PPS Chains Research Articles

Study on wall-slipping mechanism of nano-injection polymer under the constant temperature fields

Abstract Polyphenylene sulfide (PPS) and copper (Cu) were used as the polymer and substrate material to simulate the nano-injection molding process by molecular dynamics method. The results show that the PPS chain obeys Einstein’s diffusion law in the early stage of injection molding then deviates from it in the late stage due to the entanglement and limitation of surrounding nanoparticles. In addition, the process of conformational isomerization of polymer chains is accompanied by the twisting and stretching of fixed chains. There are two kinds of adhesion phenomena, one is the macromolecular slides violently in small areas of some sure nanoscale groove to form multiple anchor points. The other case involves multiple nano-grooves along the metal interface, the polymer chain slides and is bolted as multiple anchors in different grooves due to the exerted wall-drag effect on the neighboring chains. These two slipping and anchoring mechanisms are consistent with de Gennes’ slipping theory. Through the quantitative analysis of the influence of pressure on injection filling, it is found that injection pressure should be kept within a certain range to achieve the positive effect of molding.

A New Strengthening Process for Carbon-Fiber-Reinforced Thermoplastic Polyphenylene Sulfide (CFRTP-PPS) Interlayered Composite by Electron Beam Irradiation to PPS Prior to Lamination Assembly and Hot Press

Impact by hailstone, volcanic rock, bird strike, or also dropping tools can cause damage to aircraft materials. For maximum safety, the goal is to increase Charpy impact strength (auc) of a carbon-fiber-reinforced thermoplastic polyphenylene sulfide polymer (CFRTP-PPS) composite for potential application to commercial aircraft parts. The layup was three cross-weave CF plies alternating between four PPS plies, [PPS-CF-PPS-CF-PPS-CF-PPS], designated [PPS]4[CF]3. To strengthen, a new process for CFRP-PPS was employed applying homogeneous low voltage electron beam irradiation (HLEBI) to both sides of PPS plies prior to lamination assembly with untreated CF, followed by hot press under 4.0 MPa at 573 K for 8 min. Experimental results showed a 5 kGy HLEBI dose was at or near optimum, increasing auc at each accumulative probability, Pf. Optical microscopy of 5 kGy sample showed a reduction in main crack width with significantly reduced CF separation and pull-out; while, scanning electron microscopy (SEM) and electron dispersive X-ray (EDS) mapping showed PPS adhering to CF. Electron spin resonance (ESR) of a 5 kGy sample indicated lengthening of PPS chains as evidenced by a reduction in dangling bond peak. It Is assumed that 5 kGy HLEBI creates strong bonds at the interface while strengthening the PPS bulk. A model is proposed to illustrate the possible strengthening mechanism.

Synergetic toughening of poly(phenylene sulfide) by poly(phenylsulfone) and poly(ethylene‐ran‐methacrylate‐ran‐glycidyl methacrylate)

AbstractPoly(phenylene sulfide) (PPS) is a high‐performance super‐engineering plastic, but is brittle. In this study, super‐tough PPS‐based blends were successfully generated by melt blending PPS with poly(ethylene‐ran‐methacrylate‐ran‐glycidyl methacrylate) (EGMA) and poly(phenylsulfone) (PPSU) at (56/14/30) PPS/EGMA/PPSU composition, and their toughening mechanisms were investigated in detail. It was demonstrated the interfacial reaction between PPS and EGMA and partial miscibility between PPS and PPSU, both play important synergistic roles on the toughening. The interfacial reaction between PPS and EGMA contributes to the reduction of the PPSU domain size by the increased viscosity of the PPS matrix containing EGMA, and the increased mobility of EGMA chains by negative pressure effect. The partial miscibility between PPS and PPSU contributes to the increased interfacial adhesion between PPS and PPSU, resulting in effective propagation of the impact to the domains, and the increased mobility of not only PPSU chains but also PPS chains, causing a reduction in crystallization.

Structural origins of mechanical strengthening in poly(phenylene sulfide)/multiwalled carbon nanotube nanocomposites obtained via hot‐stretching

This study demonstrates that solid‐state hot‐stretching is an efficacious pathway via which to achieve interfacial enhancement between poly(p‐phenylene sulfide) (PPS) and multiwalled carbon nanotubes (MWCNTs). Samples of PPS/MWCNT composite were fabricated via a two‐fold procedure involving compression molding followed by hot‐stretching, and significant mechanical reinforcement was realized in the prepared nanocomposites. The interfacial shear strength obtained under 200% stretching strain was about eight times of that obtained in the unstretched (isotropic) counterpart. Large stretching strains, such as 200%, even could induce epitaxial crystallization of PPS lamellae on the surface of MWCNT monofilaments. Moreover, strong π–π interactions between the benzene rings on the backbones of PPS and the sp2 carbon lattice surface of MWCNTs appeared for highly oriented PPS chains and MWCNT monofilaments. A comprehensive structural analysis suggested that in addition to the orientation of both the PPS crystals and MWCNTs, the change in PPS crystallinity and the confinement effect of the amorphous PPS chains, strong π–π interactions and epitaxial crystallization induced via hot‐stretching orientation are mainly responsible for the prominent mechanical reinforcement observed. POLYM. COMPOS., 40:E589–E598, 2019. © 2018 Society of Plastics Engineers

Influence of the interlayer film thickness on the mechanical performance of AA2024-T3/CF-PPS hybrid joints produced by friction spot joining

Friction Spot Joining (FSpJ) is an innovative friction-based joining technique for metal-polymer hybrid structures. Friction spot joints of aluminium alloy 2024-T3 and carbon fibre-reinforced poly(phenylene sulphide) composite laminate (CF-PPS) were produced with an additional PPS film interlayer. Two different film thicknesses were investigated in this study: 100 and 500 μm. Lap shear testing demonstrated that the joints produced with 100-μm film (2093 ± 180 N) were stronger than the joints with 500 μm (708 ± 69 N). Additionally, the fracture surface analysis revealed a larger bonding area for the joints with 100-μm film (53 ± 2 mm2) as compared to the joints with 500-μm film (40 ± 1 mm2). Considering the low thermal conductivity of PPS, the thinnest film is more likely to soften by the frictional heat during the joining process. Hence, the low viscosity of the molten PPS favours the wettability of the parts’ surfaces. Microstructural analyses proved that the metallic nub formation and the interdiffusion of PPS chains between film and composite matrix are also favoured for thinner film use. Thus, superior adhesion between the partners is achieved. Therefore, it was concluded that the addition of the thinnest film interlayer leads to stronger joints.

Influência da Espessura do Filme Polimérico Intermediário na Resistência Mecânica de Juntas Híbridas de Alumínio 2024-T3 e CF-PPS Produzidas por União Pontual por Fricção

Resumo A União Pontual por Fricção (FSpJ) é uma técnica inovadora para união de estruturas híbridas metal-polímero e baseia-se na geração de calor por fricção. Juntas de alumínio 2024-T3 e compósito laminado de poli(sulfeto de fenileno) com fibra de carbono (CF-PPS) foram produzidas com filme intermediário de PPS. Duas espessuras de filme foram investigadas: 100 e 500 µm. Ensaios de cisalhamento sob tração demonstraram que as juntas com filmes de 100 µm são mais resistentes (2093 ± 180 N) em relação às juntas com filme de 500 µm (708 ± 69 N). Adicionalmente, as superfícies de fratura das juntas revelaram áreas de união maiores para as juntas com filmes de 100 µm (53 ± 2 contra 40 ± 1 mm2). Para o filme mais fino, a extensão do amolecimento devido ao calor friccional é maior. Consequentemente, a baixa viscosidade atingida com a fusão do polímero favorece a molhabilidade das superfícies dos componentes da junta pelo PPS amolecido, resultando em melhor adesão entre as partes. Ademais, análises microestruturais demonstraram que a formação do cerne metálico e a interdifusão das moléculas de PPS entre compósito e filme também são favorecidas. Portanto, concluiu-se que a adição do filme mais fino produziu juntas mais resistentes.

Non-isothermal crystalliztion kinetics of poly(phenylene sulfide) with low crosslinking levels

Poly(phenylene sulfide) (PPS) with different crosslinking levels was successfully fabricated by means of high-temperature isothermal treatment (IT). The crosslinking degree of PPS was increased with IT time as revealed by Fourier-transform infrared spectroscopy and dynamic viscosity measurements. Its influence on the non-isothermal crystallization behaviors of PPS was studied by differential scanning calorimeter (DSC). The crystallization peak temperature of PPS with 6 h IT was 15 K higher than that of the one with 2 h IT at 30 K/min cooling rate. The non-isothermal crystallization data were also analyzed based on the Ozawa model. The Ozawa exponent m decreased from 3.5 to 2.2 at 232°C with the increase of the IT time, suggestive of intensive thermal oxidative crosslinking reducing the crystallite dimension as PPS crystal grew. The reduced cooling crystallization function K(T) was indicative of the larger activation energy of crosslinked PPS chain diffusion into crystal lattice, resulting in a slow crystal growth rate. Additionally, the overall crystallization rate of PPS was also accelerated with the increase of crosslinking degree from the observation of polarized optical micrograph. These results indicated that the chemical crosslinked points and network structures formed during the high-temperature isothermal treatment acted as the effective nucleating sites, which greatly promoted the crystallization process of PPS and changed the type of nucleation and the geometry of crystal growth accordingly.

Nucleation effect of hydroxyl‐purified multiwalled carbon nanotubes in poly(p‐phenylene sulfide) composites

AbstractTo investigate the nucleation effect of hydroxyl‐purified multiwalled carbon nanotubes (MWNTs‐OH) in poly(p‐phenylenesulfide) (PPS), a series of composites were prepared by blending PPS with MWNTs‐OH at 1, 2, and 3 wt %, respectively. Under SEM observation MWNTs‐OH were found homogeneously dispersed in the PPS matrix. DSC thermograms revealed that the enthalpy (ΔHc) of the composites increased with increasing MWNT‐OH content, whereas the crystallization temperature (Tc) decreased progressively. The decrease in Tc was in accordance with the smaller crystallite size determined with WXRD characterization, and the increase in ΔHc was evidenced by FTIR and XPS analyses. The higher ΔHc shows that MWNTs‐OH serves as a nucleating agent, providing sufficiently multiplied sites for crystal growth. The lowering of Tc was attributed not only to MWNTs‐OH network hindrance to PPS chain fusing rearrangement, but also to a poorer affinity between MWNTs‐OH and PPS; both effects coordinately govern Tc of PPS/MWNTs‐OH composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

The High Temperature Gel Permeation Chromatography Study on Poly (Phenylene Sulfide) Linear Chain Propagation

A linear and high molecular weight poly(phenylene sulfide) (PPS) was synthesized from P-dichlorobenzene (P-DCB) and anhydrous sodium sulfide in N-methyl pyrrolidone (NMP), and the High Temperature Gel Permeation Chromatography (HTGPC) technique was utilized to investigate the effects of reaction condition on PPS chain propagation. The experiment results indicated that the high pro-reaction temperature or high post-temperature would interfere with PPS chain propagation, and post-reaction time was another important factor to influence PPS molecular weight (Mw) extension. Furthermore, the optimized ratio of high Mw PPS polymer synthesis was typically at 3-6% molar excess of Na2S over p-dichlorobenzene, and N-methyl-2-pyrrolidone (NMP) were beneficial to the production of high Mw PPS due to the formation of sodium 4-(N-methylamino) butanoate (SMAB). The alkaline reagents such as Na3PO4 and K3PO4 et al could capture the H of -SH, which changed -SH into -SNa and promoted the chain growth of PPS to achieve extension.

Nonisothermal crystallization kinetics of poly (phenylene sulphide) in composites with a liquid crystalline polymer

AbstractThe article deals with the melting and nonisothermal crystallization behavior of neat poly (phenylene sulphide) (PPS) and its composites with a thermotropic liquid crystalline polymer (TLCP)—Vectra A950, prepared by melt mixing and probed by differential scanning calorimetry. The various macrokinetic models namely, the Ozawa, the modified Avrami, the Tobin, and the Mo models were applied to describe the crystallization kinetics under nonisothermal conditions. The kinetic crystallizabilty of PPS/TLCP composites calculated using the approach of Ziabicki varies depending on these two composite composition‐induced effects. Similarly Mo model predicts that to obtain a higher degree of crystallizabilty for PPS/TLCP composites, a higher cooling rate should be used. The effective energy barrier based on the differential isoconversional method of Friedman is found to be an increasing function of relative degree of melt conversion. The effect is explained in terms of nucleation theory proposed by Wunderlich to crystallization of polymers. The Lauritzen–Hoffman parameters are estimated using G = 1/t0.5 effective activation energy equation proposed by Vyazovkin and Sbirrazzuoli. The Kg values estimated from latter equations are more comparable with values obtained using isothermal crystallization data than 1/t0.5 method. Furthermore, the kinetic analysis using this equation shows a regime transition from regime II to regime III for 100/00, 90/10, 80/20 PPS/TLCP composites, basically attributed to reduced mobility of PPS chains in composites. This regime II to III transition is accompanied by a morphological transition from defective spherulitic sheaf‐like structures to ordered sheaf‐like structures. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1070–1100, 2010

Miscibility of biodegradable poly(propylene succinate)/poly(propylene adipate) blends: Effect of the transesterification reactions

The miscibility of poly(propylene succinate)/poly(propylene adipate) blends was investigated by means of DSC, WAXS and NMR techniques. Poly(propylene succinate) and poly(propylene adipate) were found to be completely immiscible in as blended-state. The miscibility changes upon extended mixing at elevated temperature: for enough long mixing time, the original two phases gradually merged into a single one because of transesterification reactions. The NMR analysis showed that the transesterifications led to block copolymers whose average sequence length decreased as the mixing time is increased at a fixed temperature. Upon very long mixing time (150 min), all PPS and PPA chains are fully transformed into a random copolymer characterized by a single amorphous phase.

Isothermal crystallization kinetics of poly(phenylene sulfide)/TLCP composites

AbstractThe isothermal crystallization kinetics, the morphology, and the melting behavior of melt‐processed composites of poly(phenylene sulfide) (PPS) with a thermotropic liquid crystalline copolyester, Vectra A950, (TLCP) were studied by differential scanning calorimetry (DSC) and optical microscopy. The crystallization behavior of PPS in PPS/TLCP composites is observed to be highly sensitive to Tc and immiscible TLCP content in the composites. The spherulite growth rate, the overall crystallization rate, and the activation energy of PPS in PPS/TLCP composites are markedly depressed by the presence of TLCP. The analysis of the Avrami kinetic parameters (n and k) indicates that blending of TLCP with PPS causes heterogeneous growth process and nucleation mechanisms. At low Tcs, the PPS crystallization rate is faster than that neat PPS with ≤30 wt% TLCP loading whereas at high Tcs it remains almost unchanged. The analysis of the melting behavior of these composites indicates that the stability of PPS crystals and their reorganization is influenced both by the Tcs and the composite compositions. The sizes and the number of spherulites change a great extent with composite composition with a drop of spherulite rapid growth rate, at constant Tc, with increasing content of TLCP in composites. The analysis based on the Lauritzen‐Hoffmann secondary nucleation theory, using present DSC data, indicates that present data predominantly follow a linear growth trend over a present range of Tcs and PPS crystallization in composites still occurs according to regime II kinetics, whereby multiple surface nuclei form on the substrate with multiple nucleation acts commencing before initially formed growth layer is completed. The fold surface free energy of PPS chains in composites is found higher than that of neat PPS, leading to an average higher work of chain folding and is ascribed to a general development of the PPS chain mobility in the composite melt. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers

Thermal and dynamic mechanical properties of PES/PPS blends

Blends of poly(ether-sulfone) (PES) and poly(phenylene sulfide) (PPS) with various compositions were prepared using an internal mixer at 290°C and 50 rpm for 10 min. The thermal and dynamic mechanical properties of PES/PPS blends have been investigated by means of DSC and DMA. The blends showed two glass transition temperatures corresponding to PPS-rich and PES-rich phases. Both of them decreased obviously for the blends with PES matrix. On the other hand, Tg of PPS and PES phase decreased a little when PPS is the continuous phase. In the blends quenched from molten state the cold crystallization temperature of PPS was detected in the blends of PES/PPS with mass ratio 50/50 and 60/40. The melting point, crystallization temperature and the crystallinity of blended PPS were nearly unaffected when the mass ratio of PES was less than 60%, however, when the amount of PES is over 60% in the blends, the crystallization of PPS chains was hindered. The thermal and the dynamic mechanical properties of the PPS/PES blends were mainly controlled by the continued phase.

Phase separation in semicrystalline blends of poly(phenylene sulfide) and poly(ethylene terephthalate). I. Preparation of poly(phenylene sulfide)-graft-poly(ethylene terephthalate) copolymers by ester interchange and characterization utilizing the model compound 2,4-bis(phenylthio benzoic acid)

Blends of carboxyl functionalized poly(phenylene sulfide) (PPS) and poly(ethylene terephthalate) (PET) were shown to undergo an ester interchange reaction during melt blending. Pendent carboxyl functionality randomly incorporated along the PPS chain reacts with the ester moiety of PET to form a graft copolymer. A model compound, 2,4-bis(phenylthio benzoic acid), has been synthesized to assist in defining the level of carboxyl functionality on the PPS chain. Evidence of the grafting reaction has been gathered from infrared spectroscopy, solubility measurements, and electron microscopy. When added to blends of PPS and PET homopolymers, the graft copolymer significantly reduces the average domain size of the dispersed phase across the entire composition range. This study describes the role that graft copolymers formed by ester interchange reactions can play in compatibilizing this immiscible blend system, with particular focus on the conditions leading to increased grafting efficiency. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3473–3485, 1999

New Coupling Agents as Adhesion Promoters at the Poly(Phenylene Sulfide)/Glass Interface-Studies with Micro and Macro Composites

Carboxy-functionalized poly(phenylene sulfide) having different molar masses and amount of the functional group were prepared in order to be used with γ-aminopropyltriethoxysilane as surface treatment of E-glass fibers. These grafted polymer chains act as connecting chains in order to improve the interfacial shear strength of the PPS-glass interface. According to their chemical nature, which is the same as the PPS matrix, and their ability to crystallize in the same crystalline form as the pure PPS, a continuum of bonding from the fiber surface to the bulk matrix is achieved. A chemical linkage is established at the glass surface by means of hydrolyzed ethoxysilane groups of the γ-APS and from the formation of amide units resulting from the reaction of amine functions of the silane and the carboxylic groups of the modified PPS. A “physical” linkage is expected between the grafted PPS and the PPS chains by means of entanglements and co-crystallization. A large improvement of the interfacial shear strength measured from the microdroplet test is observed when a modified-PPS having a medium molar mass and a low amount of functional groups is used in comparison with untreated or silane-treated glass fibers. This improvement is also observed for short glass fibers/PPS composite materials. In fact, a large improvement is obtained on mechanical properties such as the tensile, flexural, and impact strengths.

Melt viscosity increase during rheological testing of poly(phenylene sulfide)

AbstractPoly(phenylene sulfide) (PPS) made via the melt polymerization of p‐diiodobenzene and sulfur has previously been reported to increase in melt viscosity with time during rheological testing. Analysis of the oligomer from cleavage of PPS chains at the disulfide bonds via solution in 1‐chloronaphthalene demonstrated that the disulfide content of the polymer decreased with rheological testing time. DSC of the polymer before and after rheological testing in combination with the Tcc and Tm of the chain fragments after the dissolution/cleavage in 1‐chloronaphthalene showed that many samples exhibited primarily chain extension rather than chain branching, whereas for many others, some degree of chain branching occurred. This is currently only qualitatively understood. Chain branching as the exclusive mechanism of melt viscosity increase during rheological testing appears untenable in light of the Tm, in particular, of the chain fragments and also the polymer prior to chain cleavage. © 1993 John Wiley & Sons, Inc.

Raman studies of crystalline and amorphous poly(p‐phenylene sulfide) films

AbstractRaman spectra of biaxial crystalline and amorphous poly(p‐phenylene sulfide) (PPS) films were recorded using the micro‐Raman technique. The Raman spectra of its corresponding trimer and tetramer from KBr pellets and the infrared spectrum from the PPS film were also recorded in order to elucidate the normal vibrational modes in PPS. The difference in the Raman spectra between biaxial and amorphous films is presented. New modes are observed at 840 and 919 cm−1 in the polymer films which had been missing in a previous study and the phenylene—sulfur stretching vibrations in the PPS chain, which are used to characterize the peak at 1076 cm−1, are discussed. It was also found that the broad fluorescence background, when excited at 514.5 nm, reaches its peak value at about 598 nm for the biaxial film and at about 616 nm for the amorphous film.

Some characteristics of a new and novel melt preparation method for poly(phenylene sulfide)

AbstractPreparation of poly(phenylene sulfide) (PPS) by the new and novel melt phase reaction of p‐diiodobenzene and sulfur is reported. This new, unique polymerization process can be carried out either entirely in the melt or by a combination of melt and solid state polymerization. Elemental iodine was the reaction by‐product. This process produced very high melt viscosity PPS with degrees of polymerization of several hundred or more. A more Newtonian viscosity over a range of shear rates indicated more linearity of the PPS chains than commercial materials. IR analysis of meta‐ and ortho‐copolymers showed a very high reaction specificity for ipso substitution. Disulfide linkages present in the polymer appeared to be involved in rapid chain equilibration of melt‐mixed samples but did not appear to adversely affect overall stability of the final polymer. Disulfides also appeared to be a reactive species for chain buildup, and an initial mechanism based on this is proposed. Crystallization rates can be tailored from moderate to very fast. Although only PPS has been addressed in this report, extensions to other poly(arylene sulfide)s are obvious.

Conduction mechanism of doped polyphenylenesulfide

The structure of doped polyphenylenesulfide (PPS) is discussed from the results of XPS, IR and 13C-NMR along with CNDO/2 calculation on PPS cation. The experimental results indicate that doping increases double bond character between sulfur atoms and adjacent phenyl rings, which results from the removal of electrons from the sulfur atoms upon doping. The crystal orbital calculation on PPS cation reveals that planar geometry of benzene-s +-benzene is stable conformation and has metallic band structure. Inferring from these results, it is suggested that doping gives rise to a distortion (planar geometry) in PPS chain, which enhances the delocalization of π-electron in phenyl rings through sulfur cation.

Electrical Conductivity and Optical Properties of Poly(p-phenylene sulflde) Doped with Some Organic Acceptors

Poly(p-phenylene sulfide) films were doped with four organic acceptors (tetracyanoethylene (TCNE), dicyanodichlorobenzoquinone (DDQ), p-chloranil, and trinitrofluorenone (TNF)). The sample films remained flexible and tough after doping. The optical and electrical properties of the doped PPS have been measured and discussed in terms of electron affinity of the acceptor molecule. The systematic variation of optical transmission spectra of PPS by doping indicated that a charge-transfer complex was formed between PPS chains and acceptor molecules. Doping with TCNE and DDQ gave a 10 order increase of the conductivity, while chloranil and TNF possessed little effect to enhance the conductivity. The chemical reaction accompanied by doping was found to also give the effect to increase the conductivity of doped PPS. A good correlation between the conductivities and activation energies obtained from the temperature dependences of conductivity was found in all doped PPS samples. It was pointed out that the electronic conduction in PPS/dopant systems must be governed by the mechanism which was independent of dopant content and dopant species.