallization rate and a low crystallinity under conventional processing conditions, which limits its wider application. One of the most effective ways to enhance the crystallization ability of PLA is to add nucleating agents. In the context of increasing global environmental awareness and the decreasing reserves of traditional petroleum-based materials, biomass nucleating agents, compared with commonly used petroleum-based nucleating agents, have received widespread attention in recent years due to their abundance, biodegradability and renewability. This paper summarizes the research progress on biomass nucleating agents for regulating the crystallization behavior of polylactic acid. Examples of biomass nucleating agents include cellulose, hemicellulose, lignin, amino acid, cyclodextrins, starch, wood flour and natural plant fiber. Such green components from biomass for PLA are believed to be a promising solution for the development of a wholly green PLA-based system or composites.

Hemicellulose has shown great potential in food packaging due to its excellent biodegradability and low oxygen permeability. However, its strong hydrophilicity leads to poor moisture resistance and hinders its wide application. To address this issue, herein a ternary carboxylic acid, citric acid (CA), was incorporated into hemicellulose as esterifying agent to form a crosslinking structure via the esterification reaction. The CA-modified hemicellulose films showed an increased contact angle of 87.5° (vs. 40.5° for unmodified film), demonstrating that the hydrophobicity of hemicellulose had been improved significantly. In addition, the esterification/cross-linking modification enhanced oxygen barrier performance with oxygen permeability decreasing from 1053 (cm³ μm) (m² d kPa)⁻¹ to 1.8 (cm³ μm) (m² d kPa)⁻¹. Moreover, the tensile strength rose to a peak value and then fell back at higher CA content. Effect of CA addition on elongation at break exhibited an opposite trend. The modified hemicellulose films with 20% CA addition possessed the highest tensile strength and the lowest elongation at break. Morphology observation with scanning electron microscopy indicated that at CA content exceeding 20%, the modified films were dense with a smooth surface, illustrating the improvement of phase compatibility. A possible mechanism for esterification/cross-linking was proposed to elucidate the connection between CA addition and film performances.

Self-healing polyurethanes (PUs) represent a new type of functional material which are highly desirable for applications such as surface protection coatings and transparent films. However, it is still challenging to obtain self-repairable PUs with good mechanical properties and excellent optical properties. Herein, in view of molecular design, a self-healing thermoplastic polyurethane (TPU) was designed with polytetramethylene ether glycol (PTMEG) as the soft segment and aliphatic isocyanate (m-xylylene diisocyanate, XDI) and aliphatic disulfide (bis(2-hydroxyethyl)disulfide, HEDS) as the hard segment. The TPU exhibited widely tunable mechanical properties, i.e., tensile stress values of 3.51–8.12 MPa with elongation at break values of 825–1320%. The cooperation of dynamic disulfide bonds and hydrogen bonding endowed the TPU elastomer with self-healing capacity and a self-healing efficiency of about 39% at a moderate temperature. Both the amorphous phase structure and XDI chemical structure contributed to a colorless, transparent and anti-yellowing TPU film with nearly 97% transparency and long-term optical stability. The tough, colorless and transparent self-healable elastomers have wide applications in optical and protective fields, including in automotive laminated glass, flexible displays, printers, and photographic equipment cleaning scrapers.

Full biobased, water soluble and low cell cytotoxicity cellulose levulinate esters were prepared via the reaction of cellulose with α-AL, and CLE film has a tensile strength up to 72 MPa and an elongation at break up to 26.7%.

With the gradual depletion of petroleum resources and the increasing global awareness of environmental protection, biodegradable plastics are receiving more and more attention as a green substitute for traditional petroleum-based plastics. Poly (lactic acid) is considered to be the most promising biodegradable material because of its excellent biodegradability, biocompatibility, and good processability. However, the brittleness and high cost limit its application in more fields. Lignin, as the second largest renewable biopolymer in nature after cellulose, is not only rich in reserves and low in cost, but it also has an excellent UV barrier, antioxidant activity, and rigidity. The molecular structure of lignin contains a large number of functional groups, which are easy to endow with new functions by chemical modification. Currently, lignin is mostly treated as waste in industry, and the value-added utilization is insufficient. The combination of lignin and poly (lactic acid) can on the one hand solve the problems of the high cost of PLA and less efficient utilization of lignin; on the other hand, the utilization of lignocellulosic biomass in compounding with biodegradable synthetic polymers is expected to afford high-performance wholly green polymer composites. This mini-review summarizes the latest research achievements of poly (lactic acid)/lignin composites. Emphasis was put on the influence of lignin on the mechanical properties of its composite with poly (lactic acid), as well as the compatibility of the two components. Future research on these green composites is also prospected.