Moving Die Rheometer Research Articles

Enhancing Rubber Vulcanization Cure Kinetics: Lowering Vulcanization Temperature by Addition of MgO as Co-Cure Activator in ZnO-Based Cure Activator Systems.

Vulcanization is a chemical modification of rubber that requires a considerable amount of thermal energy. To save thermal energy, the kinetics of rubber vulcanization should be improved. In this article, the curing properties of rubber vulcanization are thoroughly investigated using the moving die rheometer (MDR) technique. To enhance the kinetics in different stages of ZnO-based sulfur vulcanization systems, small amounts of MgO were added. The results revealed that the small amount of 1 to 2 phr (per hundred grams of rubber) of MgO in the controlled 5 phr ZnO-based curing systems can significantly improve the curing kinetics. For example, the optimum curing time of 1 phr MgO added to the 5 phr ZnO-containing semi-efficient vulcanization system at different temperatures was more than half that of the controlled 5 phr ZnO-only compound. While maintaining a similar rate of vulcanization, the vulcanization temperature can be reduced by up to 20 °C by using MgO as a co-cure activator, which exhibits similar or better rheometric mechanical properties compared to the controlled compounds. With the addition of MgO as a co-cure activator, the vulcanization reactions become very fast, enabling vulcanization to be completed, even at the boiling point of water (100 °C) with an affordable curing time (<1 h). By reducing the vulcanization temperature, the scorch safety time can be enhanced in the ZnO/MgO-based binary cure activator-containing vulcanizates. Overall, MgO could be a potential candidate as a co-cure activator with ZnO for the vulcanization of rubber, offering better economical and eco-friendly methods.

Effect of phthalate-free plasticizer addition on thermal, mechanical, and aging properties of nitrile rubber (NBR)

Nitrile rubber (NBR) is widely used in the automotive, aerospace, and chemical sectors due to its resistance to fuels, oil, thermal aging, and fatigue. A typical NBR compound is prepared with several components that are added to obtain a product to meet specific industry requirements. Plasticizer is one of the main components used in NBR compounds. Typically, phthalates like DBP (dibutyl phthalate) or DOP (dioctyl phthalate) are used for NBR plasticization. However, these phthalates-based plasticizers are associated with toxicity and often prohibited by international regulatory standards. In this way, in the pursuit of a non-toxic NBR compound, the use of phthalate-free plasticizer, namely dioctyl terephthalate (DOTP), has been proposed. In this work, NBR compounds with DOTP, DBP, or DOP were processed in an open mill and vulcanized in hydraulic press. The unvulcanized samples were tested in a moving die rheometer (MDR). Subsequently, thermal, mechanical, and aging analyses were conducted for the vulcanized samples. The lowest torque observed in the rheometric curve, the displacement value of glass transition temperature (Tg), the smaller Shore A hardness, and the high elongation at break indicate that the addition of DOTP results in higher plasticization. The better-aging properties indicate lower migration of the DOTP plasticizer. Thus, the use of DOTP as a plasticizer holds promise as a viable alternative to replace the phthalates-based plasticizer in NBR compounds.

Acoustical, vibrational, and thermal investigations of pyrolytic carbon black reinforced natural rubber composites

The present study aims to utilize the carbonaceous filler (pyrolytic carbon black (PCB)) obtained from tire waste to fabricate composites for thermal, vibrational, and acoustical applications. Four composites were fabricated by increasing the PCB content (0, 10, 20, and 30 parts per hundred rubber (phr)) in the natural rubber (NR) matrix following ASTM D3182-21a standard. The optimum curing time was determined using a Moving Die Rheometer based on the ASTM D2084-19 standard. The physical, functional, microstructural, wettability, thermal, and mechanical properties of fabricated NR/PCB composites were comprehensively examined. Further, from an application standpoint, the study influence of increasing PCB content in a polymer matrix on thermal conductivity (TC), vibration damping, and sound transmission loss (STL) of the fabricated NR/PCB composites was investigated following ASTM E1530-19, ASTM E756-05, and ASTM E2611-17 standards, respectively. The study results indicate significant enhancement in the properties of the composites with increased PCB content. Specifically, the reinforcement of 30 phr of PCB in the polymer matrix led to a notable increase in TC (at 40 °C) by approximately 21.16% compared to NR/PCB0 composite. Also, the configuration mild steel (MS) + NR/PCB30 achieved the highest damping ratio, measuring 6.56 at the third vibration mode. Moreover, the average STL value of the NR/PCB30 composite showed a notable improvement of approximately 17.19% when compared to the NR/PCB0 composite, underscoring the effectiveness of PCB in enhancing the desired properties of the NR-based composites.

Systematic Investigation of the Degradation Properties of Nitrile-Butadiene Rubber/Polyamide Elastomer/Single-Walled Carbon Nanotube Composites in Thermo-Oxidative and Hot Oil Environments.

The physical blending method was used in order to prepare nitrile-butadiene rubber/polyamide elastomer/single-walled carbon nanotube (NBR/PAE/SWCNT) composites with better thermal-oxidative aging resistance. The interactions between SWCNTs and NBR/PAE were characterized using the Moving Die Rheometer 2000 (MDR 2000), rheological behavior tests, the equilibrium swelling method, and mechanical property tests. The 100% constant tensile stress and hardness of NBR/PAE/SWCNT composites increased from 2.59 MPa to 4.14 MPa and from 62 Shore A to 69 Shore A, respectively, and the elongation decreased from 421% to 355% with increasing SWCNT content. NBR/PAE/SWCNT composites had improved thermal-oxidative aging resistance due to better interactions between SWCNTs and NBR/PAE. During the aging process, the tensile strength and elongation at break decreased with the increase in aging time compared to the unaged samples, and the constant tensile stress gradually increased. There was a more significant difference in the degradation of mechanical properties when aged in a variety of oils. The 100% constant tensile stress of NBR/PAE/SWCNT composites aged in IRM 903 gradually increased with aging time while it gradually decreased in biodiesel. The swelling index gradually increased with increasing SWCNT content. Interestingly, the swelling index of the composites in cyclohexanone decreased with the increase in SWCNT content. The reasons leading to different swelling behaviors when immersed in different kinds of liquids were investigated using the Hansen solubility parameter (HSP) method, which provides an excellent guide for the application of some oil-resistant products.

Investigation of The Effect of Micronized Ethylene-Propylene-Diene Monomer (EDPM) Powder Wastes on Physical and Mechanical Properties in EPDM Mixtures

In this study, micronized-ethylene-propylene-diene monomer powders (m-EPDM) by the physical crushing method were added to EPDM rubber, and their effects on physical and mechanical properties were examined. Micronized EPDM powders were added at rates of 10-20-30%. EPDM rubber was pulped with micronized EPDM powder using a 1.5-liter laboratory type mini banbury. The obtained paste was vulcanized in the press at 180 °C for 20 min., and test plates were acquired. Rheological and fluidity properties of EPDM rubber with m-EPDM powder added were examined by pre-press rheometer (Moving Die Rheometer_MDR) and Mooney viscosity tests. Tensile and permanent deformation tests were performed to determine mechanical properties density, Shore A hardness tests were performed to determine physical properties and dispersion analysis was performed to distribute the additives in EPDM rubber. As a result of the study, minimum torque (ML) values increased while maximum torque (MH) values decreased depending on the amount of m-EPDM. Mooney viscosity of EPDM/30m-EPDM rubber increased by 40.9%. It was observed that cure rate index (CRI) did not change depending on the amount of m-EPDM. With the addition of 30% m-EPDM, breaking strength decreased by 39.2%, and elongation at break was reduced by 9.87%.

Effect of ionizing radiation on mechanical and damping properties of phenyl‐vinyl‐methyl‐polysiloxane elastomers cured with platinum

AbstractIn this study, phenyl‐vinyl‐methyl‐polysiloxane (PVMQ) elastomers were cured with a Pt catalyst and irradiated with different doses (0–80 kGy) using electron beams. Before irradiation studies, rheological analyses were carried out for the three different Platinum‐A (PtA)/Platinum‐B (PtB) ratios by using a Moving Die Rheometer. End of rheological and mechanical analyses 1/2 PtA/PtB ratio was chosen for irradiation studies. To examine the effect of absorbed dose on the mechanical properties of platinum‐cured PVMQ (Pt‐PVMQ) elastomers, stress–strain behavior, stress relaxation, and energy‐damping behavior at static conditions were investigated by cyclic compression analyses. The effect of absorbed dose on the stiffness, permanent deformation, and crosslink densities of Pt‐PVMQ elastomers was also examined. For the identification of the effect of irradiation on the vibration‐damping properties of Pt‐PVMQ elastomers, dynamic mechanical properties were investigated by using an elastomer testing system, and variation of transmissibility, stiffness, and tan delta values with frequency were examined. As a result of this study, the effect of ionizing radiation on the mechanical and dynamic properties of PVMQ elastomer cured with platinum catalyst has been revealed, and it has been shown that some of these properties can be altered with ionizing radiation. The results obtained in this study also showed that Pt‐PVMQ elastomers have higher damping properties than the damping behavior of Pt‐VMQ elastomers, and these Pt‐PVMQ elastomers can be defined as high damping systems.

Natural Rigid and Hard Plastic Fabricated from Elastomeric Degradation of Natural Rubber Composite with Ultra-High Magnesium Carbonate Content.

It is known that natural rubber is an elastomeric polymer; hence, the main uses are usually limited to soft applications. For the process to reverse the elastomeric effect of natural rubber to obtain rigid plastic from a natural material, an ultra-high amount of magnesium carbonate particles was added to the natural rubber to study the effect of magnesium carbonate in the reduction of elastomeric properties. High magnesium carbonate ratios of 80-180 phr were mixed in the natural rubber in the latex form to maximize the mixing capability since it was more difficult to achieve these mixture ratios with only two roll mill or extruder processes. The more magnesium carbonate powders in the composite, the higher torques were measured from the moving die rheometer (MDR) test. The powder was thoroughly mixed inside the composite, which was observed from energy-dispersive X-ray spectrometer (EDX) mapping; however, the matrix of composites was filled with porosity due to the CO2 formation when latex with magnesium carbonate was assimilated with acid during the vulcanization process. The strength of the composite dropped, and the elongations were shortened. On the other hand, the hardness of composites was drastically increased. The composite lost the elastomeric property, and the hard natural rubber composites were obtained.

A Microsphere-Based Rubber Curing Model for Tire Production Simulation

ABSTRACT In this contribution, a constitutive model for rubber is presented that describes the material in its unvulcanized and vulcanized state as well as during its phase transition. The model is based on the microsphere approach to represent the three-dimensional macroscopic behavior by a set of one-dimensional microscopic chains. When the uncured rubber is exposed to large temperature, the polymer chains build-up crosslinks among each other and the material changes its properties from soft viscoplastic to stiffer viscoelastic behavior. The state of cure over time at different temperatures is identified via a moving die rheometer (MDR) test. Based on this experimental data, a kinetic model is fitted to represent the state of cure in the simulation. The material model changes from the description of an unvulcanized state to a vulcanized state based on the current degree of cure in a thermomechanically consistent manner and fulfills the second law of thermodynamics. The curing model framework is suitable to combine any given material models for uncured and cured rubber. The presented material formulation is applied to an axisymmetric tire production simulation. Therefore, the kinetic state of cure approach is fitted to MDR experimental data. The uncured and cured material model parameters are fitted separately to experiments by a gradient based fitting procedure. The in-molding and curing process of a tire production is simulated by a finite element approach. Subsequently, the simulated footprint of the tire is compared to experimental results. It can be shown that the quality of the footprint could be optimized solely by changing the shape of the green tire.

Preparation of skim natural rubber and polypropylene blends via melt blending: A study on processability

Processability of thermoplastic natural rubber (TPNR) blends is a vital aspect in the preparation of blends for industrial applications and is assessed using different techniques. In this study, skim natural rubber/Polypropylene (SNR/PP) blends were prepared using melt mixing and their processability was examined in terms of mixing torque development, long-term processability, moving die rheometer (MDR) torque, thermo-gravimetric analysis (TGA), melt flow index (MFI) and morphological studies. A series of unvulcanized (UV) and dynamically vulcanized (DV) blends having 70/30, 60/40, 50/50, 40/60, and 30/70 SNR/PP compositions were prepared. Standard Lanka Rubber (SLR) and PP blends having corresponding ratios were also studied for the purpose of comparison. The study reveals that a high percentage of non-rubbers present in the SNR has positively influenced the processability of both UV and DV SNR/PP blends compared to SLR/PP blends as assessed by the mixing torque values. As suggested by the mixing torque development and long-term processability, natural rubber dominant both DV blends cannot be processed. However, they can be processed under low shear rates as shown in the MDR studies irrespective of the rubber type. Therefore, it can be inferred that these rubber dominant blends can be processed into molded products via compression molding technique. TGA studies revealed that a similar degree of protection has been offered to the blends against thermal degradation by SNR and SLR. MFI studies showed that there is no significant difference in flowability between UV SNR/PP blends and SLR/PP blends. However, for DV blends, SNR/PP blends showed a higher flowability than SLR/PP blends. In addition, increase in PP percentage in the blend enhances the flowability while dynamic vulcanization reduces the flowability irrespective of the type of rubber used in the blends. Morphological studies suggest continuous or co-continuous phase structures for UV blends and two-phase structures for DV blends where the plastic phase acts as the continuous phase.

Preparation and characterization of natural rubber–based new elastomers for high-damping base isolation systems

Natural rubber (NR)–based vulcanizates have been used as base isolation materials for many years. Combining good damping properties, low cost, and availability with acceptable mechanical and aging performance, these materials have always been the first choice for base isolation applications. In this research, we try to formulate a natural rubber base recipe with increased damping properties, which can fulfill mechanical and aging requirements of base isolation systems. For this purpose, a series of blends have been formulated by incorporating chloroprene (CR) or butadiene (BR) and acrylonitrile butadiene rubber (NBR) into the natural rubber base. Filler content accelerator type and vulcanization system have been chosen to optimize damping while maintaining a reference point. All vulcanizates have been tested for their mechanical properties. Moving die rheometer (MDR) and rubber process analyzer (RPA) have been used to obtain general cure data as well as storage (G′) and loss modulus and loss angle (η). Crosslink densities have been calculated using RPA and Lee and Pawlowsky’s Coran approach. Dynamic material tests have been performed to obtain dynamic shear properties, equivalent damping ratio, and shear modulus. The results indicated that NR/NBR and NR/CR compounds with viscous damping values of 10.4% and 8.9% at frequency of .5 Hz can lay bases for formulating high-damping rubber (HDR) materials for base isolation systems due to their increased damping and rather good mechanical and relaxation performance.

A novel practical approach for monitoring the crosslink density of an ethylene propylene diene monomer compound: Complementary scanning acoustic microscopy and FIB-SEM-EDS analyses

Tuning of the crosslink density (CLD) in the rubber compounds is very crucial for optimizing the physical and mechanical properties of the ultimate rubber products. Conventionally, CLD can be measured via rheological methods such as moving die rheometer (MDR), via mechanical tests such as temperature scanning stress relaxation analysis (TSSR), or via direct swelling experiments using Flory–Rehner approach. In the current study, two novel techniques, focused ion beam - scanning electron microscopy (FIB-SEM) processing, with simultaneous energy dispersive X-ray spectrometry (EDS) mapping analysis and scanning acoustic microscopy (SAM) were combined and correlated to conventional methods on a model recipe of ethylene propylene diene monomer (EPDM) compound having different sulphur contents. Depending on the applied technique, the increase in the crosslink density with sulphur content was found to be 1.7 fold for the Flory–Rehner approach and 1.2 fold for both TSSR and MDR. It is directly monitored from the FIB-SEM-EDS analysis that the sulphur distribution and agglomeration behavior increased in line with ZnO content, which is an indirect indication of the rise in crosslink density. The impedance maps of the crosslinked samples obtained through SAM analysis revealed that the impedance of the samples increased with the increasing sulphur content, which can be attributed to higher level of crosslink density. A quantified correlation was obtained between SAM images and the crosslink density of the samples. It was shown that SAM is a promising tool for practical and non-destructive analysis for determining the formation of crosslink density of the rubbers.

Development of green materials from ENR-25/PHBV blends: Curing characteristics and mechanical performance

The objective of this work was to develop green materials from epoxidized natural rubber (25% epoxidation), (ENR-25), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), (PHBV), and polybutadiene adducted with maleic anhydride, (PB-g-MA) as compatibilizer. The ENR-25/PHBV blends were prepared at the ratio of 100/0, 90/10, and 80/20 with 0 and 10 %wt. PB-g-MA. The blends were prepared using an internal mixer, where PHBV was first melted at a temperature of 175 °C before mixing with ENR-25 and the incorporation of a compatibilizer. The mixing of ENR-25 and PHBV was continued at a temperature of 175 °C and mixing speed of 50 rpm until it reaches the complete blending time. All ENR-25/PHBV blends were then mixed with curing agents in an internal mixer at a temperature of 50 °C. The cure characteristics were determined using a moving die rheometer (MDR). Then vulcanization proceeded in a compression molding machine. The result shows that the addition of PHBV enhanced the modulus of ENR-25 for every blend ratio with and without compatibilizer owing to the mechanical properties of PHBV. Significantly, the PB-g-MA compatibilizer successfully improved the interface adhesion between ENR-25 and PHBV and the decrease in phase size was clearly seen in the SEM images.

Investigation on the mechanical properties and oil resistance of sulfur cured nitrile rubber/hydrogenated nitrile butadiene rubber blends

AbstractNitrile rubber (NBR)/hydrogenated nitrile butadiene rubber (HNBR) blends with various ratios were compounded with internal mixer and two‐roll open mill. Mechanical properties and low‐temperature performance (TR10) of the NBR/HNBR blends after aging under different conditions were investigated. Furthermore, equilibrium swelling test and moving die rheometer (MDR) test were used to systematically investigate the effects of HNBR dosage on the crosslink densities and curing behaviors. Vulcanization torque and crosslink densities decreased with an increase in HNBR content. The crosslink density of pure HNBR is higher than that of pure NBR, which is related to the macromolecular structures of the rubber. Compression sets of the NBR/HNBR vulcanizates were correlated with HNBR dosage indicating a linear relationship. Low‐temperature performance of the NBR/HNBR blends was improved after being aged in the synthetic hydrocarbon hydraulic oils (SH‐1 and SH‐2). This work shows that the low‐temperature performance and oil resistance could be better balanced by blending NBR with HNBR, while the mechanical properties maintain relatively high level.

An evaluation of the curing characteristics of thermosetting epoxy carbon fiber sheet molding compounds and validation through computer simulations and molding trials

AbstractSheet molding compounds (SMC) are ready‐to‐mold thermoset composite materials reinforced with discontinuous fibers, usually compression molded. Finite element (FE) based compression molding tools can be employed to optimize this process; FE tools require to define material models using raw material data measured through different characterization techniques. In this study, the cure kinetics of an epoxy‐based carbon fiber SMC has been characterized by means of differential scanning calorimetry (DSC) and moving die rheometer (MDR) techniques. Based on these datasets, Claxton‐Liska and Kamal‐Souror models have been set and the compression molding of a validation plate was performed, both experimentally and virtually. The results indicate that, even if both characterization techniques are valid for SMC curing characterization, MDR technique enables the characterization of the material at real molding temperatures and the model based on MDR leads to more accurate results.

A metal-ceramic-rubber composite for hybrid gamma and neutron radiation shielding

In this study, silicone rubber (polydimethylsiloxane) matrix was incorporated with bismuth (III) oxide and hexagonal boron nitride (hBN) functional fillers to develop a flexible composite material that can shield both neutron and X/gamma radiations. Bismuth, as having a high atomic element weight is a very effective material for X/gamma electromagnetic radiation shielding, while hBN has a very high neutron cross-section due to its boron and nitrogen contents. On the other hand, the matrix material that is high temperature vulcanized (HTV) silicone rubber has superior properties of good flexibility, high transparency, and mechanical properties. Hexagonal boron nitride has unique properties and has a similar structure with graphite that is used for neutron moderation. Mechanical test results showed that the elastic modulus of the optimum sample has improved 4 times compared to control sample. Thermal, X ray and neutron attenuation tests were carried out for the developed composite materials. The curing behaviour was investigated in detail using Moving Die Rheometer. Kinetic studies of the vulcanization process were carried out in a very detailed way and high regression values up to 0.98 has been achieved. Non-destructive radiography images were taken to investigate the particle distribution and radiation attenuation of the prepared composites. It was seen that the composite material developed has a considerable attenuation ratio for both neutron and X/gamma radiations. X-ray attenuation test results for silicone rubber containing 20% Bi2O3 and 20% hBN with thickness of 6.4 mm were shown that the intensity of the incoming rays attenuated by 84.1%. Metal-ceramic-rubber composite material with 6.6 mm thickness shielded 65.8% of incoming neutrons.

Effects of in‐situ reactive phenolic resin on shape memory performance of polynorbornene

AbstractIn this paper, resorcinol prepolymer (HT1005) in‐situ reacted with hexamethoxymethyl melamine (HMMM, formaldehyde donor) to produce cured phenolic resin to modify polynorbornene (PNB) as a shape memory polymer (SMP). A moving die rheometer (MDR) was used to characterize the crosslinking degree of phenolic resin. Fourier transform infrared spectroscopy, differential scanning calorimeter, universal electronic tensile testing machine, dynamic mechanical analysis and X‐ray diffraction was used to investigated the mechanical properties and shape memory performance of PNB composites. Infrared results showed that HT1005 reacted with HMMM forming a chemical cross‐linking network in PNB. With the increase of HT1005 and HMMM, the phenolic resin network was gradually improved. When stress was applied to the composite, the phenolic resin rigid network first beared part of the external force, which improved the mechanical properties of the composite. When the content of HT1005 was too much, its dispersibility will become poor, and the rigid phenolic resin network will be too dense, which limited the recovery of PNB molecular chains. A small amount of HT1005 will be more uniformly dispersed in the PNB, the strength of the phenolic resin network was moderate, and the composite material had excellent shape memory and mechanical properties.

In-situ dielectric cure monitoring as a method of measuring the influence of cure temperature on natural rubber vulcanization

Real-time determination of the optimum curing time for molded rubber parts is a challenge in the rubber industry. This research focused on the development of an in-situ rubber cure monitoring system (RCMS) capable of real-time monitoring of the natural rubber vulcanization process in a compression molding machine. The influence of vulcanization temperature (150 °C, 160 °C and 170 °C) on the cure characteristic properties, degree of cure and cure rate of a natural rubber compound in a conventional vulcanization system were compared when monitored with both a moving die rheometer (MDR) and the RCMS testing system. The degree of correlation between the measurements of the cure characteristics at the various vulcanization temperatures obtained from MDR and RCMS was established. The study found that RCMS can be used to determine the scorch time and the optimum cure time in a compression mold in real time.

Using KH590-Polybutadiene as the New Compatilizer to Improve Carbon Black / Ethylene-Propylene-Diene Terpolymer Composites

Rubber materials could be widely used with the reinforcement of inorganic materials, the combination of inorganic materials and rubber needs compatilizer that play an important role in the polymeric composites. The ethylene-propylene-diene terpolymer (EPDM) has considerable radiation stability for gamma or neutron radiation, so it can be applied to cable insulating materials. The EPDM has to be reinforced with carbon black (CB) of inorganic fillers, which are hardly compatible with the EPDM matrix due to EPDM saturated bonds. In this work, The EPDM matrix modified with (3-Mercaptopropyl) trimethoxysilane (KH590)-polybutadiene (KHBR) was studied in details, and the changes in the mechanical, thermal and rheological properties and curing kinetics were investigated by tensile tests, dynamic thermal mechanical analysis (DMA), thermogravimetric analysis (TG), differential scanning calorimetry (DSC) and moving die rheometer (MDR). The results showed that the addition of KHBR improved the mechanical and thermal properties of the EPDM, and the optimized content was 2.5%.

The investigations of mechanical, thermal and rheological properties of polydimethylsiloxane/bismuth (III) oxide composite for X/Gamma ray shielding

Different types of materials are used for radiation shielding owing to the wide usage of radioactive materials in different applications and practices. However, the flexible nature of the shielding material provides a significant advantage in various applications. In this context, the usage of elastomeric materials in a radiation accident situation or normal operating conditions would be a great asset. Although lead is generally used as the gamma ray shielding material, bismuth is also preferred in gamma shielding due to its non-toxic structure and high atomic number. In this study, an X/gamma-ray shielding composite material that contains silicone rubber and bismuth (III) oxide was developed. Silicone rubber (polydimethylsiloxane) and bismuth (III) oxide compound were vulcanized and the curing behavior of the composite was investigated in detail, using both Moving Die Rheometer and Differential Scanning Calorimeter and analyzing the results concomitantly. Mechanical and thermal analyses were carried out and it was concluded from the analysis results that the addition of the bismuth (III) oxide into the silicone matrix was significantly improved the elastic modulus and thermal stability of the developed material. It was also concluded that bismuth (III) oxide addition into the silicone rubber matrix resulted in a flexible X/gamma shielding material with an attenuation rate of 96.4%. Moreover, half-value layer (HVL) decreased with the increment of bismuth (III) oxide content. We propose that the flexible silicone material with different bismuth content, which has both thermal and kinetic properties examined in detail, can be used as flexible X/gamma shielding material.

Vulcanization, interfacial interaction, and dynamic mechanical properties of in-situ organic amino modified kaolinite/SBR nanocomposites based on latex compounding method

With the help of soluble amino modifiers, the vulcanization delay of kaolinite/SBR composites is investigated to shorten the optimum curing time of the filled rubber system based on the latex compounding method (LCM). Compared to the traditional dry blending method, the LCM had better kaolinite dispersion in the rubber matrix. The two different amino modifiers, i.e., quaternary ammonium salt ((CH3)3-N-CH2-) and amino silane (H2N–(CH2)2–NH–(CH2)2–NH–(CH2)3–) were selected in the in-situ modification through two different routes: physical adsorption and chemical bonding. The Moving Die Rheometer revealed that the curing process with the amino group could accelerate the crosslinking reaction, and the kaolinite grafted KH892 nanocomposite showed the best vulcanization performance. An improvement in the curing rate and mechanical properties of kaolinite/SBR composite is ascribed to the outstanding distribution and chemical bonding of nanokaolinite lamellae in the vulcanizate. Furthermore, SEM, HR-TEM, and DMA results demonstrated that both the dispersion of kaolinite in the vulcanizate and the wet skid resistance of the kaolinite/SBR hybrid materials are superior to the composite made by the dry blending method.