Dicumyl Peroxide Content Research Articles

PHYSICAL-MECHANICAL PROPERTIES OF DYNAMICALLY VULCANIZED BASALT CONTAINING PLASTICS BASED ON COMPATIBILIZED POLYPROPYLENE

The influence of the content of basalt and Exxelor PО1020 compatibilizer on the main physical-mechanical and thermophysical characteristics of composites based on polypropylene is considered. It has been established that the use of a compatibilizer in an amount of 1.0–3.0 wt. % can significantly improve such properties of basalt plastics as tensile strength, yield strength, elongation at break, flexural strength, Vicat softening temperature, and melt flow rate. The possibility of cross-linking basalt plastics with sulfur and dicumyl peroxide is considered, and their role in changing their basic physical-mechanical parameters is determined. A theoretical analysis is given of the formation of an interfacial region with the participation of a compatibilizer and basalt. A micrograph showing the redistribution of basalt in the composition of compatibilized polypropylene is given by electron microscopy. The optimal concentrations of vulcanizing agents are determined, at which the highest strength properties are achieved, provided that elongation at break and the melt flow rate are maintained at a satisfactory level. It has been established that the optimal content of dicumyl peroxide is 0.25–0.5% wt

Combination of a Viscoelastic and a Tribological Analysis of a Low‐Density Polyethylene with a High Degree of Cross‐linking

AbstractCross‐linking of polymers is an efficient method to tailor the end‐use properties of polymer materials. Cross‐linking using a chemical agent, e.g., dicumyl peroxide (DCP), allows for a spatially uniform network formation in the melt state. In addition, it is also associated with side reactions which influence the final properties of the plastic part. This work investigates the influence of DCP concentration on the tribological properties of a cross‐linked low‐density polyethylene (LDPE) grade. In particular, high DCP concentrations up to 20 phr are chosen in order to explore the effect of a high degree of cross‐linking. The viscoelastic properties below and above the melting temperature are studied in detail to support the interpretation of the tribological results. Rheological investigations allow one to monitor the cross‐linking of the long‐chain branched LDPE. The data and the subsequent optical analysis show that wear already is significantly reduced at a low DCP concentration of 1 phr because of the covalent bonds caused by cross‐linking. A high DCP concentration of 20 phr yields an increase of coefficient of friction which can be explained by the low stiffness and the resulting high contact area in the case of highly cross‐linked LDPE.

Reactive melt‐grafting of maleic anhydride onto olefin block copolymer toward high‐performance polar polyolefin thermoplastic elastomer

AbstractThe block structure of olefin block copolymer (OBC) elastomer gives it good elasticity and heat resistance relative to other polyolefin elastomers. However, the non‐polar nature of OBC chains limits its comprehensive properties like dyeing and toughening for polar engineering plastics. In this work, maleic anhydride (MA) and dicumyl peroxide (DCP) were selected as a typical polar monomer and a radical initiator to modify the polarity of OBC elastomer. During the melt‐grafting process, the DCP content was tuned to optimize the grafting efficiency while the MA‐to‐OBC ratio was fixed at 5 wt%. It was found that all the melt‐grafting reactions show high efficiency and can be finished in 3 min at 170 °C. With the increase of DCP content, the estimated grafting degree of OBC‐g‐MA elastomer increases from 0.40% to 1.16% along with increased gel content from 4.27% to 22.44%. A suitable grafting process was obtained with a DCP content of 3.0 wt% by balancing grafting efficiency and final mechanical properties. The optimized OBC‐g‐MA elastomer with a grafting degree of 0.92% has a mechanical strength of 17.15 MPa, a Young's modulus of 26.35 MPa, elongation of 1564% and strain recovery of 59.73%. Additionally, the contact angle test shows that polar grafting can increase surface hydrophilicity while excessive crosslinking promotes hydrophobicity. Therefore, our work has demonstrated the feasibility of the reactive melt‐grafting method to prepare OBC‐g‐MA elastomer and can also provide a processing reference for other chemical functionalization of polyolefin thermoplastic elastomers. © 2024 Society of Industrial Chemistry.

Influence of Crosslink Density on Electrical Performance and Rheological Properties of Crosslinked Polyethylene.

To investigate the influence of the crosslinked polyethylene (XLPE) structure on electrical performance, various analytical methods were employed to study polyethylene structures with different degrees of crosslinking. Dynamic rheological analysis was conducted to determine material shear viscosity, dynamic viscosity, storage modulus (G'), loss modulus (G″), and other rheological parameters. Additionally, the electrical performance of the material was analyzed by studying the phenomenon of space charge accumulation under direct current voltage. The results indicate that with an increasing mass fraction of the crosslinking agent, the crosslink density of crosslinked polyethylene initially increases and then decreases. When the dicumyl peroxide (DCP) content exceeds 1.0 wt.%, there is an accumulation of like-polarity space charges. The best rheological processing performance of crosslinked polyethylene is observed when the DCP content is in the range of 1.0-1.5 wt.%.

Mechanical, Rheological, and Heat Seal Properties of 1‐Octene Grafted Low Density Polyethylene Films

AbstractHeat seal and mechanical properties of 1‐octene grafted low density polyethylene films containing various concentrations of Dicumyl peroxide as the initiator and 1‐octene grafting agent is investigated through using experimental measurements. The results of differential scanning calorimeter (DSC) measurements revealed that the melting temperature shifts to higher values and the peak of the DSC curve becomes wider with the increase of 1‐octene concentrations. Thermogravimetric analysis (TGA) revealed a higher thermal stability up to 20 °C for 1‐octene grafted PE compared with neat LDPE alloy. The results of stress–strain measurements revealed that the 1‐octene grafted PE alloys has higher tensile strength in comparison with neat PE alloy and samples containing only DCP initiator. The results of heat seal analysis indicated that both DCP initiator and 1‐octene tended to offer a moderate increase peel strength of PE alloy. DMTA measurements for various grafted PE alloys show a higher damping factor in comparison with neat LDPE alloy. Rheological measurements indicated a higher storage modulus up to 25% and higher complex viscosity for grafted PE samples containing 1‐octene comonomer.

Preparation of water swellable rubber from epoxidized natural rubber and sodium acrylate by in‐situ polymerization: Effect of vulcanization system, epoxide, and dicumyl peroxide, and sodium acrylate content

AbstractWater swellable rubber (WSR) was prepared from epoxidized natural rubber (ENR) and sodium acrylate (NaAA) by in‐situ polymerization using sulfur and dicumyl peroxide (DCP) as a vulcanizing agent and an initiator, respectively. The ENR, NaAA, and other additives were mixed in an internal mixer and a two‐roll mill. The effect of the vulcanization system, epoxide, and DCP, and NaAA content on the vulcanization, physical, and mechanical properties of WSR were investigated in this research. As the results, the scorch and curing time of WSR compounded with ENR 25 and vulcanized with a mixture of sulfur‐peroxided or mixed vulcanization system were less than other systems. Furthermore, the scorch and curing time decreased with the increase in DCP content. The WSR with ENR 50 vulcanized with DCP (1.5 phr) in the mixing system provided the highest tensile strength. However, the volume change of WSR with the mixing system (WSR/M) was lower than the WSR cured with peroxide (WSR/P). For WSR/P, the tensile strength, hardness, and volume change in water increased with increasing DCP, and NaAA content, while the elongation at break decreased. These results suggest that WSR has the potential for diverse applications, including waterproofing and sealing solutions in civil construction projects.Highlights Water swellable rubber (WSR) was prepared from epoxidized natural rubber (ENR) and sodium acrylate (NaAA) by in‐situ polymerization using sulfur and dicumyl peroxide (DCP) as a vulcanizing agent and an initiator. The scorch and curing time of WSR compounded with ENR 25 and vulcanized with a mixed vulcanization system were less than those of other systems. During the vulcanization process, ENR 50 can be generated by the ring‐opening of the adjacent epoxide groups more than ENR 25, and the self‐crosslink of ENR 50 was higher than ENR 25. Water swelling and volume change of WSR tended to decrease with increasing epoxide, and DCP content, whereas those properties increased with increasing NaAA content. Tensile strength, elongation at break, and hardness of WSR with the mixing system (WSR/M) were higher than those of WSR with the peroxide system (WSR/P). Swelling and volume change of WSR/P were higher than those of WSR/M.

The effect of cross-linking system and reinforcement on the cross-linking reaction of peroxide vulcanized ethylene-propylene-diene terpolymer (EPDM) matrix

In this work, the effect of using of dicumyl-peroxide (DCP) (2, 5 & 8 phr) and co-agent triallyl-cyanurate (TAC) (2, 4 & 6 phr) as cross-linking system as well as multi-walled carbon nanotubes (MWCNTs) (5, 8 και 10 phr) as a filler, for ethylene-propylene-diene terpolymer (EPDM) was investigated. Differential scanning calorimetry (DSC) was employed in order to study the progress of the cross-linking reaction, based on the exothermic vulcanization peaks of isothermal (at 160, 170, 180, 190 °C) and non-isothermal experiments (with heating rates 5, 10, 25, 50 °C min−1). The autocatalytic model was successfully applied to the results of isothermal experiments and the activation energy (Ea) of the reaction was calculated, based on the Arrhenius equation. The Ozawa-Kissinger equations were also applied to the data obtained from the non-isothermal study. From the results obtained from isothermal DSC experiments, an increase was observed in the reaction rates accompanied with a decrease in Ea with the increase of DCP content, whereas a proportional relationship between TAC content and the enthalpy and Ea of the reaction was recorded. The incorporation of MWCNT’s in EPDM increased its Ea. From the non-isothermal DSC experiments, a significant increase in the enthalpy and Ea of the cross-linking reaction was observed at higher DCP content, whereas TAC content did not show any notable effect on the reaction. Based on the results of this research, it is concluded that the increase of peroxide content facilitates the vulcanization of EPDM, whereas inhibition was observed by the incorporation of MWCNT’s.

The effect of chemical crosslinking on the properties of Rotomolded high density polyethylene

AbstractIn this study, high density polyethylene (HDPE) was combined with dicumyl peroxide (DCP) to produce crosslinked parts via rotational molding. The effect of DCP content (0.1–2.5 phr) on the crosslinking degree was investigated to determine its effect on the chemical, mechanical, physical, and thermal properties of HDPE. The gel content and crosslink density was found to increase with DCP content. These trends led to a reduction in the degree of crystallinity, melting, and crystallization temperature. Thermogravimetric analysis (TGA) showed that crosslinked HDPE (xHDPE) has higher thermal stability than the neat matrix in both air and nitrogen atmosphere. In addition, a direct relationship was observed between improved thermal resistance and higher impact strength. Finally, relationships between the tensile properties of xHDPE and the degree of crystallinity were observed, which were all controlled by the level of crosslinking. These results have the potential to advance the manufacturing of high performance materials suitable for a wide range of applications such as automotive parts, agricultural products, chemical storage tanks, large waste containers, and fuel tanks in general.

The effect of peroxides on the structure of high‐melt‐strength polylactide with long‐chain branched architecture or micro‐crosslinking

AbstractLong‐chain branched polylactides (PLA‐LCB) with high melt strength were prepared through a melting reaction using Trigonox301 or dicumyl peroxide (DCP). During this reaction, random chain scissions, branching reactions, and cross‐linking reactions took place, as confirmed by the torque‐time rheograms and gel permeation chromatography profiles. It is evident that the random chain scissions are more prominent in PLA‐LCBD compared to PLA‐LCBT. The rheological characterization further elucidated the formation of LCB architecture. With an increase in the content of Trigonox301 or DCP, both branch‐on‐branch architecture and cross‐linked architecture were observed. The preference for branch‐on‐branch architectures was found to be higher in PLA‐LCBT as compared to PLA‐LCBD. Additionally, the presence of gel fraction was more easily detectable in PLA‐LCBD samples, indicating a higher likelihood of cross‐linking reactions in these samples. The emergence of new peaks at the positions of 1.82 and 1.47 ppm establishes a solid theoretical foundation for the potential reaction mechanism. One possible explanation proposed is that the reaction rate of free radicals originating from PLA‐LCBD samples is significantly higher than the diffusion rate of macromolecular free radicals. Consequently, the occurrence of a free radical chain transfer reaction is limited to a very small region, resulting in the formation of a cross‐linked structure. While the free radicals that are produced by the cyclic peroxide actively contribute to the graft reaction, thereby promoting the formation of the LCB structure with a micro‐crosslinking component.

Simultaneous crosslinking and foaming of ethylene‐propylene diene terpolymers (EPDM) organoclay composite foams

AbstractThis study used ethylene‐propylene diene monomers (EPDM), an elastomer, to develop foams incorporating clay as filler using simple compounding, chemical foaming, and peroxide‐mediated light crosslinking methods. The low‐temperature batch mixer was employed for compounding azodicarbonamide (ADC) as a foaming agent, dicumyl peroxide (DCP) as a crosslinker, followed by compression molding for sheet preparation and the high‐temperature foaming process. Fourier transform infrared spectroscopy (FTIR) equipped with a hot stage attenuated total reflection (ATR) was employed to elucidate the ADC decomposition and foaming. The DCP (0.25 phr) content was optimized based on the foaming expansion ratio (>4) and stability, which was further optimized in conjuncture with clay to generate high‐performance composite foams. The incorporation of 1% organoclay enhances the expansion ratio and specific tensile strength by >7 and ~ 270%, respectively, compared with EPDM foams without clay while displaying a density of 0.11 g/cm3. Overall, the developed foaming process can be extended to other elastomeric polymers for various applications such as protective gears (e.g., helmets and shin guards), thermal/sound insulation, packaging/containment, footwear soles, oil absorption, etc.

Tailoring the performance of poly(lactic acid)‐based reactive blends: The effect of vinyl acetate and dicumyl peroxide content

AbstractPoly(lactic acid) has been gaining prominence in academia and industry, mainly due to being a biopolymer and biodegradable material. Nevertheless, mainly due to its high fragility, work has been carried out in order to seek alternatives to improve this drawback. Hence, this work aims to evaluate the effect of the vinyl acetate content using two types of EVA (EVA1 with 28% and EVA2 with 19%) in dynamically vulcanized PLA/EVA blends, using several dicumyl peroxide (DCP) contents, that is, 0.3, 0.5, and 0.7 phr. Blends were produced using an internal mixer, and the tensile, impact and HDT specimens were injection molded. By FTIR and torque rheometry, it was verified that, upon DCP addition, there was evidences of reticulation, resulting in crosslinked PLA, crosslinked EVA, as well as PLA‐g‐EVA. Through tensile and impact strength tests, it was observed substantial increases in the elongation at break, and in impact strength, mainly for the compounds with higher content of vinyl acetate (EVA1). Impact specimens made with PLA/EVA120 0.7 DCP, PLA/EVA130 0.5 DCP, and 0.7 DCP, did not completely break, due to the probable development of the in situ PLA‐g‐EVA compatibilizer among the present phases. Therefore, it is believed that a more homogeneous microstructure was obtained, as observed by SEM images, highlighted upon the DCP content increase. It was verified that the highest vinyl acetate content is of paramount importance for obtaining PLA/EVA blends with better compatibility as well as EVA1 being more susceptible to crosslinking using DCP, resulting in blends with greater toughness.

Peroxide‐based crosslinking of solid silicone rubber, part II: The counter‐intuitive influence of dicumylperoxide concentration on crosslink effectiveness and related network structure

AbstractApplication of elastomers in general demands the conversion of their soluble networks into crosslinked structures. This abrupt change causes several modifications, both in the atomic/molecular level and at the macro‐scale. In this study, solid silicone rubber (high molecular weight poly(dimethylsiloxane)), was crosslinked with dicumylperoxide (DCP), a widely used crosslinking agent by the rubber industry. The changes caused by different DCP concentrations were investigated, aiming to bring attention to the molecular transformations, usually neglected when processing‐oriented studies are conducted. DCP concentration showed a limited contribution to the network's molecular dynamics, which was found to be mainly dominated by entanglements. The dominance of entanglements over other molecular constraints, like crosslink points, justifies the threshold and counter‐intuitive behavior of tensile and hardness properties. However, differences were found in the crystallization ability after crosslinking, when the more crosslink points were introduced, the lower the crystallinity was and the less stable the PDMS crystallites were. In addition to providing a deeper understanding of an industrially applied rubber system n terms of the effective concentration of DCP, and the reasoning behind such concentration, the findings of this study add to the state‐of‐the‐art comprehension of elastomeric networks, and how they behave on a molecular level.

Cure kinetics and mechanical properties of carbonized chicken feather reinforced styrene butadiene rubber composites

AbstractPolymers are part and parcel of our life and society due to the immense applications resulting from their unique properties. High performing products based on bio feed stocks have gained special attention compared to non‐renewable resources. In the present research work, carbon black (CCF) prepared from waste chicken feathers has been used as reinforcement in styrene butadiene rubber (SBR). Cure kinetics of SBR‐CCF composites and their mechanical properties have been evaluated with respect to loading of filler and concentration of dicumyl peroxide crosslinking agent. The cure reaction of all compounds obeys first order kinetics and the rate constants increase with filler loading as well as temperature. A decrease in energy of activation of cure has been noted with increase of loading of CCF filler, which assists for an increase in the rate of production of articles using the filled SBR compounds. The improvement in tensile properties with CCF has been supported by the fractography of the composites and by the crosslink density values obtained using equilibrium swelling method. The performance of the developed composites points to their applications in the area of car‐tire industry, tread rubber sector and structural applications such as drive and shaft couplings.

Trans-Polyisoprene/Poly (Ethylene-co-Vinyl Acetate) Polymer Composites as High-Performance Triple Shape Memory Materials.

The performance and programming conditions of the triple shape memory of crosslinked trans-polyisoprene/poly (ethylene-co-vinyl acetate) (TPI/EVA) composites with different contents of dicumyl peroxide (DCP) were investigated. The effect of triple shape memory in the TPI/EVA composites was studied by tensile loading, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and dynamic thermomechanical analysis (DMA). It was demonstrated that the content of DCP increased, the crystallization temperature of TPI decreased from 55.2 to 38.3 °C, and the crystallization temperature of EVA decreased slightly. The SEM results showed that DCP, as an initiator, could form a graft copolymer of TPI-g-EVA at the interface of the two phases, which could improve the adhesion of the two phases. The DMA showed that the higher the content of DCP, the higher the first-stage shape recovery ratio. Moreover, the composites exhibited favorable shape fixity ratio (Rf) and shape recovery ratio (Rr) with the incorporation of 0.4 phr DCP. At the same time, it was demonstrated that the TPI/EVA composites showed excellent mechanical strength, including tensile strength up to 24.3 MPa, as well as elongation at break reaching 508%.

Peroxide-Based Crosslinking of Solid Silicone Rubber, Part I: Insights into the Influence of Dicumylperoxide Concentration on the Curing Kinetics and Thermodynamics Determined by a Rheological Approach.

Predicting the curing behaviour of industrially employed elastomeric compounds under typical processing conditions in a reliable and scientifically driven way is important for rubber processing simulation routines, such as injection moulding. Herein, a rubber process analyser was employed to study the crosslinking kinetics of solid silicone rubber based on the concentration of dicumylperoxide. A model was proposed to describe the optimal cure time variation with peroxide concentration and temperature, based on the analysis of processing parameters applying kinetic and thermodynamic judgments. Additionally, the conversion rate was described with the aid of a phenomenological model, and the effect of dicumylperoxide concentration on the final crosslink state was investigated using kinetic and thermodynamic explanations. Optimal curing time was affected both by temperature and dicumylperoxide concentration. However, the effects were less pronounced for high temperatures (>170 C) and high concentrations (>0.70 phr). A limit on the crosslink state was detected, meaning that the dicumylperoxide capacity to crosslink the silicone network is restricted by the curing mechanism. Curing restrictions were presumed to be primarily thermodynamic, based on the proton abstraction mechanism that drives the crosslinking reaction. In addition to providing more realistic crosslinking models for rubber injection moulding simulation routines, the results of this study may also explain the chemical behaviour of organic peroxides widely used for silicone crosslinking.

Improving the DC Dielectric Properties of XLPE with Appropriate Content of Dicumyl Peroxide for HVDC Cables Insulation

In this research, crosslinked polyethylene (XLPE) is developed with selective content of dicumyl peroxide (DCP), and the influence of microstructural properties and chemical composition on the mechanical and direct current (DC) dielectric properties are investigated. The measurements for the microstructural analysis are taken by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), gel content test and Fourier transform infrared (FTIR). The mechanical properties of XLPE are evaluated by hot-set test. The results of microstructural and chemical composition show that the increase in DCP content increases the crosslinking degree from 74.3% to 81.6%, reduces the crystallinity/lamella thickness from 36.8% to 35.5%/7.6–7.1 nm, reduces the average molecular weight between two crosslinks by 0.01 kg/mol and reduces the oxidation level/carbonyl index. The increase in DCP in XLPE samples decreases the permanent elongation from 2.2% to 0% and elongation rate from 300% to 80% of the cable insulation. The rise in DCP content increases the crosslinking degree due to which the DC resistivity and activation energy is increased. The DC breakdown strength at 30–90 °C is increased due to the increase in crosslinking degree and reduction in carbonyl index/oxidation level. The space charge accumulation is measured at 30 °C under 20–60 kV/mm, resulting in less homo-charges and hetero-charges with the increase in DCP. It is proven that the role of appropriate DCP content is vital in increasing the DC dielectric performance, internal material characteristics and mechanical performance of XLPE.

Effects of dicumyl peroxide on cross‐linking pure poly(butylene succinate) foaming materials for high expansion and high mechanical strength

AbstractThis paper fabricated the cross‐linking poly(butylene succinate) foaming materials with high expansion ratio, high mechanical strength, and high degradation rate though cross‐linking and molding compression methods. With dicumyl peroxide content increasing, complex viscosity, and storage modulus appear to increase tendency. The properties of cell size, distribution, mechanical properties, and thermal conductivity all appear the first increasing and then decreasing trend with dicumyl peroxide content increasing. When dicumyl peroxide concentration is 6 wt% and azodicarbonamide concentration is 1 wt%, pure cross‐linking poly(butylene succinate) foaming material's expansion ratio and compression strength could reach 7.03 and 5.61 MPa, respectively. In addition, this pure cross‐linking poly(butylene succinate) foaming material has high degradability, and the degradation ratio could get 80% in alkaline aqueous solution.

Ground Tire Rubber Modified by Elastomers via Low-Temperature Extrusion Process: Physico-Mechanical Properties and Volatile Organic Emission Assessment.

In this paper, low-temperature extrusion of ground tire rubber was performed as a pro-ecological waste tires recycling method. During this process, ground tire rubber was modified with constant content of dicumyl peroxide and a variable amount of elastomer (in the range: 2.5–15 phr). During the studies, three types of elastomers were used: styrene-butadiene rubber, styrene-ethylene/butylene-styrene grafted with maleic anhydride and ethylene-octene copolymer. Energy consumption measurements, curing characteristics, physico-mechanical properties and volatile organic compounds emitted from modified reclaimed GTR were determined. The VOCs emission profile was investigated using a passive sampling technique, miniature emission chambers system and static headspace analysis and subsequently quantitative or qualitative analysis by gas chromatography. The VOCs analysis showed that in the studied conditions the most emitted volatile compounds are dicumyl peroxide decomposition by-products, such as: α-methylstyrene, acetophenone, α-cumyl alcohol, methyl cumyl ether, while the detection level of benzothiazole (devulcanization “marker”) was very low. Moreover, it was found that the mechanical properties of the obtained materials significantly improved with a higher content of styrene-butadiene rubber and styrene-ethylene/butylene-styrene grafted with maleic anhydride while the opposite trend was observed for ethylene-octene copolymer content.

Термодеформационные характеристики нанокомпозитов на основе полипропилена и термозолы бытовых отходов

The paper presents the results of a study of the influence of the concentration and particle size of the filler on the thermomechanical properties of composite materials based on polypropylene and waste from waste processing industry (thermal ash). Three grindings of thermal ash were used with particle sizes: 90 nm, 300 – 500 nm and 1200 – 2000 nm. It has been established that with an increase in the size of thermal ash particles, the deformation curve in the region of the viscous-flow state shifts to the region of high temperatures. As a compatibilizer used functionalized with 5.6 wt. % maleic anhydride polypropylene grade Exxelor PO1020 to improve miscibility and compatibility of non-polar polypropylene with thermal ash particles. It is shown that the introduction of different amounts of the cross-linking agent dicumyl peroxide contributes to a significant change in the pattern of deformation of nanocomposites with temperature. The concentration of dicumyl peroxide was varied within 0.25 – 2.0 wt. %. Peroxide crosslinking using 0.25 – 0.5 wt. % dicumyl peroxide contributed to the appearance of a region of highly elastic deformation on composites with 5.0 and 40 wt. % thermal ash. With an increase in the concentration of dicumyl peroxide over 0.5 wt. % vitrification of nanocomposites was observed. In this state, the samples are completely crosslinked and pass into the infusible state. Such an infusible state is highly undesirable since it is not possible to process them by injection molding and extrusion.

Achieving multimodal locomotion by a crosslinked poly(ethylene-co-vinyl acetate)-based two-way shape memory polymer

Locomotion is a critically important topic for soft actuators and robotics, however, the locomotion applications based on two-way shape memory polymers (SMPs) have not been well explored so far. In this work, a crosslinked poly(ethylene-co-vinyl acetate) (cPEVA)-based two-way SMP is synthesized using dicumyl peroxide (DCP) as the crosslinker. The influence of the DCP concentration on the mechanical properties and the two-way shape memory properties is systematically studied. A Venus flytrap-inspired soft actuator is made by cPEVA, and it is shown that the actuator can efficiently perform gripping movements, indicating that the resultant cPEVA SMP is capable of producing large output force and recovering from large deformations. This polymer is also utilized to make a self-rolling pentagon-shaped device. It is shown that the structure will efficiently roll on a hot surface, proving the applicability of the material in making sophisticated actuators. With introducing an energy barrier, jumping can be accomplished when the stored energy is fast released. Finite element simulations are also conducted to further understand the underlying mechanisms in the complex behavior of actuators based on cPEVA SMP. This work provides critical insights in designing smart materials with external stimulus responsive programmable function for soft actuator applications.