Impact resistance of fibrous glass reinforced plastics using polycarbonate‐polydimethylsiloxane block copolymer

By using reactive polydimethylsiloxanes that have phenolic hydroxyl groups at the ends of the chain, a polycarbonate‐polydimethylsiloxane (PC‐PDMS) block copolymer was prepared, and the properties of fibrous glass reinforced plastics (GF‐PC) using this copolymer were examined. The Izod impact value of the PC‐PDMS/GF composite increases with an increase in the degree of polymerization of reactive PDMS (n) between 40 and 160. When n is 40, the Izod impact value of the PC‐PDMS/GF composite is equal to that of the PC/GF composite. The Izod impact value is independent of the PDMS content of the copolymer when it is between 2 and 4 wt %. The PC‐PDMS/GF composite is superior, in the balance between fluidity and impact resistance, to the PC/GF composite. From the results of SEM, adhesion between the polymer and GF of the PC‐PDMS/GF composite is superior to that of the PC/GF composite. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1123–1127, 2002     

Synthesis and characterization of poly[(butylene succinate)‐co‐(butylene terephthalate)]‐b‐poly(tetramethylene glycol) segmented block copolymer

Polyester‐polyether segmented block copolymers of poly[(butylene succinate)‐co‐poly(butylene terephthalate)] (PBS–PBT) and poly(tetramethylene glycol) (PTMG) (M_n = 2000) with various compositions were synthesized. PBT content in the PBS was adjusted to ca. 5 mol %. Their thermal and mechanical properties were investigated. In the case of copolymer, the melting point of the PBS–PBT control was 107.8°C, and the melting point of the copolymer containing 70 wt % of PTMG was 70.1°C. Crystallinity of soft segment was 5 ∼ 17%, and that of hard segment was 42 ∼ 59%. The breaking stress of the PBS–PTMG control was 47 MPa but it decreased with increasing PTMG content. In the case of copolymer containing 70 wt % of PTMG, breaking stress was 36 MPa. Contrary to the decreasing breaking stress, breaking strain increased from 300% for PBS–PBT control to 900% for a copolymer containing 70 wt % of PTMG. The shape recovery ratios of the copolymer containing 70 wt % PTMG were almost twice of those of copolymers containing 40 wt % PTMG. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2067–2075, 2001     

Flame retardancy of polycarbonate–polydimethylsiloxane block copolymer/silica nanocomposites

This report describes the flame retardancy and the thermal degradation behavior of polycarbonate–polydimethylsiloxane (PC–PDMS) block copolymer/silica nanocomposites. PC–PDMS block copolymer with dimethylsiloxane (DMS) block size 40 units increased the dispersibility of nanosized amorphous silica. Addition of the slight nanosized silica caused the increment of flame retardancy of PC–PDMS block copolymer, and the PC–PDMS block copolymer with 1.0 wt % PDMS had the highest limiting oxygen index value when the nanosized silica was added 0.5 wt %. The maximum rate temperature of the PC–PDMS block copolymer increased with the addition of silica and the maximum loss rate was the lowest when silica content is 0.5 wt %. The monodisperse nanosized silica had an effect that enhances the flame retardant mechanism of PDMS for PC. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3862–3868, 2006     

Synthesis and surface properties of polydimethylsiloxane‐based block copolymers: poly[dimethylsiloxane‐block‐ (ethyl methacrylate)] and poly[dimethylsiloxane‐block‐(hydroxyethyl methacrylate)]

A polydimethylsiloxane (PDMS) macroazoinitiator was synthesized from bis(hydroxyalkyl)‐terminated PDMS and 4,4′‐azobis‐4‐cyanopentanoic acid by a condensation reaction. The bifunctional macroinitiator was used for the block copolymerization of ethyl methacrylate (EMA) and 2‐(trimethylsilyloxy)ethyl methacrylate (TMSHEMA) monomers. The poly(DMS‐block‐EMA) and poly(DMS‐block‐TMSHEMA) copolymers thus obtained were characterized using Fourier transform infrared and ¹H NMR spectroscopy and differential scanning calorimetry. After the deprotection of trimethylsilyl groups, poly(DMS‐block‐HEMA) and poly(DMS‐block‐EMA) copolymer film surfaces were analysed using scanning electron microscopy and X‐ray photoelectron spectroscopy. The effects of the PDMS concentration in the copolymers on both air and glass sides of films were examined. The PDMS segments oriented and moved to the glass side in poly(DMS‐block‐EMA) copolymer film while orientation to the air side became evident with increasing DMS content in poly(DMS‐block‐HEMA) copolymer film. The block copolymerization technique described here is a versatile and economic method and is also applicable to a wide range of monomers. The copolymers obtained have phase‐separated morphologies and the effects of DMS segments on copolymer film surfaces are different at the glass and air sides. Copyright © 2010 Society of Chemical Industry     

Effect of aluminum hydroxide on low‐molecular‐weight siloxane distribution and microstructure of high‐temperature vulcanized silicone rubber

This paper investigates the effect of aluminum hydroxide (ATH) content on the free volume and surface recovery property of polydimethylsiloxane (PDMS)–based silicone rubber containing low‐molecular‐weight siloxanes. With increasing ratio of ATH up to 43.1 wt %, the concentration of cyclic siloxanes (D_n = [(CH₃)₂SiO]_n, n = 4–12) in the PDMS matrix increases remarkably, indicative of a spacing effect of ATH particles on the crosslinking of PDMS chains. When more ATH is added, the concentration of D₄–D₁₂ began to decrease. PDMS network variation is verified by free volume size corresponding to τ₃ in positron annihilation lifetime spectroscopy. The o‐Ps intensity decreases linearly with ATH content. Data obtained from X‐ray photoelectron spectroscopy suggest the surface recovery property is weakened by ATH. This process is dominated by the amount of free volume holes in the sample. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45803.     

Solvent effects on the miscibility of poly(methyl methacrylate)/poly(bisphenol a carbonate) blends

Blends of atactic or syndiotactic poly(methyl methacrylate) (designated as aPMMA or sPMMA) and poly(bisphenol A carbonate) (PC) were prepared from solution casting. Tetrahydrofuran (THF) and chloroform were used as solvent. Experimental results indicated that the as‐cast blends from THF were quite different from the chloroform‐cast ones. After film preparation, THF‐cast blends did not show any visible phase separation. However, chloroform‐cast blends formed a phase‐separated structure. The as‐cast PC from either solvent was not completely amorphous, and had a melting point at 239–242°C, indicating a certain degree of crystallinity. In contrast, the quenched samples of aPMMA/PC blends prepared from the two solvents behaved virtually the same. They both showed aPMMA dissolves better in PC, but PC solubility in aPMMA is very little. Using sPMMA instead of aPMMA to blend with PC, different results were obtained. The quenched sPMMA/PC blends cast from THF showed only one T_g. However, immiscibility (i.e., two T_gs) was found in the same blend system when cast from chloroform. THF was believed to cause the observation of single T_g due to the following kinetic reason. sPMMA and PC were still trapped together even after THF removal in a homogeneous, but nonequilibrium state below the glass transition. Therefore, the quenched sPMMA/PC blends were not truly thermodynamically miscible. From the results of aPMMA or sPMMA with PC, increasing syndiotacticity seemed to improve the miscibility between PMMA and PC. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2842–2850, 2001     

Effect of tacticity of poly(methyl methacrylate) on the miscibility with poly(styrene‐co‐acrylonitrile)

Isotactic, atactic, and syndiotactic poly(methyl methacrylates) (PMMAs) (designated as iPMMA, aPMMA, and sPMMA) with approximately the same molecular weight were mixed separately with poly(styrene‐co‐acrylonitrile) (abbreviated as PSAN) containing 25 wt % of acrylonitrile in tetrahydrofuran to make three polymer blend systems. Differential scanning calorimetry (DSC) was used to study the miscibility of these blends. The results showed that the tacticity of PMMA has a definite impact on its miscibility with PSAN. The aPMMA/PSAN and sPMMA/PSAN blends were found to be miscible because all the prepared films were transparent and showed composition dependent glass transition temperatures (T_gs). The glass transition temperatures of the two miscible blends were fitted well by the Fox equation, and no broadening of the glass transition regions was observed. The iPMMA/PSAN blends were found to be immiscible, because most of the cast films were translucent and had two glass transition temperatures. Through the use of a simple binary interaction model, the following comments can be drawn. The isotactic MMA segments seemed to interact differently with styrene and with acrylonitrile segments from atactic or syndiotactic MMA segments. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2894–2899, 1999     

Nanoheterogeneities in PEO/PMMA blends: A modulated differential scanning calorimetry approach

Modulated differential scanning calorimetry has been carried out on melt‐mixed blends of poly(ethylene oxide)/atactic‐poly(methyl methacrylate) (PEO/PMMA). Two PEO molecular weights have been used to prepare blends in the concentration range 10 to 80 wt % of PEO. Two glass transitions temperatures were observed for the fully amorphous blends, in the 10 to 30 wt % PEO range, using the differential of heat capacity with respect to temperature [dC_p/dT] signal. The semicrystalline blends, 40, 60, and 80 wt % PEO, exhibited melting of PEO crystallites and the PEO‐rich phase glass transition at −30 to −50°C. A second glass transition around 30°C was detected for the 40 wt % PEO blend when a cooling run was carried out, because PEO crystallization was avoided under these conditions. Therefore, heterogeneous amorphous phases were observed not only for fully amorphous blends, but also for semicrystalline ones. Further analysis of the dC_p/dT signal, obtained from the MTDSC experiments by fitting with Gaussian curves, showed that there is an interphase that varies in amount between 10 to 50 wt %. Correlation of the MTDSC observations with NMR spectroscopy and SAXS/SANS literature results are discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2034–2043, 2000     

Nanophase morphology and crystallization in poly(vinylidene fluoride)/polydimethylsiloxane‐block‐poly(methyl methacrylate) blends

A polydimethylsiloxane‐block‐poly(methyl methacrylate) (PDMS‐b‐PMMA) diblock copolymer was synthesized by the atom transfer radical polymerization method and blended with a high‐molecular‐weight poly(vinylidene fluoride) (PVDF). In this A‐b‐B/C type of diblock copolymer/homopolymer system, semi‐crystallizable PVDF (C) and PMMA (B) block are miscible due to favorable intermolecular interactions. However, the A block (PDMS) is immiscible with PVDF and therefore generates nanostructured morphology via self‐assembly. Crystallization study reveals that both α and γ crystalline phases of PVDF are present in the blends with up to 30 wt% of PDMS‐b‐PMMA block copolymer. Adding 10 wt% of PVDF to PDMS‐b‐PMMA diblock copolymer leads to worm‐like micelle morphology of PDMS of 10 nm in diameter and tens of nanometers in length. Moreover, morphological results show that PDMS nanostructures are localized in the inter‐fibrillar region of PVDF with the addition of up to 20 wt% of the block copolymer. Increase of PVDF long period by 45% and decrease of degree of crystallization by 34% confirm the localization of PDMS in the PVDF inter‐fibrillar region. © 2018 Society of Chemical Industry     

Development of thin layer polymers to concentrate and detect aquatic contaminants

Poly(dimethylsiloxane) (PDMS) and a poly(DMS‐styrene) block copolymer were compared as extraction and optical detection media for hydrophobic compounds in water and water/ethanol solutions. Partitioning to both polymers increased exponentially with increased percent water in ethanol. Partition coefficients to the copolymer were 10–30‐fold higher than to PDMS. Ultraviolet absorbance spectra of pyrene showed a 4‐nm red‐shift in copolymer versus PDMS, providing evidence of π–π interactions, accounting for greater partitioning. The extinction coefficient coefficient of pyrene at 334 nm was twice as high in the copolymer as in PDMS. The combination of higher affinity for polycyclic aromatic hydrocarbons with higher absorbance make poly(DMS‐styrene) copolymers promising material for extraction and in situ detection of hydrophobic aromatic compounds in water. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Miscibility of C60‐containing poly(methyl methacrylate)/poly(vinylidene fluoride) blends

The miscibility of C₆₀‐containing poly(methyl methacrylate) (PMMA‐C₆₀) with poly(vinylidene fluoride) (PVDF) was studied. Two PMMA‐C₆₀ samples containing 2.6 and 7.4 wt % C₆₀ were found to be miscible with PVDF based on single glass transition temperature criterion and melting point depression of PVDF. However, the interaction parameters of the two blend systems are less negative than that of the PMMA/PVDF blend system, showing that the incorporation of C₆₀ reduces the ability of carbonyl groups of PMMA to interact with PVDF. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1393–1396, 2000     

Radiation‐initiated graft polymerization of methylmethacrylate onto poly(tetrafluoroethylene): Characterization by 1H‐NMR

A broad‐line ¹H‐NMR study was carried out to examine the local structure of poly(methylmethacrylate) (PMMA) grafted onto Poly(tetrafluoroethylene) (PTFE). The NMR spectra were observed for three different samples with 1.0, 5.4, and 7.0 wt % PMMA over the temperature range from 150 to 380 K. With the help of selectively deuterated PMMA (PMMA‐d₅ and PMMA‐d₈)‐grafted samples, the NMR spectra were analyzed in terms of two components—a Gaussian (G) component, and a Lorentzian (L) component. Based on the second moments (〈ΔH²〉) analysis, the L and G components were attributed to the ¹H–¹H dipolar interactions within one CH₃ group and the interactions of CH₃ groups that are closely located in aggregated PMMA chains. Combining the results with the temperature dependence of 〈ΔH²〉 and the angular resolved XPS, the location and rotational motion of PMMA grafted onto PTFE are discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1386–1394, 1999     

The effect of side chains on the reactive rate and surface wettability of pentablock copolymers by ATRP

The reactive rate and surface wettability of three pentablock copolymers PDMS‐b‐(PMMA‐b‐PR)₂ (R = 3FMA, 12FMA, and MPS) obtained via ATRP for coatings are discussed. Poly(dimethylsiloxane) (PDMS) is used as difunctional macroinitiator, poly(methyl methacrylate) (PMMA) as the middle block, while poly(trifluoroethyl methacrylate) (P3FMA), poly(dodecafluoroheptyl methacrylate) (P12FMA) and poly(3‐(trimethoxysilyl)propyl methacrylate) (PMPS) as the end block, respectively. Their reactive rates obtained by gas chromatography (GC) analysis indicate that 3FMA gains 8.053 × 10^?5 s^?1 reactive rate and 75% conversion, higher than 12FMA (4.417 × 10^?5 s^?1, 35%), but MPS has 1.9389 × 10^?4 s^?1 reactive rate and 96% conversion. The wettability of pentablock copolymer films is characterized by water contact angles (WCA) and hexadecane contact angles (HCA). The PDMS‐b‐(PMMA‐b‐P12FMA)₂ film behaves much higher advancing and receding WAC (120° and 116°) and HCA (60° and 56°) than PDMS‐b‐(PMMA‐b‐P3FMA)₂ film (110° and 106° for WAC, 38° and 32° for HAC) because of its fluorine‐rich surface (20.9 wt % F). However, PDMS‐b‐(PMMA‐b‐PMPS)₂ film obtains 8° hysteretic contact angle in WAC (114°–106°) and HAC (32°–24°) due to its higher surface roughness (138 nm). Therefore, the fluorine‐rich and higher roughness surface could produce the lower water and oil wettability, but silicon‐rich surface will produce lower water wettability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40209.     

Flame retardancy of a polycarbonate–polydimethylsiloxane block copolymer: The effect of the dimethylsiloxane block size

This report describes the flame retardancy of a polycarbonate (PC)–polydimethylsiloxane (PDMS) block copolymer with a dimethylsiloxane (DMS) block size of 15–350 units, and the effects of the block size and amount of DMS on the flame retardancy are studied. PC–PDMS block copolymers with DMS units of 40–130 had high limiting oxygen index values with 1.0 wt % PDMS. The PDMS block size influenced the PDMS dispersibility in PC, and a moderate PDMS dispersion (ca. 50 nm) caused high flame retardancy for PC. These PC–PDMS block copolymers could form a lot of fine bubbles in the role of good thermal insulators through the reaction of PC and PDMS in combustion. Furthermore, the silica particles from PDMS remained mostly on the surface of the char, so the amount of char with high oxidation resistance increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 565–575, 2006     

Novel polyisobutylene stars. XXIII. Thermal,mechanical, and processing characteristics of poly(phenylene ether)/polydivinylbenzene(polyisobutylene‐b‐polystyrene)37 blends

The objective of these investigations was to increase the use temperature of novel star‐block polymers consisting of a crosslinked polydivinylbenzene (PDVB) core from which radiate multiple poly(isobutylene‐b‐polystyrene) (PIB‐b‐PSt) arms, abbreviated by PDVB(PIB‐b‐PSt)_n. We achieved this objective by blending star‐blocks with poly(phenylene oxide) (PPO) that is miscible with PSt. Thus, various PPO/PDVB(PIB‐b‐PSt)_n blends were prepared, and their thermal, mechanical, and processing properties were investigated. The hard‐phase glass‐transition temperature of the blends could be controlled by the amount (wt %) of PPO. The blends displayed superior retention of tensile strengths at high temperatures as compared to star blocks. The melt viscosities of blends with low weight percentages of PPO were lower than those of star blocks. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2866–2872, 2002     

Enhancement of mechanical and optical performance of commercial polystyrenes by blending with siloxane‐based copolymers

Well‐defined poly(styrene‐block ‐dimethylsiloxane) copolymers (PS‐b ‐PDMS) with low polydispersity index (M_w /M_n ) and different compositions were synthesized by sequential anionic polymerization of styrene (S) and hexamethyl(ciclotrisiloxane) (D₃) monomers. Synthesized PS‐b ‐PDMS copolymers were characterized by ¹H‐nuclear magnetic resonance, size exclusion chromatography, Fourier transform infrared spectroscopy, and transmission electron microscopy. The physicochemical characterization determined that block copolymers have molar mass values close to ～135,000 g mol^?1, narrow M_w /M_n < 1.3, and chemical composition ranging from low to intermediate PDMS content. Blends of these copolymers with a commercial polystyrene (PS) were obtained by melt mixing and subsequently injection. Films obtained were flexible, and showed lower transparency than the original PS matrix. On the other hand, a 10 wt % incorporation of PS‐b ‐PDMS copolymers leads to better mechanical performance by enhancing elongation at break (～8.8 times higher) and opacity values (～18 times higher). In addition, UV–Vis barrier capacity of the resulting blends is also increased (up to 400% higher). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45122.     

ABA-type block copolymers containing poly(dimethylsiloxane) and ketonic resins

Block copolymer containing segments of poly(dimethylsiloxane) (PDMS) and ketonic resins were synthesized. Dihydroxy-terminated PDMS were reacted with the isophorone diisocyanate (IPDI) to obtain the diisocyanate-terminated PDMSs (urethane). These urethanes were reacted with reactive hydroxyl groups in the cyclohexanone–formaldehyde, acetophenone–formaldehyde, and in situ melamine-modified cyclohexanone–formaldehyde resins. Formation of block copolymers was illustrated by several characterization methods, such as chemical and spectroscopic analysis and gel permeation chromatography. The solubilities of the block copolymers were determined, and their surface properties were investigated by contact angle measurements. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 643–648, 1998     

Biodegradability of poly(ethylene terephthalate) copolymers with poly(ethylene glycol)s and poly(tetramethylene glycol)

Poly(ethylene terephthalate) copolymers were prepared by melt polycondensation of dimethyl terephthalate and excess ethylene glycol with 10–40mol% (in feed) of poly(ethylene glycol) (E) and poly(tetramethylene glycol) (B), with molecular weight (MW) of E and B 200–7500 and 1000, respectively. The reduced specific viscosity of copolymers increased with increasing MW and content of polyglycol comonomer. The temperature of melting (T_m), cold crystallization and glass transition (T_g) decreased with the copolymerization. T_m depression of copolymers suggested that the E series copolymers are the block type at higher content of the comonomer. T_g was decreased below room temperature by the copolymerization, which affected the crystallinity and the density of copolymer films. Water absorption increased with increasing content of comonomer, and the increase was much higher for E1000 series films than B1000 series films. The biodegradability was estimated by weight loss of copolymer films in buffer solution with and without a lipase at 37°C. The weight loss was enhanced a little by the presence of a lipase, and increased abruptly at higher comonomer content, which was correlated to the water absorption and the concentration of ester linkages between PET and PEG segments. The weight loss of B series films was much lower than that of E series films. The abrupt increase of the weight loss by alkaline hydrolysis is almost consistent with that by biodegradation.     

A novel method for preparing silver/poly(siloxane‐b‐methyl methacrylate) nanocomposites with multiple properties in the DMF‐toluene mixture solvent

A novel method for preparing silver/poly(siloxane‐b‐methyl methacrylate) (Ag/(PDMS‐b‐PMMA)) hybrid nanocomposites was proposed by using the siloxane‐containing block copolymers as stabilizer. The reduction of silver nitrate (AgNO₃) was performed in the mixture solvent of dimethyl formamide (DMF) and toluene, which was used to dissolve double‐hydrophobic copolymer, as well as served as the powerful reductant. The presence of the PMMA block in the copolymer indeed exerted as capping ligands for nanoparticles. The resultant nanocomposites exhibited super hydrophobicity with water contact angle of 123.3^° and the thermogravimetry analysis (TGA) revealed that the resultant nanocomposites with more PDMS were more heat‐resisting. Besides, the antimicrobial efficiency of the most desirable nanocomposite (Ag/PDMS₆₅‐b‐PMMA₃₀ loaded with 7.3% silver nanoparticle) could reach up to 99.4% when contacting with escherichia coli within 120 min. As a whole, the resultant nanocomposites by the integration of excellent properties of silver nanoparticles as well as siloxane‐block copolymers can be a promising for the development of materials with hydrophobic, heat‐resisting and outstanding antibacterial properties from the chemical product engineering viewpoint. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4780–4793, 2013