含硅-氮木质素协同聚磷酸铵阻燃聚乳酸

宋艳; 林肯; 周宇彤; 单雪影; 李锦春; 赵彩霞

含硅-氮木质素协同聚磷酸铵阻燃聚乳酸

1.
常州大学　材料科学与工程学院, 常州 213164
2.
常州大学　安全科学与工程学院, 常州 313164

基金项目: 国家自然科学基金 (51473024)；江苏省科技厅产学研联合创新资金资助项目(BY2019080)

详细信息

通讯作者:
宋艳，博士，副教授，硕士生导师，研究方向为生物基阻燃高分子材料　E-mail: ysong@cczu.edu.cn

中图分类号: TQ317.9;TB332
计量
- 文章访问数: 127
- HTML全文浏览量: 69
- PDF下载量: 4
- 被引次数: 0
出版历程
- 收稿日期: 2023-09-21
- 修回日期: 2023-11-22
- 录用日期: 2023-11-24
- 网络出版日期: 2023-12-09
- 刊出日期: 2024-07-15

Synergistic flame retardant effect of lignin containing silicon-nitrogen with ammonium polyphosphate on polylactic acid

1.
School of Materials Science and Engineering, Changzhou University, Changzhou 213164, China
2.
School of Safety Science and Engineering, Changzhou University, Changzhou 213164, China

Funds: National Natural Science Foundation of China (51473024)；Industry-academic joint innovative fund of Jiangsu Province (BY2019080)

摘要

摘要: 聚乳酸(PLA)作为生物基可降解塑料逐渐成为研究热点，但由于其极易燃烧，在包装、电器等领域的应用受到限制，为了解决此类问题，对碱木质素(Lig)改性合成了含硅-氮元素的木质素(Si-NLig)，通过热失重分析(TGA)发现，Si-NLig在空气中的T_5%提高了20 ℃，且高温残留量由2.3%提高至25.5%。将 Si-NLig作为成炭剂，与聚磷酸铵(APP)复配，通过熔融共混法制成阻燃聚乳酸材料(Si-NLig-APP/PLA)，对其阻燃性能、力学性能、燃烧行为等进行了研究。研究表明，Si-NLig与APP质量比为1∶4，10wt%的添加量可使Si-NLig-8%APP/PLA的极限氧指数(LOI)值达到27%，UL-94垂直燃烧达到V-0级别，而同等条件下Lig-8%APP/PLA的LOI值为26%，UL-94仅为V-2级别。同时，与Lig-8%APP/PLA相比，Si-NLig-8%APP/PLA的热释放速率峰值(PHRR)降低了27%；残炭的拉曼光谱分析发现Si-NLig-8%APP/PLA的石墨化程度比Lig-8%APP/PLA提高了36.7%，为其良好的阻燃性能提供了理论依据。Si-NLig的引入使得阻燃PLA力学性能得到了改善，拉伸强度提升了21%。可见Si-NLig在无卤阻燃PLA领域中具有潜在的应用前景。
- 含硅-氮木质素 /
- 聚乳酸 /
- 成炭剂 /
- 阻燃性能 /
- 力学性能.
Abstract: Polylactic acid (PLA) as a biobased degradable plastic has increasingly become a research hotspot. However, PLA’s application in packaging and electrical appliances is limited due to its high combustibility. In order to solve the above problem, lignin containing silicon-nitrogen synergistic(Si-NLig) was synthesized by modification of alkali lignin (Lig), and its thermogravimetric analysis (TGA) results showed that the T_5% increased by 20℃ and the high temperature residue increased from 2.3% to 25.5% in air. And Si-NLig was used as a charring agent, and compounded with ammonium polyphosphate (APP) to prepared flame retardant polylactic acid (Si-NLig-APP/PLA) by melt blending and hot-press molding, and the PLAs’ flame retardant properties, mechanical properties, and combustion behavior, were investigated. The results showed that addition of 10wt% Si-NLig-APP with the mass ratio 1∶4 made Si-NLig-8%APP/PLA reach the limiting oxygen index (LOI) value of 27% and the vertical burning UL-94 V-0 level, while the LOI value of Lig-8%APP/PLA with Lig as charring agent at the same condition was 26% and the vertical burning UL-94 only passed V-2 rating. Meanwhile, the peak heat release rate (PHRR) reduced by 27% compared to Lig-8%APP/PLA. Raman spectroscopy was used to characterize the structure of the residual char after cone calorimeter testing, it was found that the degree of graphitization of Si-NLig-8%APP/PLA increased by 36.7% compared to that of Lig-8%APP/PLA, which provides a theoretical basis for its good flame retardancy. Introduction of Si-NLig led to the enhancement of mechanical properties of the flame retardant PLA with tensile strength increasing by 21%. It can be seen that Si-NLig has potential application prospect in the field of halogen-free flame retardant PLA.
- Lignin containing silicon-nitrogen /
- Polylactic acid /
- Charring agent /
- Flame retardant properties /
- Mechanical properties.

HTML全文

图 1 Si-NLig的合成路线图

Figure 1. Synthetic route of Si-NLig

下载: 全尺寸图片幻灯片

图 2 Lig和Si-NLig的红外光谱

Figure 2. FTIR spectra of Lig and Si-NLig

下载: 全尺寸图片幻灯片

图 3 Lig和Si-NLig的XPS谱图

Figure 3. XPS spectra of Lig and Si-NLig

下载: 全尺寸图片幻灯片

图 4 Lig和Si-NLig空气氛围下的TG(a)和DTG(b)曲线

Figure 4. TG (a) and DTG (b) curves of Lig and Si-NLig in air

下载: 全尺寸图片幻灯片

图 5 Lig和Si-NLig氮气氛围下的TG(a)和DTG(b)曲线

Figure 5. TG (a) and DTG (b) curves of Lig and Si-NLig in N₂

下载: 全尺寸图片幻灯片

图 6 PLA(a, b)、Lig-8%APP/PLA(c, d)、10%APP/PLA(e, f)、Si-NLig-8%APP/PLA(g, h)、 Si-NLig-12%APP/PLA(i, j)和Si-NLig-16%APP/PLA(k, l)的冲击横截面SEM

Figure 6. SEM of fracture surface of PLA(a, b), Lig-8%APP/PLA(c, d), 10%APP/PLA(e, f), Si-NLig-8%APP/PLA(g, h), Si-NLig-12%APP/PLA (i, j) and Si-NLig-16%APP/PLA (k, l)

下载: 全尺寸图片幻灯片

图 7 PLA和阻燃PLA空气氛围下的TG(a)和DTG(b)曲线

Figure 7. TG (a) and DTG (b) curves of PLA and flame retardant PLA in air

下载: 全尺寸图片幻灯片

图 8 PLA和阻燃PLA的HRR(a)、THR(b)、COP(c)和TSR(d)曲线

Figure 8. HRR (a), THR (b), COP (c), TSR (d) curves of PLA and flame retardant PLA

下载: 全尺寸图片幻灯片

图 9 Lig-8%APP/PLA和Si-NLig-8%APP/PLA炭层的拉曼光谱

Figure 9. Raman spectra of Lig-8%APP/PLA and Si-NLig-8%APP/PLA char layers

下载: 全尺寸图片幻灯片

表 1 PLA和阻燃PLA配方

Table 1. Formulations of PLA and flame retardant PLA

Sample	PLA / wt%	APP / wt%	Lig / wt%	Si-NLig / wt%
PLA	100	0	0	0
10%APP/PLA	90	10	0	0
Lig-8%APP/PLA	90	8	2	0
Si-NLig-6.4%APP/PLA	92	6.40	0	1.60
Si-NLig-3.33%APP/PLA	90	3.33	0	6.67
Si-NLig-6%APP/PLA	90	6	0	4
Si-NLig-6.67%APP/PLA	90	6.67	0	3.33
Si-NLig-8%APP/PLA	90	8	0	2
Si-NLig-12%APP/PLA	85	12	0	3
Si-NLig-16%APP/PLA	80	16	0	4
Notes: PLA- Polylactic acid; APP - Ammonium polyphosphate.

下载: 导出CSV

表 2 Lig和Si-NLig的元素组成

Table 2. Element contents of Lig and Si-NLig obtained by XPS

Sample	C / (At.%)	O / (At.%)	N / (At.%)	Si / (At.%)
Lig	81.16	18.41	0.43	--
Si-NLig	80.16	15.81	1.28	1.45

下载: 导出CSV

表 3 Lig和Si-NLig空气氛围下的热降解参数

Table 3. Thermal degradation parameters of Lig and Si-NLig in air

Sample	T_5% / ℃	T_max / ℃			V_max / (%·min⁻¹)			Residue at 550℃/ %
Sample	T_5% / ℃	T_max1	T_max2	T_max3	V_max1	V_max2	V_max3	Residue at 550℃/ %
Lig	212	270	371	500	2.8	4.0	15.9	2.3
Si-NLig	232	317	474	556	7.5	5.4	5.3	25.5
Notes: T_5% - Temperature corresponding to mass loss 5% of material; T_max - Temperature corresponding to the maximum thermal degradation rate; V_max - Degradation rate at the maximum degradation temperature.

下载: 导出CSV

表 4 Lig和Si-NLig氮气氛围下的热失重参数

Table 4. Thermal degradation parameters of Lig and Si-NLig in N₂

Sample	T_5% / ℃	T_max / ℃	V_max / (%·min⁻¹)	Residue at 700℃ / %
Lig	222	350	5.5	41.3
Si-NLig	228	377	3.7	48.6
Notes: T_5% - Temperature corresponding to mass loss 5% of material; T_max - Temperature corresponding to the maximum thermal degradation rate; V_max - Degradation rate at the maximum degradation temperature.

下载: 导出CSV

表 5 PLA和阻燃PLA阻燃性能测试结果

Table 5. Results of flame retardant performances for PLA and flame retardant PLA

Sample	LOI / %	UL-94 vertical burning
Sample	LOI / %	t₁ / s	t₂ / s	Rating	Dripping	Ignition cotton
PLA	19.5	＞60	--	NR	YES	YES
10%APP/PLA	28	2	1	V-0	YES	NO
Lig-8%APP/PLA	26	5	2	V-2	YES	YES
Si-NLig-6.4%APP/PLA	27	3	1	V-2	YES	YES
Si-NLig-3.33%APP/PLA	25	6	1	V-2	YES	YES
Si-NLig-6%APP/PLA	27	9	7	V-2	YES	YES
Si-NLig-6.67%APP/PLA	27	4	0	V-2	YES	YES
Si-NLig-8%APP/PLA	27	2	0	V-0	YES	NO
Si-NLig-12%APP/PLA	28	1	0	V-0	YES	NO
Si-NLig-16%APP/PLA	30	0	0	V-0	YES	NO
Notes: t₁/ t₂ - Duration of sample burning; LOI - Limiting oxygen index.

下载: 导出CSV

表 6 PLA和阻燃PLA力学性能测试结果

Table 6. Test results of mechanical properties of PLA and flame retardant PLA

Sample	Tensile strength / MPa	Elongation at break / %	Impact strength / (kJ·m^-2)
PLA	70.0±4.6	14.2±0.9	5.6±0.3
10%APP/PLA	39.8±1.1	10.7±1.4	4.5±0.1
Lig-8%APP/PLA	51.9±2.9	9.9±0.7	4.7±0.4
Si-NLig-8%APP/PLA	62.8±3.1	8.3±1.1	5.5±0.4
Si-NLig-12%APP/PLA	65.8±4.3	8.1±0.6	4.5±0.1
Si-NLig-16%APP/PLA	49.1±3.9	8.0±0.6	3.8±0.5

下载: 导出CSV

表 7 PLA和阻燃PLA空气氛围下的热降解参数

Table 7. Thermal degradation parameters of PLA and flame retardant PLA in air

Sample	T_5% / ℃	T_max / ℃	V_max / (%·min⁻¹)	Residue at 800℃ / %
PLA	337	371	65.7	0
Lig-8%APP/PLA	335	372	59.4	8.4
Si-NLig-8%APP/PLA	337	368	61.3	8.4
Notes: T_5% - Temperature corresponding to mass loss 5% of material; T_max - Temperature corresponding to the maximum thermal degradation rate; V_max - Degradation rate at the maximum degradation temperature.

下载: 导出CSV

表 8 PLA和阻燃PLA的锥形量热仪测试分析结果

Table 8. Cone calorimeter testing analysis results of PLA and flame retardant PLA

Sample	TTI / s	T_PHRR / s	PHRR / (kW·m⁻²)	MHRR / (kW·m⁻²)	THR / (MJ·m⁻²)	FPI / (m²s·kW⁻¹)	Mean COY / (kg·kg⁻¹)	Mean CO₂Y / (kg·kg⁻¹)
PLA	74	200	411	137.4	79.9	0.158	0.024	4.803
Lig-8%APP/PLA	61	150	356	97.6	45.7	0.171	0.080	4.162
Si-NLig-8%APP/PLA	58	110	269	99.7	48.5	0.216	0.054	4.231
Notes: TTI - Time to ignition; PHRR - Peak heat release rate; THR - Total heat release; TSR - Total smoke release; MHRR - Mean heat release rate.

下载: 导出CSV

表 9 Lig-8%APP/PLA和Si-NLig-8%APP/PLA炭层的拉曼光谱分析结果

Table 9. Raman spectroscopic analysis results of residual carbon in Lig-8%APP/PLA and Si-NLig-8%APP/PLA

Sample	A_D	A_G	A_D/A_G
Lig-8%APP/PLA	1024	327	3.13
Si-NLig-8%APP/PLA	1290	651	1.98

下载: 导出CSV

参考文献(37)

[1]	DENG S, BAI H Z, LIU Z W, et al. Toward supertough and heat-resistant stereocomplex-type Polylactide/elastomer blends with impressive melt stability via in situ formation of graft copolymer during one-pot reactive melt blending[J]. Macromolecules, 2019, 52(4): 1718-1730. doi: 10.1021/acs.macromol.8b02626
[2]	SHI W Y, CHEN Z Z. Mechanical, rheological, and crystallinity properties of polylactic acid/polyethylene glycol-polydimethylsiloxane copolymer blends by melt blending[J]. Journal of Applied Polymer Science, 2022, 140(4): 1-11.
[3]	Makovicka L O , Katarina K , Hua S L , et al. Ignition and burning of selected tree species from tropical and northern temperate zones[J]. Advanced Industrial and Engineering Polymer Research, 2023, 6 (2): 195-202.
[4]	于文灏. 聚乳酸/含磷阻燃剂共混物的制备及性能研究 [D]. 江南大学, 2022. YU Wenhao. Preparation and properties of polylactic acid/phosphorus containing flame retardant blends [D]. Jiangnan University, 2022(in Chinese).
[5]	YANG W J, ZHOU Q K, PAN W H, et al. Synthesis of vanillin-based porphyrin for remarkably enhancing the toughness, UV-resistance and self-extinguishing properties of polylactic acid[J]. Chemical Engineering Journal, 2023, 469: 143935. doi: 10.1016/j.cej.2023.143935
[6]	王自博, 吕锦翔, 肖丹. 基于生物材料阻燃PLA研究进展[J]. 塑料科技, 2022, 50(07): 96-100. doi: 10.15925/j.cnki.issn1005-3360.2022.07.020 WANG Zibo, LU Jinxiang, XIAO Dan. Research progress in flame retardant PLA based on biomaterials[J]. Plastics Science and Technology, 2022, 50(07): 96-100(in Chinese). doi: 10.15925/j.cnki.issn1005-3360.2022.07.020
[7]	ZHANG D H, PEI M, WEI K, et al. Flame retardant properties and mechanism of polylactic acid-conjugated flame retardant composites[J]. Frontiers in Chemistry, 2022, 10: 894112. doi: 10.3389/fchem.2022.894112
[8]	WANG C, WU Y C, LI Y C, et al. Flame-retardant rigid polyurethane foam with a phosphorus-nitrogen single intumescent flame retardant[J]. Polymers for Advanced Technologies, 2018, 29(1): 668-676. doi: 10.1002/pat.4105
[9]	ORTA O R, WESSEELINK A K, BETHEA T N, et al. Brominated flame retardants and organochlorine pesticides and incidence of uterine leiomyomata: A prospective ultrasound study[J]. Environmental Epidemiology, 2021, 5(1): e127. doi: 10.1097/EE9.0000000000000127
[10]	贝钰, 翁述贤, 贾普友, 等. 木质素基阻燃剂的研究进展[J]. 生物质化学工程, 2023, 57 (02): 71-78. BEI Jue, WENG Shuxian, JIA Puyou, etc. Research progress of lignin based flame retardants[J]. Biomass Chemical Engineering, 2023, 57 (02): 96-100 (in Chinese).
[11]	ZHAN Y Y, WU X J, WANG S S, et al. Synthesis of a bio-based flame retardant via a facile strategy and its synergistic effect with ammonium polyphosphate on the flame retardancy of polylactic acid[J]. Polymer Degradation and Stability, 2021, 191: 109684. doi: 10.1016/j.polymdegradstab.2021.109684
[12]	靳昕怡, 窦娟, 魏丽菲, 等. 无卤阻燃剂在聚合物阻燃中的应用研究进展[J]. 高科技纤维与应用, 2022, 47(6): 67-73. doi: 10.3969/j.issn.1007-9815.2022.06.011 JIN Xinyi, DOU Juan, WEI Lifei, et al. Research on the application of halogen-free flame retardant in polymer flame retardants[J]. Hi-Tech Fiber and Application, 2022, 47(6): 67-73(in Chinese). doi: 10.3969/j.issn.1007-9815.2022.06.011
[13]	王菁, 陈蕾, 李圣军, 等. 添加型阻燃剂的研究进展与发展趋势[J]. 合成纤维工业, 2022, 45(5): 69-74. doi: 10.3969/j.issn.1001-0041.2022.05.013 WANG Jing, CHEN Lei, LI Shengjun, et al. Research progress and development trend of additive flame retardants[J]. China Synthetic Fiber Indutry, 2022, 45(5): 69-74(in Chinese). doi: 10.3969/j.issn.1001-0041.2022.05.013
[14]	Federico U , Carlo B , Martina R , et al. Synthesis of sustainable flame retarded polypropylene by using waste material[J]. Advanced Industrial and Engineering Polymer Research, 2023, 6 (2): 165-171.
[15]	王丽琼, 李立影, 梁洁, 等. 三嗪和磷腈阻燃剂作碳源阻燃聚乳酸复合材料的性能研究[J]. 安全与环境学报, 2021, 21(03): 1040-1047. doi: 10.13637/j.issn.1009-6094.2019.1640 WANG Liqiong, LI Liying, LIANG Jie, et al. Effect to be gained by using the triazine and phosphazene flame retardants as carbon sources on the properties of polylactic acid[J]. Journal of Safety and Environment, 2021, 21(03): 1040-1047(in Chinese). doi: 10.13637/j.issn.1009-6094.2019.1640
[16]	YAO Z Y, QIAN L J, QIU Y, et al. Flame retardant and toughening behaviors of bio-based DOPO-containing curing agent in epoxy thermoset[J]. Polymers for Advanced Technologies, 2020, 31(3): 461-471. doi: 10.1002/pat.4782
[17]	MA D, LI J. Synthesis of a bio-based triazine derivative and its effects on flame retardancy of polypropylene composites[J]. Journal of Applied Polymer Science, 2020, 137(1): 245-253.
[18]	白毓黎, 白富栋, 张通等. 木质素基阻燃剂制备的研究进展[J]. 当代化工, 2020, 49(10): 2314-2317. doi: 10.3969/j.issn.1671-0460.2020.10.049 BAI Yuli, BAI Fudong, ZHANG Tong, etc. Research progress of lignin-based flame retardant[J]. Contemporary Chemical Industry, 2020, 49(10): 2314-2317(in Chinese). doi: 10.3969/j.issn.1671-0460.2020.10.049
[19]	XIA Y R, CAI W H , LIU Y H, et al. Facile fabrication of starch-based, synergistic intumescent and halogen-free flame retardant strategy with expandable graphite in enhancing the fire safety of polypropylene[J]. Industrial Crops & Products, 2022, 184: 115002.
[20]	ZHANG L Y, XUE W, GU L M. Study on properties and application of pyrophosphate flame retardant microcapsules prepared from hemicellulose maleate[J]. Cellulose, 2020, 27(7): 3931-3946. doi: 10.1007/s10570-020-03045-5
[21]	WANG M T, YIN G Z, YANG Y, et al. Bio-based flame retardants to polymers: A review[J]. Advanced Industrial and Engineering Polymer Research, 2023, 6(2): 132-155. doi: 10.1016/j.aiepr.2022.07.003
[22]	CARVALHO R M, SILVA D P S R, VEIGA S R N, et al. The influence of montmorillonite on the flame-retarding properties of intumescent bio-based PLA composites[J]. Journal of Applied Polymer Science, 2022, 139(22): 52243. doi: 10.1002/app.52243
[23]	YANG H T, YU B, XU X D, et al. Lignin-derived bio-based flame retardants toward high-performance sustainable polymeric materials[J]. Green Chemistry, 2020, 22: 2129-2161. doi: 10.1039/D0GC00449A
[24]	ZHANG R, XIAO X F, TAI Q L. Modification of lignin and its application as char agent in intumescent flame-retardant poly(lactic acid)[J]. Polymer engineering and science, 2012, 52(12): 2620-2626. doi: 10.1002/pen.23214
[25]	中国国家标准化管理委员会. 塑料用氧指数法测定燃烧行为, GB/T2406-2008[S]. 北京, 中国标准出版社, 2008. Standardization Administration of the People's Republic of China. Plastics determination of combustion behavior using the oxygen index method, GB/T2406-2008 [S]. beijing, China Standards Press, 2008(in Chines).
[26]	中国国家标准化管理委员会. 塑料燃烧性能的测定水平法和垂直法, GB/T 2408-2021[S]. 北京: 中国标准出版社, 2021. Standardization Administration of the People's Republic of China. Determination of burning properties of plastics-horizontal and vertical methods, GB/T 2408-2021 [S]. Beijing: China Standards Press, 2021(in Chinese).
[27]	ISO. Reaction-to-fire tests-Heat release, smoke production and mass loss rate−part 1: heat release rate (cone calorimeter method) and smoke production rate (dynamic measurement): ISO 5660-1: 2015 [S]. Geneva: ISO, 2015.
[28]	中国国家标准化管理委员会. 塑料拉伸性能的测定第2部分: 模塑和挤塑塑料的试验条件: GB/T 1040.2−2006[S]. 北京: 中国标准出版社, 2006. Standardization Administration of the People's Republic of China. Plastics-determination of tensile properties-part 2: test conditions for moulding and extrusion plastics: GB/T 1040.2−2006 [S]. Beijing: China Standards Press, 2006(in Chinese).
[29]	中国国家标准化管理委员会. 塑料悬臂梁冲击强度的测定: GB/T 1843−2008[S]. 北京: 中国标准出版社, 2008. Standardization Administration of the People's Republic of China. Plastics−determination of izod impact strength: GB/T 1843−2008 [S]. Beijing: China Standards Press, 2008(in Chinese).
[30]	杨晓涵, 宋艳, 林肯等. 木质素基成炭剂的制备及在膨胀阻燃聚丙烯的应用[J]. 高分子材料科学与工程, 2022, 38(12): 39-46. doi: 10.16865/j.cnki.1000-7555.2022.0270 YANG Xiaohan, SONG Yan, LIN Ken, etc. Preparation of lignin-based char-forming agent and its application in intumescent flame retardant polypropylene[J]. Polymer Materials Science and Engineering, 2022, 38(12): 39-46(in Chinese). doi: 10.16865/j.cnki.1000-7555.2022.0270
[31]	OTT M W, DIETZ C, TROSIEN S, et al. Co-curing of epoxy resins with aminated lignins: insights into the role of lignin homo crosslinking during lignin amination on the elastic properties[J]. Holzforschung, 2021, 75(4): 390-398. doi: 10.1515/hf-2020-0060
[32]	YANG H C, PU H T, GONG F H. Preparation of poly (methyl methacrylate)-grafted attapulgite by surface-Initiated radical polymerization[J]. Journal of Applied Polymer Science, 2014, 131(22): 1725-1730.
[33]	SONG Y, LI J C, YAN N, et al. Preparation of γ-divinyl-3-aminopropyltriethoxysilane modified lignin and its application in flame retardant poly(lactic acid)[J]. Materials, 2018, 11(9): 1505. doi: 10.3390/ma11091505
[34]	吴迪超, 陈超, 侯兴隆等. 热解温度对纤维素和木质素成炭结构的影响[J]. 生物质化学工程, 2021, 55(03): 1-9. doi: 10.3969/j.issn.1673-5854.2021.03.001 WU Dichao, CHEN Chao, HOU Xinglong, etc. Effect of pyrolysis temperature on structures of chars forming from cellulose and lignin[J]. Biomass Chemical Engineering, 2021, 55(03): 1-9(in Chinese). doi: 10.3969/j.issn.1673-5854.2021.03.001
[35]	HU X, SUN J H, LI X, et al. Effect of phosphorus-nitrogen compound on flame retardancy and mechanical properties of polylactic acid[J]. Journal of Applied Polymer Science, 2021, 138(7): 49829. doi: 10.1002/app.49829
[36]	王楠, 宋艳, 李锦春等. 含磷木质素基成炭剂的合成及在阻燃聚丙烯中的应用[J]. 高分子材料科学与工程, 2018, 34(04): 7-13. WANG Nan, SONG Yan, LI Jinchun, etc. Synthesis of lignin-based charring agent containing phosphorus and its application in flame retardant polypropylene[J]. Polymer Materials Science and Engineering, 2018, 34(04): 7-13(in Chinese)
[37]	JIA L J, HUANG W Z, ZHAO Y J, et al. Ultra-light polylactic acid/combination composite foam: a fully biodegradable flame retardant material[J]. International journal of biological macromolecules, 2022, 220: 754-765. doi: 10.1016/j.ijbiomac.2022.08.093