Synthesis and characterization of ABS resin using in situ transferring from emulsion to suspension polymerization

A novel approach based on an emulsion in situ suspension polymerization process for synthesizing poly(acrylonitrile–butadiene–styrene) (ABS) resin is reported. Experimental results show that the reaction system can be transformed from an emulsion state to a suspension polymerization state steadily with the content of polybutadiene (PB) in the range 0–15 wt% in ABS resin. When PB is replaced by poly(styrene‐co‐butadiene) with the content of rubber particles being kept below 20 wt%, the emulsion system can be easily transferred to the suspension polymerization state through a process of latex coagulation in the forward direction, which means that the emulsion solution was dripped slowly into the suspension reaction system in the presence of coagulating agent. The dispersion status of the rubber particles in the ABS resin was studied using transmission electron microscopy, which indicated that the rubber particles were in a dispersed state in a continuous matrix of poly(styrene‐co‐acrylonitrile) when the content of rubber particles was below 20 wt%. The mechanical properties of the ABS resins obtained are as follows: elongation at break, 9.4–45.7%; yield tensile strength, 35.1–42.2 MPa; impact strength, 98.2–116.3 J m^?1. Copyright © 2006 Society of Chemical Industry     

Copolymerization of unsaturated polyester with styrene in inverted emulsion

Copolymerization of unsaturated polyester with styrene in water-in-oil (W/O) type emulsion was carried out with the use of various basic compounds as emulsifiers. It was found that a stable, gellike W/O type emulsion of unsaturated polyester resin is formed only when pK_a's of the bases are above 6 and their concentrations are higher than some critical value. In these conditions, water can be dispersed in emulsion up to 900% to the resin. By polymerization, the stable W/O type emulsion is transformed to a white solid copolymer which is dry to the touch and which contains 90–95% of initially added water. It was confirmed that the basic compounds react with the carboxylic group of the polyester to form at the water-resin interface polyester salts, which act as true emulsifying agents. The stabilization mechanism of the emulsion at various concentrations of the polyester salt was investigated, mainly by microscopic observations, and an interpretation of the critical value of emulsifier concentration is proposed.     

Polymer/carbon nanotube composite emulsion prepared through ultrasonically assisted in situ emulsion polymerization

In this study, ultrasonic irradiation and in situ emulsion polymerization were combined to prepare stable poly(methyl methacrylate‐co‐n‐butyl acrylate) (P(MMA‐BA))/carbon nanotubes (CNTs) composite emulsion, which solves the dispersion problem of CNTs in the latex. Two stages were adopted. In Stage I, ultrasonically initiated in situ emulsion polymerization was conducted to disperse CNTs and prepare the seed emulsion containing polymer coated CNTs. In Stage II, conventional in situ emulsion polymerization was conducted to further enhance the monomer conversion and solid content. The dispersion behavior of MWCNTs in aqueous solution under ultrasonic irradiation was investigated by spectrophotometry. The effects of CNTs content on the emulsion stability and mechanical properties of composite film were studied. The results suggest that in the composite emulsion the long CNTs with a diameter of 20–40 nm are separated and dispersed by the formed polymer latex nanoparticles with a size of 20–40 nm. The spherical polymer latex nanoparticles adhere to the wall of CNTs to form a structure like “grapes on the twig.” The smooth, uniform, and flexible polymer/CNTs composite films were prepared from the composite emulsion. The CNTs can be individually dispersed in P(MMA‐BA)/CNTs composite film. Tensile tests suggest that with the increase in the CNTs content, the Young's modulus and the yield strength of the film increase. Only at 1 wt % CNTs, the Young's modulus increases from 124 to 289 MPa, and the yield strength is improved about ～14%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3123–3130, 2006     

Study on emulsion and suspension in situ polymerization

A novel and simple method of emulsion and suspension in situ polymerization was designed for preparing a composite of polystyrene containing core–shell emulsion particles. The advantage of this method was that it did not need a complex process, such as emulsion breaking, washing, drying, and so on, during transforming from emulsion polymerization to suspension polymerization. First, the core–shell particles of poly(styrene/bisphenol A dimethyl methacrylate)/polystyrene [P(St/BPADA)/PS] with crosslinking structure were synthesized by emulsion polymerization. Then the latex was broken with electrolyte dripping and the emulsion particles became swollen and transformed into the monomer in the suspension polymerization system. Thus the emulsion and suspension in situ polymerization could be carried out successfully. The mechanism of the process was investigated in detail. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 404–412, 2005     

Study on ultrasonic induced encapsulating emulsion polymerization in the presence of nanoparticles

In this paper, the ultrasonic induced encapsulating emulsion polymerization technique was used to prepare polymer/inorganic nanoparticle composites. The main affecting factors in ultrasonic induced encapsulating emulsion polymerization were studied systematically. The experimental results suggested that the pH value, the type of monomers, the type, content, and surface properties of nanoparticles, the type and concentration of surfactant have great influence on the ultrasonic induced encapsulating emulsion polymerization and the obtained latex stability. If selecting cationic emulsifier (such as cetyl trimethylammonium bromide), low water soluble monomer (such as n‐butyl acrylate and styrene), and hydrophobic nano silica, the inorganic nanoparticles could be encapsulated by polymers through ultrasonic irradiation successfully under alkalescent condition, forming a novel polymer/inorganic nanoparticles composite. The mechanism of ultrasonic induced encapsulating emulsion polymerization and the composite latex stabilization are proposed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1130–1139, 2001     

Kinetic study on the poly(methyl methacrylate) seeded soapless emulsion polymerization of styrene. I. Experimental investigation

In this work, methyl methacrylate (MMA) and styrene (ST) were used as monomers in the first stage and second stage of polymerization, respectively, and potassium persulfate (K₂S₂O₈) was used as the initiator to synthesize the poly(methyl methacrylate)-polystyrene (PMMA/PS) composite latex by the method of two-stage soapless emulsion polymerization, i.e., PMMA seeded soapless emulsion polymerization of styrene. The morphology of the latex particles was observed by transmission electron microscopy (TEM). It showed that the composite latex particles had a core–shell structure. The particlesize distribution of the composite latex was very uniform. The kinetic data of seeded soapless emulsion polymerization showed that the square root of polymer yield (Wp)^1/2 was proportional to the reaction time in the earlier period of the reaction. The slope of the line of (Wp)^1/2 vs. reaction time was independent of the content of the seed, but proportional to 0.5 power of the initiator concentration. The gel effect was apparent after monomer droplets disappeared. A glassy effect was found in the latter period of the reaction. The number-average molecular weight of the polymers increased but the weight-average molecular weight of the polymers decreased with decrease of the MMA/ST weight ratio. The number- and weight-average molecular weight increased with decreasing the temperature significantly. © 1995 John Wiley & Sons, Inc.     

Comparison of characteristics of SAN–MMT nanocomposites prepared by emulsion and solution polymerization

Nonextractable styrene–acrylonitrile copolymer–montmollironite (SAN–MMT) nanocomposites were prepared by two different intercalation process: (1) a usual one‐step emulsion copolymerization in the presence of the Na⁺–MMT; and (2) a solution copolymerization with MMT modified by dimethyl dihydrogenated tallow ammonium. For comparative purposes, the copolymerization conditions (such as comonomer feed ratio and the polymerization temperature and times) were set up to be the same. The X‐ray diffraction pattern demonstrated that the net increase of basal spacing of the purified emulsion products (0.76 nm) far exceeded that of composite (0.39 nm) prepared by solution method. The average molecular masses recovered from the composite extracts revealed M_w = 53 × 10⁴ for emulsion products, while the composite made by solution yielded M_w = 4.8 × 10⁴ g/mol. Likewise, the hybrid from the emulsion polymerization exhibited higher stress at maximum load over the solution products. The dispersibility of MMT particles in the polymer matrix was investigated by using optical microscopy (OM) and scanning electron microscopy (SEM) for those unextracted samples. It was found that almost complete hybrids were obtained when the styrene (ST)–acrylonitryl (AN) comonomer was emulsion polymerized in the presence of Na⁺–MMT, yielding both better miscibility and intercalation capability. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2811–2819, 1999     

Ab initio emulsion RAFT polymerization of vinylidene chloride mediated by amphiphilic macro‐RAFT agents

An amphiphilic copolymer poly(acrylic acid)‐block‐poly(styrene) (PAA‐b‐PS) with a trithiocarbonate reactive group was used in the ab initio reversible addition‐fragmentation chain transfer (RAFT) emulsion polymerization of vinylidene chloride (VDC). The fast polymerization and high conversion were achieved. The parameters for a good control over the formation of well‐defined PAA‐b‐PS‐b‐PVDC amphiphilic block copolymers and self‐stabilized latexes were identified. To improve the emulsion stability and prevent the desorption of water‐soluble initiating radicals, the acid groups of PAA‐b‐PS were neutralized by NaOH at the later stage of polymerization. The PAA‐b‐PS‐b‐PVDC block copolymer with a high molar mass of 30 kg mol⁻¹ and the stable latex with 30 wt % solid content was obtained. The kinetics of RAFT emulsion copolymerization of VDC in a living manner was first investigated. The as‐prepared PAA‐b‐PS‐b‐PVDC latex particles were further used as seeds in the emulsion polymerization of styrene, enabling the preparation of novel PAA‐b‐PS‐b‐PVDC‐b‐PS tetra‐block copolymers with a molar mass of 76 kg mol⁻¹ and a relatively low molecular weight distribution of 1.6. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40391.     

Preparation of soap‐free cationic emulsion using polymerizable surfactant

A kind of polymerizable surfactant, methacryloyloxyethylhexadecyldimethylammonium bromide (DMHB) was used to synthesis soap‐free cationic emulsion with styrene (St), methyl methacrylate (MMA), and methacryloyloxyethyltrimethylammonium chloride (MATMAC) by emulsion polymerization using 2,2′‐azobis(isobutylamidine hydrochloride) (AIBA) as a cationic initiator. The effects of polymerizable surfactant concentration, initiator concentration, and reaction temperature on the conversion of monomer were investigated. The results indicated that the rate of polymerization could be expressed as R_p = k_p[AIBA]^0.42[DMHB]^0.45 and the apparent activation energy (E_a) was 83.42 kJ/mol. The particle size, ζ potential, and apparent charge density of cationic latices were also measured. The average diameter of copolymer particles decreased with increasing DMHB, MATMAC, and AIBA content; the charge properties of the particles were decided by the DMHB, MATMAC, and AIBA content. The polymerization mechanism is discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1111–1116, 2006     

AM/AMPS/SSS三元反相乳液聚合体系稳定性研究

以丙烯酰胺(AM)为主单体、2-甲基-2-丙烯酰胺基丙磺酸(AMPS)、对苯乙烯磺酸钠(SSS)为抗温抗盐单体,以白油为连续相,Span 80/Tween 80为复合乳化剂,制得了AM/AMPS/SSS三元反相乳液聚合体系,考察了HLB值、乳化剂浓度、油水比、pH值、搅拌时间、搅拌速度对乳液稳定性的影响。结果表明,乳化剂含量为6%～7%(体系总量),HLB值为5.89,体系pH=8,油水体积比为1.8∶1,搅拌时间30～40 min,搅拌速度为500 r/min时得到稳定的反相乳液体系,适合进行三元反相乳液聚合。     

Emulsification in batch‐emulsion polymerization of styrene and vinyl acetate: A reaction calorimetric study

Dispersion of liquid–liquid systems is commonly applied in industrial processes such as extraction, suspension, and emulsion polymerization. This article describes the influence of the quality of emulsification on the course and outcome of a batch‐emulsion polymerization of styrene and vinyl acetate. From visualization experiments and polymerizations in combination with reaction calorimetric studies, a critical impeller speed, N*, can accurately be determined for a particular reactor setup and a given recipe. The results show that styrene–water emulsions are more difficult to emulsify than vinyl acetate–water emulsions. In general, a large turbine impeller appears to be more effective in emulsifying monomer–water dispersions than a pitched‐blade impeller. In addition, for vinyl acetate emulsion polymerization, the possibility of premixing the reaction mixture has been investigated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 944–957, 2001     

Heterocoagulation behavior of carbon black with surface encapsulation through emulsion polymerization

Nanocomposite microspheres containing styrene–acrylate resin, wax, and carbon black (CB) with desired CB dispersion were prepared through heterocoagulation. The CB surface was modified using conventional anionic emulsifier and anionic dispersants with different lengths of nonionic chains and reactivities or through polymer encapsulation via emulsion polymerization to regulate the dispersion and concentration of CB in the microspheres. Experimental results showed that anionic dispersants with long nonionic chains effectively dispersed and stabilized CB particles. Polystyrene (PS) was then encapsulated on the CB surface by using a reactive dispersant and a water‐soluble initiator of polymerization. The CB particles exhibited comparable pH stability with other heterocoagulation components. Overall, encapsulation through emulsion polymerization can be used to obtain not only high CB content but also improved CB distribution in the resulting microspheres. High coagulation efficiency can also be achieved using polystyrene‐encapsulated dispersed CB because of its high affinity to emulsifiers and reactive dispersants during dispersion. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43516.     

Modification of bitumen emulsion via heterocoagulation with SIS triblock copolymer latex

Bitumen emulsions have often been modified by styrene–butadiene rubber latex. The modified bitumen can have excellent low‐temperature cracking resistance, but rutting resistance at high temperature still remains poor. In the current work, for the first time, a stable poly(styrene‐b‐isoprene‐b‐styrene) (SIS) triblock copolymer latex is synthesized by reversible addition–fragmentation transfer (RAFT) emulsion polymerization. Based on this, a simple heterocoagulation process is developed to prepare the bitumen emulsions modified by SIS. The heterocoagulation results in hybrid particles of SIS shell and bitumen core. With addition of 5 wt % SIS, a continuous polymer‐rich phase could be formed in the modified bitumen once the modified emulsion was broken down. The bitumen modified by 5 wt % SIS shows a significant increase in complex modulus at high temperature and a significant decrease in loss tangent, suggesting excellent resistance to rutting at high temperature, which is consistent with the significant increase in softening point from 41 °C for the base bitumen up to 64 °C. Meanwhile, the ductility at 5 °C of the modified bitumen is also dramatically increased from 1.4 cm for the base bitumen to 40 cm, indicating the low‐temperature cracking resistance should also be much enhanced. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45510.     

The effect of carboxylic monomers on surfactant-free emulsion copolymerization

A study was made of the effect of carboxylic monomers on the surfactant-free emulsion polymerization of styrene and styrene–butadiene. Acid monomers, such as acrylic acid, methacrylic acid, and itaconic acid, were shown to play a critical role in particle formation and particle stabilization in such systems. In the emulsion polymerization of styrene, methacrylic acid forms particles more efficiently than acrylic acid. This difference is attributed to the more hydrophobic nature of the methacrylic monomer which allows it to diffuse more rapidly to the particle surface where it acts to prevent agglomeration. The ability of carboxyl groups to orient at the particle–water interface was studied by acid–base and soap titrations of carboxylated styrene–butadiene latices. The polymerization of itaconic acid onto the particle surface of a styrene–butadiene latex produces a surface carboxyl density much higher than is obtainable with classically adsorbed surfactants. This result is used to explain the greater stability of carboxylated versus noncarboxylated emulsion polymers. During the polymerization of styrene–butadiene latices, carboxyl groups dervied from methacrylic acid are shown to be buried more deeply into the particle as compared to carboxyls derived from the more hydrophilic acrylic acid which orient more at the particle–water interface.     

Ultrasonically irradiated emulsion copolymerization of styrene and surfmer

The nonionic surfmer AREO7 was first used in the ultrasonically irradiated emulsion polymerization of styrene. The added AREO7 could improve the emulsion solid content. Through FTIR, GC‐MS, and DSC studies, it was found that the polymer produced was the copolymer of styrene and AREO7. The copolymer latics polymerized in proper conditions displayed nanoparticles. When AREO7 concentration increased, there were more nanostructured copolymer gels, in which AREO7 molecules form an amphiphilic network, whereas polystyrene was located in hydrophobic droplet. The latics had a structured morphology that the AREO7 units were mainly on the surface of particles. The glass transition temperature (T_g) of copolymers decreased with the increase of AREO7 composition in copolymers. Freeze–thaw test showed that the freeze–thaw stability of the copolymer emulsion was improved greatly because of the increasing composition of AREO7 in copolymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2356–2362, 2004     

Poly(methyl methacrylate) nanoparticles prepared through microwave emulsion polymerization

The emulsifier‐free emulsion polymerization of methyl methacrylate (MMA) was conducted with microwave irradiation. Superfine and monodisperse poly(methyl methacrylate) (PMMA) microspheres were obtained. Microwave irradiation notably promoted the polymerization reaction. This phenomenon was ascribed to the acceleration of the initiator [potassium persulfate (KPS)] decomposition by microwave irradiation. The experimental results revealed that the apparent activation energy of KPS decomposition decreased from 128.3 to 106.0 kJ/mol with microwave irradiation. The average particle size of the prepared PMMA latex was mainly controlled with the MMA concentration; it increased linearly from 103 to 215 nm when the MMA concentration increased from 0 to 0.3 mol/L and then remained almost constant at MMA concentrations of 0.3–1.0 mol/L. The KPS concentration had no effect on the average particle size, but the particle size dispersity was significantly reduced by a high KPS concentration. With a mixed polymerization phase (water/acetone = 1:3 v/v) or a redox initiation system, PMMA nanoparticles were obtained with an average particle size of 45 or 67 nm, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2815–2820, 2004     

Kinetic study on the poly(methyl methacrylate) seeded soapless emulsion polymerization of styrene. III. Seeds with crosslinking

In this work, a seeded soapless emulsion polymerization was carried out with crosslinking (XL) poly(methyl methacrylate) (PMMA) as seeds, styrene as monomer, and potassium persulfate (K₂S₂O₈) as initiator to synthesize the PMMA XL–PS composite latex, which we knew as the latex interpenetrating polymer network (IPN). The morphology of the latex IPN was observed by transmission electron microscopy (TEM). It showed a core–shell structure. The kinetic data from the early stages of the reaction of seeded soapless emulsion polymerization showed that the square root of polymer yield (W_p)^1/2 was proportional to the reaction time. The reaction rate decreased with the increase of crosslinking density of PMMA seeds. The core–shell model proposed in our previous work^1–2 was modified to predict the conversion of polymerization over the entire course of the synthesis of PMMA (XL)–PS composite latex. Our modified core–shell kinetic model fitted well with the experimental data. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:425–438, 1997     

Methacrylic acid-based amphiphilic block-random copolymer stabilizers for emulsion polymerization

The emulsion polymerization of styrene was investigated using polystyrene-b-[polystyrene-r-poly(methacrylic acid)] amphiphilic block-random copolymers (BRCs) of different compositions as stabilizers. These stabilizers with molar masses <20,000 g/mol, which possess unique dispersion behaviour (i.e., self-assembly with low aggregation numbers) when dissolved in aqueous medium at alkaline pH, were prepared by the nitroxide-mediated bulk polymerization of styrene to achieve a desired molar mass followed by chain extension by batchwise addition of styrene and methacrylic acid monomers to obtain the stabilizing group. Emulsion polymerizations of styrene stabilized by these BRCs yielded stable latexes with particle diameters that range between 30 and 150 nm. When different concentrations of the stabilizer (2–3.5 mM) were utilized for emulsion polymerization of styrene, a similar novel emulsion polymerization mechanism observed previously by our group for the acrylic-acid based amphiphilic BRCs was also seen, further validating the difference between this class of polymeric surfactants and conventional small molecule surfactants, block copolymers, or alkali soluble resins. The performance of methacrylic-acid based BRCs was more efficient and yielded higher surface coverage of the polystyrene latexes when compared to the acrylic-acid based BRCs as a result of the more hydrophobic nature of the former.     

Core–shell emulsion polymerization of styrene and butyl acrylate in the presence of polymerizable emulsifier

A series of core–shell polymeric particles of styrene butyl acrylate were successfully prepared in the presence of polymerizable emulsifier. The compositions of the emulsions obtained were confirmed by Fourier transformed infrared spectrometry. Latexes and emulsion films were characterized by transmission electron microscopy and scanning electron microscopy, respectively. The thermostability of emulsion films was characterized by thermogravimetric analysis. The results showed that the existence of polymerizable emulsifier could enhance the solid content of the emulsion and the monomer conversion. The optimum mass ratio of polymerizable emulsifier to traditional emulsifier was 1:1, and the polymerizable emulsifier can participate in the emulsion polymerization perfectly. An emulsion with reverse core–shell particles exhibited better hydrophobic properties and thermostability than one with traditional core–shell particles. The film formed by the emulsion with reverse core–shell particles had lower water absorption, and it could be used in the fields of coatings, surface sizing agents, and spinning. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43091.     

Radiation-induced emulsion polymerization of vinyl acetate and styrene

Studies have been made of the γ-induced emulsion polymerization of styrene and comparisons made with chemically initiated emulsion polymerization. The polymerization proceeded smoothly to high conversions at 0 and 60°C, the reaction showing a high G (monomer) value. Complete conversions were obtained with total doses of less than 0.05 Mrad. In accordance with the behavior expected of systems having a constant rate of initiation, the molecular weight was found to decrease with decreasing temperature. The molecular weight and particle size distributions were narrower than those obtained in chemically initiated emulsion polymerizations at the same temperature. The radiation-induced emulsion polymerization of vinyl acetate proceeded smoothly at temperatures in the range 0–50°C to give polymers of much higher molecular weight than these obtained from chemically initiated polymerizations at the same temperature. Complete conversion was attained after a dose of 0.02 Mrad for latices approaching 50% solids. The elimination of ionic endgroups in the poly(vinyl acetate) radicals tends to drive the polymerization from the aqueous phase, resulting in faster rates and higher molecular weights than are obtained from chemically initiated systems. Rates of polymerization were found to be independent of temperature and the molecular weight of the polymer to be independent of dose rate. Latices of poly(vinyl acetate) of high solids content were evaluated for latex and film properties and found to have improvements over commercially available samples in both areas, especially in clarity of film and scrub resistance. A number of acrylate and maleate esters were copolymerized with vinyl acetate in a radiation-initiated emulsion system. High molecular weight copolymers were produced after low dose.