Advances in Polymer Technology

Polymethyl methacrylate (PMMA) bone cement is being used to fill voids that are created due to vertebral compression fractures. It is also a grouting medium in orthopedic joint replacement surgeries as they possess fast primary fixation to the bone. Considering the cement properties and in vitro bioactivity of bone cement is essential for cemented hip and knee joint replacement surgeries. In this study, commercial Simplex P bone cement (SPBC) is modified with carboxyl- (-COOH-) functionalized multiwalled carbon nanotubes (MWCNTs) to overcome high polymerization temperature, volumetric shrinkage, surface wettability, and in vitro bioactivity. A geometric dilution method is used to incorporate MWCNTs with the PMMA powder, which is in unequal proportions. The PMMA/MWCNT nanocomposite with different concentrations of reinforcements, such as 0.1, 0.3, 0.5, and 0.7 weight percentages, is prepared for the investigation. It was observed that the MWCNTs had a beneficial impact on PMMA bone cement (PMMA-BC) by enhancing its setting time (2.94%↑) and surface wettability (23.58%↑). Also, diminished polymerization temperature (29%↓) and volumetric shrinkage (40.9%↓) are observed for an optimum concentration of 0.7 wt. %. The bioactivity of the cement surface is validated by the in vitro bioactivity observed in simulated body fluid (SBF) through the development of primary and secondary apatite. It is concluded that the synthesized PMMA/MWCNT nanocomposites are found to have enhanced cement properties compared to PMMA-BC.

Wet blue leather is a waste produced by the leather industry. It is a difficult waste product to dispose of, and if not disposed of properly, it will affect the environment and cause toxicity. Therefore, recycling was considered as an alternative to waste disposal. In this study, polymer composites were prepared from two types of polymers, poly(butylene adipate-co-terephthalate) (PBAT) and poly(butylene succinate) (PBS), and wet blue leather (WBL). A twin screw extruder and injection molding were used to prepare the composites. The effect of polymer type and WBL content (5, 10, and 15 wt%) on mechanical properties, thermal properties, flammability, MFI, water absorption, and morphology was investigated. All the polymer composites showed an increase in tensile and flexural strength, Young’s modulus, and water absorption but decreased in elongation at break, impact strength, and flammability compared to neat polymers.

A series of isosorbide-based thermoplastic polyurethanes (ISB-TPUs) with different soft/hard ratios have been successfully step polymerized using individual two types of polycaprolactone diol (PCL) or poly (tetramethylene glycol) (PTMG) for soft segment and bio-based isosorbide (ISB) or methylene diphenyl diisocyanate (MDI) for hard segment, based on the similar molecular weight. The effect of the molecular structure on the mechanical and thermal properties has been evaluated in terms of the types of soft/hard and polyol, ranging from 6/4 to 9/1 ratio values. With the increasing of PCL content, the thermal properties of the ISB-TPU have enhanced gradually. When the range from PCL was 6/4, the tensile strength has achieved the maximum value in comparison with that of the PTMG block. Elongation at break has increased with the increase of hard segment concentration, due to the superior interaction between ester groups and urethane groups. The obtained ISB-TPUs can be a promising resin for soft, flexible, and biocompatible application fields.

The equibiaxial planar tension test is an important method for determining the mechanical properties of hyperplastic membranes, and it is also critical to designing an effective equibiaxial tension test rig to meet experimental accuracy requirements. However, any analysis addressing the accuracy of this test is not reported in the literature. In this paper, an equibiaxial planar tension apparatus is proposed for conducting single-corner-point tension tests on hyperelastic electroactive polymer (EAP) membranes. The experimental data were compared with those obtained from two-corner-point-fixed tension tests and fitted with nonlinear material models, and the model’s parameters were also evaluated. Finally, the widely-used finite element software ABAQUS was employed to simulate equibiaxial planar tension methods and investigate the impact of clamping mode and point number on test accuracy as well as the uniformity of overall deformation. The test results indicate that the stress-strain curves for the two tensions remain consistent across small stretch ratios. However, as the stretch ratio increases (about ) in two-corner-point-fixed tension, stress shielding may lead to a degradation of strain uniformity and result in greater stresses than single-corner-point tension. Additionally, both the three-parameter Yeoh model and the four-parameter Ogden model can provide an accurate description of the EAP membrane material. The simulation results indicate that the axial strain variation amplitudes remain below 5% within a region spanning approximately 80% of the specimen’s overall length from its center to edge and even below 1% within a region spanning 85% in the single-corner-point tension; stress inaccuracies increase with stretch ratio, while the calculated error is about 2.1% when in the single-corner-point tension test, which has the smallest stress error among the tests; when the number of tension points is increased, the overall deformation becomes more sufficient, and the test accuracy improves as well. The conclusions drawn from this paper will be beneficial in designing equibiaxial planar tension test rigs and analyzing their accuracy and uniformity of deformation.

A seal is a mechanism or a piece of material that securely shuts a hole so that air, liquid, or other substances cannot enter or exit the system. Seals are an essential component of practically all machinery and engines and have several applications in industry. The development of novel materials for sealing applications is essentially required on these days. In this research, an attempt is made to find the polymer material for the said application. Poly vinyl rubber material has been taken, and the specimens are prepared for testing the tensile properties and hardness. The specimens were prepared by using die with various temperatures and curing time. Sixteen specimens were prepared by changing the curing temperature, curing time, postcuring temperature, and postcuring time. The curing temperature 150°C and 170°C, postcuring temperature 100°C and 50°C, curing time 14 mins and 18 mins, postcuring time 120 mins and 60 mins, and the pressure of 150 kg/cm² for all the specimens were maintained. The tensile strength and hardness analysis were done as per the ASTM standard, and it was found that the specimen prepared on 150°C curing temperature, 18 min curing time, 50°C postcuring temperature, and 120 min postcuring time provides the higher tensile strength. DOE analysis is also done to determine the best values of the factors impacting the mechanical characteristics of the seal material. Simple regression analysis is used to find the influence of curing temperature and curing time on the tensile strength and hardness for every 1°C temperature rise and 1 sec curing time.

Focusing on natural fibers are the prominent substitution for synthetic fiber and reinforced into polymer matrices found unique properties such as lightweight, cost-effectiveness, and good mechanical and wear properties. Incompatibility and low adhesive behavior are the primary drawbacks found during the fabrication of natural fiber-bonded polymer matrix composites. The constant weight percentage (10 wt%) of sisal and hemp fiber is treated with a 5% NaOH solution for improving adhesive behavior and bonded with epoxy. The prepared sisal/hemp/epoxy combination is blended with 0 wt%, 3 wt%, 6 wt%, and 9 wt% silica nanoparticles, which results in reduced voids (1.32%) and increased flexural strength (56.98 MPa). Based on the compositions of fiber and reinforcement, the density of the composite varied. Samples 3-6 wt% of silica nanoparticle-blend sisal/hemp/epoxy composite offered maximum tensile and impact strength of 52.16 MPa and 2.1 J. An optical microscope analyzed the tensile fracture surface, and the failure nature was reported. The dry sliding wear performance of composite samples is tested by pin-on-disc setup with a 10 N-40 N load of 10 N interval at 0.75 m/sec. Sample 3 found good wear resistance compared to others.