Prestretching effect and recovery process of polyvinyl alcohol film crosslinked with tartaric acid

Abstract

The tartaric acid (TA)/polyvinyl alcohol (PVA) composite films were prepared with various TA concentrations from 5 to 20 wt%. The crosslinking due to TA improved the tensile characteristics such as tensile strength and the Young's modulus, and thermal stability of the films. The addition of TA in PVA led to a decrease in the crystallinity. Application of prestretching or preliminary deformation resulted in significant changes in both stress–strain behavior and tensile characteristics of both pure PVA and TA/PVA composite films. Although low preextension levels such as 5% strain did not change much the tensile characteristics, higher preextension levels improved the tensile strength but decreased the extensibility of the films. The recovery processes of the stretched films consisted of a fast recovery process for which most of the recoverable elastic deformation is seen took place within almost 30 min and a time‐dependent long‐lasting recovery process continued in time very slowly, which resulted in undesirable residual deformation. It was also observed that increasing TA concentration accelerated the recovery process, hence, improved the recovery properties of PVA. The use of TA in the membrane applications can be considered to improve the mechanical properties and reusability of the membrane technology.

Microneedle Patch Prepared from a Hydrogel by a Mild Method for Insulin Delivery

“…To improve the mechanical strength of the materials, Freeze/Thaw method was employed to promote the crystallization of PVA chains in the gel. It could be seen from Figure 2C that a sharp peak was detected at 2θ=19.87° after repeated freezing and thawing of pure PVA, and its d ‐spacing value was 4.4636 Å, corresponding to (101) reflection plane [14] . With the addition of HA‐FPBA, the diffraction peak of PVA became wider and tended to be amorphous.…”

“…With the addition of HA‐FPBA, the diffraction peak of PVA became wider and tended to be amorphous. The crystallinity of the samples was calculated according to the following equation 3: [14] …”

Cross-Linking-Density-Changeable Microneedle Patch Prepared from a Glucose-Responsive Hydrogel for Insulin Delivery

“…It can be seen from Figure 4A that A100 had a pronounced peak at 2θ = 19.88°and its d-spacing value was 4.4622 Å, which corresponded to (101) reflection plane. 40 In addition, the two peaks at 22.7 and 41.8°were also the crystalline peaks of PVA. Deconvolution into components of the diffraction pattern of A100 xerogel is shown in Figure 4B.…”

Development and characterization of sodium alginate/bifidobacterium probiotic biohybrid material used in tissue engineering

“…As a result, the decrease in the crystallinity is supposed to be associated with an increase in the number of defects and in free volumes existing in the cross-linked films and the changes in the intermolecular interactions between bacteria molecules and hydroxyl groups in the SA. 38 However, although the decrease in crystallinity is thought to make the structure less rigid, the structure becomes more rigid as the cross-linkage increases in the structure (see Table 2). The structure can be thought of as more network-like.…”