Features of high-filled composites based on various brands of polyvinyl alcohol

Composites based on polyvinyl alcohol (PVA) and polysaccharides (PS) have significant potential for use as compostable packaging materials, as well as in various fields of crop production. PVS are produced by the industry of various brands that differ in molecular weight (MM) and the residual content of vinyl acetate (BA) groups, and as a result - the degree of hydrolysis. Depending on the brand of PVA and the nature of the filler, such properties of composites based on them as water resistance, strength, degree of bioconversion, etc.will differ significantly. The purpose of the work: a comprehensive assessment of the properties of high-filled composites based on PVA of various brands, differing in the degree of hydrolysis, and polysaccharides. Objects of research: composites obtained by direct combination of a 5% solution of PVA (grades 1799, VS-05, BP-05, KurarayPoval 3-83) and PS powder (wood microcellulose - MCD, corn native starch - KK), with and without the addition of a plasticizer (P) - glycerin, followed by dehydration in air or in a vacuum drying cabinet. Based on the presence of external defects after dehydration and the strength characteristics of the material, it was found that for PVA-1799 it is possible to achieve a filling degree of 80 vol.%, for a PVA BP-05, VS-05 KurarayPoval and 3-83-no more than 50 vol.% without plasticizer and up to 70 vol.% in the presence of a plasticizer. It is noted that when filling PVA with starch up to 50 vol.% dehydrated composites are transparent or semi-transparent, which gives them additional advantages as packaging materials (including film). For composites based on PVA-1799, it was found that the maximum water absorption (250% by weight) has a PVA filled with MCD (20: 80 vol.%), and the introduction of a plasticizer (5 vol.% ) significantly reduces the degree of water absorption (up to 150% by weight), which is not typical for this brand of PVA filled with CC (water absorption was about 50% by weight with and without plasticizer). Composites based on PVA grades VS-05, BP-05, KurarayPoval 3-83 dissolve in water at room temperature for 5-10 minutes. During the preliminary assessment of the biodegradation of the studied PVA-1799 composites, it was found that micro-cracks and areas with immobilized microbiota were observed in the polymer matrix during microscopy after 6 months of composting and soil testing, however, no significant damage to the integrity of the polymer of this brand occurred during the specified composting period, which emphasizes the complex nature of the biodegradation of PVA with high MM and low content of VA groups.