缓冲包装用什么改性PP？先把一件事说清：气柱袋与气泡膜的基材是 PE 系与 PA/PE 共挤膜，不是改性PP。这篇讲两条赛道的分工——薄膜类靠阻气层保压，发泡类与硬质结构类才落在 PP 系；再给判据表、验证顺序与边界。
"气柱袋放两周就瘪了。"
一个做酒类出口的采购这么跟我说。后半句是：一个箱子摔下去，角上那几根气柱全爆，瓶子照样碎了。
两条投诉，两种机制。瘪是气体慢漏，爆是膜被刺穿或封边先破。 分开看，选材才谈得下去。
但更该先讲的是：气柱袋和气泡膜的基材，不是改性PP。
气泡膜主料是低密度聚乙烯（LDPE）与线性低密度聚乙烯（LLDPE）；气柱袋基材是 PE 与 PA（尼龙）的多层共挤膜，靠尼龙层阻气、PE 层热封。决定"能不能撑到收货"的是阻气层，跟总厚度关系不大。
改性PP 在这两类薄膜件里没有位置。它的位置在另两条赛道上：发泡类缓冲件与硬质结构缓冲件。
这个方向的薄膜基材走石化厂膜料与吹膜厂的通道，不是改性造粒线的产品；能参与的是阻气共挤层的改性粒子、发泡体系的改性侧与相容剂。
一、缓冲包装的工况六维：保压按周算，不是按"充起来就行"
结论先说：六维里最容易被漏掉的是"寿命"——缓冲件的寿命不按年算，按"从充气到开箱"的周数算，这个周期一改，保压门限跟着改。
| 维度 | 实际工况 | 对材料的要求 |
|---|
| 温度 | 夏季集装箱内可长期高于 60℃；气柱膜公开适用区间常见 −20℃ 至 +60℃ 一档；冷链件走 −18℃ 级 | 高温加速气体渗透；低温要求膜不发脆 |
| 载荷 | 单柱静态承重常见口径 ≥50 kg、优级 ≥70 kg；堆码常见 3 层以上持续数周 | 承压靠柱径与内压设计，也靠膜的抗蠕变 |
| 介质 | 海运高湿（RH 85% 级）、内容物油脂与溶剂、金属棱角与瓶盖齿 | 阻湿、耐内容物、抗穿刺 |
| 寿命 | 从充气到收货按周计：7 天内、7–28 天、28 天以上三档；公开资料有"50μm 级尼龙共挤膜常温保气 60 天以上"的口径（B 级，单一来源） | 保压门限按最长那一段定 |
| 外观 | 要看清内容物 | 透明度与雾度（GB/T 2410） |
| 合规 | 食品件走 GB 4806.7-2023；电子件防静电，表面电阻常按 10⁶–10⁹ Ω 一档约定 | 合规是入场项，不是加分项 |
表注：承重、温度区间与保气时长为公开企业技术资料转述（B 级），用于说明量级；具体门限须写进验收条件。
先看"寿命"，因为它会把另外五维的权重改一遍。同一只袋子走 7 天快递和走 60 天海运，保压门限不是一个数——前者按 24 小时压降考核就够，后者要按 7 天、28 天的保持率另定一档。保压数据还必须带上测试条件才有意义。
二、材料路线对比：薄膜类、发泡类、硬质结构类，三条赛道各管一段货
结论先说：三条路线解决的不是同一个问题，所以不存在"谁更好"，只存在"你这批货落哪一段"。
| 路线 | 主体材料 | 靠什么起作用 | 适配的货重与跌落高度 | PP 的位置 |
|---|
| ① 薄膜类缓冲 | 单层 PE（LDPE/LLDPE）膜；或 PE 与 PA 的多层共挤膜（典型 7 层 PE-PE-TIE-PA-TIE-PE-PE），也可用 EVOH 做阻气层 | 充气气柱与气泡提供缓冲行程；保压靠阻气层的气体阻隔性 | 轻到中重（几公斤到十几公斤级），跌落高度按包装等级与单件重量定 | 基本没有位置（TIE 层属相容剂方向） |
| ② 发泡类缓冲 | EPP 珠粒成型件、发泡 PP 片材 | 泡孔结构压缩吸能，靠平台段控制传递峰值 | 中到重、可复用件；跌落高度较高或反复冲击 | PP 系的主场 |
| ③ 硬质结构缓冲 | PP 中空板、PP 蜂窝板（可加玻纤增强面板） | 结构刚度与平面承压，靠结构而非材料本体变形 | 大平面、高堆码、需挺度的周转场景 | PP 系的主场 |
文字版结论：分水岭是"变形空间"和"是否复用"。 空间小、走一趟的偏薄膜类；空间够、要复用的偏发泡类；要平整挺括的走硬质结构类。三条路线里，改性PP 站在后两条上。
2.1 PP 的真实定位：薄膜不靠它，泡孔和结构靠它
气柱袋的保压能力来自阻气层，不来自 PE 层。 PE 的阻隔性一般，扛慢漏的是复合进去的尼龙层或 EVOH 层。公开企业技术资料的口径是：多层尼龙共挤结构相比普通单层 PE 膜，氧气透过率下降 65% 以上（B 级，单一来源）。所以"加厚"不是保压的正解。
这条通道的基材由石化厂膜料牌号与吹膜厂共同决定，客户买的是膜卷或成品袋，性能落点在整卷——改性造粒线接不进来，也不该去接。
发泡这条路靠泡孔结构，不靠材料的强与硬。公开行业资料给出一组可比量级：同一密度下，EPP 制品压缩强度可达 1.5 MPa 以上，传统泡沫常在 0.5 MPa 一档；反复压缩一万次以上，回弹率仍可保持 95% 以上（B 级）。硬质结构这条路同理——公开产品资料里，PP 蜂窝板压缩强度落在 1.5 MPa 级一档（B 级），堆码按 GB/T 4857.3-2008 静载荷堆码方法评价。
敢否定一个常见做法：以为"膜越厚，保压越久"，是这类件上最普遍的错法。保压的决定项是阻气层的阻隔性（气体渗透系数），不是总厚度。 加厚只是把泄漏的绝对量往后延迟一点，同时把材料用量、重量、成本和雾度一起推上去。有效做法只有两条：加阻气层（PA / EVOH 复合），或换到泡孔结构的发泡缓冲件上。
三、★ 选型判据表：保压是第一判据，七项指标各带验证方法
结论先说：这张表第一项就是气柱袋的第一判据——保压；更该被重视的是第三列"怎么测"，不是"测哪个"。
| 指标 | 门限值（典型） | 验证方法 · 标准号 | 常见失效 | 通行解法 |
|---|
| 保压（充气后压力衰减） | 按"时间口径 + 允许压降"约定：公开企业口径常见 24 h 自然漏气率 ≤5%、优级 ≤3%（B 级）；长周期按 7 天 / 28 天保持率另定 | 充至规定内压后静置读数，按 24 h / 7 d / 28 d 记压降；状态调节按 GB/T 4857.2-2005 | 到货已瘪；批次压降离散大 | 加阻气层；提高封边与阀膜一致性 |
| 抗穿刺强度 | 无统一国标门限，须按内容物尖锐程度与膜结构在验收条件里约定 | 穿刺试验（球形或锥形穿刺头恒速穿透，记录最大力），参照 ASTM F1306 口径（B 级） | 角上气柱爆；棱角处渗漏 | 多层结构 + 外层 PE 加厚；加护角 |
| 拉伸强度与断裂伸长率 | 公开企业口径 MD ≥28 MPa、TD ≥26 MPa 一档（B 级）；薄膜件真正要看的是断裂伸长率 | GB/T 1040.3-2006（薄膜和薄片的试验条件；2026 版已发布、2026-12-01 起实施）；层间剥离按 GB/T 8808 | 充气时先破；层间分层 | 选拉伸与伸长率匹配的 PE 体系；复核 TIE 层 |
| 低温柔韧性 | 低温预处理后复测拉伸与伸长率；对照口径：PP 类低温件常按 −20℃ 悬臂梁缺口冲击 ≥93 J/m 一档要求（B 级） | 低温预处理后复测；对照 GB/T 1843 悬臂梁方法 | 冬季运输脆裂；膜变硬不回弹 | 换更耐低温的体系，往高乙烯含量方向走 |
| 跌落与堆码（整箱） | 跌落高度按包装等级与单件重量定，常见 0.9–1.2 m 级；堆码按 1.5 倍额定载荷 24 h、变形量 ≤5% 级约定 | 跌落按 GB/T 4857.5-1992；堆码按 GB/T 4857.3-2008 或 GB/T 4857.4-2008；水平冲击按 GB/T 4857.11-2005 | 单件测试过了、整箱仍失败 | 先按 GB/T 4857.17-2017 编试验大纲，再排项 |
| 防静电（电子件） | 表面电阻常按 10⁶–10⁹ Ω 一档约定；公开资料里防静电气泡膜也有 10⁹–10¹¹ Ω 一档口径 | 参照 GB/T 1410 口径 | 静电击穿器件，外观看不出来 | 抗静电体系 + 先定由谁承担 |
| 食品接触合规（食品件） | 总迁移 ≤10 mg/dm² 等（GB 4806.7-2023） | GB 4806.7-2023 | 合规文件缺失导致整批退运 | 食品级原料 + 成品检测报告 |
文字版结论：保压是一票否决项——它不过，后面所有整箱试验都不用做。低温柔韧最常被漏做：常温数据看着没问题，冬季一批货集中暴露。最后两项是入场项：没有防静电数据或合规文件，性能再好也进不了供应商名单。
四、常见失效与根因：四个现象，两个来自"想当然"
结论先说：四类里有三类不是"膜不够好"，而是判据定错、方法用错、时机排错。
失效一：到货已经瘪了。 根因分三处查——阻气层结构、封边与阀膜、保压门限是否按最长运输周期定。先查前两处，再谈换膜；顺序反了会白换几轮。
失效二：摔一下就爆，破口集中在角上。 根因多数是穿刺，不是拉伸。角部是应力与穿刺双重集中的位置，提高拉伸强度解决不了。
失效三：低温季货损集中爆发。 根因是低温下膜变硬、伸长率下降，缓冲行程被吃掉。必须在低温条件下重做一遍，不是把常温数据打个折。
失效四（敢否定一个常见做法）：以为"缓冲件只要不破就行"。 缓冲件的功能是把冲击加速度降到被保护物能承受的范围内。只测"破没破"，会漏掉最坏的情况——包装完好、气柱没爆，但传递到产品的峰值加速度已经超标，里面的东西已经坏了。整箱验证要同时记录包装是否破损、内装物是否损坏。
五、验证顺序：先看外观与透明度，保压排在第五级
结论先说：验证顺序是"材料入场项 → 成品保压项 → 整箱系统项"三段；顺序反了，最贵的那次失败会落在最后一步。
`
① 外观与透明度 雾度与透光率（GB/T 2410）；膜面有无晶点、皱褶
↓ 看不清内容物或膜面异常 → 退回共挤结构与急冷工艺
② 拉伸与断裂伸长率 GB/T 1040.3-2006，纵横向都做；伸长率比强度更关键
↓ 伸长率不足 → 退回 PE 体系与层比
③ 抗穿刺 按穿刺试验口径；取角部实际接触位置复测
↓ 不过 → 退回外层结构与柱径设计
④ 低温柔韧 低温预处理后复测拉伸与伸长率
↓ 衰减超限 → 退回更耐低温的体系
⑤ 充气保压 充至规定内压，恒温恒湿静置，读 24 h / 7 d / 28 d 压降
↓ 压降超门限 → 退回阻气层结构、封边与阀膜
⑥ 整箱跌落与堆码 GB/T 4857.5-1992 跌落；GB/T 4857.3-2008 / 4857.4-2008 堆码
↓ 内装物受损 → 退回 ③ 与 ⑤，重配柱数与内压
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最常被跳过的两处：跳过 ①② 直接用成品袋做 ⑤，把材料侧的问题留到成品侧暴露；跳过 ⑤ 直接做 ⑥，一次失败就是整批样品的成本。
六、反向诚实：这几类需求该直接找石化厂与膜厂，我们接不住
结论先说：这个方向的主体不在改性造粒线上。把这句话先说清楚，比硬接一张单有用。
| 出现的情况 | 为什么落到别的通道 | 该找谁 |
|---|
| 只买基材膜料（单层 PE 膜、PA/PE 共挤膜、EVOH 共挤膜） | 膜料是石化厂按吹膜级设计的牌号体系，不是造粒线的产品形态 | 石化厂 / 膜料贸易商 |
| 要求全流程吹膜生产（配方—吹膜—分切—制袋） | 吹膜的流道、急冷与收卷，跟造粒是两套装备体系 | 吹膜厂 / 制袋厂 |
| 要求"整卷性能承诺"（整卷保压、整卷雾度、整卷厚度公差） | 承诺对象是膜卷本身，责任主体只能是膜厂 | 膜厂 |
| 要求食品接触合规文件或整箱运输认证（GB 4806.7-2023 报告、ISTA 3A 类程序） | 一个对应终端制品，一个对应包装系统 | 膜厂 / 制袋厂 / 检测机构 |
我方不接这一块，也不冒充能接。 把这条线讲清楚，客户反而更愿意把能接的那一段交过来。要 EPP 珠粒或蒸汽成型件的，走发泡料厂与发泡成型厂。
能参与的是三块：① 阻气共挤层与相容剂方向——多层共挤的粘接（TIE）层用马来酸酐接枝聚烯烃这一类相容剂；② 发泡体系的改性侧——发泡基材方向与高熔体强度方向，而珠粒预发、熟化与模内成型是发泡厂的专业范围；③ 硬质结构板的基材，以及抗静电、耐候功能母粒方向。
一条经验：这类外延方向的询盘，先分清客户要的是膜卷还是粒子。 要膜卷的，直接指到膜厂；要粒子的，才轮到我们这一步。
七、换料风险清单：薄膜挤出与共挤，动的不是模具是流道
结论先说：薄膜件的换料风险集中在"共挤结构"和"冷却收卷"两块，跟注塑件的收缩率、浇口是两套清单。
| 要动的项 | 需要确认什么 | 不做会怎样 |
|---|
| 挤出温度窗口 | 共挤各层的熔体温度区间不重合，PA 层与 PE 层尤其如此 | 层间不稳、晶点、破膜 |
| 共挤层结构与流道 | 层数、层比、分配器与模头是否支持目标结构 | 阻气层偏薄或断续，保压直接不达标 |
| 冷却（急冷辊） | 辊温与线速决定结晶状态与表面质量 | 雾度上升、膜面不平、热封窗口收窄 |
| 收卷张力 | 张力与卷径要匹配 | 皱褶与拉伸残留，充气时局部先破 |
| 层间相容 | TIE 层牌号与层比 | 剥离强度不足（GB/T 8808）、复合层分层 |
| 热封与阀膜 | 热封温度窗口与单向阀膜的一致性 | 漏气点从封边开始 |
| 验证顺序 | 外观与雾度 → 拉伸与伸长率 → 抗穿刺 → 低温柔韧 → 充气保压 → 整箱跌落与堆码 | 风险全部压到整箱试验那一步爆发 |
文字版结论：换料要动的是挤出温度、共挤结构、冷却与收卷四块，其中最该先谈的还是验证顺序。跳过材料入场项直接做整箱，就是用整箱样品的成本去发现一个膜本身能测出来的问题。
八、一页纸汇报对照表：缓冲包装选型可以直接贴进 PPT
结论先说：判断标准只有一条——客户拿这张表，能不能在一次会议里把路线定下来。
| 场景 | 推荐路线 | 关键指标 | 验证标准 | 需先确认的条件 |
|---|
| 玻璃瓶、酒类等重物，带瓶盖齿 | 薄膜类：PA/PE 多层共挤气柱袋 | 保压压降 + 抗穿刺 + 单柱承重 | GB/T 4857.2-2005 条件下读压降；GB/T 4857.5-1992 整箱跌落 | 单件重量、瓶盖齿形、运输周期 |
| 3C 小件、轻货、短途 | 薄膜类：单层 PE 气柱膜或气泡膜 | 断裂伸长率 + 雾度 | GB/T 1040.3-2006；GB/T 2410 | 存放周期、是否要透明 |
| 精密电子件、需防静电 | 薄膜类：防静电膜 + 气柱结构 | 表面电阻 + 保压 | 参照 GB/T 1410 口径 + 保压静置读数 | 防静电由包装承担还是载具承担 |
| 较重、需多次周转、堆码大 | 发泡类：EPP 珠粒成型件 / 发泡 PP 片材 | 压缩强度 + 压缩永久变形 + 复压后保持率 | GB/T 1041-2008；复压后复测 | 复用次数、堆码层数 |
| 大平面、要挺度与平面承压 | 硬质结构类：PP 中空板 / 蜂窝板 | 平压强度 + 弯曲模量 + 堆码变形 | GB/T 1041-2008、GB/T 9341-2008、GB/T 4857.3-2008 | 堆码层数、仓储时长 |
| 冷链与低温运输 | 低温更稳的体系 + 低温条件下复测保压 | 低温柔韧 + 低温保压 | 低温预处理后复测 | 最低温度、运输时长 |
文字版结论：别把"保压、抗穿刺、低温"三件事塞进"质量要好"一句里——三件事各自给门限、各自给方法。最有用的是最后一列，它决定报出去的话能不能兑现。
九、这个方向上最容易出问题的，往往不是料
这个方向上最集中的两类失效是到货已瘪与角部爆袋，归因多数不在"膜不够好"上。公开技术资料把保压讲得很直接：保压能力取决于阻气层的阻隔性——多层尼龙共挤结构相比单层 PE 膜，氧气透过率可下降 65% 以上（B 级，单一来源）。穿刺则更多落在结构设计上：柱径、柱数、外层厚度与护角，比"换一种更贵的膜"更直接。
行业通行的判据与解法：保压按时间口径加允许压降约定，解法是加阻气层而不是加厚；整箱按 GB/T 4857 系列做（跌落 GB/T 4857.5-1992，堆码 GB/T 4857.3-2008 与 GB/T 4857.4-2008），先编试验大纲再排项；要挺度与平面承压的走 PP 中空板与蜂窝板这条结构路线。
宁波市科隆新材料有限公司在这个方向上常供的是改性PP 粒子里的这几段：发泡基材方向、硬质结构板基材方向、抗静电与相容剂方向，按件的工况给基材档位与改性方向建议，可以陪客户做小样比对与验证顺序对接。膜料、整卷性能承诺与整箱认证这三段不在我们能接的范围内。
常见问答
问：气柱袋到底能不能用 PP 做？
答：做得出来，但主流不是这么用的。气柱袋靠阻气层保压，PA/PE 共挤与单层 PE 是两个成熟通道。PP 系站得住的位置是发泡缓冲件与硬质结构板。
问：为什么不干脆把膜加厚，把保压做够？
答：加厚改的是泄漏的绝对量，不是泄漏的速率。保压速率由阻气层决定；加厚同时抬高材料用量、重量与雾度，透明度最先受影响。
问：跌落测试通过了，是不是就稳了？
答：不够。跌落是新件状态下最容易过的项目。真正会一票否决的是保压与低温——前者几周后暴露，后者冬季暴露。
| 工况 | 关键判据 | 常规供应 |
|---|
| 薄膜类缓冲件（气柱袋、气泡膜） | 保压压降、抗穿刺、伸长率 | 相容剂与功能母粒方向（膜料与吹膜不在范围内） |
| 发泡类缓冲件（EPP、发泡 PP 片材） | 压缩强度、压缩永久变形、复压保持 | 改性PP 发泡基材方向 |
| 硬质结构缓冲（PP 中空板、蜂窝板） | 平压强度、弯曲模量、堆码变形 | 改性PP 板材料方向（填充 / 增韧） |
| 电子件缓冲与周转 | 表面电阻 10⁶–10⁹ Ω | 抗静电母粒方向 |
想提醒一句：件出问题，最常见的错法是先换料。瘪、爆、裂、变形——每一条的原因都不止一个。先定位，再换料；顺序反了，往往换了几轮还在原地。
十、最后说三句
第一，先分清赛道，再谈材料。 缓冲包装的三条路线——薄膜类、发泡类、硬质结构类——解决的不是同一个问题；薄膜类的基材不是改性PP，这是这个方向最该先说清的一件事。
第二，保压不是靠厚度，是靠阻气层。 这一句话能省掉的返工，比任何一次比价都多。
第三，"没破"不等于"没坏"。 缓冲件考核的是传递到内装物上的峰值加速度；只看包装是否破损，会漏掉最坏的情况。
关于我们
前两天接了个电话，第一句是"你们的 PP 耐多少度"。
这句话没法直接答。耐温要看长期连续使用温度，不是短期峰值；还要看负载、介质、有没有填充增强。同一句话，答案能从 80℃ 讲到 140℃ 以上。
宁波市科隆新材料有限公司，自产改性聚丙烯（PP）造粒，覆盖均聚 / 无规共聚 / 抗冲共聚三档基材，以及填充、玻纤增强、增韧、阻燃、低气味低 VOC、耐候、免喷涂耐划伤等改性方向；兼营各大石化厂 PP 树脂、副牌料与大包料。
Which modified PP is used for cushioning packaging? Let's clarify one thing first: the base materials for air column bags and bubble wrap are PE-based and PA/PE co-extruded films, not modified PP. This article discusses the division of the two tracks — the film type relies on barrier layers to maintain pressure, while the foamed type and rigid structure type fall under the PP system; it also provides a criteria table, verification sequence, and boundaries.
The air column bag deflated after just two weeks.
A purchaser who exports alcohol said this to me. The latter part is: if a box falls, the few air columns at the corners all burst, and the bottles still break.
Two complaints, two mechanisms. Deflation is a slow leak of gas, bursting is when the membrane is pierced or the edge seal breaks first. Looking at them separately, you can only then talk about material selection.
But what should be mentioned first is that the base material of air column bags and bubble film is not modified PP.
The main materials of bubble wrap are low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE); the base material of inflatable column bags is a multilayer co-extruded film of PE and PA (nylon), with the nylon layer acting as a gas barrier and the PE layer for heat sealing. What determines whether it 'can last until delivery' is the gas barrier layer, not the total thickness.
Modified PP has no place in these two types of film parts. Its place is in two other tracks: foamed cushioning parts and rigid structural cushioning parts.
The film substrate in this direction follows the channel between petrochemical plant film materials and film blowing factories, and is not a product of modified pelletizing lines; what can participate are the modified particles in the barrier co-extrusion layer, the modified side of the foaming system, and compatibilizers.
1. The six dimensions of operating conditions for cushioning packaging: Pressure holding is calculated weekly, not 'just fill it up'.
Conclusion first: the most easily overlooked dimension in six dimensions is 'lifespan' — the lifespan of a buffer part is not calculated by years, but by the number of weeks 'from inflation to unboxing.' When this cycle changes, the pressure maintenance threshold changes accordingly.
| Dimension | Actual operating conditions | Requirements for the materials |
|---|
| Temperature | In summer, the temperature inside containers can remain above 60°C for long periods; the commonly used range for air column films is usually −20°C to 60°C for one grade; cold chain items are transported at −18°C level. | High temperatures accelerate gas permeation; low temperatures require the membrane not to become brittle |
| Load | Common single-column static load capacity ≥50 kg, excellent grade ≥70 kg; stacking usually 3 layers or more for several weeks | Pressure resistance relies on the column diameter and internal pressure design, as well as the creep resistance of the membrane. |
| Medium | Marine transport with high humidity (RH 85%), contents of oils and solvents, metal edges and bottle cap teeth | Moisture-resistant, content-resistant, puncture-resistant |
| Lifespan | From inflation to receipt, calculated by week: within 7 days, 7–28 days, and over 28 days; public information shows a specification of '50μm grade nylon co-extruded film keeping air at room temperature for more than 60 days' (Grade B, single source) | The pressure-holding threshold is determined by the longest section. |
| Appearance | You need to see the contents clearly | Transparency and Haze (GB/T 2410) |
| Compliance | Food components comply with GB 4806.7-2023; electronic components should be anti-static, with surface resistance generally agreed to be in the range of 10⁶–10⁹ Ω. | Compliance is an entry requirement, not an extra credit. |
Table Note: Load-bearing, temperature range, and gas retention duration are paraphrased from publicly available corporate technical data (Class B), used to indicate scale; specific thresholds must be included in the acceptance criteria.
First look at "lifespan," because it will modify the weights of the other five dimensions. The same bag being shipped by express for 7 days and by sea for 60 days does not have the same pressure retention threshold—the former is evaluated based on a 24-hour pressure drop, while the latter requires separate thresholds according to 7-day and 28-day retention rates. Pressure retention data must also include the test conditions to be meaningful.
2. Comparison of material routes: thin film, foam, and rigid structure categories, each track managing a segment of goods
Conclusion first: The three routes are not solving the same problem, so there is no 'which is better,' there is only 'which segment your batch of goods falls into.'
| Route | Main material | What does it rely on to work? | Compatible load and drop height | The position of PP |
|---|
| ① Film-type cushioning | Single-layer PE (LDPE/LLDPE) film; or multilayer co-extruded film of PE and PA (typically 7 layers: PE-PE-TIE-PA-TIE-PE-PE), EVOH can also be used as the gas barrier layer | The inflatable air columns and bubbles provide cushioning stroke; the pressure holding relies on the gas barrier property of the gas layer. | Light to medium-heavy (a few kilograms to over ten kilograms), the drop height is determined according to the packaging level and the weight of a single item | Basically no position (TIE layer compatibilizer direction) |
| ② Foam Cushioning | EPP bead-molded parts, foamed PP sheets | The foam pore structure compresses to absorb energy, with the plateau region controlling the transmission of the peak value. | Medium to heavy, reusable parts; high drop height or repeated impact | PP series home court |
| ③ Rigid structure cushioning | PP hollow board, PP honeycomb board (glass fiber reinforced panel can be added) | Structural stiffness and plane compression depend on the structure rather than the deformation of the material itself | Large flat surfaces, high stacking, turnover scenarios requiring rigidity | PP series home court |
Text version of the conclusion: The watershed is 'deformation space' and 'whether it is reused.' Small space, a single pass tends to be thin-film type; sufficient space and reusable tend to be foam type; if flat and crisp is required, it goes for rigid structure type. Among the three routes, modified PP stands on the latter two.
2.1 The true positioning of PP: the film does not rely on it, the bubbles and structure rely on it
The pressure-holding ability of air column bags comes from the gas barrier layer, not from the PE layer. The barrier property of PE is average; what resists slow leakage is the nylon layer or EVOH layer incorporated in the composite. According to publicly available corporate technical data: compared with ordinary single-layer PE film, multilayer co-extruded nylon structures reduce oxygen permeability by more than 65% (Grade B, single source). Therefore, "thickening" is not the correct solution for pressure retention.
The substrate of this channel is determined jointly by the membrane material grade from the petrochemical plant and the film-blowing factory. Customers are buying film rolls or finished bags, with performance targeting the whole roll — it cannot be connected to the modified granulation line, nor should it be.
The foaming approach relies on the cell structure, not on the material's strength or hardness. Public industry data provide a comparable magnitude: at the same density, EPP products can reach a compressive strength of over 1.5 MPa, while traditional foams are usually around 0.5 MPa; after more than ten thousand cycles of compression, the rebound rate can still maintain over 95% (Grade B). The rigid structure approach is similar—according to publicly available product data, PP honeycomb panels have a compressive strength around the 1.5 MPa level (Grade B), and stacking is evaluated according to the static load stacking method of GB/T 4857.3-2008.
Daring to challenge a common practice: thinking that 'the thicker the film, the longer it maintains pressure' is the most widespread mistake with this type of part. The determining factor for maintaining pressure is the gas barrier property of the barrier layer (gas permeability coefficient), not the total thickness. Increasing thickness only slightly delays the absolute amount of leakage while simultaneously increasing material usage, weight, cost, and haze. There are only two effective approaches: increase the barrier layer (PA/EVOH composite) or switch to a foamed cushioning part with a cellular structure.
3. ★ Selection Criteria Table: Pressure holding is the first criterion, with verification methods provided for all seven indicators
Conclusion first: the first item on this table is the first criterion for the air column bag—holding pressure; what should be paid more attention to is the third column, 'how to measure,' not 'what to measure.'
| Indicator | Threshold Value (Typical) | Verification Method · Standard Number | Common Failures | Common solution |
|---|
| Pressure holding (pressure decay after inflation) | According to the 'time standard', the allowable pressure drop is 'agreed as follows: the common public enterprise standard for a 24-hour natural leakage rate is ≤5%, and the premium grade is ≤3% (Grade B); for long-term periods, the retention rate for 7 days / 28 days is determined separately. | After filling to the specified internal pressure, let it sit and read the value, recording the pressure drop at 24 hours / 7 days / 28 days; state adjustment according to GB/T 4857.2-2005 | The delivered goods are already deflated; the batch pressure reduction is highly variable | Add a resistance gas layer; improve the consistency between edge sealing and the valve diaphragm |
| Puncture Resistance | There is no unified national standard threshold; it must be agreed upon in the acceptance conditions according to the sharpness of the contents and the membrane structure. | Puncture test (spherical or conical puncture head penetrates at a constant speed, recording the maximum force), referring to ASTM F1306 caliber (Class B) | Corner gas column explosion; leakage at edges and corners | Multi-layer structure: outer layer PE thickened; reinforced corners |
| Tensile strength and elongation at break | According to public company standards, MD ≥28 MPa, TD ≥26 MPa is grade B; what really matters for film components is the elongation at break. | GB/T 1040.3-2006 (Test conditions for films and sheets; 2026 version has been released, effective from 2026-12-01); interlayer peeling according to GB/T 8808 | Burst when inflating; delamination between layers | Select a PE system that matches the stretch and elongation rate; review the TIE layer |
| low-temperature flexibility | Re-test tensile strength and elongation after low-temperature pretreatment; reference standard: PP type low-temperature parts often follow the requirement of ≥93 J/m for −20°C cantilever beam notched impact (Grade B) | Retested after low-temperature pretreatment; compared with GB/T 1843 cantilever beam method | Brittle cracking during winter transport; film becomes hard and does not rebound | Switch to a system that is more resistant to low temperatures and move towards higher ethylene content. |
| Drop and Stacking (Full Carton) | The drop height is determined according to the packaging grade and the weight of a single item, commonly 0.9–1.2 m grade; stacking is based on 1.5 times the rated load for 24 hours, with deformation ≤5% as the agreed standard. | Drop according to GB/T 4857.5-1992; stacking according to GB/T 4857.3-2008 or GB/T 4857.4-2008; horizontal impact according to GB/T 4857.11-2005 | The single item passed the test, but the entire box still failed. | First, prepare the test outline according to GB/T 4857.17-2017, then arrange the items. |
| Anti-static (electronic components) | Surface resistance is usually specified at the 10⁶–10⁹ Ω range; in public materials, anti-static bubble wrap also has a 10⁹–10¹¹ Ω range specification. | Refer to GB/T 1410 caliber | Electrostatic breakdown device, cannot be seen from the outside | Anti-static system: first determine who will bear it |
| Food Contact Compliance (Food Parts) | Total migration ≤10 mg/dm², etc. (GB 4806.7-2023) | GB 4806.7-2023 | The entire batch was returned due to missing compliance documents | Food-grade raw materials Finished product inspection report |
Text version conclusion: Pressure holding is a veto item—it’s just that, without it, all subsequent full-box tests don’t need to be done. Low-temperature flexibility is most often missed: ambient temperature data looks fine, but a batch of goods is exposed in winter. The last two items are entry requirements: without anti-static data or compliance documents, no matter how good the performance is, the supplier cannot be listed.
4. Common Failures and Root Causes: Four Phenomena, Two Arising from 'Assumptions'
Conclusion first: Among the four types, three are not due to 'insufficient membranes,' but rather due to incorrect criteria, wrong methods, or incorrect timing.
Failure 1: The goods were already deflated upon arrival. The root cause should be checked in three areas — the air barrier structure, the edge sealing and the valve membrane, and whether the pressure-holding threshold is set according to the longest transportation cycle. Check the first two areas first, then discuss replacing the membrane; reversing the order would waste several rounds of replacement.
Failure Type 2: It bursts with a single drop, with the break concentrated at the corners. The root cause is mainly puncture, not tension. Corners are areas of combined stress and puncture concentration, and increasing tensile strength does not solve the problem.
Failure Three: Concentrated outbreak of cargo damage during the cold season. The root cause is that the film hardens and the elongation rate decreases at low temperatures, consuming the cushioning stroke. It must be redone under low-temperature conditions, not just applying a discount to the room temperature data.
Failure Four (Daring to challenge a common practice): Believing that 'as long as the cushioning component doesn't break, it's fine.' The function of the cushioning component is to reduce the impact acceleration to a level that the protected item can withstand. Only testing 'whether it breaks or not' will miss the worst-case scenario—packaging remains intact and the air column hasn't burst, but the peak acceleration transmitted to the product has already exceeded the limit, and the contents inside are already damaged. Whole-box testing should record both whether the packaging is damaged and whether the contents are damaged.
5. Verification sequence: first check the appearance and transparency, pressure holding is placed at the fifth level
Conclusion first: the verification sequence is three stages: 'Material Entry Items → Finished Product Pressure-Holding Items → Complete Box System Items'; if the sequence is reversed, the most expensive failure will occur in the last step.
`
① Appearance and Transparency Haze and Light Transmittance (GB/T 2410); Presence of Crystal Points or Wrinkles on the Film Surface
↓ Unable to see the contents clearly or abnormal membrane surface → Return to co-extrusion structure and rapid cooling process
② Tensile and Elongation at Break GB/T 1040.3-2006, performed in both longitudinal and transverse directions; elongation is more critical than strength
↓ Insufficient elongation → Return to PE system and layer ratio
③ Puncture Resistance According to the puncture test caliber; re-measure at the actual contact position of the corner
↓ However → Revert to outer structure and column diameter design
④ Low-temperature flexibility Retest tensile strength and elongation after low-temperature pre-treatment
↓ Excessive attenuation → Revert to a system more resistant to low temperatures
⑤ Inflation and pressure maintenance: Inflate to the specified internal pressure, keep at constant temperature and humidity, and read the pressure drop at 24 hours / 7 days / 28 days
↓ Pressure drop exceeds the threshold → Return to gas barrier layer structure, edge sealing, and valve diaphragm
⑥ Full carton drop and stacking GB/T 4857.5-1992 Drop test; GB/T 4857.3-2008 / 4857.4-2008 Stacking test
↓ Interior damage → Return ③ and ⑤, reallocate the number of columns and internal pressure
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The two most commonly skipped steps: skip ①② and go straight to making the finished bag ⑤, leaving side issues with the materials to be exposed on the finished product side; skip ⑤ and go straight to ⑥, where a single failure results in the cost of the entire batch of samples.
6. Reverse honesty: These types of demands should be directly directed to petrochemical plants and membrane manufacturers; we can't handle them.
Conclusion first: The main body in this direction is not on the modified granulation line. It's more useful to clarify this sentence first than to just directly accept an order.
| The situation that occurred | Why did it fall to another channel | Who should I find? |
|---|
| Only purchase base film materials (single-layer PE film, PA/PE coextruded film, EVOH coextruded film) | Film material is a grade system designed by petrochemical plants for blown film, not the product form of the pelletizing line. | Petrochemical Plant / Membrane Material Trader |
| Require full-process blown film production (formulation — film blowing — slitting — bag making) | The flow channel, rapid cooling, and winding in film blowing are a separate set of equipment systems from granulation. | Blown Film Factory / Bag Making Factory |
| Require 'full roll performance commitment' (full roll pressure, full roll haze, full roll thickness tolerance) | The object of the commitment is the film roll itself, and the responsible party can only be the film manufacturer. | Film factory |
| Require food contact compliance documents or full-box transportation certification (GB 4806.7-2023 report, ISTA 3A type procedure) | One corresponds to the terminal product, one corresponds to the packaging system | Film Factory / Bag Manufacturing Factory / Testing Organization |
We do not take on this part, nor do we pretend we can. Explaining this clearly to the client actually makes them more willing to hand over the part we can handle. For EPP beads or steam-formed parts, go through the foam material factory and the foam forming factory.
There are three areas that can be involved: ① The gas barrier co-extrusion layer and compatibilizer direction — using compatibilizers such as maleic anhydride-grafted polyolefins for the adhesive (TIE) layers in multilayer co-extrusion; ② The modification side of the foaming system — in terms of foamed substrate and high melt strength, while bead pre-foaming, aging, and in-mold forming fall within the professional scope of foaming factories; ③ The substrate of rigid structural panels, as well as the directions of anti-static and weather-resistant functional masterbatches.
A piece of experience: For inquiries in this type of extension direction, first distinguish whether the customer wants film rolls or particles. For those who want film rolls, directly refer them to the film factory; for those who want particles, that's when it comes to our turn.
7. Material Change Risk List: Film extrusion and co-extrusion, it’s the flow channel that moves, not the mold
Conclusion first: The risk of material change for film parts is concentrated in the 'co-extrusion structure' and 'cooling and winding' areas, which are a different list from the shrinkage rate and gate of injection-molded parts.
| Items to move | What needs to be confirmed | What will happen if I don't do it? |
|---|
| Extrusion temperature window | The melt temperature ranges of each co-extruded layer do not overlap, especially between the PA layer and the PE layer. | Interlayer instability, crystal spots, broken membrane |
| Co-extrusion layer structure and flow channel | Whether the number of layers, layer ratio, distributor, and die head support the target structure | The gas barrier layer is thin or discontinuous, and the pressure maintenance directly fails to meet the standard. |
| Cooling (quench roll) | Roll temperature and line speed determine the crystallization state and surface quality | Increase in haze, uneven film surface, narrowing of the heat-sealing window |
| Rewinding tension | Tension must match the roll diameter | Wrinkles and stretching residue, local rupture occurs first when inflated |
| Interlayer compatibility | TIE Layer Number and Layer Ratio | Insufficient peel strength (GB/T 8808), delamination of composite layers |
| Heat Sealing and Valve Membrane | Consistency between heat sealing temperature window and check valve diaphragm | The leak point starts from the edge sealing |
| Verification order | Appearance and haze → Tensile and elongation → Puncture resistance → Low-temperature flexibility → Inflation and pressure retention → Full-case drop and stacking | All the risks are pushed to the point of the full-scale test explosion |
Text version conclusion: Changing materials involves adjustments in four areas: extrusion temperature, co-extrusion structure, cooling, and winding, among which the verification sequence should still be discussed first. Skipping the material entry step and going straight to a full-box trial means using the cost of a full-box sample to discover a problem that can be detected from the film itself.
8. One-page report comparison table: The selection of cushioning packaging can be directly pasted into the PPT
Conclusion first: there is only one criterion—to determine whether the client can use this sheet to finalize the route in a single meeting.
| Scene | Recommended Route | Key indicators | Verification Standard | Conditions that need to be confirmed first |
|---|
| Glass bottles, alcoholic beverages, and other heavy items, with bottle caps | Film type: PA/PE multi-layer co-extruded air column bag | Pressure holding pressure drop Puncture resistance Single-column load-bearing | Pressure drop reading under GB/T 4857.2-2005 conditions; full box drop according to GB/T 4857.5-1992 | Single item weight, bottle cap teeth, transportation cycle |
| 3C small items, light goods, short distance | Film types: single-layer PE air column film or bubble film | Elongation at break Haze | GB/T 1040.3-2006; GB/T 2410 | Storage period, whether it needs to be transparent |
| Precision electronic components, require anti-static protection | Film type: Antistatic film Air column structure | Surface Resistance Pressure Holding | Refer to GB/T 1410 caliber Pressure holding and static reading | Is electrostatic protection handled by the packaging or by the carrier? |
| Heavy, requires multiple handling, large stacking | Foamed products: EPP bead molded parts / foamed PP sheets | Compressive Strength Compressive Permanent Deformation Retention Rate After Recompression | GB/T 1041-2008; re-test after recompression | Number of reuse times, number of stacking layers |
| Large flat surface, requires stiffness and planar pressure resistance | Rigid structures: PP hollow sheet / honeycomb panel | Flat crush strength Bending modulus Creep deformation under stack | GB/T 1041-2008, GB/T 9341-2008, GB/T 4857.3-2008 | Number of stacking layers, storage duration |
| Cold Chain and Low-Temperature Transportation | A more stable system at low temperatures; re-test pressure holding under low temperature conditions | Low temperature flexibility Low temperature pressure holding | Retest after low-temperature pre-treatment | Minimum temperature, transport duration |
Textual Conclusion: Don’t cram the three things 'pressure maintenance, puncture resistance, low temperature' into the single phrase 'good quality'—each of the three should have its own threshold and its own method. The most useful part is the last column, as it determines whether promises can be fulfilled when reported.
9. The most likely to have problems in this direction is often not the material
The two most concentrated types of failures in this area are deflated packages upon arrival and corner bag bursts, and most of the time, the cause is not 'the film isn’t good enough.' Public technical materials explain pressure retention quite directly: the ability to retain pressure depends on the barrier properties of the gas barrier layer—compared to a single-layer PE film, a multilayer nylon co-extruded structure can reduce oxygen permeability by more than 65% (B grade, single source). As for punctures, they mostly relate to structural design: column diameter, number of columns, outer layer thickness, and corner protection are more direct factors than 'switching to a more expensive film.'
Common industry criteria and solutions: For pressure holding, use the agreed allowable pressure drop based on the time criterion; the solution is to add a gas barrier layer rather than increasing thickness. For whole boxes, follow the GB/T 4857 series (drop test GB/T 4857.5-1992, stacking tests GB/T 4857.3-2008 and GB/T 4857.4-2008), first prepare the test outline and then schedule the items. For rigidity and planar pressure resistance, follow the structural route of PP hollow board and honeycomb board.
Ningbo Kolon New Material Co., Ltd. commonly supplies these segments in modified PP pellets in this area: foam substrate direction, rigid structural board substrate direction, and antistatic and compatibilizer direction. Based on the working conditions of each part, we provide recommendations for the substrate grade and modification direction, and can assist customers with sample comparison and verification sequencing. The three segments of film materials, full-roll performance commitment, and full-box certification are not within the scope we can handle.
Frequently Asked Questions
Question: Can air column bags actually be made from PP?
Answer: It can be done, but this is not how the mainstream uses it. Air column bags rely on a gas barrier layer to maintain pressure, and PA/PE co-extrusion and single-layer PE are two mature approaches. The position where PP can stand is in foam cushioning components and rigid structural panels.
Question: Why not just make the membrane thicker and maintain the pressure long enough?
Answer: Increasing the thickness changes the absolute amount of leakage, not the leakage rate. The pressure-holding rate is determined by the gas barrier layer; increasing the thickness also raises the material usage, weight, and haze, with transparency being affected first.
Question: If it passes the drop test, does that mean it's stable?
Answer: Not enough. Drop tests are the easiest tests to pass when the item is new. The real deal-breakers are pressure holding and low temperature — the former is revealed after a few weeks, the latter in winter.
| Operating condition | Key criterion | Regular supply |
|---|
| Film-type cushioning materials (air column bags, bubble wrap) | Pressure holding drop, puncture resistance, elongation | Compatibilizers and functional masterbatch direction (film material and blown film not included) |
| Foamed cushioning components (EPP, foamed PP sheets) | Compressive strength, compressive permanent deformation, resilient modulus | Direction of modified PP foam substrate |
| Rigid structure cushioning (PP hollow board, honeycomb board) | Flat crush strength, bending modulus, stacking deformation | Direction of modified PP sheet materials (filled / toughened) |
| Electronic Component Buffering and Turnover | Surface resistance 10⁶–10⁹ Ω | Direction of anti-static masterbatch |
Just a reminder: when something goes wrong, the most common mistake is to replace the material first. Dents, bursts, cracks, deformations—each of these has more than one cause. Identify the cause first, then replace the material; if the order is reversed, you can go through several rounds of replacement and still be in the same place.
Ten, Lastly Say Three Sentences
First, distinguish the track before talking about materials. The three routes of cushioning packaging—film type, foam type, and rigid structure type—do not solve the same problem; the substrate of the film type is not modified PP, and this is the first thing that should be clarified in this direction.
Second, pressure holding does not rely on thickness, but on the vapor barrier layer. The rework saved by this sentence alone is more than any price comparison.
Third, 'not broken' does not equal 'not damaged.' The cushioning components are assessed based on the peak acceleration transmitted to the contents; only looking at whether the packaging is damaged will miss the worst-case scenario.
About Us
A couple of days ago, I received a call, and the first sentence was, 'How heat-resistant is your PP?'
This sentence cannot be answered directly. The temperature resistance depends on the long-term continuous use temperature, not the short-term peak; it also depends on the load, the medium, and whether there is filling reinforcement. For the same sentence, the answer can range from 80°C to over 140°C.
Ningbo Cologne New Materials Co., Ltd. produces modified polypropylene (PP) granules, covering homopolymer, random copolymer, and block copolymer base materials, as well as modifications including filled, glass fiber reinforced, toughened, flame-retardant, low odor and low VOC, weather-resistant, and scratch-resistant without coating; it also deals in PP resins from major petrochemical plants, off-spec materials, and bulk materials.
