The preparation and characteristics of poly(methyl methacrylate–methylacrylate acid)/nano-ZnO composite latex particles

In this work, poly(methyl methacrylate-co-methylacrylate acid)/ZnO (poly(MMA–MAA)/ZnO) composite latex particle was synthesized by three steps The first step was to synthesize poly(MMA–MAA) copolymer latex particles by soapless emulsion polymerization. Following the first step, the second step was to polymerize MMA, MAA and 3,3-(trimethoxysilyl) propyl methacrylate (MPS) in the presence of poly(MMA–MAA) seed latex particles to form the poly(MMA–MAA)/poly(MMA–MAA–MPS) core–shell latex particles. In the third step, the poly(MMA–MAA)/poly(MMA–MAA–MPS) latex particles reacted with ZnO nanoparticles, which were synthesized by a traditional sol gel method, to form the polymer/inorganic poly(MMA–MAA)/poly(MMA–MAA–MPS)/ZnO composite latex. In this study, MPS with silanol groups essentially was used as the coupling agent to couple with ZnO nanoparticles, while the results of the study showed that there was not covalent bond existed between ZnO particles and polymer latex. The ZnO particles were adsorbed on the surface of polymer latex by electrostatic interaction. Besides, the linear poly(MMA–MAA)/crosslinking poly(MMA–MAA–MPS) core–shell latex particles which were synthesized in the second step were heated in the presence of ammonia to form the hollow poly(MMA–MAA–MPS) latex particles. The factors of heating time and concentration of crosslinking agent significantly influenced the morphology of hollow poly(MMA–MAA–MPS) latex particles.     

The diacetone acrylamide crosslinking reaction and its control of core‐shell polyacrylate latices at ambient temperature

Self crosslinkable core‐shell polyacrylate latices (PAs) cured at ambient temperature were synthesized by semicontinuous‐seeded emulsion polymerization with diacetone acrylamide (DAAM) and adipic dihydrazide (ADH) as crosslinkable monomers. The influences of DAAM monomer mass content, neutralizer, and curing temperature on the properties of self crosslinkable core‐shell latices and the keto‐hydrazide crosslinking were discussed. The spectroscopic techniques such as Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), atomic force microscopy (AFM), transmission electron microscopy (TEM), and contact angle instruments were used to determine the structure and properties of PAs. The water evaporating rate during the film‐forming process of self crosslinkable core‐shell latices was also investigated. FTIR analyses demonstrate that the keto‐hydrazide crosslinking reaction does not occur in the latex environment but occurs at ambient temperature with the evaporation of water during the film‐forming process. The results of DSC show that the core‐shell crosslinkable PAs have two glass transition temperatures (T_g), and T_gs of crosslinked film are higher than that of non crosslinked fim. Moreover, the keto‐hydrazide reaction is found to be acid catalyzed and favored by the loss of water and the simultaneous decrease in pH arising from the evaporation of ammonia or amines during film‐forming process. Hence, in the volatile ammonia or amines neutralized latices, the latex pH value adjusted to 7–8, which not only ensure the crosslinkable latex with good storage stability but also obtain a coating film with excellent performances by introducing the keto‐hydrazine crosslinking reaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Curing behavior of self-crosslinkable polyacrylate coating: TBA and in situ FTIR studies

The curing behavior of a self-crosslinkable polyacrylate coating system was studied by torsion braid analysis (TBA), thermogravimetric analysis (TGA), and in situ Fourier transform infrared (FTIR). The results of heating TBA showed that the curing process consisted of two stages: The first stage was the deblocking and crosslinking period—the major period of the curing process. The second stage was the deep-curing period. At the end of this stage, a tighter crosslinking network was obtained. In addition, the detecting results of heating in situ FTIR proved that the reaction occurring in the second stage concerned the reaction of the deblocked isocyanate group and the NH group which came from urethane. In the end, the results of isothermal in situ FTIR showed that the curing temperature affected the extent of crosslinking. The higher the curing temperature, the deeper the curing extent. From the synthetical consideration of the curing temperature and curing time, the optimum curing condition was 170°C/10 min. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 69: 1599–1606, 1998     

Synthesis and characteristics of poly(methacrylic acid–co–N-isopropylacrylamide)/Nano ZnO thermosensitive composite hollow latex particles

In this work, the poly(methacrylic acid–co–N-isopropylacrylamide)/Nano ZnO thermosensitive composite hollow latex particles was synthesized by three processes. The first process was to synthesize the poly(methyl methacrylate-co- methacrylic acid) (poly(MMA–MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second process was to polymerize MAA, N-isopropylacrylamide (NIPAAm) and N,N′-Methylenebisacrylamide (MBA) in the presence of poly(MMA–MAA) latex particles to form the linear poly(MMA–MAA)/crosslinking poly(MAA-NIPAAm) core–shell latex particles, and then the core–shell latex particles were heated in the presence of ammonia solution to form the poly(MAA-NIPAAm) thermosensitive hollow latex particles. In the third process, the poly(MAA-NIPAAm) hollow latex particles reacted with ZnO nanoparticles to form the poly(MAA-NIPAAm)/ZnO thermosensitive composite hollow latex particles on which the ZnO nanoparticles were adsorbed. Besides, a novel process was used to synthesize the poly(MAA-NIPAAm)/ZnO composite latex particles in which the ZnO nanoparticles were encapsulated. The effects of various variables on the morphology of poly(MAA-NIPAAm)/ZnO composite hollow latex particle were studied.     

Synthesis and characteristics of poly(methyl methacrylate-methacrylic acid-3,3-(trimethoxysilyl) propyl methacrylate) hollow latex particles and their application to drug carriers

In this study, the hollow latex particle was synthesized by three processes. The first process was to synthesize the poly(methyl methacrylate-co-methacrylic acid) (poly(MMA-MAA)) copolymer latex particles by the method of soapless emulsion polymerization. Following the first process, the second process was to polymerize MMA, MAA, 3,3-(trimethoxysilyl) propyl methacrylate (MPS), and ethylene glycol dimethacrylate in the presence of poly(MMA-MAA) latex particles to form the linear poly(MMA-MAA)/crosslinking poly(MMA-MAA-MPS) core–shell latex particles. In the third process, the core–shell latex particles were heated in the presence of ammonia to form the poly(MMA-MAA-MPS) hollow latex particles. A sufficient heating time and high-heating temperature were necessary for the ammonia to dissolve the linear poly(MMA-MAA) core to form a perfect hollow structure. The crosslinking poly(MMA-MAA-MPS) shell was a barrier for the ammonia to diffuse into the latex particles so that the latex particle with the high-crosslinking shell showed an imperfect hollow structure. Besides, the hollow poly(MMA-MAA-MPS) latex particles reacted with ZnO nanoparticles, which were synthesized by a traditional sol-gel method, to form the polymer/inorganic poly(MMA-MAA-MPS)/ZnO composite hollow latex particles. With the increase of crosslinking degree would increase the amount of ZnO bonding. Moreover, the poly(MMA-MAA-MPS) hollow latex particles were used as carriers to load with the model drug, caffeine. The release of caffeine from poly(MMA-MAA-MPS) hollow latex particles was investigated.     

Characterization and in vitro drug release properties of core–shell hydrogel prepared by gamma irradiation

A hydrogel system was prepared based on core–shell approach for the delivery of trifluoperazine. Acrylonitrile (AN) core and methacrylic acid (MAA) shell copolymer were performed using gamma irradiation. The resulted system has been characterized by FTIR, TGA, TEM, and SEM techniques. The in vitro release study showed that the maximum drug released was 6.11?mg?g^?1 for AN–MAA copolymer through 120?min and 22.34?mg?g^?1 for AN-core–MAAc shell through 240?min. The results demonstrated that AN-core–MAAc had better properties than AN–MAA copolymer which means the preparation technique highly affects the properties of the system.     

Interfacial aspects of strength development in poly(methyl methacrylate)-based latex systems

Film formation from poly(methyl methacrylate) (PMMA) latex and PMMA copolymer latex incorporating N-(iso-butoxymethyl)acrylamide (IBMA) or methacrylic acid (MAA) has been investigated in terms of the development of tensile strength as a function of annealing time and temperature. Tensile strength is developed through a combination of macromolecular interdiffusion and interfacial crosslinking. The relative rates of interdiffusion vs. crosslinking reactions were studied as a function of temperature and the chemical nature and concentration of the IBMA and MAA functional groups. For low concentrations of these two functional monomers it appears that polymer chain interdiffusion between adjacent latex particles during the film formation process dominates the kinetics of strength development. However, at higher IMBA and MAA concentrations, the higher glass transition temperature at the latex particle surface and intraparticle crosslinking hinders interdiffusion, as reflected by differences in the power law exponent values obtained from the log-log dependence of tensile strength on annealing time. The power law exponents were higher in the case of PMMA than for both IBMA- and MAA-containing copolymers. There was a greater influence temperature on the tensile behavior for the MAA copolymer system as compared to the IBMA copolymer. In the interfacially crosslinked latex polymer system, there is competition between the interdiffusion and crosslinking mechanisms in determining the final mechanical strength of films during the annealing process. © 1995 John Wiley & Sons, Inc.     

Preparation of nano-ZnO/PMMA composite particles via grafting of the copolymer onto the surface of zinc oxide nanoparticles

The grafting of polymers onto the surface of zinc oxide nanoparticles and radical copolymerization of methyl methacrylate (MMA) and methacrylic acid (MAA) were investigated. The copolymer chains encapsulating nanoparticles were anchored onto the surface of nano-ZnO through reactions of carboxyl groups with ZnO. Grafting percentage and grafting efficiency of composite particles were investigated by employing thermogravimetric analysis (TGA). FT-IR and ¹³C NMR showed that there existed a strong interaction at the interface of nano-ZnO and copolymer, which implied that the copolymer chains were grafted onto the surface of ZnO nanoparticles. Nano-ZnO being encapsulated by copolymer was confirmed by using transmission electron microscopy (TEM). Additionally, TGA plots showed that the presence of ZnO nanoparticles improved the thermal stability of copolymer to a certain extent. Another important finding is the copolymerization and grafting reaction did not alter the crystalline structure of the ZnO nanoparticles according to the X-ray diffraction patterns. It can also be seen from scanning electron microscope (SEM) that grafted polymer chains on nanoparticles interfere with the aggregation of ZnO nanoparticles in polymer matrix and improve their compatibility with the polymeric matrix.     

Preparation and characterization of silica sol/fluoroacrylate core–shell nanocomposite emulsion

The silica sol/fluoroacrylate core?Cshell nanocomposite emulsion was successfully synthesized via traditional emulsion polymerization through grafting of KH-570 onto silica particles. Comparing the performance of the polyacrylate copolymer, the fluorinated polyacrylate copolymer and the silica sol/fluoroacrylate core?Cshell nanocomposite emulsion, we can come to a conclusion that the silica sol/fluoroacrylate core?Cshell nanocomposite emulsion presents significantly excellent performance in all aspects. The products were characterized by Fourier transform infrared (FTIR), photon correlation spectroscopy (PCS), transmission electron microscopy (TEM), thermogravimetry (TGA), Contact angle and UV?Cvis analyses techniques. The chemical structure of polyacrylate copolymer, fluorinated polyacrylate copolymer and silica sol/fluoroacrylate nanocomposite were detected by FTIR. The size and stability of emulsion latex particles were determined by PCS technique. TEM analysis confirmed that the resultant latex particle has the core?Cshell structure, obviously. The water absorption and contact angle data also showed that the silica sol/fluoroacrylate nanocomposite film has good hydrophobic performance. TGA analysis indicated the weight loss of the silica sol/fluoroacrylate nanocomposite film begins at around 350?°C which testifies its good thermal stability. The UV?Cvis spectroscopy analysis showed that the silica sol/fluoroacrylate nanocomposite film possess UV?Cvis shielding effect when the added volume amount of KH570 modified silica sol is up to 5?mL. Therefore, the excellent properties of hydrophobicity, thermodynamics and resistance to ultraviolet provide the silica sol/fluoroacrylate nanocomposite film with potential applications in variety fields. In addition, the formation mechanism of core?Cshell structure silica sol/fluoroacrylate nanocomposite latex particles was speculated.     

Highly Efficient Room Temperature Synthesis of Silver‐Doped Zinc Oxide (ZnO:Ag) Nanoparticles: Structural,Optical, and Photocatalytic Properties

Synthesis of silver‐doped zinc oxide (ZnO:Ag) nanoparticles through precipitation method has been reported. The synthesis was conducted at room temperature and no subsequent thermal treatment was applied. ZnO nanoparticles were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), fourier transmission infrared spectroscopy (FTIR), and ultraviolet‐visible (UV–Vis) spectroscopy. Detailed crystallographic investigation was accomplished through Rietveld refinement. The effect of silver content on structural and optical properties of resultant ZnO nanoparticles has been reported. It was found that silver doping results in positional shifts for the XRD peaks and the absorption band edge of ZnO. These were attributed to the substitutional incorporation of Ag⁺ ions into Zn²⁺ sites within the ZnO crystal. In addition, higher silver incorporation resulted in smaller size for ZnO nanoparticles. The photocatalytic activity of the ZnO:Ag nanoparticles was also determined by methylene orange (MO) degradation studies and compared to that of undoped ZnO. Improved photocatalytic activity was obtained for ZnO:Ag nanoparticles. It has been shown that an optimum amount of silver dopant is required to obtain maximum photocatalytic activity.     

In situ preparation of zinc salts of unsaturated carboxylic acids to reinforce NBR

Through the neutralization reaction of zinc oxide (ZnO) and methacrylic acid (MAA) or acrylic acid (AA), zinc methacrylate (ZMA) or zinc acrylate (ZA) was in situ prepared in nitrile rubber (NBR). The mechanical properties and crosslinking structure of the resulting peroxide‐cured NBR vulcanizates were studied. The results showed that ZnO/MAA (AA) had a great reinforcing effect for NBR, and their amounts and ratio played important roles in influencing the mechanical properties. Such vulcanizate contains both covalent crosslinks and salt crosslinks, and the change in the tensile strength of the vulcanizate was related to the variation of the salt crosslink density. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2740–2748, 2000     

自交联封闭性乳液的合成与性能

以双丙酮丙烯酰胺（DAAM）、甲基丙烯酸甲酯（MMA）、丙烯酸丁酯（BA）和甲基丙烯酸（MAA）为共聚单体,采用半连续种子乳液聚合工艺合成自交联封闭性聚丙烯酸酯乳液（PAE）,考察了DAAM和复合乳化剂对乳液聚合稳定性以及涂膜性能的影响。研究发现：随着DAAM含量的增加,乳液聚合稳定性下降,粒径增大,涂膜的耐介质性能和交联度提高,合适的DAAM加入量为总单体质量的3.0%,DAAM和己二酰肼(ADH)的最佳摩尔比为2∶1。采用SDBS+OP-10+OP-40为复合乳化剂体系,选用乳化剂的含量为2.35%,阴/非离子乳化剂质量比为1∶1.25;复合乳化剂在种子、核、壳比例为1.5∶1∶2,制备的乳液具有较好的聚合稳定性（乳液凝胶率低和单体转化率高）,乳液耐电解质（钙离子）稳定性好,涂膜具有优异的封闭性。傅里叶红外光谱（FTIR）表明在涂膜形成过程中DAAM的酮羰基与ADH的酰肼基反应生成腙（C=N）,TEM分析显示乳液的乳胶粒子呈核壳结构,TGA分析发现DAAM改性的PAE降低了涂膜的热稳定性。     

Structural,electrical, thermal,and gas sensing properties of new conductive blend nanocomposites based on polypyrrole/phenothiazine/silver‐doped zinc oxide

The main aim of this study is to investigate the effect of silver‐doped zinc oxide (Ag‐ZnO) loading on the structural, morphological, thermal and electrical properties, and gas sensing behavior of polypyrrole (PPy)/phenothiazine (PTZ)‐blend nanocomposites. The composites are characterized by FTIR, XRD, SEM, TEM, DSC, TGA, and impedance studies. FTIR spectra exhibit the presence of Ag‐ZnO in the PPy/PTZ blend. XRD analysis shows that the semicrystalline behavior of the polymer blend is greatly enhanced by the addition of Ag‐doped ZnO particles. Uniform dispersion of nanoparticles in the polymer is obtained from SEM analysis. The TEM images confirm the presence of spherically shaped nanoparticles in PPy/PTZ blend with a size of 10–25 nm. The DSC measurement indicates that the glass transition temperature of PPy/PTZ blend was significantly improved in the presence of Ag‐doped ZnO nanoparticles. The thermal decomposition temperature of nanocomposite obtained from TGA shows an increase with increase in the content of Ag‐ZnO particles. The incorporation of Ag‐doped ZnO nanoparticles to PPy/PTZ blend exhibit increase in the AC conductivity and dielectric properties of the nanocomposite, due to the pilling of charges at the extended interface of the composite system. The DC conductivity of the nanocomposite increases with the loading of nanoparticles. The ammonia gas sensing performance of PPy/PTZ/Ag‐ZnO nanocomposite is analyzed, and the result shows that the fabricated blend composite can be used as a promising candidate for the easy access of gas molecules. J. VINYL ADDIT. TECHNOL., 26:187–195, 2020. © 2019 The Authors. Journal of Vinyl and Additive Technology published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers.     

Effects of ionomer characteristics on reactions and properties of poly(lactic acid) ternary blends prepared by reactive blending

Toughening of poly(lactic acid) (PLA) was studied by reactive blending PLA with ethylene/n-butyl acrylate/glycidyl methacrylate (EBA-GMA) terpolymer and zinc ion-containing ionomer. The ionomer was prepared by neutralizing the ethylene/methacrylic acid copolymer (EMAA), i.e., ionomer precursor, with ZnO. The reactive interfacial compatibilization between PLA and EBA-GMA and the crosslinking of EBA-GMA during blending was studied in detail. Fractography and FT-IR analysis indicated that both the degree of neutralization (DN) of ionomer and methacrylic acid (MAA) content of ionomer precursor exhibited significant effects on interfacial compatibilization. Dynamic mechanical analysis also suggested that the crosslinking level of EBA-GMA varied with these two factors. Particle size and polydispersity of the dispersed phase were measured by image analysis of TEM micrographs of the ternary blends and correlated with the impact strength of the blends and the characteristics of the ionomer. Ionomers derived from precursor of high MAA content and/or having high DN tended to yield superior impact strength of the PLA blends.     

乙烯/乙酸乙烯酯/甲基丙烯酸离聚体的合成、表征及性能

以乙烯/乙酸乙烯酯/甲基丙烯酸三元嵌段聚合物为基体合成了它的钠、锌盐离聚体。通过FT IR谱图以及DSC、TGA曲线证明了钠、锌离子与甲基丙烯酸发生了反应,玻璃化温度、熔点有提高;同时经过力学性能测试表明合成的离聚体在力学性能方面有改进。硬脂酸锌是离聚体的有效增塑、增强剂,离聚体的拉伸强度随着硬脂酸锌用量的增加而增加,其最大用量为30%。     

Effect of zinc precursor ratio on morphology and luminescent properties of ZnO nanoparticles synthesized in CTAB medium

In this study, the effect of zinc precursor ratio on structural, morphology and luminescent properties of zinc oxide (ZnO) nanoparticles (NPs) prepared by cationic surfactant-assisted method was studied. ZnO NPs were prepared at room temperature by increasing Zn²⁺: CTAB mole ratio. The pristine ZnO samples showed phase-purity (without need for calcination) as shown by X-ray diffractograms (XRD). Nitrogen adsorption ? desorption analysis showed that the samples exhibit Type III isotherm and H3 hysteresis with mesoporosity. The triangular- to quadrilateral-shaped morphological evolution of the ZnO NPs with increasing concentrations of zinc ions was confirmed by SEM and TEM images of the samples. The UV–Vis–DRS studies showed blue-shifted λ_max (band gap) in all the ZnO samples which indicated their nanostructured nature. The photoluminescence spectra of these ZnO samples show emissions in UV and visible regions. The mechanism of formation of nanostructured ZnO was suggested based on the model reported for mesoporous silica synthesized in CTAB medium.     

Preparation and structure control of hollow polymer particles: Influence of seeded emulsion polymerization and alkalization treatment process

Hollow polymer latex particles containing a hydrophilic core were prepared by seeded emulsion polymerization with MAA/BA/MMA/St as comonomers, followed by stepwise alkalization treatment with ammonia. The size and morphology of composite latex particles was determined by TEM. The effects of the seeded emulsion polymerization conditions and alkalization treatment on the size and hollow structure of latex were investigated. The results showed that the optimum content of crosslinking agent in the shell polymers was about 0.5–1.0 wt %, emulsifier was about 0.8–1.1 wt %, and the core/shell weight ratio was 1/7. To obtain uniform hollow latex particles with large size, the starved feeding technique should be adopted in seeded emulsion polymerization, and the neutralization temperature should equal to the T_g of the shell polymer. Then, the obtained polymer particles under this condition had an excellent hollow structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and properties of reactive polyurethane polyacrylate blends based on carbonyl‐hydrazide reaction

A new reactive polyurethane/polyacrylate (PU/PA) blend was developed by mixing a core–shell polyacrylate latex containing keto groups in shell layer and a polyurethane dispersion incorporating multiple hydrazide groups which was synthesized by introducing the poly‐hydrazide groups into the end of the vinyl‐terminated polyurethane chains. Fourier transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC) results indicated that poly‐hydrazide groups had been incorporated in the polyurethane chains. Transmission electron microscopy (TEM) micrograph revealed that polyacrylate particles had a clear core–shell structure. The results of FTIR, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) indicated that the crosslinking reaction between two polymer systems had happened and crosslinking structure could effectively improve the compatibility between PA and PU. Thermogravimetric analysis (TGA) and mechanical tests results suggested that crosslinking structure could enhance the thermal stability and mechanical properties of blends. The influence of the PA content and the n(? CO? )/n(? NHNH₂) ratio on the hardness, water resistance, solvent resistance, and gel fraction of the blend films were comprehensively studied. The optimal PA content and n(? CO? )/n(? NHNH₂) ratio was 30% and 1.5:1 in this experiment, respectively. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44443.     

Effect of chitosan addition to BTCA/CA processed cotton fabrics for adsorbing metallic ions from waste water

One of the most important properties of chitosan, a derivative of chitin, is that it is able to chelate with certain heavy metal ions, and this property can be applied to process waste water containing heavy metal ions. In this research, using BTCA/CA as a crosslinking reagent with chitosan added, cotton fabrics were cured and allowed to undergo an adsorption reaction in CuSO₄ and ZnSO₄ solutions. The effect of different curing temperatures and time, as well as different adsorptive temperatures and time, were studied. The cotton processed fabrics were analyzed by Fourier transform infrared analysis (FTIR), scanning electronic microscope (SEM), and thermal gravity analysis (TGA) to study the crosslinking reaction with the cotton‐processed fabrics. The results indicate: (1) the BTCA/CA‐processed cotton fabrics with an addition of chitosan have a better adsorptive capacity than the processed fabrics without chitosan; (2) the crosslinked fabrics are better in adsorbing copper ions as chitosan concentration, curing temperature and time, and adsorptive temperature and time increase; (3) the adsorption rate of copper and zinc ions are linearly proportional to the changes of time, so that the slope shows that the adsorption rate of crosslinked fabrics for copper ions is faster than for zinc ions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3264–3269, 2006     

原位生成甲基丙烯酸锌对AEM补强的研究

研究了过氧化物硫化体系下的氧化锌(ZnO)、甲基丙烯酸(MAA)原位生成的甲基丙烯酸锌(ZDMA)对乙烯-丙烯酸酯橡胶(AEM)的补强作用。结果表明,原位生成的甲基丙烯酸锌对AEM具有较明显的补强作用。随甲基丙烯酸锌生成量的增加,体系的硫化速率加快,交联密度提高。当甲基丙烯酸锌的生成量为40份、ZnO/MAA摩尔比为0.75时,硫化胶具有较好的综合力学性能。