Toughening polystyrene by core–shell grafting copolymer polybutadiene-graft-polystyrene with potassium persulfate as initiator

Core–shell polybutadiene-graft-polystyrene rubber particles with different ratios of polybutadiene core to polystyrene shell were synthesized by an emulsion polymerization using K₂S₂O₈ as an initiator. Then the core–shell rubber particles were blended with PS to prepare PS/PB-g-PS. The rubber particles with a size of 0.3–0.5 μm could toughen polystyrene significantly. The mechanical properties, morphologies and deformation mechanisms of samples were extensively investigated. The experimental results showed that the dispersion of rubber particles in a “cluster” state leads to better impact resistances. Crazing occurred from rubber particles and extended in a bridge-like manner to neighboring rubber particles parallel to the equatorial direction.     

Surface modification of lignosulfonates for reinforcement of styrene–butadiene rubber compounds

In this study, surface modification of lignosulfonates (LSs) was investigated for potential reinforcement of styrene–butadiene rubber compounds. Lignins are naturally occurring amorphous, highly branched polymers consisting of aromatic and aliphatic segments with polar functional groups such as hydroxyl, methoxy, carbonyl, and carboxyl. The polarity and hydrophilic nature render lignin incompatible with nonpolar rubber materials. In this study, cyclohexylamine (CA) modification of LS was evaluated for enhancement of compatibility with rubber via proton transfer and hydrogen bonding interactions. X‐ray photoelectron spectroscopy data confirm attachment of CA onto the surface of LS. The cure and scorch times of rubber compounds were shortened, and the crosslink density enhanced with an increase of the amount of CA in modified LS. The tensile strength at break increased by almost 45%; the 100% modulus and elongation at break also showed significant improvements. The values of storage modulus and loss tangent increased by 13% and 18%, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40123.     

In situ dispersion and compatibilization of lignin/epoxidized natural rubber composites: reactivity,morphology and property

Lignin, a naturally occurring polymer, was viewed as a potential substitute of carbon black for reinforcing rubber materials. However, it shows no reinforcing effect if directly mixed with rubber. In this study, lignin was in situ dispersed at submicrometer size and highly compatible with epoxidized natural rubber (ENR) by using a high‐temperature dynamic heat treatment (HTDHT). Rheology analysis indicated that the ring opening reaction between lignin and ENR occurred at 160°C or above, which was further confirmed by infrared spectroscopy. Due to the consumption of acidic groups of lignin by ENR, the retardant vulcanization effect of lignin was weakened. Morphology observation and dynamic mechanical analysis demonstrated the perfect lignin dispersion and the strong interactions between lignin and ENR. The mechanical properties of the lignin/ENR composites were significantly improved by using HTDHT. Compared to the directly mixed rubber composites, the tensile strength and tear strength of the heat treated rubber composites filled with 40 phr lignin were increased by 114% and 23%, respectively. Especially, the 300% modulus of the heat treated rubber composite was increased by ca. 400%. X‐ray diffraction results indicated that the reinforcement of the composites originated from the presence of lignin rather than the strain‐induced crystallization of ENR. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42044.     

Contribution of Ungrafted Segments in Core-Shell Impact Modifier in the Toughening of PBT Resins by Epoxy Functionalized Poly(Butadiene-graft-Styrene)

A series of poly(butadiene-graft-styrene) core-shell impact modifiers and glycidyl methacrylate functionalized PB-g-PS (PB-g-PSG) with different glycidyl methacrylate content were synthesized by seeds emulsion polymerization. The modifiers were used to toughen poly(butylene terephthalate) resins. The results showed that poly(butylene terephthalate) was efficiently toughened by functionalized PB-g-PSG but not by poly(butadiene-graft-styrene). The introduction of glycidyl methacrylate improved the miscibility and properties. The effects of the ungrafted segments in modifiers on the properties of blends were investigated. The miscibility and properties dropped after the ungrafted segments in modifiers were separated. Results indicated that ungrafted PS segments showed positive effect on toughening of poly(butylene terephthalate).     

碱木质素填充天然橡胶的特性研究

研究了碱木质素填充天然橡胶的规律,考察了胶料内填料网络结构特点及其对动态力学性能的影响。通过扫描电镜（SEM）、力学性能测试和动态力学性能测试对硫化胶进行观察和分析。结果表明：填充10%~50%碱木质素时,碱木质素在天然橡胶中几乎没有填料-填料相互作用,且橡胶-填料相互作用很弱,碱木质素颗粒之间发生了团聚;碱木质素填充后胶料的力学性能没有大的降低,填充10%碱木质素时,硫化胶的拉伸强度为30MPa,高于未填充碱木质素时的28.7MPa;碱木质素的加入一定程度地促进了橡胶的硫化,交联密度随着碱木质素的加入而增大,当碱木质素用量达到50%时交联密度有所下降,拉伸强度未20.1MPa;胶料的老化性能随碱木质素的加入得到改善;碱木质素的加入对硫化胶的抗湿滑性和滚动阻力没有明显影响。     

Hybrid fillers of lignin and carbon black for lowering of viscoelastic loss in rubber compounds

This study investigates novel hybrid fillers for lowering of viscoelastic dissipation in rubber compounds by exploiting non-covalent interactions between lignin and carbon black (CB). Lignin is naturally occurring three-dimensional amorphous polymer consisting of phenyl propane units with hydroxyl, methoxy, and carbonyl substitutions and is capable of producing non-covalent interactions via π–π stacking with CB particles. The hybrid fillers are obtained by precipitating lignin from solutions onto carbon black particles. The fractal nature similar to CB particles and the presence of lignin coating layers on CB particles are confirmed by electron microscopy images. The coating layers are promoted by strong π–π interactions as revealed from Raman spectroscopy and ¹H spin-lattice relaxation data and supported by a drop in zeta potential values. The hybrid fillers show much less networking than CB and reduce the viscoelastic dissipation in model rubber compounds by as much as 10% in comparison to the compounds of only CB.     

Effects of reactive compatibilizer on the core-shell structured modifiers toughening of poly(trimethylene terephthalate)

Poly(trimethylene terephthalate)/polybutadiene grafted polymetyl methacrylate (PB-g-PMMA, MB) blends were prepared by melt processing with varying weight ratios (0-5 wt%) of diglycidyl ether of bisphenol-A (DGEBA) epoxy resin as a reactive compatibilizer. DMA result showed PTT was partially miscible with MB particles in the presence of the compatibilizer. Fourier transform infrared (FTIR) and rheological measurements further identified the reactions between PTT and DGEBA epoxy resin. Scanning electron microscopy (SEM) displayed that the core-shell structured modifiers exhibit a smaller dispersed domain size with the addition of DGEBA epoxy resin. Mechanical tests showed the impact and tensile properties of PTT blends are improved by the introduction of DGEBA epoxy resin to the blends. SEM and TEM results showed shear yielding of PTT matrix and cavitation of rubber particles were the major toughening mechanisms.     

Improvement of properties of silica‐filled styrene–butadiene rubber compounds using acrylonitrile–butadiene rubber

Since silica has strong filler–filler interactions and adsorbs polar materials, a silica‐filled rubber compound has a poor dispersion of the filler and poor cure characteristics. Improvement of the properties of silica‐filled styrene–butadiene rubber (SBR) compounds was studied using acrylonitrile–butadiene rubber (NBR). Viscosities and bound rubber contents of the compounds became lower by adding NBR to the compound. Cure characteristics of the compounds were improved by adding NBR. Physical properties such as modulus, tensile strength, heat buildup, abrasion, and crack resistance were also improved by adding NBR. Both wet traction and rolling resistance of the vulcanizates containing NBR were better than were those of the vulcanizate without NBR. The NBR effects in the silica‐filled SBR compounds were compared with the carbon black‐filled compounds. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1127–1133, 2001     

Preparation and characterization of lignin‐layered double hydroxide/styrene‐butadiene rubber composites

Lignin‐layered double hydroxide (lignin‐LDH) complex was synthesized by in situ method, and then styrene‐butadiene rubber (SBR)/lignin‐LDH composites were prepared by the melt compounding method. X‐ray diffraction analysis showed that crystal lignin‐LDH was successfully obtained and transmission electron microscopy analysis showed well dispersion of lignin‐LDH in SBR matrix. The tensile strength, elongation at break, 300% modulus and hardness of lignin‐LDH/SBR were significantly improved compared to LDH/SBR composites. Thermogravimetric analysis indicated that the thermal degradation temperature of the lignin‐LDH/SBR at 10% weight loss (T₁₀) decreased whereas 50% weight loss (T₅₀) was much higher than that of pristine LDH/SBR due to barrier property of the well dispersed Lignin‐LDH in SBR matrix. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1308‐1312, 2013     

Enhanced oil resistance and mechanical properties of nitrile butadiene rubber/lignin composites modified by epoxy resin

This is probably the first report on developing nitrile butadiene rubber (NBR) composites with enhanced performance s via lignin bridged epoxy resin in the rubber matrix. NBR/lignin masterbatch has been prepared through latex‐compounding method, and then epoxy resin (F51) was added in the NBR/lignin compounds by the melt compounding method. Lignin‐epoxy resin networks were synthesized in situ during the curing process of rubber compounds through epoxide?hydroxyl reactions. Compared with lignin filler, lignin‐F51 networks showed an improved oil resistance ability and led to increased mechanical properties, crosslinking density, and thermal stability of the rubber composites. This method provides a new insight into the fabrication of novel interpenetrating polymer networks in rubber composites and enlarges the potential applications of lignin in high performance rubber composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42922.     

Multiphase materials with lignin. XV. Blends of cellulose acetate butyrate with lignin esters

Commercially available cellulose acetate butyrate (CAB, unplasticized) was blended in melt and solution with lignin esters having different ester substituents—acetate (LA), butyrate (LB), hexanoate (LH), and laurate (LL). All lignin esters formed phase‐separated blends with CAB with domain size depending on processing conditions and the interaction between phases depending on blend components. CAB/LA and CAB/LB revealed the strongest interactions with domain sizes on the 15–30 nm scale as probed by dynamic mechanical thermal analysis and differential scanning calorimetry. The glass transitions (T_g) followed the Fox equation. Broader transitions corresponding to the T_gs of the two parent components were observed for CAB blends with LH and LL. Transmission electron micrographs revealed differences in the phase dimensions of the blends in accordance with chemical and processing (i.e., melt vs solvent) differences. Modest gains in modulus were observed for low contents (<20 wt %) of LA and LB. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 448–457, 1999     

Polyamide 6/maleated ethylene–propylene–diene rubber/organoclay composites with or without glycidyl methacrylate as a compatibilizer

Polyamide 6 (PA6)/maleated ethylene–propylene–diene rubber (EPDM‐g‐MA)/organoclay (OMMT) composites were melt‐compounded through two blending sequences. Glycidyl methacrylate (GMA) was used as a compatibilizer for the ternary composites. The composite prepared through via the premixing of PA6 with OMMT and then further melt blending with EPDM‐g‐MA exhibited higher impact strength than the composite prepared through the simultaneous blending of all the components. However, satisfactorily balanced mechanical properties could be achieved by the addition of GMA through a one‐step blending sequence. The addition of GMA improved the compatibility between PA6 and EPDM‐g‐MA, and this was due to the reactions between PA6, EPDM‐g‐MA, and GMA, as proved by Fourier transform infrared analysis and solubility (Molau) testing. In addition, OMMT acted as a compatibilizer for PA6/EPDM‐g‐MA blends at low contents, but it weakened the interfacial interactions between PA6 and EPDM‐g‐MA at high contents. Both OMMT and GMA retarded the crystallization of PA6. The complex viscosity, storage modulus, and loss modulus of the composites were obviously affected by the addition of OMMT and GMA. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Novel natural rubber-g-N-(4-hydroxyphenyl)maleimide: synthesis and its preliminary blending products with polypropylene

Graft copolymer of natural rubber and N-(4-hydroxyphenyl)maleimide (i.e., NR-g-HPM) was synthesized. It was found that the grafting yield increased upon increasing the grafting temperature and the highest grafted HPM content was obtained at 200 °C. Furthermore, increases in concentration of HPM led to drop in grafted HPM. Therefore, an optimum grafting temperature and dose of HPM were found to be 200 °C and 2 phr, respectively. Dynamically cured 60/40 NR-g-HPM/PP blends with various loading levels of HPM in graft copolymerization were then achieved by dynamic vulcanization. It was found that the blend with 2 phr of HPM exhibited the highest tensile strength, elongation-at-break, mixing torque during dynamic vulcanization, storage modulus and complex viscosity and the lowest tension set (i.e., the highest elasticity). This was attributed to the highest grafted HPM which created greater possibility to form linkage between NR-g-HPM and the phenolic modified PP compatibilizer molecules which promoted easier interactions between the blend components. TGA analysis found that the NR-g-HPM/PP blends exhibited two stages of weight loss while the pure PP exhibited a single stage. Furthermore, the NR-g-HPM/PP blend exhibited higher degradation temperature than that of the unmodified NR/PP blend which was the confirmation of higher heat resistance of NR-g-HPM.     

Properties of natural rubber/recycled ethylene–propylene–diene rubber blends prepared using various vulcanizing systems

The role of various vulcanizing systems on the curing characteristics, mechanical properties, morphology and dynamic mechanical analysis of natural rubber and recycled ethylene–propylene–diene rubber blends was investigated. Accelerated sulfur-vulcanizing systems (semi-EV and EV), peroxide, and mixed sulfur/peroxide-vulcanizing systems (semi-EV/peroxide and EV/peroxide) were observed and compared. The blends were processed on a two-roll mill, and a fixed amount of carbon black was also incorporated. Amongst the blends, accelerated sulfur-vulcanizing systems exhibited higher torques, state of cure, tensile strength and elongation-at-break, in comparison with the peroxide-vulcanizing system, whereas the tensile modulus, hardness and cross-link density showed lower trend. In the mixed sulfur/peroxide-vulcanizing systems, it showed intermediate behavior to the individual sulfur- or peroxide-vulcanizing systems. This was associated to the interference of peroxide during the cross-linking formation. SEM micrographs of semi-EV-vulcanizing system exhibited more roughness and cracking path indicating that higher energy was required towards the fractured surface. The high cross-link density observed from the swelling study could be verified from the storage modulus (E′) where peroxide vulcanized blends provided a predominant degree of cross-linking followed by semi-EV, semi-EV/peroxide, EV and EV/peroxide-vulcanizing systems, respectively. The glass transition temperature (T _g) depicted at maximum peak of mechanical loss factor (tanδ _max), indicating that semi-EV-vulcanizing system showed highest T _g value. The T _g values can be ordered as semi-EV > peroxide > semi-EV/peroxide > EV > EV/peroxide-vulcanizing systems. The T _g of rubber vulcanizates can be increased due to the restriction of molecular movement such as cross-link density.     

Effect of carbon black loading on curing characteristics and mechanical properties of waste tyre dust/carbon black hybrid filler filled natural rubber compounds

Curing characteristics, tensile properties, fatigue life, swelling behavior, and morphology of waste tire dust (WTD)/carbon black (CB) hybrid filler filled natural rubber (NR) compounds were studied. The WTD/CB hybrid filler filled NR compounds were compounded at 30 phr hybrid filler loading with increasing partial replacement of CB at 0, 10, 15, 20, and 30 phr. The curing characteristics such as scorch time, t₂ and cure time, t₉₀ decreased and increased with increment of CB loading in hybrid filler (30 phr content), respectively. Whereas maximum torque (M_HR) and minimum torque (M_L) increased with increasing CB loading. The tensile properties such as tensile strength, elongation at break, and tensile modulus of WTD/CB hybrid filler filled NR compounds showed steady increment as CB loading increased. The fatigue test showed that fatigue life increased with increment of CB loading. Rubber–filler interaction, Q_f/Q_g indicated that the NR compounds with the highest CB loading exhibited the highest rubber–filler interactions. Scanning electron microscopy (SEM) micrographs of tensile and fatigue fractured surfaces and rubber–filler interaction study supported the observed result on tensile properties and fatigue life. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Toughness improvement of novel biobased aromatic polyamide/SEBS/organoclay ternary hybrids

Biobased aromatic polyamide/organoclay (Cloisite30B, C30B) nanocomposites were melt-compounded with reactive and nonreactive styrene–ethylene–butylene–styrene (SEBS) rubbers at different weight contents to form ternary and quaternary blends. The mechanical properties were investigated as a function of the blend composition. The elongation at break and the impact strength increase with increasing SEBS rubber content, whereas the Young's modulus logically decreases proportionally to SEBS amount. Extra addition of SEBS grafted maleic anhydride (SEBS-g-MA) induces a synergistic effect. The SEBS-g-MA makes it possible to limit the aforementioned rigidity loss and to greatly increase the impact strength. The critical strain energy release rate increases significantly when both reactive and nonreactive rubbers are combined. Three types of microstructures appear depending on the blend composition: (1) small and numerous well-dispersed particles when reactive rubber is used, (2) about 10 times bigger and less numerous well-dispersed particles in the case of nonreactive rubber, and (3) a flocculated dispersion of small particles when both reactive and nonreactive rubber are added. Finally, the polyamide performances were significantly increased when the flocculated morphology was noticed due to a better PAXD/SEBS interfacial adhesion given by the SEBS-g-MA compatibilization and to a thinner rubber distribution in the matrix. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48888.     

Improvement of properties of silica‐filled natural rubber compounds using polychloroprene

Because silica has strong filler–filler interactions, a silica‐filled rubber compound is characterized by a poor dispersion of the filler. Properties of silica‐filled natural rubber (NR) compounds were improved using polychloroprene (chloroprene rubber [CR]). The bound rubber content of the compound increases and the filler dispersion is also improved by adding CR to the compound. Physical properties such as modulus, tensile strength, abrasion, and crack resistance are improved by adding CR. Elongation at break of the vulcanizates containing CR is longer than that of the vulcanizate without CR, although crosslink density of the former is higher than that of the latter. The improved physical properties are attributed to the good dispersion of silica by adding CR. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2609–2616, 2002     

Ring-opening polymerization of macrocyclic(aromatic disulfide) oligomer derived from 4,4′-oxybis(benzenethiol)

Ring-opening polymerization of macrocyclic(aromatic disulfide) oligomer derived from 4,4′-oxybis(benzenethiol) was studied. Ring-opening reactions were carried out in nitrogen and oxygen atmosphere, respectively. Oxidation reaction and cross-linking reaction took place in oxygen atmosphere. The melt copolymerization between cyclic 1 and elemental sulfur was studied using DSC, and TGA techniques. With increasing the contents of sulfur in the polymer, the T_g values, and 5% weight loss temperatures decreased. When the ratio of sulfur to cyclic reached 5, the polymer appeared as a rubber with a T_g of 23.0 °C and a 5% weight loss temperature of 269.4 °C. A series of poly(thiol aromatic)s were prepared from cyclic 1 and dibromo aromatic compounds in diphenyl ether at 260 °C. The dibromo aromatic compounds can be bis(4-bromophenyl) ether, 4,4′-dibromobiphenyl, and 1,4-dibromobenzene. 4,4′-Dibromobiphenyl gave poly(thiol aromatic) with a T_g of 122.2 °C and a T_m of 221.3 °C by reacting with the cyclic 1.     

Ultrafine full-vulcanized powdered rubbers/PVC compounds with higher toughness and higher heat resistance

A new type of rigid PVC compound with higher toughness and higher heat resistance was prepared by using a new type of PVC modifier, ultrafine full-vulcanized powdered rubber (UFPR). The UFPRs used in this paper were butadiene nitrile UFPR-1 (NBR-UFPR-1) with particle size of about 150 nm and butadiene nitrile UFPR-2 (NBR-UFPR-2) with particle size of about 90 nm. Dynamic mechanical thermal analysis (DMTA) showed that glass transition temperature (T_g) of PVC in compounds increased from 77.52 °C of neat PVC to 82.37 and 85.67 °C, while the notched impact strengths increased from 3.1 kJ/m² of neat PVC to 5.2, 5.5 kJ/m², respectively. It can be found that both T_g and toughness of PVC have been improved simultaneously, and the smaller the particle size of NBR-UFPRs, the higher the T_g and the impact strength. The property could be attributed to larger interface and more interfacial interaction between NBR-UFPRs and PVC matrix. Transmission electron microscopy (TEM) showed that NBR-UFPRs could be well dispersed in PVC matrix.     

Effects of the polybutadiene/poly(styrene‐co‐acrylonitrile) ratio in a polybutadiene‐g‐poly(styrene‐co‐acrylonitrile) impact modifier on the morphology and mechanical behavior of acrylonitrile–butadiene–styrene blends

Polybutadiene‐g‐poly(styrene‐co‐acrylonitrile) (PB‐g‐SAN) impact modifiers with different polybutadiene (PB)/poly(styrene‐co‐acrylonitrile) (SAN) ratios ranging from 20.5/79.5 to 82.7/17.3 were synthesized by seeded emulsion polymerization. Acrylonitrile–butadiene–styrene (ABS) blends with a constant rubber concentration of 15 wt % were prepared by the blending of these PB‐g‐SAN copolymers and SAN resin. The influence of the PB/SAN ratio in the PB‐g‐SAN impact modifier on the mechanical behavior and phase morphology of ABS blends was investigated. The mechanical tests showed that the impact strength and yield strength of the ABS blends had their maximum values as the PB/SAN ratio in the PB‐g‐SAN copolymer increased. A dynamic mechanical analysis of the ABS blends showed that the glass‐transition temperature of the rubbery phase shifted to a lower temperature, the maximum loss peak height of the rubbery phase increased and then decreased, and the storage modulus of the ABS blends increased with an increase in the PB/SAN ratio in the PB‐g‐SAN impact modifier. The morphological results of the ABS blends showed that the dispersion of rubber particle in the matrix and its internal structure were influenced by the PB/SAN ratio in the PB‐g‐SAN impact modifiers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2165–2171, 2005