Wear Failures of Plastics

This article presents the mechanisms of polymer wear and quantifies wear in terms of wear rate (rate of removal of the material). Interfacial and bulk wear are discussed as well as a discussion on the wear study of "elastomers," "thermosets," "glassy thermoplastics," and "semicrystalline thermoplastics." The article also discusses the effects of environment and lubricant on the wear failures of polymers. It presents a case study on considering nylon as a tribological material and failure examples, explaining wear resistance of polyurethane elastomeric coatings and failure of an acetal gear wheel.

Improved Wear-Resistant Performance of Epoxy Resin Composites Using Ceramic Particles

This work investigated the effects of using a new fabrication technique to prepare polymer composite on the wear-resistant performance of epoxy resin composites under dry friction conditions. Polymer composite samples with different weight contents of silicon carbide (SiC) particles were manufactured. This paper addresses the wear behavior of the obtained samples. With the suggested technique, the samples were prepared from epoxy/silicon carbide particles using a layer of thin kraft paper to prevent the sedimentation of the ceramic particles and to control the weight content of ceramic in the polymer. Kraft paper was used as a layer in the polymer composite. The hardness, wear resistance, and water absorption capacity of the produced epoxy composite samples prepared using the kraft paper technique were evaluated. The morphology of epoxy composite samples showed a significant improvement in the ceramic distribution and enhancement of interface bonding between ceramic and the polymer. The hardness values of the developed polymer composites were enhanced by up to 42.8%, which was obtained at 18 wt.% SiC particles. Increasing the ceramic content in the epoxy also led to the enhancement of wear resistance compared with pure epoxy. The results of the microstructure study also showed that the kraft paper layers helped in maintaining the distribution of the ceramic particles according to the previously specified content in each layer in the sample. Wear tests showed that the wear rate of the polymer composite decreased with the increase in the ceramic content. This study provides a new recycling method for using old kraft paper in polymer composite manufacturing to improve the distribution of ceramic particles in the polymer matrix.

Mechanical Properties of Bisacryl-, Composite-, and Ceramic-resin Restorative Materials

SUMMARY Objective: Resin-based materials used in restorative dentistry are introduced at a fast pace with limited knowledge about their properties. Comparing properties of these materials from different restorative categories is lacking but can help the clinician in material selection. This study aimed to compare mechanical properties and wear resistance of bis-acryl-, composite-, and ceramic-resin restorative materials. Methods and Materials: Bisacryl-resin (Bis-R, LuxaCrown, DMG), composite-resin (Com-R, Filtek Supreme Ultra, 3M Oral Care), and ceramic-resin (Cer-R, Enamic, VITA Zahnfabrik) specimens were prepared for mechanical tests: fracture toughness (FT) with and without initial thermomechanical loading using a mastication simulator, flexural strength (FS), and flexural modulus (FM), compressive strength (CS), and volumetric wear loss measurement. The datasets for FT and wear resistance were each analyzed using two-way ANOVA followed by pairwise comparisons or Tukey testing as appropriate. The datasets for FS, FM, and CS were analyzed using one-way ANOVA followed by the Tukey test. Results: Analysis of FS, FM, and CS showed significant differences between materials, with all pairwise comparisons between materials showing significance. Analysis of FT resulted in a significant interaction between the material and treatment, with analysis of wear loss showing a significant interaction between the material and the number of cycles. Conclusions: Cer-R demonstrated superior FT, CS, and wear resistance compared to Bis-R and Comp-R materials. Fracture toughness of Bis-R increased after thermomechanical loading.

The Effect of Salinized Nano ZrO2 Particles on the Microstructure, Hardness, and Wear Behavior of Acrylic Denture Tooth Nanocomposite

The wear of acrylic denture teeth is a serious problem that can change the vertical dimensions of dentures. This study evaluates the effect of adding salinized nano ZrO2 particles on the microstructure, hardness, and wear resistance of acrylic denture teeth. Heat polymerizing polymethyl methacrylate resin was mixed with salinized ZrO2 at concentrations of 5 wt% and 10 wt%. Acrylic resin specimens without filler addition were used as a control group. SEM/EDS analyses were performed and the Vickers’ hardness was evaluated. Two-body wear testing was performed using a chewing simulator with a human enamel antagonist. After subjecting the samples to 37,500 cycles, both height loss and weight loss were used to evaluate the wear behavior. The microstructural investigation of the reinforced-denture teeth indicates sound nanocomposite preparation using the applied regime without porosity or macro defects. The addition of zirconium oxide nanofillers to PMMA at both 5% and 10% increased the microhardness, with values of up to 49.7 HV. The wear mechanism in the acrylic base material without nanoparticle addition was found to be fatigue wear; a high density of microcracks were found. The addition of 5 wt% ZrO2 improved the wear resistance. Increasing the nanoparticles to 10 wt% ZrO2 further improved the wear resistance, with no microcracks found.

Multi-objective optimization of alloying elements to enhance the wear resistance and impact strength of HCCI produced by furan sand mold

High Chromium White Cast Iron (HCWCI) plays a major role in manufacturing of wear-resistant components. Due to unique wear resistance property, attribution to the additions of carbide forming elements, they have been used for mill liner applications. By varying the wt% of alloying elements such as Cr, Ti, and Mo, the wear resistance and impact strength of High Chromium Cast Iron (HCCI) can be increased. To enhance the wear resistance property according to Central Composite Design (CCD), 16 samples were fabricated by varying the wt% of alloying elements. To fabricate the samples, furan sand molds were prepared and used for the further casting process. The properties of Furan sand mold enhance the mechanical properties and reduce the mold rejection rate, production time, etc. To attain the optimum Wear Rate (WR) and Impact Strength (IS) value without dominance, optimization techniques such as Response Surface Methodological (RSM) and Particle swarm optimization (PSO) are employed to solve the multi-objective problem. The RSM and PSO predicted optimum solutions are compared by using the Weighted Aggregated Sum Product Assessment (WASPAS) ranking method. The WASPAS result revealed that when compared to the RSM result, the PSO predicted optimal wt% of chemical composition (22 wt % Cr, 3 wt % Ti, and 2.99 wt % Mo) gives the optimum WR value (53 mm3/min) and IS value (3.77 J). To validate the PSO result, experiments were carried out for the predicted wt% of alloying elements and tested. The difference between the PSO predicted result and experimental result is less than 5% error which clearly shows that PSO is an effective method to solve the multi-objective problem.