Surface defects are frequently observed in calendered polyvinyl chloride (PVC) films. Their evaluation in production environments is typically qualitative and operator dependent. Using the common gas entrapment defects as the test case, the present study develops a four-step image-processing workflow that converts scanned film images into pixel intensity matrices and groups defect pixels using density-based clustering (DBSCAN). The procedure provides quantitative measures of defect count, size, and spatial distribution without manual labeling. The effects of roll gap, calendering speed, upstream mixing time, and plasticizer type were examined under controlled conditions. Larger roll gaps and higher speeds reduced degassing efficiency and increased both defect number and defect area. Short mixing times led to incomplete gelation and higher defect frequency. Among the tested plasticizers, TOTM produced the lowest defect counts, followed by DEHP and ESBO. Design-of-experiments analysis ranked parameter sensitivity and identified operating ranges that limit defect formation. The method provides a practical basis for routine surface inspection and supports process adjustment using measurable defect metrics rather than visual judgment alone.

Surface and interfacial engineering of additives is crucial for enhancing the compatibility between inorganic additives and polymer matrices. Thermal stabilizers are particularly prevalent in polyvinyl chloride (PVC) compounding. Recently, layered double hydroxidehydroxide (LDH) structures have been explored as a new class of efficient and environmentally-friendly stabilizers. This study uses oleic acid (OA) as a bio-sourced surface-active agent for improved compatibility between MgAlZn-CO3 LDH and the PVC matrix. Scanning electron microscopy (SEM) results indicated that OA substantially influences the distribution of LDHs throughout PVC matrix. Additionally, Raman spectroscopy confirmed that the incorporation of OA enhances the HCl absorption capability of LDHs, leading to an over two-fold increase in the static thermal stability of PVC. Correspondingly, color stability of PVC compounds with the modified LDH also improves significantly. The surface-functionalized LDH developed in this work exhibits tremendous potential as a highly potent and yet environmentally-friendly stabilizer for PVC processing as well as for PVC recycling and its circular economy.

This study compared the effectiveness of three fiber treatment methods for reinforcing polyvinyl chloride (PVC) with aramid fibers. Two of them used phosphoric and nitric acids, respectively, the latter of which was introduced for the first time. Acid etching roughens the fiber surface for increased friction and mechanical interlocking with PVC. The third approach treated fibers with a dimethyl sulfoxide (DMSO)/potassium hydroxide (KOH) deprotonation procedure. A more streamlined procedure was introduced in this study which omitted alkyl functionalization in favor of ethanol precipitation. Deprotonation disrupts the crystalline structure in the fibers and unbundle them into aramid nanofibers (ANFs). All treatment procedures lead to substantial improvements in composite mechanical properties. Compared with phosphorous acid, treatment by nitric acid results in higher tensile strength and Young’s modulus. Composites with ANFs show highest tensile strength among all cases. Fractography reveals distinct failure mechanisms between composites with acid-treated fibers versus those with ANFs. The acid-treated fibers exhibit interfacial delamination during material failure, indicating that enhanced composite strength is mainly attributed to stronger interfacial forces. In contrast, ANFs do not carry load in the same way as the original fibers do, but their smaller dimensions allow nanoscale dispersion, which can suppress microcrack formation during deformation. Our systematic evaluation of fiber treatment options provides critical insights for tailoring fiber-matrix interactions in non-reactive thermoplastic systems, advancing the application potential of flexible PVC in load-bearing environments.