Toughening of nylon 6 with core-shell impact modifiers: Effect of matrix molecular weight

Rubber particle size is an important issue in toughening of engineering thermoplastics. Use of core-shell impact modifiers offers the advantage of a predetermined particle size; however, these particles must be appropriately dispersed in the matrix polymer to be effective for toughening. Recent work has shown that core-shell modifiers having a poly(methyl methacrylate) (PMMA) shell can be dispersed in nylon 6 with the aid of certain styrene/maleic anhydride (SMA) copolymers. These materials are miscible with PMMA and can also react with polyamides during melt processing. Enhanced interaction between the rubber and matrix phases as a result of the formation of in situ graft copolymers at the interface was suggested to contribute to the improved dispersion. However, rheological issues also influence the dispersion of core-shell modifier particles in the matrix. This article examines the influence of the matrix melt viscosity on the dispersion of the core-shell particles in the nylon 6 matrix and the resulting mechanical properties of the blends using four nylon 6 materials of different molecular weights. © 1996 John Wiley & Sons, Inc.     

Toughening and phase separation behavior of nylon 6–PEG block copolymers and in situ nylon 6–PEG blend via in situ anionic polymerization

We have prepared in situ molded products of morphologically different nylon 6/polyethylene glycol (PEG) copolymers and their blends via anionic polymerization of ε-caprolactam in the presence of several kinds of PEG derivatives using sodium caprolactamate as a catalyst and carbamoyl caprolactam derivative as an initiator. Three carbamoyl caprolactams, such as tolylene dicarbamoyl dicaprolactam (TDC), hexamethylene dicarbamoyl dicaprolactam (HDC), and cyclohexyl carbamoyl caprolactam (CCC), with different functionalities and activities were used. Phase separation behavior was investigated by dynamic mechanical thermal analysis (DMTA) and DSC during in situ polymerization and melt crystallization. The mechanical properties of these molded products were evaluated. PEG segments in the block copolymers showed amorphous characteristics, whereas a large fraction of unreacted PEG segments was crystallized in as-polymerized samples, except for the products obtained using the CCC activator. The presence of PEG derivatives retarded the crystallization of nylon 6 part during in situ polymerization as well as melt crystallization. However, PEG segments did not alter the crystalline structure of nylon 6, showing α-crystalline modification. The nylon 6–PEG–nylon 6 triblock copolymers showed the highest impact strength, whereas the nylon 6–PEG diblock copolymers and in situ nylon 6–PEG blends showed no improved toughness. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1285–1303, 1999     

热引发官能化HDPE、PP、EPDM及其增韧PA66研究

采用热引发熔融接技方法研究了不同反应条件下马来酸酐（MAH）接枝HDPE、接枝共聚PP及接枝EPDM弹性体的接枝反应。结果表明：本热引发接枝法可避免接枝过程中的交联副反应，制得具有较高接枝率（接枝率在0.3%以上），较好熔体流动性能，较少凝胶含量的马来酸酐接枝HDPE、接枝共聚PP及接枝EPDM。采用机械共混法对已官能化的聚烯烃弹性体和聚烯烃塑料分别和混合增韧PA66的情况进行了比较，结果显示：采用PA66／改性聚烯烃弹性体／改性聚烯烃塑料三元共混体系，可以在较少用量的改性橡胶条件下使PA66的缺口冲击强度达到原材料的10倍以上，并且材料弯曲模量损失减少。SEM对PA66／EPDM－g-MHA/PP-g-MAH三元共混体系脆韧转变的研究结果表明：体系分散相中的EPDM－g-MAH向PA66基体扩散、渗透或形成嵌段共聚物的部分是增韧PA66中的有效成分。     

Rubber toughening of an amorphous polyamide by functionalized SEBS copolymers: morphology and Izod impact behavior

Rubber toughening of an amorphous polyamide (Zytel 330) using combinations of triblock copolymers of the type SEBS and a maleic anhydride functionalized version, SEBS-g-MA, was investigated and the results compared with those of nylon 6 and nylon 66. The effects of rubber content and the type of extruder on the morphology, Izod impact behavior and the ductile-brittle transition temperature were explored. The shape and sizes of the rubber particles in blends with this amorphous polyamide were found to be more similar to those in nylon 6 than in nylon 66 blends. The twin screw extruder produced smaller particles with a more narrow distribution of sizes than the single screw extruder. Higher rubber contents generally yielded tougher blends; there is a critical rubber particle size above which the ternary blends are brittle at 20 wt% total rubber. The ductile-to-brittle temperature was found to decrease with increased rubber content and decreased rubber particle size. In general, the trends for this amorphous polyamide are rather similar to those reported earlier for semi-crystalline nylon 6 and nylon 66.     

Compatibilization of blends of polyethylene with a semirigid liquid crystalline polymer by PE-g-LCP copolymers

The blends of thermoplastics with liquid crystalline polymers show, in general, poor properties because of the lack of adherence between the two phases. The use of ad hoc synthesized copolymers containing the monomer units of the two polymers has been recently considered by some of us for blend compatibilization, and the results appear promising. In this work, new PE-g-LCP copolymers, prepared either by the synthesis of the LCP in the presence of a functionalized PE, or by reactive blending of the latter polymer with preformed LCP, have been employed as compatibilizing additives for blends of PE with a semirigid LCP. The morphology and the rheological and mechanical properties of the ternary blends, compared with those of samples without compatibilizers, or containing conventional maleic anhydride grafted PE, indicate that the PE-g-LCP copolymers do in fact lead to an improvement of interfacial adhesion, both in the melt and in the solid state, as well as to a modest enhancement of the mechanical properties. The results may be rationalized considering that the PE-g-LCP copolymers used by us consist of fairly short PE backbones with LCP grafts of various length. The molecules with longer LCP branches are thought to become mixed at the surface of the LCP particles and to give rise to fairly weak interaction with the PE matrix. It is argued that new PE-g-LCP copolymers synthesized from higher molar mass functionalized PE samples might show much better compatibilizing performance.     

Structure and properties of polyimide‐g‐nylon 6 and nylon 6‐b‐polyimide‐b‐nylon 6 copolymers

Polyimide‐g‐nylon 6 copolymers were prepared by the polymerization of phenyl 3,5‐diaminobenzoate with several diamines and dianhydrides with a one‐step method. The polyimides containing pendant ester moieties were then used as activators for the anionic polymerization of molten ε‐caprolactam. Nylon 6‐b‐polyimide‐b‐nylon 6 copolymers were prepared by the use of phenyl 4‐aminobenzoate as an end‐capping agent in the preparation of a series of imide oligomers. The oligomers were then used to activate the anionic polymerization of ε‐caprolactam. In both the graft and copolymer syntheses, the phenyl ester groups reacted quickly with caprolactam anions at 120°C to generate N‐acyllactam moieties, which activated the anionic polymerization. All the block copolymers had higher moduli and tensile strengths than those of nylon 6. However, their elongations at break were much lower. The graft copolymers based on 2,2′‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride and 2,2′‐bis[4‐(4‐aminophenoxy)phenyl]propane displayed elongations comparable to that of nylon 6 and the highest moduli and tensile strengths of all the copolymers. The thermal stability, moisture resistance, and impact strength were dramatically increased by the incorporation of only 5 wt % polyimide into both the graft and block copolymers. The graft and block copolymers also exhibited improved melt processability. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 300–308, 2006     

Self-Reinforced composites of two thermotropic liquid crystalline polymers

Blends of two thermotropic liquid crystalline polymers (LCP) based on 6-oxy-2-naphthoyl and p-oxybenzoyl moieties and p-oxybenzoyl, terephthaloyl and hydroquinone moieties have been studied. The blends were prepared by melt mixing using a twin screw extruder. Thermal, rheological, mechanical, and morphological studies were carried out. Based on the dynamic mechanical thermal analysis and the morphological observations, the blends are found to be immiscible. The viscosity ratios of pure LCP melts exceed values of 10 over a wide range of shear rates, with the viscosity of the blends lying between those of the pure components. The prepared blends are shown to be self-reinforced composites in which one LCP enhances the molecular orientation of the other. Studies of the injection molded bars by scanning electron microscopy indicate a complicated hierarchical morphology with microfibrils of submicron level in diameter, bundled, and intertwined into fibrils of a substantially larger diameter. Due to self reinforcement, impact and tensile properties of the blends show significant synergism when compared to those of the pure LCP components. The properties obtained are remarkably higher than those known for any high performance engineering thermoplastics.     

Compatibilizing Effects of In Situ Formed Block Copolymers in Binary Blends

Four types of binary blends—Type A, Type B, Type C, and Type D—were prepared by melt mixing them in a single screw extruder, with an emphasis on the compatibilizing effect of in situ formed block copolymers between MAH-g-PP and nylon 6. The effects were examined in terms of morphological, rheological, thermal, dynamic mechanical, and mechanical properties for four types of binary blends using various methods.     

In situ polarity functionalization and properties of styrenic triblock copolymers synthesized via RAFT emulsion polymerization

The in situ polarity functionalization of the styrenic triblock copolymers was accomplished via the block introduction of polar monomer, n‐butyl acrylate, with the help of reversible addition‐fragmentation chain transfer (RAFT) emulsion polymerization. The polarity functionalization, microphase separation, static and dynamic mechanical properties, water resistance, transparency, and thermal stability of the synthesized polarity‐functionalized triblock copolymers, polystyrene‐block‐poly(n‐butyl acrylate)‐block‐polystyrene (SAS), were extensively studied. The poly(n‐butyl acrylate) (PBA) middle block higher than 10 wt % has the favorable toughening effect on polystyrene (PSt) two‐end block due to the microphase separation in SAS. The glass transition of the continuous plastic phase (mainly composed of PSt block) has a much greater influence on the storage modulus than that of the dispersed rubber phase (mainly composed of PBA block). The polarity‐functionalized SAS has good water resistance, high transparency, and robust thermal stability. The polarity‐functionalized SAS will have such a potential application broadening as polar adhesive. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44603.     

Compatibilization of polymer blends by reactive processing

This review examines some recent developments in the field of reactive compatibilization of polymer blends by melt processing in extruders and intensive batch mixers. Three routes to reactive compatibilization are considered, namely, the use of suitably functionalized blend constituents, the incorporation of polymeric compatibilizers, and the addition of low molecular weight compounds. Representative systems from the recent patent and open literature are classified according to method and assumed mechanism of compatibilization, and the types of chemical reactions involved. A variety of polymer blends are discussed, including impact modified thermoplastics, polymer modified engineering thermoplastics, dynamically vulcanized thermoplastic elastomers, and co-crosslinked rubber/rubber blends. Examples of potential opportunities in reactive compatibilization are also presented.     

Effect of extruder type on the properties and morphology of reactive blends based on polyamides

The morphology and mechanical properties of polyamide-based blends prepared in single and corotating twin-screw extruders were compared using transmission electron microscopy (TEM) techniques. Reactive polyamide blends with SEBS-g-MA (a maleated styrenic triblock copolymer with ethylene–butvlene midblocks), EPR-g-MA (a maleated ethylene/propylene rubber), and ABS were selected for the purpose of this investigation. For blends of SEBS-g-MA with difunctional (nylon x,y) polyamides (e.g., nylon 6,6; nylon 12,12), the twin-screw extruder was more effective in producing a finer dispersion of the rubber phase, which resulted in a significant lowering of the ductile–brittle transition temperature in case of the nylon 6,6 blend. On the other hand, blends of SEBS-g-MA with the mono-functional nylon 6 material led to rubber particles that were too small for toughening for both extruder types employed in this work. For nylon 6/EPR-g-MA blends, the single-screw extruder led to blends with excellent low-temperature impact properties for both single-step and masterbatch mixing techniques, whereas nylon 6/EPR-g-MA blends prepared in a single-step operation in the twin-screw extruder were brittle under ambient conditions. For difunctional polyamide blends with ABS (compatibilized with an imidized acrylic polymer), the morphology and mechanical properties were found to be independent of the extruder type employed for processing. © 1994 John Wiley & Sons, Inc.     

Reactive mixing of PET and PET/PP blends with glycidyl methacrylate–modified styrene‐b‐(ethylene‐co‐olefin) block copolymers

Styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene (SEBS) and styrene‐b‐(ethylene‐co‐propylene) (SEP, SEPSEP) block copolymers with different styrene contents and different numbers of blocks in the copolymer chain were functionalized by melt radical grafting with glycidyl methacrylate (GMA) and employed as compatibilizers for PET‐based blends. Binary blends of PET with both functionalized (SEBS‐g‐GMA, SEP‐g‐GMA, SEPSEP‐g‐GMA) and neat (SEBS, SEP, SEPSEP) copolymers (75 : 25 w/w) and ternary blends of PET and PP (75 : 25 w/w) with various amounts (2.5–10 phr) of both modified and unmodified copolymers were prepared in an internal mixer, and their properties were evaluated by SEM, DSC, melt viscosimetry, and tensile and impact tests. The roles of the chemical structure, grafting degree, and concentration of the various copolymers on blend compatibilization was investigated. The blends with the grafted copolymers showed a neat improvement of phase dispersion and interfacial adhesion compared to the blends with nonfunctionalized copolymers. The addition of grafted copolymers resulted in a marked increase in melt viscosity, which was accounted for by the occurrence of chemical reactions between the epoxide groups of GMA and the carboxyl/hydroxyl end groups of PET during melt mixing. Blends with SEPSEP‐g‐GMA and SEBS‐g‐GMA, at concentrations of 5–10 phr, showed a higher compatibilizing effect with enhanced elongation at break and impact resistance. The effectiveness of GMA‐functionalized SEBS was then compared to that of maleic anhydride–grafted SEBS. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2201–2211, 2005     

Synthesis of Chain-end Functionalized Polyolefins and Polyolefin Diblock Copolymers via the Combination of Metallocene Catalysts and Reactive Chain Transfer Agents

This paper discusses a facile route to prepare chain-end functionalized polyolefins containing a terminal functional group (OH, COOH, NH₂, etc.), and polyolefin diblock copolymers containing a polyolefin block and a functional polymer block. The chemistry is centered at an in situ chain transfer reaction during metallocene-mediated α-olefin polymerization using two reactive chain transfer (CT) agents, including dialkylborane (R₂B-H) and styrenic molecule/H₂, to form polyolefin containing a reactive alkylborane and styrenic terminal group, respectively. With the appropriate choice of metallocene catalyst, the polymer formed shows narrow molecular weight distribution (M_w/M_n∼2), and the polymer molecular weight is inversely proportional to the molar ratio of [CT agent]/[α-olefin]. In turn, the terminal borane group is very versatile in interconversion to various polar groups. More importantly, it can be quantitatively transformed to a living radical initiator for chain extension reaction with functional monomers. On the other hand, the terminal styrenic group was then selectively metallated and transformed to a stable polymeric anion for living anionic polymerization. The overall diblock co-polymer process resembles a transformation reaction from metallocene-mediated α-olefin polymerization to a living free radical or a living anionic polymerization of functional monomers.     

Performance blends based on recycled polymers

The recent growth in the post-consumer recycling of plastics presents an opportunity for developing new, value-added blend products from the recycled polymers. However, in order to develop blends with useful performance characteristics, suitable techniques of compatibilization and impact modification must be employed. In this study, reactive toughening and compatibilization techniques have been found to be particularly useful in achieving high thermal embrittlement resistance in the blends of recycled poly(ethylene terephthalate) containing functionalized ethylene copolymers and polycarbonate. Reactive compatibilization of recycled polyolefin blends with poly(ethylene terephthalate) and polyamide has also been investigated.     

Comparison of the toughening behavior of nylon 6 versus an amorphous polyamide using various maleated elastomers

The toughening effect of two types of elastomers based on ethylene/α-olefin copolymers, viz, an ethylene/propylene copolymer (EPR) with its maleated version, EPR-g-MA, and an ethylene/1-octene copolymer (EOR) with its maleated versions, EOR-g-MA-X% (X=0.35, 1.6, 2.5), for two classes of polyamides: semi-crystalline nylon 6 versus an amorphous polyamide (Zytel 330 from DuPont), designated as a-PA, was explored. The results are compared with those reported earlier based on a styrenic triblock copolymer having a hydrogenated midblock, SEBS, and its maleated version, SEBS-g-MA, elastomer system. Izod impact strength was examined as a function of rubber content, rubber particle size and temperature. All three factors influence the impact behavior considerably for the two polyamide matrices. The a-PA is found to require a somewhat lower content of rubber for toughening than nylon 6. Very similar optimum ranges of rubber particle sizes were observed for ternary blends of EOR-g-MA/EOR with each of the two polyamides while blends based on mixtures of EPR-g-MA/EPR and SEBS-g-MA/SEBS (where the total rubber content is 20% by weight) show only an upper limit for a-PA but an optimum range of particle sizes for nylon 6 for effective toughening. Higher EPR-g-MA contents lead to lower ductile-brittle transition temperatures (T_db) as expected; however, a-PA binary blends with EPR-g-MA have a much lower T_db than do nylon 6 blends when the content of the maleated elastomer is not high. A minimum in plots of ductile-brittle transition temperature versus particle size appears for ternary blends of each of the matrices with EOR-g-MA/EOR; blends based on SEBS-g-MA/SEBS, in most cases, show higher ductile-brittle transition temperatures, regardless of the matrix. However, blends with EPR-g-MA/EPR show comparable T_db with those based on EOR-g-MA/EOR for the amorphous polyamide but show the lowest ductile-brittle transition temperatures for nylon 6 within the range of particle sizes examined. For the blends with a bimodal size distribution, the global weight average rubber particle size is inappropriate for correlating the Izod impact strength and ductile-brittle transition temperature. In general, trends for this amorphous polyamide are rather similar to those of semi-crystalline nylon 6.     

Copolymerization of caprolactam with polyoxybutylene diamine

Nylon 6-polyoxybutylene block copolymers were prepared by reacting polyoxybutylene diamine with caprolactam in the presence of phosphoric acid. The copolymerization was carried out in a Helicone-type reactor and the effect of time, temperature, and caprolactam concentration on the properties of the products was recorded. Differential Scanning Calorimetry studies of the products suggest the presence of both the ABA and AB types of sequences, where A and B represent nylon 6 and polyether blocks, respectively. Dynamic mechanical measurements of typical copolymers revealed the presence of at least two different nylon moieties. The melt rheology data reflect a general increase in the pseudoplasticity of the copolymer with the increase of the polyether content. Increases of the polyether content in the copolymer result in an increased elongation and a decreased tensile strength and modulus.     

Properties of a propylene-ethylene block copolymer

Although polypropylene has a unique combination of properties, its impact strength at low temperatures is sometimes insufficient. This need has been met by polypropylene/polyisobutylene blends. Today, polypropylene type copolymers (block copolymers) are available with low temperature toughness and property and processing advantages over the above blends. Ordinarily, copolymers from addition polymerization are random. In a block copolymer, the monomeric units of propylene are segregated from those of the second monomer. A block copolymer, propylene, low pressure polyethylene, ABS and polypropylene-polyisobutylene blends are compared as to general and mechanical properties, stress relaxation, stress rupture performance, low temperature performance (impact strength), high temperature performance (flexural stiffness) and processability. Not every material was used in each test. Block copolymers find applications in automotive and appliance industries, industrial parts and packages for cosmetics and food.     

Recent advances in flamesprayed thermoplastic powder coatings

The types of thermoplastics suitable for the plastic flamespray process and the effect of the flamespray on the physical properties and degree of crystallinity in semicrystalline thermoplastics are investigated. Novel coating application techniques and the use of polymer blends to produce viable coatings are also reported. Ethylene-carboxylic acid copolymers, aliphatic polyketones, polyether block amides, and liquid crystal polymers as flamesprayable coating materials are reviewed. The flamespray process does not significantly affect the crystallinity in the polymers studied; however, polymers possessing functional hydrolyzable groups in the backbone such as the polyether block amide may experience some reduction in physical properties during the flamespray process.     

New developments in flame retardancy of styrene thermoplastics and foams

This review provides an insight into new developments in flame retardancy of the broad class of styrenic polymers but mostly focuses on commercially important styrene thermoplastics, on some blends based on polystyrene as well as on polystyrene foams. Although halogen‐based systems continue to dominate in flame retardancy of styrenic polymers, various alternative systems are being developed. Especially, activity is observed with phosphorus‐based flame retardants, where some systems are already commercially available. There is also significant activity with nanocomposites, where good results in retarding flame spread have been achieved, but the problem of ignition resistance has not been solved yet. Critical discussion of various flame‐retardant systems developed for styrenics is given. Copyright © 2007 Society of Chemical Industry     

The effect of polyamide end-group configuration on morphology and toughness of blends with maleated elastomers

The effect of polyamide end-group configuration on morphology generation and toughness of blends with maleated elastomers was investigated. Two difunctional polyamides, a copolymer containing 15% nylon 6,6 and an amine enriched nylon 6, were compared to monofunctional nylon 6 materials of equivalent molecular weight and melt viscosity. Difunctional polyamides have some chains with amine groups on both ends capable of reacting with the maleated rubber phase resulting in crosslinking-type effects. The elastomers used included styrene-butadiene-styrene block copolymers with a hydrogenated midblock, SEBS, and versions with X% grafted maleic anhydride, SEBS-g-MA-X%, and a maleated ethylene/propylene random copolymer, EPR-g-MA. Blends based on difunctional polyamides form large, complex rubber particles when compounded in a single-screw extruder; however, by compounding with an appropriate twin-screw extruder, the size and complexity of the particles can be reduced to levels similar to blends with the monofunctional nylon 6 controls. Measurement of the extent of reaction between the amine end groups and the grafted maleic anhydride revealed that a larger number of amine groups are consumed for the difunctional polyamides than for their monofunctional controls. The room-temperature Izod impact strength of blends with the difunctional polyamides is greater than are the corresponding blends with the controls; however, subambient toughness depends mainly on the inherent ductility of the polyamide matrix. © 1996 John Wiley & Sons, Inc.