Search Results (100)

In response to growing global concerns about plastic waste, the development of efficient recycling technologies for thermoplastics has become increasingly important. Polypropylene (PP), a widely used commodity resin, is of particular interest because of the urgent need to establish sustainable material circulation. However, conventional mechanical property evaluations of injection-molded products typically require dedicated specimens, which involve additional material and energy costs. As described herein, we propose a simplified mechanical model to derive Poisson’s ratio and critical expansion stress directly from standard uniaxial tensile tests of molded thermoplastics. The method based on the true stress–true strain relationship in the small deformation region was validated using various thermoplastics (PP, POM, PC, and ABS), with results showing good agreement with those of the existing literature. The model was applied further to assess changes in mechanical properties of Homo-PP and Block-PP subjected to repeated extrusion. Both materials exhibited reductions in elastic modulus and critical expansion stress with increasing extrusion cycles, whereas Block-PP showed a slower degradation rate because of thermo-crosslinking in its ethylene–propylene rubber (EPR) phase. DSC and chemiluminescence analyses suggested changes in stereoregularity and radical formation as key factors. This method offers a practical approach for evaluating recycled PP and contributes to high-quality recycling and material design. Full article

Aiming at the problems of serious pavement temperature diseases, low efficiency and high loss of ice-breaking methods, high occupancy rate of waste tires and the low utilization rate and insufficient durability of rubber particles, this paper aims to improve the service level of roads and ensure the safety of winter pavements. A pavement material with high efficiency, low carbon and environmental friendliness for active snow melting and ice breaking is developed. Firstly, NaOH, NaClO and KH550 were used to optimize the treatment of rubber particles. The hydrophilic properties, surface morphology and phase composition of rubber particles before and after optimization were studied, and the optimal treatment method of rubber particles was determined. Then, the optimized rubber particles were used to replace the natural aggregate in the polyurethane gel mixture by the volume substitution method, and the optimum polyurethane gel dosages and molding and curing processes were determined. Finally, the influence law of the road performance of RPGM was compared and analyzed by means of an indoor test, and the ice-breaking effect of RPGM was explored. The results showed that the contact angles of rubber particles treated with three solutions were reduced by 22.5%, 30.2% and 36.7%, respectively. The surface energy was improved, the element types on the surface of rubber particles were reduced and the surface impurities were effectively removed. Among them, the improvement effect of the KH550 solution was the most significant. With the increase in rubber particle content from 0% to 15%, the dynamic stability of the mixture gradually increases, with a maximum increase of 23.5%. The maximum bending strain increases with the increase in its content. The residual stability increases first and then decreases with the increase in rubber particle content, and the increase ranges are 1.4%, 3.3% and 0.5%, respectively. The anti-scattering performance increases with the increase in rubber content, and an excessive amount will lead to an increase in the scattering loss rate, but it can still be maintained below 5%. The fatigue life of polyurethane gel mixtures with 0%, 5%, 10% and 15% rubber particles is 2.9 times, 3.8 times, 4.3 times and 4.0 times higher than that of the AC-13 asphalt mixture, respectively, showing excellent anti-fatigue performance. The friction coefficient of the mixture increases with an increase in the rubber particle content, which can be increased by 22.3% compared with the ordinary asphalt mixture. RPGM shows better de-icing performance than traditional asphalt mixtures, and with an increase in rubber particle content, the ice-breaking ability is effectively improved. When the thickness of the ice layer exceeds 9 mm, the ice-breaking ability of the mixture is significantly weakened. Mainly through the synergistic effect of stress coupling, thermal effect and interface failure, the bonding performance of the ice–pavement interface is weakened under the action of driving load cycle, and the ice layer is loosened, broken and peeled off, achieving efficient de-icing. Full article

Tire shape prediction presents significant engineering challenges due to the complex behavior of cord-rubber composites during manufacturing processes. Fabric cord components undergo thermal shrinkage and permanent deformation that substantially influence final tire dimensions, creating discrepancies between mold geometry and cured tire shape. While Post-Cure Inflation (PCI) helps control these dimensional changes, accurate prediction methods remain essential for reliable performance forecasting. This study addresses this challenge through a systematic experimental characterization of fabric cord behavior under manufacturing conditions. Thermal shrinkage and permanent set were quantified under various combinations of in-mold strain and PCI force, with distinct patterns identified for different cord materials (PET and nylon). Based on these experimental findings, a comprehensive finite element analysis methodology was developed to predict cured tire shape. Validation against 65 tire profiles demonstrated remarkable improvements over conventional approaches, with dimensional error reductions of 54.2% for the outer diameter and 49.5% for the section width. Profile and footprint predictions also showed significantly enhanced accuracy, particularly in capturing geometric features critical for tire–road contact characteristics. The proposed methodology enables more precise tire design optimization, improved performance prediction, and reduced prototype iterations, ultimately enhancing both product development efficiency and final tire performance. Full article

To enhance the high-temperature resistance of silicone rubber and meet the application requirements of flexible conductive silicone rubber under elevated temperature conditions, this study adopts a chemical modification strategy by introducing phenyl groups into the molecular chains of silicone rubber to improve its thermal resistance. High-phenyl-content hydroxyl-terminated silicone oil (MPPS) was used as the polymer backbone, and vinylmethyldimethoxysilane (VDMS) served as the chain extender. Through a silanol condensation reaction, vinylmethylphenyl polysiloxane (VMPPS) with a crosslinkable structure was synthesized, providing reactive sites for subsequent vulcanization and molding. Subsequently, needle-like silver-coated glass fiber (AGF) conductive fillers were prepared via a green and environmentally friendly electroless silver plating method. These fillers were incorporated into the phenyl polysiloxane matrix to impart electrical conductivity to the phenyl silicone rubber while synergistically enhancing its thermal resistance. Finally, thermally resistant conductive silicone rubber was fabricated through high-temperature vulcanization, and the key properties of the material were systematically characterized. The synthesized phenyl polysiloxane exhibited a number-averaged molecular weight of up to 181,136, with a PDI of 2.43. When the loading of AGF reached 25 phr, the phenyl silicone rubber composite achieved the electrical percolation threshold, exhibiting a conductivity of 7.12 S/cm. With a further increase in AGF content to 35 phr, the composite demonstrated excellent thermal stability, with a 5% weight loss temperature of 478 °C and a residual mass of 37.36% at 800 °C. Moreover, after thermal aging at 100 °C for 72 h, the conductivity degradation of the phenyl silicone rubber was significantly lower than that of commercial silicone rubber, indicating outstanding electrical stability. This study provides an effective approach for the application of flexible electronic materials under extreme thermal environments. Full article

This study aimed to optimize the injection mold for oil production single-screw pump rubber stators. MOLDFLOW2023 analysis post-design determined the optimal gate position and gating system, and it also analyzed the impact of key parameters on quality. The optimization led to a significant improvement in product quality. The most influential factors were mold temperature, melt temperature, and injection time. The best settings were a mold temperature of 100 °C, a melt temperature of 70 °C, an injection time of 30 s, a holding time of 10 s, and a holding pressure of 60 MPa. This resulted in a 1.8–2.7% decrease in volume shrinkage and a 1.3–0.9% decrease in sink index, enhancing the quality of rubber stators and advancing injection molding technology. Full article

Ammonia is commonly used as a preservative in the production of concentrated natural rubber latex (CNRL) and latex products; however, it poses a serious risk to human health and the environment. In this study, we investigated a thioacetamide derivative (TD) as a preservative of ammonia-free CNRL and the optimization of a stabilization system comprising potassium hydroxide (KOH), lauric acid (LA), and sodium dodecyl sulfate (SDS) to enhance its preservation effect. The results revealed that an optimal amount of TD (0.03%) can effectively maintain the stability of CNRL, inhibit the increase in volatile fatty acid number (VFA number), maintain stable viscosity values, and improve the mechanical stability time (MST). However, increasing the TD dosage results in an increase in both the viscosity and VFA number and a decrease in MST. KOH was used to regulate the pH value of CNRL. It was also found that it can enhance considerably the mechanical properties of CNRL dry films and accelerates the vulcanization of vulcanized film; however, an excessive amount causes latex thickening. LA proved essential for improving the MST and reducing latex viscosity, thereby substantially enhancing the stability and processability of pre-vulcanized latex, but an excessive amount is detrimental to the curing speed and final mechanical strength. SDS can rapidly improve the MST and reduce the viscosity, but it negatively affects the surface molding of dry rubber films. In conclusion, KOH, LA, and SDS at appropriate dosages play a balancing and complementary role in the preparation of ammonia-free CNRL. Upon analyzing diverse performance metrics of CNRL, it has been determined that the optimal TD dosage ranges from 0.02 to 0.03% for maximum efficacy. The KOH dosage should be maintained within 0.1–0.15% to achieve the most favorable outcome, while the LA dosage is advisable to be kept between 0.06 and 0.1%. Full article

An innovative modeling approach for the simulative description of the part quality of rubber materials, including the processing history, is presented in this paper. This modeling approach, the so-called average curing speed (ACS) model, is based on the degree of cure and the average curing speed instead of the conventionally considered temperature approach. Such approach neglects the processing history by calculating only the degree of cure. Thus, the correlation with part quality has to be performed either after the simulation or with the aid of other numerical analysis programs. Instead, by applying the ACS model, the key advantage is that the processing history is already taken into account during the filling and curing simulation, demanding a single calibration step with quality information to be able to calculate the part quality. For this purpose, parts were manufactured at mold temperatures ranging from 140 °C to 170 °C and degrees of cure from 24% to 99% via compression molding and subsequently the permanent deformation, i.e., the compression set (CS), of each part was analyzed. The CS results show that one and the same degree of cure; for example, 80%, which was defined on the basis of reaction isotherms, causes an almost twofold higher CS value for parts manufactured at 170 °C. Consequently, considerable deviations may occur when real part qualities are correlated with degrees of cure from simulations with common state-of-the-art kinetic models. By applying the ACS model, it was demonstrated that this challenge could be solved. Parts manufactured by compression molding exhibited the same quality as those simulated with the ACS model. Finally, this innovative modeling approach (fully implemented in the SIGMASOFT^® v$6.0$ simulation routine) provides enormous potential for understanding local differences in the quality of rubber parts, being an ideal tool for optimizing rubber parts through simulation routines. Full article

This study examined the effect of partially replacing semi-reinforcing carbon black grade N550 (up to 10 pts. wt.) and fully replacing industrial chalk with natural shungite mineral in industrial formulations of elastomer compositions intended for manufacturing various rubber technical products. It has been shown that due to the high content of carbon and silicon components in the composition of shungite mineral micropowders, their use as a filler in elastomer formulations significantly improves the physical and mechanical properties of rubber technical products (RTPs) manufactured using such compositions. It was determined that the use of SM as a partial replacement for carbon black in rubbers intended for molded rubber technical products contributes to a reduction in Mooney viscosity (up to 26.8%) and optimal vulcanization time (up to 23.7%), achieving rubbers with the required set of physical–mechanical properties and with an enhancing sealing capability (up to 19.7%). It has been established that the use of shungite mineral micropowders as a complete replacement for industrial chalk increases the strength of rubber products (RTPs) by up to 18.5% and enhances their resistance to liquid aggressive environments. Full article

Background: This study aimed to evaluate the color-matching and light transmission properties of a newly developed aesthetic flowable resin composite, OCFB-001. Methods: Rubber molds containing cylindrical cavities were filled with Estelite Sigma Quick, and 40 resin composite (CR) molds with simulated Class I cavities were prepared in shades A1, A2, A3, and A4, resulting in a total of 160 samples. Following bonding procedures, four different flowable resin composites (n = 10) were introduced into the cavities. The color difference (ΔE₀₀) was calculated using two methods. A two-way analysis of variance was performed, and the interaction was significant, so a post hoc analysis was performed for each shade using Bonferroni’s correction. The morphology of the filler in each material was observed via scanning electron microscopy (SEM). Results: In the A1 shade, OCFB-001 demonstrated color differences comparable to those of other materials. However, in the A2, A3, and A4 shades, OCFB-001 exhibited significantly lower color differences (ΔE₀₀) than the other materials, with a more consistent distribution. SEM analysis revealed that the OCFB-001 structure resembled that of Estelite Bulk Fill Flowable. Conclusions: OCFB-001 showed excellent shade matching in the A2, A3, and A4 ranges and good matching in the A1 shade, on par with existing universal-shade flowable bulk-fill resin composites. Full article

Non-pneumatic tires (NPTs) have garnered significant attention due to their advantages, such as energy efficiency, safety, versatile applications, and superior performance, compared to traditional rubber-based pneumatic tires (PTs). This mini review provides a concise overview of NPTs, beginning with their definition, structural design, and classification based on structural variations. The review then examines recent advancements in the materials used for NPTs, including those for the tread, elastic support structure, skeleton, and adhesives, with a focus on their specific properties. Furthermore, it summarizes various manufacturing techniques such as compression molding, centrifugal casting, injection molding, 3D printing, and mechanical assembly. Lastly, the review outlines the general manufacturing procedures of NPTs, discusses the challenges currently faced by the technology, and offers insights into future development directions. This mini review aims to support NPT researchers and practitioners, particularly in the fields of process and materials engineering, in advancing their work on NPTs. Full article

Year by year, more and more plastic is used worldwide. A large part of post-consumer waste is still stored in landfills instead of being reused. The solution to this problem may be recycled materials (recyclates) or biodegradable materials. The method of 3D printing, regarded as a clean processing technology, can significantly contribute to addressing global plastic pollution by utilizing post-consumer recycled polymers to create new components and parts. Therefore, this study focuses on the assessment of various properties and characteristics of 3D-printed compositions based on post-consumer polypropylene (PP) and rubber crumbs, recycled from packages foils and car tires, respectively. Moreover, within this study, we compared the mechanical performance of the injection molding material with the one obtained from 3D printing. A characterization was made considering the thermal and mechanical properties as well as the “print quality” through the microscopic and tomographic analysis of subsequent print passes, the number of free spaces, and imperfections in the polymer melt. Samples obtained using the FDM and injection methods exhibited comparable melting temperatures, while the samples obtained by injection molding exhibited slightly better mechanical performance, higher hardness, and impact strength. Full article

Polyoxymethylene (POM), polypropylene (PP), and poly(methyl methacrylate) (PMMA) have been blended with adhesive-grade ethylene vinyl acetate (EVA), propylene elastomer (VMX), isobutylene–isoprene rubber (IIR) and an acrylic block copolymer (MMA-nBA-MMA). The blends were prepared using a two-roll mill and injection molding. The mechanical properties of the blends, such as tensile strength, tensile modulus, elongation at maximum load, and impact resistance, were investigated. The water contact angle, melt flow rate (MFR), and differential scanning calorimetry were ascertained to evaluate the blends. The blend samples exhibited the following properties: all POM/EVA blends showed reduced crystallinity compared to neat POM; the 80% PMMA/20% MMA-nBA-MMA blend showed improved impact resistance by 243% compared to the neat PMMA. An antiplasticization effect was observed for POM/EVA 1% blends and PMMA/EVA 1% blends, with MFR reduced by 1% and 3%, respectively. The MFR of the PP/IIR 1% blend increased by 5%, then decreased below the MFR near the polymer for the remaining IIR concentrations. Full article

Styrene–butadiene rubber (SBR) waste from the shoe industry was repurposed to produce polypropylene (PP)-based compounds, with the aim of evaluating their antistatic potential. Styrene–ethylene–propylene (SEP) was added as a compatibilizing agent, while carbon nanotubes (MWCNT) were incorporated as a conductive nanofiller. The polymer compounds were processed in an internal mixer, and injection molded. The properties evaluated included torque rheometry, melt flow index (MFI), impact strength, tensile strength, Shore D hardness, electrical conductivity, heat deflection temperature (HDT), and differential scanning calorimetry (DSC), along with scanning electron microscopy (SEM) for morphology analysis. The production of the PP/SBR/SEP (60/30/10 wt%) compound resulted in a ductile material, enhancing impact strength and elongation at break to 161.2% and 165.2%, respectively, compared to pure PP. The addition of SEP improved the compatibility of the PP/SBR system, leading to an increase in the torque curve and a reduction in the MFI. Furthermore, the SBR/SEP combination in PP accelerated the crystallization process and increased the degree of crystallinity, suggesting a nucleating effect. Carbon nanotubes, in concentrations ranging from 0.5 to 2 phr (parts per hundred resin), were added to the PP/SBR/SEP system. Only the PP/SBR/SEP/MWCNT compound with 2 phr of MWCNT was suitable for antistatic applications, exhibiting an electrical conductivity of 4.52 × 10⁻⁰⁷ S/cm. This was due to the greater distribution of MWCNT in the PP matrix, as demonstrated by SEM. In addition, remains tough at room temperature, with a 166% increase in impact strength compared to PP. However, there was a reduction in elastic modulus, tensile strength, Shore D hardness, and HDT due to increased flexibility. SBR waste can be reintegrated into the production chain to produce antistatic polymeric compounds, obtaining a tough material at room temperature. Full article

Esthetically pleasing temporary prostheses are often necessary for extended periods in a variety of clinical scenarios. Adjustments to the occlusion or margins are commonly needed before cementing the temporary prosthesis. Therefore, it is clinically necessary to repolish the rough surface to avoid biological and esthetic issues associated with rough surfaces. The purpose of this in vitro study was to assess and compare the impact of various polishing protocols on the surface roughness and color stability of three resin materials used for provisional crowns. A total of 150 specimens were fabricated from auto-polymerizing polymethyl methacrylate, bis-acryl composite, and Methyl methacrylate-LC resin using a stainless steel mold. Each material group was divided into five groups (n = 10) based on the applied surface treatment: positive control group (G1): no roughening or surface treatment, Negative control group (G2): acrylic bur-roughened surface without any polishing, the different surface treatment groups of silicon carbide and aluminum oxide stone polishing (G3), diamond-coated rubber twist (G4), and Surface Glaze (G5). An optical profilometer was used to assess the surface roughness of all samples. After undergoing 6000 cycles of thermocycling followed by immersion in a coffee solution for 15 days at 37 °C, color parameters were measured using a spectrophotometer both before and after a storage period to evaluate color differences. A two-way ANOVA test with α = 0.05 significance level was carried out to determine the impacts of both the materials utilized and the polishing protocol. Among the three types of resin examined, the bisacryl group exhibited superior surface quality in positive control groups, while PMMA resin demonstrated higher polishability. The diamond-coated rubber twits resulted in lower Ra values of 0.36 (0.01) µm, 0.52 (0.11) µm, and 0.28 (0.05) µm for PMMA, BAMA, and MMLC resins, respectively. The application of photo-polymerized surface glaze led to a plaque accumulation threshold of 0.2 µm across all resin groups. The greatest mean color change occurred in the negative control group, indicating a propensity for more staining on rougher surfaces. The Bisacryl resin exhibited higher ΔE values, whereas PMMA showed better color stability. The lowest ΔE values were found when the surface glaze was applied to all of the provisional crown resins. Untreated Bisacryl resin exhibited the lowest Ra values, while PMMA resins demonstrated superior surface morphology after polishing. PMMA provisional crown resins showed increased resistance to staining. The use of surface glaze enhanced both smoothness and color stability on the surfaces. Full article

In practical applications, polyurethane (PU) foam must be rigid to meet the demands of various industries and provide comfort and protection in everyday life. PU foam components are extensively used in structural foam, thermal insulation, decorative panels, packaging, imitation wood, and floral foam, as well as in models and prototypes. Conventional technology for producing PU foam parts often leads to defects such as deformation, short shots, entrapped air, warpage, flash, micro-bubbles, weld lines, and voids. Therefore, the development of rigid PU foam parts has become a crucial research focus in the industry. This study proposes an innovative manufacturing process for producing rigid PU foam parts using silicone rubber molds (SRMs). The deformation of the silicone rubber mold can be predicted based on its wall thickness, following a trend equation with a correlation coefficient of 0.9951. The volume of the PU foam part can also be predicted by the weight of the PU foaming agent, as indicated by a trend equation with a correlation coefficient of 0.9824. The optimal weight ratio of the foaming agent to water, yielding the highest surface hardness, was found to be 5:1. The surface hardness of the PU foam part can also be predicted based on the weight of the water used, according to a proposed prediction equation with a correlation coefficient of 0.7517. The average surface hardness of the fabricated PU foam part has a Shore O hardness value of approximately 75. Foam parts made with 1.5 g of water added to 15 g of a foaming agent have the fewest internal pores, resulting in the densest interior. PU foam parts exhibit excellent mechanical properties when 3 g of water is added to the PU foaming agent, as evidenced by their surface hardness and compressive strength. Using rigid PU foam parts as a backing material in the proposed method can reduce rapid tool production costs by about 62%. Finally, an innovative manufacturing process for creating large SRMs using rigid PU foam parts as backing material is demonstrated. Full article